The body of literature on vitamin D is so big that it’d be impossible to cover in a single article. Here are just a few highlights about the vitamin, particularly relevant for us fitness-obsessed folks:
Our main source of vitamin D is the sun – we synthesize vitamin D3 in our skin from 7-dehydrocholesterol upon exposure to UVB radiation from sunlight. We can find it in very few foods (mackerel, salmon, sardines, fish liver oils, certain eggs, and mushrooms). Milk is fortified with vitamin D here in the U.S., as are some dairy products and plant-based milk). Multivitamins generally provide 400-1,000IU of D2 or D3, and vitamin D supplements typically provide 400-50,000 IU.
We cannot get vitamin D toxicity from too much sun exposure, but we CAN get it from too much supplementation. Doses of up to 10,000 IU per day seem to be safe, although the IOM has set the U.L. (the highest amount known to be safe) at 4,000 IU per day. People with hyperparathyroidism, sarcoidosis, tuberculosis, or lymphoma could experience complications from vitamin D supplementation and should speak with a doctor.
Supplementation isn’t necessary if you have optimal serum levels; however, ~24-41% of the U.S. is vitamin D insufficient, and 5.9-28.9% is deficient (depending on the thresholds used). The prevalence of insufficiency in athletes has been reported to be as high as 56%.
Besides supporting bone health, supplementing with vitamin D MIGHT reduce mortality risk, improve insulin sensitivity, reduce the risk for heart disease and certain cancers.. Emerging literature suggests that it might be protective against COVID-19.
But what about us lifters?
Because vitamin D receptors are present in a lot of tissues, supplementation could improve performance via reduced myostatin and improved calcium handling in muscles, increasing recovery by reducing inflammation and increasing testosterone, improving cardiac muscle and vascular health, and reducing the risk for infection and injury by improved immune and bone health.
Some evidence suggests that vitamin D supplementation to correct a deficiency can improve athletic performance, and correcting an insufficiency might improve strength and power. However, other evidence suggests that vitamin D supplementation might not improve performance.
As Eric Helms @helms3dmj noted in a 2018 issue of the MASS research review, given that supplementation with vitamin D can indeed be harmful, it probably makes sense to get your serum levels of 25-hydroxyvitamin D checked first before you consider supplementation. Rather than vitamin D “enhancing” performance, it’s probably more accurate to view it as “correcting” suppressed performance due to a deficiency or insufficiency.
If your levels are 25-hydroxyvitamin D are low, you ought to supplement 🙂
- Taylor, P N. et al (2018). A review of the growing risk of vitamin D toxicity from inappropriate practice.
- Liu, et al (2018). Vitamin D deficiency and insufficiency among U.S. adults: prevalence, predictors and clinical implications
- Schleicher, et al (2016). National Estimates of Serum Total 25-Hydroxyvitamin D and Metabolite Concentrations Measured by Liquid Chromatography-Tandem Mass Spectrometry in the U.S. Population during 2007-2010
- Farrokhyar, et al (2015). Prevalence of vitamin D inadequacy in athletes: a systematic-review and meta-analysis
- Melamed, et al (2008) 25-hydroxyvitamin D levels and the risk of mortality in the general population
- Ford, et al (2011) Vitamin D and all-cause mortality among adults in USA: findings from the National Health and Nutrition Examination Survey Linked Mortality Study
- Bjelakovic, et al (2014). Vitamin D supplementation for prevention of mortality in adults
- Sepehrmanesh, et al (2015)Vitamin D Supplementation Affects the Beck Depression Inventory, Insulin Resistance, and Biomarkers of Oxidative Stress in Patients with Major Depressive Disorder: A Randomized, Controlled Clinical Trial
- Wang, Lu et al (2010). Systematic review: Vitamin D and calcium supplementation in prevention of cardiovascular events
- Gorham, E et al (2007). Optimal vitamin D status for colorectal cancer prevention: a quantitative meta analysis
- Skinner, et al (2006) Vitamin D intake and the risk for pancreatic cancer in two cohort studies
- Liu, et al (2021). Low vitamin D status is associated with coronavirus disease 2019 outcomes: a systematic review and meta-analysis
- Dahlquist, et al (2015). Plausible ergogenic effects of vitamin D on athletic performance and recovery
- Cannell, et al (2009). Athletic performance and vitamin D
- Jung, et al (2018). Correcting Vitamin D Insufficiency Improves Some But Not All Aspects of Physical Performance During Winter Training in Taekwondo Athletes
- Farrokhyar, et al (2017). Effects of Vitamin D Supplementation on Serum 25-Hydroxyvitamin D Concentrations and Physical Performance in Athletes: A Systematic Review and Meta-analysis of Randomized Controlled Trials
- Helms, E (2018). Vitamin D Impacts Strength and Anaerobic Performance. Mass Research Review, issue 2, volume 8