Compositions and Methods of Use of β-Hydroxy-β-methylbutyrate (HMB) for Improving Muscle Mass, Strength and Muscular Function Without Exercise Background of the Invention This application claims the benefit of United States Provisional Patent Appln. No. 63/040,241 filed June 17, 2020 and herein incorporates United States Provisional Patent Appln. No. 63/040,241 by reference. 1. Field The present invention relates to a composition comprising β-hydroxy-β-methylbutyrate (HMB) and Vitamin D, and methods of using a combination of HMB and Vitamin D to improve muscle mass, strength, or functionality in non-exercising humans. The present invention further comprises methods of using a composition of HMB to improve muscle mass, strength, or functionality in vitamin D sufficient, non-exercising humans. 2. Background Lean body mass (LBM) decreases at a rate of about 8% per decade after the age of 40 and accelerates to about 15% per decade after the age of 70. Decreasing lean mass typically reflects a loss of muscle mass and is accompanied by reduced muscular strength and physical function. These losses have serious, wide-ranging implications for older adults. Lean body mass and strength are inversely associated with loss of independence, fall risk, morbidity, and mortality. Thus, attenuating the age-related losses of muscle mass and function has great potential to improve health and quality of life. Several strategies have been proposed to slow age-related muscle loss but to date only resistance training, alone or in combination with nutritional interventions, has been consistently shown to be effective. However, nutritional interventions alone are generally only effective in cases of restricted food intake or overt malnutrition. Insufficient protein intake (less than the recommended daily allowance [RDA] of 0.8 g per kg per day) is associated with reduced LBM and physical performance. While protein insufficiency affects relatively few older adults (~10%), increasing protein intake above the RDA increases muscle mass but does not improve muscle strength or global physical functioning. Similarly, pharmacologic interventions, primarily using anabolic agents, have been less convincing with some studies showing beneficial and others showing adverse outcomes. Additionally, the use of anabolic hormones have been associated with significant morbidities limiting their utility in the general population. HMB The only product of leucine metabolism is ketoisocaproate (KIC). A minor product of KIC metabolism is β-hydroxy-β-methylbutyrate (HMB). HMB has been found to be useful within the context of a variety of applications. Specifically, in U.S. Patent No. 5,360,613 (Nissen), HMB is described as useful for reducing blood levels of total cholesterol and low- density lipoprotein cholesterol. In U.S. Patent No. 5,348,979 (Nissen et al.), HMB is described as useful for promoting nitrogen retention in humans. U.S. Patent No. 5,028,440 (Nissen) discusses the usefulness of HMB to increase lean tissue development in animals. Also, in U.S. Patent No. 4,992,470 (Nissen), HMB is described as effective in enhancing the immune response of mammals. U.S. Patent No. 6,031,000 (Nissen et al.) describes use of HMB and at least one amino acid to treat disease-associated wasting. It has previously been observed that HMB alone or in combination with other amino acids is an effective supplement for restoring muscle strength and function in young athletes. Further, it has been observed that HMB in combination with two amino acids, glutamine and lysine, is effective in increasing muscle mass in elderly persons. It has been shown that HMB has beneficial effects on muscle mass, muscle strength, muscle function, and protein kinetics in older and young adults. In a year-long study by Baier et al., daily supplementation with HMB/Arg/Lys significantly improved LBM in supplemented older adults but showed no improvements in muscle strength or function. HMB is an active metabolite of the amino acid leucine. The use of HMB to suppress proteolysis originates from the observations that leucine has protein-sparing characteristics (1-4). The essential amino acid leucine can either be used for protein synthesis or transaminated to the α-ketoacid (α-ketoisocaproate, KIC)(1, 3). In one pathway, KIC can be oxidized to HMB. Approximately 5% of leucine oxidation proceeds via the second pathway (5). HMB is superior to leucine in enhancing muscle mass and strength. The optimal effects of HMB can be achieved at 3.0 grams per day, or 0.38g/kg of body weight per day, while those of leucine require over 30.0 grams per day (3). Once produced or ingested, HMB appears to have two fates. The first fate is simple excretion in urine. After HMB is fed, urine concentrations increase, resulting in an approximate 20-50% loss of HMB to urine (4, 6). Another fate relates to the activation of HMB to HMB- CoA (7-16). Once converted to HMB-CoA, further metabolism may occur, either dehydration of HMB-CoA to MC-CoA, or a direct conversion of HMB-CoA to HMG-CoA (17), which provides substrates for intracellular cholesterol synthesis. Several studies have shown that HMB is incorporated into the cholesterol synthetic pathway (12, 16, 18-20) and could be a source for new cell membranes that are used for the regeneration of damaged cell membranes (3). Human studies have shown that muscle damage following intense exercise, measured by elevated plasma CPK (creatine phosphokinase), is reduced with HMB supplementation within the first 48 hrs. The protective effect of HMB lasts up to three weeks with continued daily use (21-23). In vitro studies in isolated rat muscle show that HMB is a potent inhibitor of muscle proteolysis (24) especially during periods of stress. These findings have been confirmed in humans; for example, HMB inhibits muscle proteolysis in subjects engaging in resistance training (4). The results have been duplicated in many studies (25) (21-23, 26-28). The molecular mechanisms by which HMB decreases protein breakdown and increases protein synthesis have recently been reported (29-31, 31-33). In mice bearing the MAC16 cachexia-inducing tumor, HMB attenuated protein degradation through the down-regulation of key activators of the ubiquitin-proteasome pathway (30). Furthermore, HMB attenuated proteolysis-inducing factor (PIF) activation and increased gene expression of the ubiquitin- proteasome pathway in murine myotubes, thereby reducing protein degradation (31). PIF inhibits protein synthesis in murine myotubes by 50% and HMB attenuates this depression in protein synthesis (29). Eley et al demonstrated that HMB increases protein synthesis by a number of mechanisms, including the down-regulation of eukaryotic initiation factor 2 (eIF2) phosphorylation through an effect on dsRNA-dependant protein kinase (PKR) and upregulation of the mammalian target of rapamycin/70-kDa ribosomal S6 kinase (mTOR/p70 ^S6k ) pathway. The net result is increased phosphorylation of 4E-binding protein (4E-BP1) and an increase in the active eIF4G·eIF4E complex. Leucine shares many of these mechanisms with HMB, but HMB appears to be more potent in stimulating protein synthesis (29). HMB can also increase protein synthesis by attenuating the common pathway that mediates the effects of other catabolic factors such as lipopolysaccharide (LPS), tumor necrosis factor- α/interferon- γ (TNF-α /IFN-γ), and angiotensin II (Ang II) (32, 33). HMB acts by attenuating the activation of caspases-3 and -8, and the subsequent attenuation of the activation of PKR and reactive oxygen species (ROS) formation via down-regulation of p38 mitogen activated protein kinase (p38MAPK). Increased ROS formation is known to induce protein degradation through the ubiquitin-proteasome pathway. HMB accomplishes this attenuation through the autophosphorylation PKR and the subsequent phosphorylation of eIF2α, and in part, through the activation of the mTOR pathway. Numerous studies have shown an effective dose of HMB to be 3.0 grams per day as CaHMB (~38 mg/kg body weight-day ^-1 ). This dosage increases muscle mass and strength gains associated with resistance training, while minimizing muscle damage associated with strenuous exercise (34) (4, 23, 26). HMB has been tested for safety, showing no side effects in healthy young or old adults (35-37). HMB in combination with L-arginine and L-glutamine has also been shown to be safe when supplemented to AIDS and cancer patients (38). Studies in humans have also shown that dietary supplementation with 3 grams of CaHMB per day plus amino acids attenuates the loss of muscle mass in various conditions such as cancer and AIDS. (3, 