Evidence from animal studies suggest that high doses of vitamin D3 may increase aerobic capacity, muscle growth, and force and power production, thereby offering potential ergogenic effects, wrote scientists from the University of British Columbia (Canada), Providence Sacred Heart Medical Center and Children’s Hospital (USA), and Simon Fraser University (Canada).
The review, published in the Journal of the International Society of Sports Nutrition, also highlighted the need to consider vitamin K whenever considering the potential performance benefits of vitamin D because K and D work synergistically.
“Based on the research presented on recovery, force and power production, 4,000-5,000 IU/day of vitamin D3 in conjunction with a mixture of 50 to 1,000 micrograms per day of vitamin K1 and K2 seems to be a safe dose and has the potential to aid athletic performance,” they wrote.
“However, both deficiency (12.5 to 50 nmol/L) and high levels of vitamin D (greater than 125 nmol/L) can have negative side effects, with the potential for an increased mortality. Thus, maintenance of optimal serum levels between 75 to 100 nmol/L and ensuring adequate amounts of other essential nutrients including vitamin K are consumed, is key to health and performance.”
The sunshine vitamin
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. Both D3 and D2 precursors are transformed in the liver and kidneys into 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D).
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Vitamin D deficiency in adults is reported to precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases.
While our bodies do manufacture vitamin D on exposure to sunshine, the levels in some northern countries are so weak during the winter months that our body makes no vitamin D at all, meaning that dietary supplements and fortified foods are seen by many as the best way to boost intakes of vitamin D.
Despite the potential ergogenic benefits of the sunshine vitamin, the reviewers not that large portions of athletic populations are deficient in the vitamin.
“Based on the literature presented, it is plausible that vitamin D levels above the normal reference range (up to 100 nmol/L) might increase skeletal muscle function, decrease recovery time from training, increase both force and power production, and increase testosterone production, each of which could potentiate athletic performance,” they wrote.
However, “no study in the athletic population has increased serum 25(OH)D levels past 100 nmol/L, (the optimal range for skeletal muscle function) using doses of 1,000 to 5,000 IU/day,” they noted.
“Thus, future studies should test the physiological effects of higher dosages (5,000 IU to 10,000 IU/day or more) of vitamin D3 in combination with varying dosages of vitamin K1 and vitamin K2 in the athletic population to determine optimal dosages needed to maximize performance.”
Source: Journal of the International Society of Sports Nutrition
2015, 12:33, doi: 10.1186/s12970-015-0093-8
“Plausible ergogenic effects of vitamin D on athletic performance and recovery”
Authors: D.T. Dahlquist, B.P. Dieter, M.S. Koehle