Here’s a list of studies about vitamin D and muscular strength:

High Prevalence of Hypovitaminosis D in Patients Presenting with Proximal Muscle Weakness: A Sub-Himalayan Study (2017)

Conclusion: This study of 99 adult medical patients complaining of muscle weakness (difficulty standing and walking up stairs) found that literally 98.98% had inadequate vitamin D levels, with 90% being clinically deficient and 31% being severely deficient. Only one individual out of the 99 had a normal level. Those with lower vitamin D levels suffered from more severe muscle weakness compared to those with higher levels. The patients were put on a 6-month regimen of high-dose vitamin D therapy, 83 of them reported back for a two and six-month follow up, and of those 83 patients, 85% enjoyed improvement in their physical performance.


Vitamin D Concentration in 342 Professional Football Players and Association with Lower Limb Isokinetic Function (2014)

Conclusion: A study of 342 Qatar soccer players found that those with higher vitamin D levels also had higher lean body mass compared to players with lower vitamin D levels.


Occurrence in Elite Ballet Dancers: A Controlled Study (2014)

Conclusion: A four-month study of 24 ballet dancers found that those supplementing with 2000 IU of vitamin D daily were isometrically stronger, could jump higher, and suffered fewer injuries compared to the control group.


Vitamin D Sufficiency Associates with an Increase in Anti-Inflammatory Cytokines After Intense Exercise in Humans (2014)

Conclusion: A study of young adult males found that those with higher vitamin D levels experienced less muscular inflammation post-exercise compared to those with lower vitamin D levels.


Higher Serum 25-Hydroxyvitamin D Concentrations Associate with a Faster Recovery of Skeletal Muscle Strength After Muscular Injury (2013)

Conclusion: A study of 14 physically active adults found that those with higher vitamin D levels experienced less muscular weakness following intense physical exercise, both immediately and days after the exercise.


Vitamin D Status and Muscle Function in Post-Menarchal Adolescent Girls (2009)

Conclusion: Adolescent girls with higher vitamin D levels are able to jump faster and higher compared to girls with lower vitamin D levels.


Low Vitamin D Status Has an Adverse Influence on Bone Mass, Bone Turnover, and Muscle Strength in Chinese Adolescent Girls (2009)

Conclusion: In a study of 301 young Chinese girls, those with the higher vitamin D levels demonstrated superior handgrip strength and had higher bone mass.


A Higher Dose of Vitamin D Reduces the Risk of Falls in Nursing Home Residents: A Randomized, Multiple-Dose Study (2007)

Conclusion: In a 5-month study of 124 nursing home residents, those given 800 IU of vitamin D daily suffered 72% fewer falls compared to the placebo group.


Association Between Vitamin D Status and Physical Performance: The InCHIANTI Study (2007)

Conclusion: A study of 976 elderly people found that those with higher vitamin D levels had higher handgrip strength.


Effect of Vitamin D Replacement on Musculoskeletal Parameters in School Children: A Randomized Controlled Trial (2006)

Conclusion: For a one-year period 179 girls ages 10-17 were given either a weekly placebo, a low dose of vitamin D, or a higher dose of vitamin D. After one year the girls given the higher dose of vitamin D showed the biggest increase in lean muscle mass and bone density, especially among the younger girls.


Effect of Cholecalciferol Plus Calcium on Falling in Ambulatory Older Men and Women: A 3-Year Randomized Controlled Trial (2006)

Conclusion: In a 3-year-long randomized, double-blind, placebo-controlled experiment of elderly men and women, 700 IU of vitamin D and 500mg of calcium supplemented daily proved to be effective for reducing the risk of falling in the women by 46%.


Low-Dose Vitamin D Prevents Muscular Atrophy and Reduces Falls and Hip Fractures in Women After Stroke: A Randomized Controlled Trial (2005)

Conclusion: A two-year study of 96 elderly, female stroke victims found that those supplementing with 1000 IU of vitamin D2 daily suffered fewer falls and hip fractures, demonstrated improved muscular strength, and enjoyed an increase in the number and size of type 2 muscle fibers compared to the placebo group.


Vitamin D Supplementation Improves Neuromuscular Function in Older People who Fall (2004)

Conclusion: In this randomized, placebo-controlled experiment, 139 elderly patients with a history of falls were given either a 600,000 IU megadose of vitamin D2 or a placebo. At baseline and 6 months later they were evaluated for postural sway, reaction time, physical performance, and leg strength. At 6 months, the supplemented group had higher vitamin D levels and demonstrated superior reaction time and functional performance compared to the placebo group – who actually exhibited deteriorating physical performance. It’s important to note that almost all studies comparing vitamin D2 and D3 have found D2 to be only about 25% as potent as D3 and a dose of 600,000 IU per 6 months averages out to only about 3,500 IU per day, which is unlikely enough for elderly people to get their levels into an optimal range. “Vitamin D supplementation, in fallers with vitamin D insufficiency, has a significant beneficial effect on functional performance, reaction time and balance, but not muscle strength. This suggests that vitamin D supplementation improves neuromuscular or neuroprotective function, which may in part explain the mechanism whereby vitamin D reduces falls and fractures.”