4, 26, 34, 39, 40) A meta-analysis of supplements to increase lean mass and strength with weight training showed HMB to be one of only 2 dietary supplements that increase lean mass and strength with exercise (34). More recently it was shown that HMB and the amino acids arginine and lysine increased lean mass in a non-exercising, elderly population over a year-long study. Vitamin D Vitamin D has classically been associated with calcium and phosphorous metabolism and bone strength. Until recently, an adequate Vitamin D level has been defined using the Vitamin D deficiency disease rickets. While 1,25OH2-VitD3 is the active metabolite of Vitamin D, a measure of Vitamin D status widely accepted is serum (blood) circulating 25OH-VitD3. A circulating blood level between 10 and 15 ng 25OH-VitD3/mL will cause rickets in young children and has been accepted as the deficiency level for Vitamin D. Vitamin D can be synthesized by humans with adequate sun exposure or can be obtained through the diet and through supplements to the diet. Many factors influence the amount and effectiveness of Vitamin D found in the body. These factors include dietary intake, sun exposure, Vitamin D receptor number (VDR), conversion rate from cholecalciferol to 25OH-VitD3 and finally the conversion of 25OH-VitD3 to 1,25OH2-VitD3. Most of the population in northern latitudes (most of the United States) do not produce Vitamin D in the winter regardless of sun exposure because the sun’s ultraviolet B rays do not reach the earth during that time and therefore the only source of Vitamin D is dietary (42). As the 25 hydroxylation occurs in the liver and the 1 hydroxylation occurs primarily in the kidney, these two organs play a large role in determining the circulating levels of Vitamin D, and the functioning of these organs and thus Vitamin D status tends to decrease with age (42). In a recent review, Holick details research showing that circulating levels of 25OH-VitD3 must reach as high as 30-40 ng/mL before parathyroid hormone (PTH) levels begin to plateau (43). Other researchers have found that increasing 25OH-VitD3 from 20 to 32 ng/mL increased intestinal calcium transport (44). Both of these criteria would point to a 25OH-VitD3 level of 30 ng/mL or greater being required for optimal regulation of calcium metabolism in the body. A recent review by Heaney describes the optimal level of 25OH-VitD3 to be 32ng/mL or greater for optimal health which takes into account a number of aspects other than bone health and calcium metabolism (45). By these standards, from 40 to 100% of independent elderly men and women are Vitamin D deficient (43). The 1-alpha, 25-Vitamin D hydroxylase in the kidney has been considered the primary source for synthesis of the circulating active metabolite of Vitamin D, 1,25OH2-VitD3. The activity of this enzyme is regulated on a whole body level by parathyroid hormone (PTH). Regulating 1,25OH2-VitD3 on a whole body level probably does not provide for optimal levels of the active vitamin for all body tissues at one time. Relatively recently tissue specific 1-alpha, 25-Vitamin D hydroxylases have been identified and are thought to mediate autocrine responses of Vitamin D at the tissue specific level (46, 47). Human vascular smooth muscle has 1-alpha, 25-Vitamin D hydroxylase activity with a Km of 25 ng/mL. This means that the enzyme is operating at one half maximal capacity at a 25OH-VitD3 concentration of 25 ng/mL (48). Therefore serum levels of >25 ng/mL may be necessary for optimal active Vitamin D for vascular smooth muscle cells. Muscle strength declines with age and a recently characterized deficiency symptom of Vitamin D is skeletal muscle weakness (43). Deficiency of Vitamin D and its hormonal effect on muscle mass and strength (sarcopenia) has been described as a risk factor in falls and bone fractures in the elderly (49). Loss of muscle strength has been correlated with a loss of Vitamin D receptors (VDR) in muscle cells (50). Supplemental Vitamin D of at least 800 IU per day may result in a clinically significant increase in VDR in muscle cells which may be in part be the mechanism whereby other studies have shown improvement in body-sway, muscle strength and falling risk were seen with Vitamin D supplementation at this level (51). While this muscular weakness associated with Vitamin D may not be surprising at classical Vitamin D deficiency levels (blood 25OH-VitD3 of <15 ng/mL), Bischoff-Ferrari et al continued to see improvement in lower extremity function up to and beyond 40 ng 25OH-VitD3/mL which are levels well above what previously might have been thought necessary for maximal benefit (52). This observation has been confirmed by other researchers that in fact minimal Vitamin D levels necessary to prevent rickets do not allow for maximal physical performance (53). A recent editorial in American Journal of Clinical Nutrition stated that all the literature available would indicate a 25OH-VitD3 level of at least 30 ng/mL is most optimal for health and disease (54). While the exact mechanism is still unclear, it is clear that both the active metabolite, 1,25OH2-VitD3 and its precursor, 25OH-VitD3, play a significant role in normal functioning of muscle. Muscle contains VDRs for 1,25OH ₂ -VitD ₃ , found in both the nucleus and at the cell membrane (55-57) and these are also involved in non-specific binding 25OH-VitD3 as well (58). Studies by Haddad and Birge, published in the 1970s, show that feeding D3 to vitamin D deficient rats 7 hours prior to measurement increased protein synthesis as measured by ³ H - leucine incorporation into muscle cell proteins. However, when the muscles were removed from the Vitamin D deficient rats and studied, only 25-OH Vit D ₃ acts directly in the muscles (58-60). Early clinical evidence pointed to a reversible myopathy associated with Vitamin D deficiency (61). Vitamin D receptors were discovered in muscle tissue, thus providing direct evidence of Vitamin D’s effect on muscle function (51, 62). Muscle biopsies in adults with Vitamin D deficiency exhibit mainly type II muscle fiber atrophy (63). Type II fibers are important because they are the first initiated to prevent a fall. A recent randomized controlled study found that daily supplementation of 1,000 IU of Vitamin D2 in elderly stroke survivors resulted in an increase in mean type II fiber diameter and in percentage of type II fibers (64). There was also a correlation between serum 25OH-VitD3 level and type II fiber diameter. Vitamin D conveys its action by binding to VDR. VDR is expressed in particular stages of differentiation from myoblast to myotubes (55, 65, 66). Two different VDRs have been described. One is located at the nucleus and acts as a nuclear receptor and the other is located at the cell membrane and acts as a cellular receptor. VDR knockout mice are characterized by a reduction in both body weight and size as well as impaired motor coordination (67). The nuclear VDR is a ligand-dependent nuclear transcription factor that belongs to the steroid-thyroid hormone receptor gene superfamily (68). Bischoff et al (69) reported the first in situ detection of VDR in human muscle tissue with significant associated intranuclear staining for VDR. Once 1,25OH ₂ -VitD ₃ binds to its nuclear receptor, it causes changes in mRNA transcription and subsequent protein synthesis (70). The genomic pathway has been known to influence muscle calcium uptake, phosphate transport across the cell membrane, phospholipid metabolism, and muscle cell proliferation and differentiation. 1,25OH-VitD ₃ regulates muscle calcium uptake by modulating the activity of calcium pumps in sacroplasmic reticulum and sacrolemma (61). Modifications of calcium levels impact muscle function (71). In vitro experiments support these findings by demonstrating an increased uptake of ⁴⁵ Ca in cells exposed to physiological levels of 1,25OH2-VitD3 (72). The calcium binding protein calbindin D-9K is synthesized as a result of activation of nuclear VDR (62). 1,25OH2-VitD3 plays a role in regulating phosphate metabolism in myoblasts by accelerating phosphate uptake and accumulation in cells. 