Vitamin D has gotten its fair share of attention from sports science researchers in the last decade. Although vitamin D is an organic compound that can be found in some (albeit, very limited) foods, requirements in humans can be met entirely through exposure to UVB rays and synthesis through the skin, which is why it’s been coined as “the sunshine vitamin”. The role of vitamin D in the maintenance of bone and skeletal health through calcium and phosphorus metabolism is well documented. The latest research on vitamin D in athletes also points to its role in non-skeletal functions such as skeletal muscle growth, inflammatory modulation and immunity. The need for certain micronutrients such as vitamin D, calcium and iron may also be increased in athletes due to the metabolic stress of training as well as muscle adaptations. Conclusions from current evidence show that insufficient levels of vitamin D may negatively affect athletic performance.
Blood vitamin D (serum 25(OH)D) is the best indicator of vitamin D status. A large survey showed that over 30% of Canadians have insufficient circulating levels of vitamin D. Additionally, data shows that athletes in most countries do not come close to meeting the minimum dietary recommendations.
Table -1 Vitamin D status
Status |
Circulating 25(OH)D |
Deficient |
<50nmol/L (20ng/mL) |
Insufficient |
<75-80nmol/L (30-32ng/mL) |
Sufficient |
>75-80nmol/L (30-32ng/mL) |
Optimal |
<100-250nmol/L (40-100ng/mL) |
Toxic |
>375nmol/L (>150ng/mL) |
Several factors may influence vitamin D status in athletes, including:
Dietary Sources
The recommended intake of vitamin D for healthy adults is 600 IU/day (USA & Canada, Institute of Medicine). Vitamin D is found in small amounts in a limited number of natural and fortified foods, which makes it very hard to reach the recommended intake through food alone.
Table -2 Vitamin D in foods
Food |
IU/serving* |
Salmon (100g cooked) |
275 IU |
Fortified milk (250 mL) |
100 IU |
Egg yolk, large (1) |
30 IU |
Margarine (1 tsp/5 mL) |
20 IU |
*Canadian Nutrient File database.
IU: international units. 1000 IU = 25 micrograms.
As a general recommendation, a combination of sun exposure, dietary intake and supplementation can help keep you on the right track:
It is important to note that there is no ergogenic effect of providing doses of supplemental vitamin D above the recommended levels.
If you are unsure about your vitamin D status, have a history of stress fracture, frequent illness, bone and joint injury, skeletal pain or weakness, or signs of overtraining, talk to your health care professional about having your vitamin D levels checked and individualized guidance on acceptable levels of vitamin D intake.
Written by:
Stephanie Jamain, M.Sc, RD, CSSD
Sports Nutritionist
References:
Larson-Meyer, E. The Importance of Vitamin D for Athletes. Sports Science Exchange (2015) Vol. 28, No. 148, 1-6.
Owens DJ et al. Vitamin D and the Athlete: Current Perspectives and New Challenges. Sports Med (2018) 48 (Suppl 1):S3–S16.
Statistics Canada. (2013) Vitamin D Blood Levels of Canadians.
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