Higher 25-Hydroxyvitamin D Concentrations are Associated with Better Lower-Extremity Function in Both Active and Inactive Persons Aged > or =60 y. (2004)

Conclusion: In an experiment involving people over the age of 60, those with higher vitamin D levels demonstrated a superior ability to walk and ability to transition from a sitting to standing position.


Effect of Vitamin D on Falls: A Meta-Analysis (2004)

Conclusion: Vitamin D supplementation significantly reduces the risk of falling in older people.


Low Vitamin D and High Parathyroid Hormone Levels as Determinants of Loss of Muscle Strength and Muscle Mass (Sarcopenia): The Longitudinal Aging Study Amsterdam (2003)

Conclusion: In a three-year study of 1,008 elderly people, those with lower vitamin D levels demonstrated weaker grip strength and lower muscle mass compared to those with higher vitamin D levels.


Relation Between Vitamin D, Physical Performance, and Disability in Elderly Persons (2002)

Conclusion: Vitamin D levels, arm strength, and leg strength were tested in 269 elderly people over a 6-month period. Women with low vitamin D levels were found to have significantly weaker arm and leg strength.


Vitamin D and Muscle Function (2002)

Note: Extremely detailed scholarly article explaining the role of vitamin D in muscle functioning.


Neuromuscular and Psychomotor Function in Elderly Subjects who Fall and the Relationship with Vitamin D Status (2002)

Conclusion: Vitamin D-deficient elderly people were found to have “slower functional performance, weaker quadriceps, slower reaction times, and worse stability” compared to those with higher levels.


Vitamin D Status, Trunk Muscle Strength, Body Sway, Falls, and Fractures Among 237 Postmenopausal Women with Osteoporosis (2001)

Conclusion: Among osteoporotic postmenopausal women, those with lower vitamin D levels have an increased risk of falling and suffering fall-related fractures.


Effects of a Short-Term Vitamin D and Calcium Supplementation on Body Sway and Secondary Hyperparathyroidism in Elderly Women (2000)

Conclusion: A 1-year study of 148 elderly women found that those given a daily dose of 800 IU of vitamin D enjoyed 9% less body sway and fewer falls than the non-vitamin D group. Researchers concluded that vitamin D and calcium supplementation may prevent falls and fall-related fractures.


Severe Myopathy Associated with Vitamin D Deficiency in Western New York. (2000)

Conclusion: This documents five case studies where patients with severe myopathy (reduced muscle function) bad enough to need wheelchairs were found to have low vitamin D levels. After undergoing 4-6 weeks of high-dose vitamin D therapy, four of the five patients achieved full mobility and muscle strength restoration, with the fifth also enjoying improved mobility.


Muscle Strength in the Elderly: Its Relation to Vitamin D Metabolites (1999)

Conclusion: The vitamin D levels of 319 elderly people were tested along with their leg extension power. In both the men and the women, vitamin D levels were strongly correlated with their leg extension power.


Low Serum Calcidiol Concentration in Older Adults with Reduced Muscular Function (1999)

Conclusion: This randomized population survey of 349 elderly people found that those with higher vitamin D levels demonstrated better arm strength, a better ability to climb stairs, better overall physical activity, and fewer falls.


Vitamin D Deficiency, Hypocalcemia, and Increased Skeletal Muscle Degradation in Rats. (1983)

Conclusion: This study took two groups of rat pups and raised one on a vitamin D-deficient diet and raised the other group on a vitamin D-supplemented diet. The pups raised on the vitamin D-deficient diet gained weight at a significantly lower rate compared to the supplemented group and had lower muscle mass.The vitamin D-deficient group eventually developed hypocalcemia, at which point their growth rate declined even more. Later, the vitamin D-deficient rats were given vitamin D, leading to an increase in muscle mass and weight gain.


Myopathy in Bone Loss of Ageing: Improvement by Treatment With 1 Alpha-Hydroxycholecalciferol and Calcium. (1979)

Conclusion: Vitamin D supplementation improves old age-related myopathy.


25-Hydroxycholecalciferol Stimulation of Muscle Metabolism (1975)

Conclusion: Vitamin D supplementation rapidly improves muscle function in vitamin D-deficient rats.


Also see studies on vitamin D and 

Athletic Performance

Physical Performance


Recommended Reading

Athlete’s Edge: Faster, Quicker, Stronger with Vitamin D by Dr. John Cannell (Amazon link)

Order from Amazon


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