1,25OH2-VitD3 acts rapidly, presumably through cell membrane VDRs (56, 57). While binding to these receptors, there is an activation of second-messenger pathways (G-proteins, cAMP, inositol triphosphate, arachidonic acid) (73-75) or the phosphorylation of intracellular proteins. These would in turn activate protein kinase C (PKC), leading to release of calcium into muscle cells, and ultimately resulting in active transport of Ca into the sacroplasmic reticulum by Ca-ATPase. This process is important for muscle contraction. Additionally, PKC affects enhancements of protein synthesis in muscle cells (76). Recent data (77) indicate that 1,25OH-VitD3 has a fast activation of mitogen-activated protein kinase (MAPK) signaling pathways, which in turn forward signals to their intracellular targets that effect the initiation of myogenesis, cell proliferation, differentiation, or apoptosis. Vitamin D may also regulate formation and regeneration of tight junctions and neuromuscular junctions. In vitro studies that found that Vitamin D regulates expression of VDR and the neural growth factor (NGF) in Schwann cells (78). Recent studies have shown that Vitamin D enhances glial cell line-derived neurotrophic factor (GDNF) in rats and that this may have beneficial effects in neurodegenerative disease (79). Therefore, Vitamin D could act through several mechanisms of cellular function and neural interaction to improve overall muscle strength and function. A need exists for a composition and methods to increase muscle mass and improve function and strength. The present invention comprises a composition and methods of using a combination of Vitamin D and HMB that results in such an increase in muscle mass and improvements in strength and function. The present invention comprises a composition and methods of using a combination of HMB and Vitamin D to control progressive loss of lean muscle mass, including loss of muscle mass due to aging. The composition of the present invention can be used in non-exercising individuals to achieve effects on muscle function and strength that are similar to those achieved with exercise. A significant portion of older adults are unable or unwilling to exercise regularly and the use of the composition of the present invention results in enhancements to muscle strength and function that are similar to the enhancements seen with exercise. Additionally, the effects on muscle strength and muscle function in non- exercising humans are not tied to inclusion of individual amino acids in the formulation. The composition may include less than 0.5 g per day of individual amino acids and still achieve the effects of improved muscle strength and muscle function. Summary of the Invention One object of the present invention is to provide a composition for increasing muscle mass, strength, or functionality in non-exercising mammals that achieves similar results to exercise only. Another object of the present invention is to provide a composition for increasing muscle mass, strength, or functionality for humans unable or unwilling to exercise that achieves effects on muscle similar to those achieved by exercise. A further object of the present invention is to provide a composition of HMB and Vitamin D that is used to increase muscle mass, improve strength and/or improve muscular function in the elderly. Another object of the present invention is to provide a composition of HMB to a vitamin D sufficient, non-exercising human to increase muscle mass, improve strength and/or improve muscular function to levels similar to those achieved by an exercising human. An additional object of the present invention is to provide a composition of HMB and Vitamin D to a non-exercising human to increase muscle mass, improve strength and/or improve muscular function to levels similar to those achieved by an exercising human. A further object of the present invention is to provide a composition of HMB and Vitamin D that has less than 0.5 grams of individual amino acids to increase muscle mass, improve strength, and/or improve muscular function in non-exercising humans. These and other objects of the present invention will become apparent to those skilled in the art upon reference to the following specification, drawings, and claims. The present invention intends to overcome the difficulties encountered heretofore. To that end, a composition comprising HMB and Vitamin D is provided. The composition is administered to a subject in need thereof to increase muscle mass, strength and functionality. All methods comprise administering to the animal HMB with or without Vitamin D. Brief Description of the Drawings Figure 1 is a CONSORT Flow Diagram. Figure 2 depicts changes in lean body mass. Figure 3 depicts a the effects of supplementation on a composite functional index to assess additive improvements across multiple muscle groups Figure 4 depicts the effect of HMB + Vitamin D Supplementation on change in Get Up performance test. Figure 5 depicts the effect of HMB + Vitamin D supplementation on change in total (sum right + left) handgrip strength. Figure 6 depicts changes in total (sum right and left legs) peak torque. Figure 7 depicts changes in lower composite extremity strength index. Figure 8 depicts the intent to treat analysis of effect of HMB + D supplementation on changes in composite function index. Figure 9 depicts intent to treat analysis of effect of HMB + D supplementation on changes in lower composite extremity strength index. Detailed Description of the Invention The present invention comprises a combination of HMB and Vitamin D that has a synergistic effect and improves overall muscle strength and function. The combination of HMB and Vitamin D results in significant enhancements in overall muscle mass, function and strength. This combination can be used on all age groups seeking enhancement in overall muscle mass, function and strength. The following methods describe and show increased overall muscle mass, function and strength even in non-exercising animals, and the effect on muscle mass, function and strength in non-exercising animals is similar to the effect of exercise on muscle mass, function and strength. The present invention comprises a combination of HMB and Vitamin D. Vitamin D is administered with HMB to optimize the efficacy of HMB, as it has been unexpectedly and surprisingly discovered that optimal effectiveness of HMB for increasing muscle mass, and improving muscle function and/or muscle strength occurs when a mammal has blood serum levels of Vitamin D of at least about 25 ng/ml, including 26 ng/ml, 27 ng/ml, 28 ng/ml, 29 ng/ml, 30 ng/ml, 31 ng/ml and higher. One specific use HMB and Vitamin D is in the older or elderly population. Current estimates place a large portion of the older population at risk for falls with potential significant associated morbidities. The combination of HMB and Vitamin D specifically targets muscle mass, strength and function and consequently may produce significant improvement in health, quality of life, and in particular, decreased falls and injury in this group. The strength and functionality tests and indices described herein, including but not limited to the hand grip test, the timed get up and go test and the get up test are correlated with improved quality of life, including the ability to carry out daily activities such as climbing stairs and carrying groceries. Improved muscle function and/or strength results in increased energy. The younger population also benefits from the administration of HMB and Vitamin D, in part due to the widespread occurrence of Vitamin D deficiency. Women also benefit from the administration of HMB and Vitamin D as women are prone to Vitamin D deficiency. Newborn babies and children twelve months and younger can benefit from the administration of HMB and Vitamin D. Baby formula is Vitamin D fortified, and the American Academy of Pediatrics (AAP) recommends that all infants, children and adolescents take in enough Vitamin D through supplements, formula or cow’s milk to prevent complications from deficiency of this vitamin. The present invention provides a composition comprising HMB and Vitamin D. The composition is administered to an animal in need of improvement in overall muscle mass, strength or function. As used herein, muscle function includes muscle performance, muscle strength, physical performance and physical functionality. The composition of HMB and Vitamin D is administered to an animal in any suitable manner. Acceptable forms include, but are not limited to, solids, such as tablets or capsules, and liquids, such as enteral or intravenous solutions. Also, the composition can be administered utilizing any pharmaceutically acceptable carrier. Pharmaceutically acceptable carriers are well known in the art and examples of such carriers include various starches and saline solutions. In the preferred embodiment, the composition is administered in an edible form. The composition of HMB and Vitamin D includes administration of the composition as baby formula and nutrition drinks for all ages. B-hydroxy-β-methylbutyric acid, or β-hydroxy-isovaleric acid, can be represented in its free acid form as (CH3)2(OH)CCH2COOH. The term “HMB” refers to the compound having the foregoing chemical formula, in both its free acid and salt forms, and derivatives thereof. While any form of HMB can be used within the context of the present invention, preferably HMB is selected from the group comprising a free acid, a salt, an ester, and a lactone. HMB esters include methyl and ethyl esters. HMB lactones include isovalaryl lactone. HMB salts include sodium salt, potassium salt, chromium salt, calcium salt, magnesium salt, alkali metal salts, and earth metal salts. Methods for producing HMB and its derivatives are well-known in the art. For example, HMB can be synthesized by oxidation of diacetone alcohol. One suitable procedure is described by Coffman et al., J. Am. Chem. Soc. 80: 2882-2887 (1958). As described therein, HMB is synthesized by an alkaline sodium hypochlorite oxidation of diacetone alcohol. The product is recovered in free acid form, which can be converted to a salt. For example, HMB can be prepared as its calcium salt by a procedure similar to that of Coffman et al. in which the free acid of HMB is neutralized with calcium hydroxide and recovered by crystallization from an aqueous ethanol solution. The calcium salt of HMB is commercially available from Metabolic Technologies, Ames, Iowa. CaHMB has historically been the preferred delivery form of HMB. Previously, numerous obstacles existed to both extensive testing and commercial utilization of the free acid form of HMB, and since it was thought there was no difference between the two forms from a pharmacokinetic perspective, the calcium salt was adopted as a commercial source of HMB. Until recently packaging and, in particular, distribution of dietary supplements has been better suited to handle nutrients in a powdered form and therefore the calcium salt of HMB was widely accepted. HMB-acid is a liquid and much more difficult to deliver or incorporate into products. Currently, the manufacturing process for HMB has allowed for HMB free acid to be produced in a purity that allows for oral ingestion of the HMB free acid. Besides having a commercial source that is pure enough for oral ingestion, the HMB- acid needs to be buffered for oral ingestion, a process which only recently was determined due to the factors listed above which precluded previous use of HMB-acid. It was assumed that ingestion of CaHMB would result in a rather quick dissociation of HMB from the calcium salt form. However, a recent study and corresponding patent application (U.S. App. Publication No. 20120053240) has shown that HMB in the free acid form has rather unique pharmacokinetic effects when compared to CaHMB ingestion. Use of HMB free acid (also called HMB-acid) improves HMB availability to tissues and thus provides a more rapid and efficient method to get HMB to the tissues than administration of CaHMB. Vitamin D is present in the composition in any form. In the preferred embodiment, Vitamin D ₃ (cholecalciferol) is administered, but the invention is not limited to that form of Vitamin D. While Vitamin D3 is the synthesized and preferred form of Vitamin D for mammals, mammals can also use supplemental Vitamin D2. Vitamin D2 may be less potent than Vitamin D ₃ , hence additional D ₂ may be required in order to raise blood levels of 25-OH VitD ₂ . When the composition is administered orally in an edible form, the composition is preferably in the form of a foodstuff or pharmaceutical medium, more preferably in the form of a foodstuff. Any suitable foodstuff comprising the composition can be utilized within the context of the present invention. In order to prepare the composition as a foodstuff, the composition will normally be blended with the appropriate foodstuff in such a way that the composition is substantially uniformly distributed in the foodstuff. Alternatively, the composition can be dissolved in a liquid, such as water. The composition can be incorporated into emulsions, such as a liquid or slurry containing protein, fats, vitamins, and/or minerals, etc. The composition can also be incorporated into a substantially clear liquid containing protein, fats, vitamins, and/or minerals, etc. The composition can be a powder, tablet, gelcap, capsule, etc. Although any suitable pharmaceutical medium comprising the composition can be utilized within the context of the present invention, preferably, the composition is blended with a suitable pharmaceutical carrier, such as dextrose or sucrose, and is subsequently tabulated or encapsulated as described above. Furthermore, the composition can be intravenously administered in any suitable manner. For administration via intravenous infusion, the composition is preferably in a water-soluble non-toxic form. Intravenous administration is particularly suitable for hospitalized patients that are undergoing intravenous (IV) therapy. For example, the composition can be dissolved in an IV solution (e.g., a saline or glucose solution) being administered to the patient. Also, the composition can be added to nutritional IV solutions, which may include amino acids and/or lipids. The amounts of the composition to be administered intravenously can be similar to levels used in oral administration. Intravenous infusion may be more controlled and accurate than oral administration. Methods of calculating the frequency by which the composition is administered are well- known in the art and any suitable frequency of administration can be used within the context of the present invention (e.g., one 6g dose per day or two 3g doses per day) and over any suitable time period (e.g., a single dose can be administered over a five minute time period or over a one hour time period, or, alternatively, multiple doses can be administered over an eight week time period). The combination of HMB and Vitamin D can be administered over an extended period of time, such as months or years. It will be understood by one of ordinary skill in the art that HMB and Vitamin D do not have to be administered in the same composition to perform the claimed methods. Stated another way, separate capsules, pills, mixtures, etc. of Vitamin D and of HMB may be administered to a subject to carry out the claimed methods. Any suitable dose of HMB can be used within the context of the present invention. Methods of calculating proper doses are well known in the art. The dosage amount of HMB can be expressed in terms of corresponding mole amount of Ca-HMB. The dosage range within which HMB may be administered orally or intravenously is within the range from 0.01 to 0.2 grams HMB (Ca-HMB) per kilogram of body weight per 24 hours. For adults, assuming body weights of from about 100 to 200lbs., the dosage amount orally or intravenously of HMB (Ca- HMB basis) can range from 0.5 to 30 grams per subject per 24 hours. The amount of Vitamin D in the composition can be selecting an amount of Vitamin D within the range of greater than 500IU, as the below examples indicate that 500IU is the lower threshold for an effective amount in individuals with inadequate levels of Vitamin D in the bloodstream, yet not too much Vitamin D as to be toxic. While the examples indicate a threshold of 500IU, lower amounts such as 400IU, may be appropriate, in some individuals, to raise blood Vitamin D levels to an appropriate amount. In another embodiment, the amount of Vitamin D in the composition can be selecting an amount of Vitamin D within the range of greater than 400IU, yet not too much Vitamin D as to be toxic. The toxic level of vitamin D is a person-specific amount and depends on a person’s blood level of vitamin D. For example, administration of 100,000IU of vitamin D may be toxic for healthy individuals, but not toxic for a person suffering from rickets. One of skill in the art will recognize toxicity levels for an individual. Further, the composition may include Vitamin D in amounts sufficient to raise blood levels of Vitamin D to at least around 25ng/ml. In the preferred embodiment, the composition comprises HMB in the form of its calcium salt, and Vitamin D in the form of 25-0H Vit D ₃ . Preferably, a composition in accordance with the present invention comprises HMB in an amount from about 0.5g to about 30g and Vitamin D in an amount greater than 500IU, but not in an amount high enough to be toxic. One range of Vitamin D in accordance with this invention is around 1000IU to around 4000IU. For examples, 1001IU, 1002IU, 1003IU. . . 1995IU, 1996IU, 1997IU, 1998IU, 1999IU, 2000IU, 2001IU, 2002IU, 2003IU, 2004IU, 2005IU. . .3997IU, 3998IU, 3999IU, and all numbers between around 1000IU and 4000IU and not otherwise stated. In another example, a range of Vitamin D in accordance with this invention is around 400IU to around 100,000IU. The specific amount of vitamin D that is appropriate to administer to a particular individual routinely varies. A healthy individual likely requires supplementation with vitamin D in an amount lower than an individual with certain disease conditions. For example, it would be appropriate in some circumstances to administer vitamin D to an individual with rickets in an amount of 100,000IU daily. One of skill in the art is able to readily determine the amount of vitamin D that should be given to a particular individual without causing toxicity. The amount of vitamin D used in the present invention depends on the individual’s vitamin D status. In some individuals, around 400-500IU of vitamin D is all that would be required to achieve a serum blood level of around 25 ng/ml. In others, 2,000, 4,000 or even 100,000IU of vitamin D may be required. For example, 400IU, 401U, 405IU, 450IU, 500IU, 550IU, 1000IU, 1001IU, 2000IU, 5000IU, 10,000IU, 20,000IU, 50,000IU, 75,000IU and 100,000IU and all numbers around and between 400IU and 100,000IU that have not been otherwise stated are included in this invention. The Food and Nutrition Board at the Institute of Medicine of The National Academies has developed intake reference values for Vitamin D and other nutrients. These values include the Recommended Dietary Allowance (“RDA”), which is defined as the average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%-98%) healthy people; and Adequate Intake (“AI”), which is established when evidence is insufficient to develop an RDA and is set at a level assumed to ensure nutritional adequacy. The RDA for Vitamin D is currently set at 600IU, or 15mcg, for males and females ages 1-70. For people over the age of 70, the RDA is set at 800IU of vitamin D (20mcg). For babies from 0-12 months, an AI has been established of 400IU (10mcg). Daily Values (DVs) are established by the Food and Drug Administration (FDA) and are used on food and dietary supplement labels. DVs suggest how much of a nutrient serving of the food or supplement provides in the context of a total daily diet. DVs are presented on food and supplement labels as a percentage. The Daily Value for Vitamin D, based on a caloric intake of 2,000 calories, for adults and children age 4 years or more, is 400IU. The Daily Value for Vitamin D is also 400IU for infants, children less than 4 years old, and pregnant and lactating women. These amounts are determined such that a large percentage of the population taking these amounts will have sufficient Vitamin D levels. Heaney et al. have determined that a dose of 400IU per day will elevate serum 25(OH)D ₃ levels by 7.0 nmol/L (or 2.8 ng/mL) (99). In one example of the present invention, the amount of vitamin D used can be expressed in terms of the Recommended Dietary Allowance (RDA), Adequate Intake (AI), and/or Daily Value (DV). For example, the present invention includes compositions of HMB and Vitamin D in an amount around at least as much as the Recommended Daily Allowance of RDA; compositions of HMB and Vitamin D in an amount around at least as much as the Daily Value; and compositions of HMB and Vitamin D in an amount around at least as much as the Adequate Intake. The amount of vitamin D needed to reach appropriate blood serum levels of vitamin D in accordance with the present invention may routinely vary from person to person, and determination of the optimum amount in each instance can be readily obtained by routine procedures. In an additional embodiment, the composition in accordance with the present invention comprises HMB in an amount from about 0.5g to about 30g and Vitamin D in an amount sufficient to increase circulating blood levels of 25OH-VitD3 or 25-OH VitD2, depending on the form supplemented, to at least about 25ng/ml. In general, an amount of HMB and vitamin D in the levels sufficient to improve overall muscle strength, function, and overall mass is administered for an effective period of time. The invention provides a method of administering a composition of HMB and Vitamin D to an animal such that the animal’s muscle mass increases. The animal may or may not engage in exercise. Exercising in conjunction with the administration of HMB and Vitamin D results in an even greater improvement in strength and muscle function, but exercise is not necessary to improve strength and muscle function. The amount of HMB and Vitamin D in the composition administered that are effective for increasing the animal’s muscle mass can be determined in accordance with methods well-known in the art. In one embodiment, the effective amount of HMB in the composition may be from about 0.5g to about 30g and the effective amount of Vitamin D in the composition may be from greater than about 500IU per 24 hour period. In another embodiment, the effective amount of HMB is the same, and the effective amount of Vitamin D is that which is sufficient to increase blood levels of Vitamin D to at least about 25ng/ml. The invention provides a method of administering a composition of HMB and Vitamin D to an animal such that the animal’s strength increases. The animal may or may not engage in exercise. The amount of HMB and Vitamin D in the composition administered that are effective for increasing the animal’s muscle mass can be determined in accordance with methods well- known in the art. In one embodiment, the effective amount of HMB in the composition may be from about 0.5g to about 30g and the effective amount of Vitamin D in the composition may be from greater than about 500IU per 24 hour period. In another embodiment, the effective amount of HMB is the same, and the effective amount of Vitamin D is that which is sufficient to increase blood levels of Vitamin D to at least about 25ng/ml. The invention further comprises a method of administering a composition of HMB and Vitamin D in an effective amount for improving muscle function. The amount of HMB and Vitamin D in the composition administered that are effective for increasing the animal’s muscle mass can be determined in accordance with methods well-known in the art. In one embodiment, the effective amount of HMB in the composition may be from about 0.5g to about 30g and the effective amount of Vitamin D in the composition may be from greater than about 500IU. In another embodiment, the effective amount of HMB is the same, and the effective amount of Vitamin D is that which is sufficient to increase blood levels of Vitamin D to at least about 25ng/ml, 26 ng/ml, 27 ng/ml, 28 ng/ml, 29 ng/ml, 30 ng/ml, 31 ng/ml and/or higher. Experimental Examples The following examples further illustrate the invention but should not be construed as in any way limiting its scope. For example, the amounts of HMB and Vitamin D administered and the duration of the supplementation are not limited to what is described in the examples. The amount of Vitamin D used in certain experimental examples was 2000 IU per day. This amount of Vitamin D was used to quickly raise blood serum levels of Vitamin D to at least around 25 ng/mL, but the invention is not limited to this amount. Any amount of Vitamin D sufficient to raise blood serum levels to at least around 25 ng/mL, including at least around 30 ng/L, is within the scope of the invention. Amounts of Vitamin D included in this invention include 500 IU per day, 2000 IU per day, 4000 IU per day, and any amount of Vitamin D per day between 500 IU per day and 4000 IU per day. Methods This 12-month clinical trial employed a randomized, double-blind, placebo-controlled 2 × 2 factorial design. The experiment was double-blind with respect to calcium HMB plus Vitamin D3 (HMB+D) and control supplementation. Participants were stratified by sex and assigned to one of four treatment arms using computer-generated random numbers. The treatment arms consisted of: (a) Control + no exercise; (b) HMB+D + no exercise; (c) Control + exercise, and (d) HMB+D + exercise. The clinical trial consisted of multiple measurements over the 12 months. Assessments (except for dual energy x-ray absorptiometry, DXA) were performed at baseline and again at 3, 6, 9, and 12 months. Participants: Men and women ≥ 60 years of age with insufficient, but not clinically deficient 25- hydroxy-vitamin D (25OH-D) levels (baseline concentration between 15 and 30 ng/mL) were recruited for this study. Volunteers were solicited from a willing recruitment list, electronic mailings, USPS mailings, and flyers for the study. Participants had a starting BMI of < 40 kg/m ² , were free of liver and kidney diseases or other serious medical illnesses, had no evidence of uncontrolled hypertension; did not have osteoporosis or a bone density T-score < -2.0 or chronic diseases affecting calcium or bone metabolism; had no history of blood clots and/or the use of blood thinning medications; were able and willing to participate in 3-day-a-week monitored strength-training program; had no major surgery in the previous six weeks, and did not have any restrictions placed on physical exercise by their primary care physician. If at follow-up, a participant had a 25OH-D < 12 ng/ml or T-Score < -2.5, the participant was referred to a physician and was dropped from the study. Nutritional supplements: Supplements consisted of either a placebo (calcium lactate) in the no supplement (control) group or the combination of calcium HMB (3.0 g/day) plus Vitamin D3 (2,000 IU/day) in the supplemented (HMB+D) group. This HMB dosing strategy (3 g/d, split into 2 doses) has been utilized in the majority of previous studies examining the effects of HMB on body composition and physical and function performance in older adults (19, 20). Vitamin D doses ranging from 800-2000 IU per day have been recommended to achieve a minimum serum 25OH-D of 30 ng/ml at 3 months (29). The Vitamin D3 dosing strategy (2,000 IU/day, split into 2 doses) was utilized in this study to rapidly increase circulating levels of 25OH-D ₃ to be within the sufficient range (30-100 ng/ml) where HMB has been previously shown to be efficacious for muscle strength improvements (26). Both nutritional supplements were provided in capsules of equal size, color, and taste and were produced in a cGMP facility and obtained through TSI Innovative Products Division (Missoula, MT). The purity of calcium HMB used in the capsules was determined by the manufacturer using high-pressure liquid chromatography (HPLC) to be greater than 98%. The calcium HMB and Vitamin D3 concentrations of the capsules were verified throughout the study (Heartland Assays, Ames, IA). Capsules were consumed twice daily with the morning and evening meals. Both supplements contained equal amounts of calcium (102 mg), phosphorus (26 mg), and potassium (49 mg). Prior to enrollment in the study, participants were instructed to discontinue any supplements containing HMB or vitamin D, but a multivitamin was allowed; this was maintained throughout the study period. Exercise: Participants assigned to the moderate resistance exercise training program performed approximately 60 minutes of supervised strength training three times per week (30) in two dedicated exercise studios located in Ames, IA and Des Moines, IA. Participants were permitted to exercise outside of the studios with bands when traveling or confined to home. The strength program consisted of bicep curls, triceps extensions, chair squats, calf raises, ankle dorsiflexion, shoulder front raises and lateral raises, latissimus dorsi pull-down, chest press, seated row, knee flexion and extension, and hip flexion. Participants completed 3 sets of each exercise, including 2 sets up to 15 repetitions and a final set of up to 20 repetitions. Initially, Thera-Band ^® (Duluth, GA) stretch cords were used for exercise resistance. Once a participant was able to complete 20 repetitions with good form, the resistance was increased by moving to the next color of resistance band. Hops or small jumps were performed between exercises (5 hops after each set, increasing by 5 hops per week until 25 hops were achieved). Resistance band exercise has been shown to safely increase strength and functionality when used in an older adult population (31, 32). However, once participants increased their muscle strength beyond use of Thera-Bands, they were transitioned to strength training on machines to perform the same exercises. The exercise machines utilized were commercially available cable-pulley and plate loaded equipment pieces. While the repetition range and number of exercises were similar to the Thera- Band ^® phase, transition to use of machine equipment allowed participants to achieve larger resistance loads. The participants’ rest time between sets and weekly exercise session number were kept similar to the protocol for the Thera-Band phase. Progression of load for machine exercises followed the guidelines set by the American College of Sports medicine, whereby load was increased by 2-10% when the participant felt they could achieve 1-2 more repetitions over the 20 ^th repetition on the third set (33). Increasing load for the exercise machines was an addition of weighted plates to a load stack being moved by the participants (33). The same exercise session supervisors were also utilized to minimize variability with resistance prescription and progression. The modifications between equipment phases were augmentation from chair squats to a machine sled leg press, standing unilateral knee flexion with Thera-Bands to a seated bilateral knee flexion movement, and overhead unilateral triceps extensions to a bilateral triceps extension using a pulldown movement. The non-exercise groups were instructed not to perform resistance exercise during the study period. Measurements Body weight and composition: Body weight was measured without shoes following an overnight fast. DXA (Hologic Discovery v.12.3) was used to assess regional body composition (lean and fat mass) and bone density data at 0, 6, and 12 months only. Bioelectrical impedance analysis (BIA; BIA-101S, RJL Systems, Clinton Township, MI) and air displacement plethysmography (ADP; BOD POD ^® , LMI, Concord CA) (34) were used to measure body composition at all timepoints. BIA data were analyzed using the Fluid & Nutrition Analysis Software, version 3.1b (RJL Systems) (35) and ADP calculations were performed using the Siri equation (36). Previous publications have shown a high correlation between ADP, BIA, and DXA measurements (37). Muscle Strength: Muscle strength was assessed via isokinetic dynamometry. Bilateral knee and elbow extension/flexion peak torque were measured at multiple speeds (knee: 60, 90, and 180°/sec; elbow: 60 and 120°/sec) using the BIODEX Isokinetic Dynamometer (System 3 Quickset, Shirley, NY). Peak torque generation for each movement and speed were also analyzed independently. Additionally, a total lower composite extremity strength index was calculated to examine the effect of the intervention on overall lower extremity muscle function. Lower Extremity Strength Index = (left leg extension peak torque at 60°/sec + 90°/sec + 180°/sec) + (right leg extension peak torque at 60°/sec + 90°/sec + 180°/sec) + (left leg flexion peak torque at 60°/sec + 90°/sec + 180°/sec) + (right leg flexion peak torque at 60°/sec + 90°/sec + 180°/sec). Physical Function: The “Timed Up-and-Go” and “Get-up” tests were used to assess physical function. The “Up-and-Go” test requires the subject to, starting from a seated position, stand, walk forward 3 meters, turn around, walk back to the chair, and sit down as quickly as possible without running (38); three “Up-and-Go” trials were performed, and the average time was recorded. The “Get-up” test (30 second sit to stand) requires the subject to stand up from a seated position as many times as possible within 30 seconds (38). Handgrip strength was measured using a handgrip dynamometer (Lafayette Instrument Co., Lafayette, IN); three trials were completed per side, the average for each side was recorded, and the sum of left and right handgrip was used for analysis. A composite functional index was developed to assess additive improvement across multiple muscle groups and has transitional properties that captures changing improvement in functional status. The index of changes (Composite Functional Index) was calculated as the sum of fractional changes in all functionality measures [left handgrip + right handgrip + Get Up + (- Get Up and Go)]. Dietary Assessment: Food recalls (3 days) were used to estimate vitamin D and nutrient intake at all timepoints. Records were analyzed using the Food Processor (ESHA Research, Salem OR). Blood Sampling: Blood and urine samples collected after an overnight fast were analyzed by LabCorp (Urbandale, IA) for basic chemistry profile, complete blood count with differential, and urinalysis at screening and at all timepoints. In addition, blood levels of bone alkaline phosphatase, 25OH-VitD, and parathyroid hormone (PTH) were analyzed by Heartland Assays (Ames, IA) using the Liaison XL automated chemiluminescence analyzer. Questionnaires: A health form questionnaire, quality of life questionnaire (SF-36 Health Survey) (39), and Circumplex effect questionnaire (40) were completed by participants at each visit. Each participant also maintained a falls calendar. Compliance: Compliance to the supplement protocol was monitored using participant logs, capsule counts, and by measuring serum 25OH-VitD concentrations. Statistics: The primary outcome of this study was the improvement in muscle function and strength in an older adult population over 12 months. We hypothesized that combined supplementation with calcium HMB and Vitamin D ₃ would also lead to decreased falls and to improved quality of life for older adults. We further hypothesized that the addition of a modest exercise regimen to these supplements would enhance the synergistic effects of calcium HMB and Vitamin D ₃ . A priori power analysis (G-Power, v3.0, Universität Kiel, Germany) was completed based on knee strength data and Vitamin D status from a retrospective data analysis from the study by Baier et al. (17). For the power analysis calculation, a 33.9 Nm increase in total leg strength was anticipated for the treatment group during the 12-month study, whereas a 10.0 Nm change in total leg strength was expected to occur in the control group. The power analysis was based on an F-test (ANOVA: Repeated measure with 5 time observations and 4 treatment groups) with an α error probability of 0.05, and power of 0.8, it was estimated that 20 participants per treatment with adequate vitamin D status would be needed to detect significant changes in muscle strength. To assure adequate numbers of subjects finished the entire protocol, we assumed a drop rate of 33% and planned to enroll 40 subjects per treatment. Body composition, function, and strength data were analyzed using a SAS Proc Mixed model ANOVA (Version 9.4, SAS Institute Inc., Cary, NC) on the change at 3, 6, 9, and/or 12 months. The model included sex, treatment, exercise, and treatment by exercise interaction and included the starting value as the covariate. Only those subjects completing 12 months of study were included in the per-protocol analysis. Participants who completed at least 6 months of the study (n=129) were included in a modified intent-to-treat analysis. Post-hoc t-tests were performed where significant treatment by exercise interactions were observed. As the primary aim of this study was to evaluate the effect of HMB+D on muscle function and strength, pre-planned contrasts were used to evaluate the effect of HMB+D vs. control supplementation on LBM, strength, and functional tests within exercising and non-exercising groups. Clinical laboratory data was analyzed using a SAS Proc Mixed repeated measure ANOVA. The model included starting value, sex, treatment, exercise, time, treatment by exercise interaction, treatment by time interaction, exercise by time interaction, and treatment by exercise by time interaction. Adverse event questionnaires were analyzed as categorical data; the main effect of treatment was determined using the Cochran-Mantel-Haenszel test. Statistical significance was defined as p<0.05 for all tests. Effect sizes were calculated from adjusted means and SE using Cohen’s d.

Results A total of 591 older adults were screened for this study. Of these, 238 participants were enrolled. A total of 117 participants completed the study and were included in the per-protocol analysis (Figure 1). Baseline participant characteristics and functional data are shown in Table 1. There were no differences in capsule supplementation and exercise compliance between groups. The average group capsule compliance based on capsule count was 96.0 ± 0.4% and the average exercise compliance between the two exercise groups was 83.3 ± 0.3% based on attended exercise sessions and reported home exercise sessions. Table 1 includes the baseline participant characteristics: aData are expressed as number (sex) or mean ± standard error of the mean. BMI, body mass index. bMeasured using dual x-ray absorptiometry. HMB+D supplementation alone had a significant benefit on lean body mass within the non-exercise group at 6 months (Figure 2) (0.44 ± 0.27 in HMB+D vs. -0.33 ± 0.28 in control, p<0.05, d=0.55), which was attributed to improvements in trunk lean mass (Trt main effect, p < 0.05) Functional Outcomes A composite functional index was developed to assess additive improvements across multiple muscle groups [left handgrip + right handgrip + Get Up + (- Get Up and Go)]. The effect of HMB+D supplementation on the functional index was most prominent in the non- exercise group. HMB+D supplementation alone resulted in a larger increase in composite functional index than was observed in the control group at 3 months (p=0.03, d=0.58); even greater increases were observed at 6 months (p=0.04, d=0.70) and 12 months (p=0.04, d=0.67), as shown in Figure 3. Supplementation with HMB+D did not further improve the functional index within the exercising group (Figure 3). Examination of each component of the functional index (Get Up, Get Up and Go, hand grip strength) in the exercising groups revealed similar patterns across the three components. The non-exercising non-supplemented control group generally showed little to no improvement. However, improvements were observed amongst the supplemented HMB+D alone group and the exercise group, with or without HMB+D. Figure 4 shows the effect of HMB+D supplementation on change in Get Up test performance in non-exercising (A) and exercising (B) older adults. There was a tendency for a main effect of a HMB+D supplementation at 3 months (p=0.065) and a tendency for a supplementation*exercise interaction at 12 months (p=0.07). HMB+D supplementation alone tended to improve performance at 6 months (p=0.071, d=0.49) and significantly improved performance at 12 months (increase of 4.5 ± 0.9 reps in HMB+D vs. 1.7 ± 0.9 reps in control, p=0.03, d=0.61) in non-exercisers (A). Exercise resulted in a numerically similar improvement in Get Up test performance, but HMB+D supplementation did not further improve performance within the exercising group (B). *significant difference between HMB+D and control within group (no exercise or exercise); pre-planned contrast, p<0.05. Data are expressed and Mean ± SE. Figure 8 shows the intent-to-treat analysis of effect of HMB+D supplementation on changes in composite functional index (sum of fractional improvement in Get Up, Get Up and Go, and right and left handgrip strength). There was a significant treatment main effect (p=0.02) of HMB+D supplementation at 6 months. *significant difference between HMB+D and control within group (no exercise or exercise); pre-planned contrast, p<0.05. Data are expressed and Mean ± SE. Figure 9 shows the intent-to-treat analysis of effect of HMB+D supplementation on changes in lower composite extremity strength index [(left leg extension peak torque at 60°/sec + 90°/sec + 180°/sec) + (right leg extension peak torque at 60°/sec + 90°/sec + 180°/sec) + (left leg flexion peak torque at 60°/sec + 90°/sec + 180°/sec) + (right leg flexion peak torque at 60°/sec + 90°/sec + 180°/sec)]. Strength Outcomes In non-exercisers, improvement in knee extension peak torque (60°/sec) was significantly greater in HMB+D supplemented participants than in non-supplemented group at 3 months (10.9 ± 5.7 Nm vs. -5.2 ± 5.9 Nm, respectively, p=0.04). Though the differences between groups at subsequent timepoints were not statistically significant, the control-supplemented participants continued to lose leg extension strength (-10.1 ± 7.4 Nm at 12 months) whereas strength was maintained at baseline levels in the HMB+D-supplemented subjects. There was no additional benefit of combining exercise and HMB+D supplementation on knee extension peak torque. HMB+D supplementation did not significantly affect knee flexion peak torque. However, it is worth noting that among non-exercisers, peak torque decreased from baseline to 12 months in the non-supplemented participants (-3.71 ± 3.91 Nm). Exercise, either alone or in combination with HMB+D, showed similar improvements in knee flexion peak torque (main effect of exercise, p<0.05). Figure 5 shows the effect of HMB+D supplementation on change in total (sum right+left) handgrip strength in non-exercising (A) and exercising (B) older adults. There were no significant main or interaction effects for treatment on handgrip strength, but there was a main effect of exercise at 12 months (p=0.03). Though there were no significant differences between treatment groups, only the non-exercise control group experienced negative average changes in handgrip strength during the study period (3, 6, and 9 months). Data are expressed and Mean ± SE. Figure 6 shows changes in total (sum right and left legs) peak torque at 90°/sec. Panels A (no exercise) and B (with exercise) represent knee extension, and panels C (with no exercise) and D (with exercise) represent knee flexion. There were main effects of exercise (p<0.05) on leg flexion peak torque at 3, 6, 9, and 12 months. Data are expressed and Mean ± SE. HMB+D supplementation tended to improve lower extremity strength index values among non-exercisers at 3 months (p=0.10, d=0.45). This tendency persisted at 9 and 12 months (p=0.10 and 0.07, respectively). Among non-exercisers, HMB+D supplemented participants maintained a similar improvement to that observed at 3 months (0.82 ± 0.29) throughout the year-long study while control participants remained near baseline values (0.04 ± 0.30, d=0.51) (Figure 7). These examples demonstrate the surprising result that the combination of vitamin D and HMB improves strength and muscle function and increases muscle mass. These improvements and gains are seen in humans who don’t engage in exercise and the improvements seen are similar to those achieved by exercise. It was previously known that HMB supplementation increases muscle mass, but no corresponding improvement in strength and muscle function was seen with HMB alone. The examples demonstrate that when serum levels of Vitamin D reach appropriate levels, most typically through supplementation, muscle strength and function improve. The increases in strength, muscle mass, and improved muscle function described and observed in the examples below demonstrate that HMB and Vitamin D are synergistic; when vitamin D levels reach an adequate amount, administration of HMB works better, more effectively or more efficiently than HMB when administered without adequate vitamin D levels. A composition containing HMB and Vitamin D in sufficient amounts will be more efficient and more effective than a composition containing HMB that does not also include adequate amounts of Vitamin D. The studies below examine the effects of vitamin D levels on the efficacy of HMB as related to muscle function, strength and muscle mass, but the improved efficacy of HMB as described in this invention includes all known uses of HMB, including but not limited to the use of HMB for disease associated wasting, aging, cachexia, and nitrogen retention. Further, the efficacy of HMB as related to immune function and lowering cholesterol are also within the scope of this agreement. The amount of Vitamin D administered with HMB must be in an effective amount to raise the blood level of Vitamin D. In this example, it is demonstrated that 500IU of Vitamin D does not sufficiently raise the blood level of Vitamin D; this finding however, is based on the subjects in this study. As stated hereinabove, the amount of Vitamin D necessary to raise blood serum levels of Vitamin D to an adequate amount depends on the individual’s Vitamin D status; in some instances, as little as 400IU of Vitamin D is an appropriate amount to raise blood levels to around at least 25 ng/ml. Combined supplementation with HMB and Vitamin D for 12 months was safe and increased circulating levels of 25OH-D to within the sufficient range (25-100 ng/ml) previously shown to support a beneficial effect of HMB on lower body strength. A main finding of this study was that co-supplementation with HMB and Vitamin D to healthy older adults improved the composite functional strength index. These findings underscore the potent effects of supplementation with HMB on improving functionality in healthy older adults with Vitamin D sufficiency, even in the absence of exercise. Further, these findings demonstrate that the effectiveness of HMB is independent of the additional amino acids often included in the nutritional supplement formulas previously shown to be efficacious in older adults. Skeletal muscle loss and decreased functionality are hallmarks of aging, and if left unattended can result in sarcopenia and loss of essential daily functions necessary for mobility and quality of life. It is well established that sarcopenia is a universal prelude for worsening of multiple chronic diseases and for the development of frailty. Assessment of functionality in this aging population can be quite complex and is one of the greatest challenges to healthcare professionals. The loss of functional status that leads to physical frailty is associated with adverse health outcomes, long-term institutionalization, and mortality. The present study utilized a functional composite index to represent the primary end point of estimating changes in strength and physical function over the one-year period. This index incorporated several tests (Get Up test, the Get Up & Go test, and the handgrip strength test) frequently used to evaluate deficits in common daily function related to muscle strength and/or muscle function. Among the individual functional tests, the largest relative improvement was observed for the Get Up test, which evaluates a common critical function (getting up from a chair); its performance requires muscle strength, power, and balance. There is extensive evidence that exercise training, including both aerobic and resistance exercise, results in improved skeletal muscle strength and mass and balance in older adults; unfortunately, a significant portion of older adults are either unable or unwilling to exercise regularly. In contrast, the evidence for nutritional interventions is at best modest, even when combined with exercise, in the presence or absence of sarcopenia. The data supporting the present invention demonstrates that supplementation with both HMB and Vitamin D is crucial for the enhancement of muscle function in non-exercising older adults. Supplementation with HMB+D resulted in significant improvements in the emotion of “High Activation” on the Circumplex questionnaire. The findings in the current study are related to the improvements in the functional composite index, representing an enhanced state of functional reserve. Such an increase in functional reserve would lessen the relative effort of daily activities (e.g. climbing stairs, carrying groceries), resulting in feeling more energetic. These effects represent another potential cross talk between the improvements in muscle function and the brain, as those seen with exercise, with a consequent beneficial effect by reducing depression- like symptoms. This positive effect has been ascribed to the enhancement in muscular expression of the enzyme kynurenine aminotransferase (KAT), which converts neurotoxic KYN into neuroprotective kynurenic acid (KYNA). The positive long-term effects on functional composite index observed in the supplemented, but non-exercising older adults, are primarily attributed to the benefits of HMB that are fully realized in Vitamin D sufficiency. This study demonstrates the benefits of co-supplementation with HMB and Vitamin D to enhance physical functionality and muscle strength in adults, even in individuals not engaged in an exercise training program. The combined supplementation with HMB and Vitamin D provides a unique protective effect for the substantial population of older adults who are unable or unwilling to exercise. Supplementation with HMB and vitamin D improves physical performance, including muscle function, even in the absence of exercise. The benefits of HMB+D are valuable in sarcopenic/pre-sarcopenic individuals given their lower baseline functional status. This combination can provide protection against developing sarcopenia in those at risk, including those who are vitamin D deficient. Older people with vitamin D deficiency are extremely exposed to develop sarcopenia, thus providing a further indication for supplementation with HMB and vitamin D. This study also demonstrates that administration of HMB to vitamin D sufficient person results in to improvements in muscle mass, strength, or functionality in non-exercising humans to an extent similar to the improvements seen in exercising individuals. The foregoing examples demonstrate the use of HMB and Vitamin D to increase muscle mass and/or improve strength and/or improve physical (muscle) function. Vitamin D is supplemented with HMB to optimize and/or maximize the effects of HMB. Vitamin D is supplemented to raise blood serum vitamin D levels to at least 25-30 ng/ml and sustain blood serum levels in a sufficient amount. The foregoing description and drawings comprise illustrative embodiments of the present inventions. The foregoing embodiments and the methods described herein may vary based on the ability, experience, and preference of those skilled in the art. 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