Exercise and Vitamin D are both important for musculoskeletal health and bone health. Vitamin D may also have a beneficial effect on some types of cancer, in particular colorectal cancer, and other immune-related diseases. Skin exposure to UVB radiation from sunlight promotes Vitamin D production in the skin. While outdoor exercise is the cause of higher Vitamin D levels in many athletes, this effect is seasonal and is likely only seen in younger athletes who train outside between the months of April and November, between the hours of 10 am and 4 pm. Why?
- In Canada, for most of the winter months, there is insufficient UVB radiation from sunlight to have an effective amount of Vitamin D production.
- Throughout the summer months, the time to get some UVB radiation is during the day – so for those of you who train inside or train outside early in the morning or late in the afternoon/early in the evening…you are not going to get that dose of UVB radiation.
- Most Canadians do not get enough dietary Vitamin D. It is found in the skin of fatty fish, some mushrooms, cow’s milk, soy beverages, and some yogurts. Unless you are eating and drinking these foods daily, you likely are not meeting your needs for Vitamin D from foods.
- Skin cells get old too – and the skin’s production of Vitamin D decreases with aging. 50 years of age seems to be the cut-off.
Which athletes are at greatest risk for inadequate vitamin D?
- Master athletes (> 50 yrs) – as one ages, there is reduced production of Vitamin D in the body. If this is combined with eating few dietary sources of Vitamin D then risk of inadequate Vitamin D is even greater.
- Athletes who avoid key dietary sources of Vitamin D due to food intolerance, allergies or food preferences.
- Athletes with dark skin – the ability to produce Vitamin D from sunlight exposure varies with the amount of skin pigmentation; the darker one’s skin, the lower the production of Vitamin D.
What should you do?
- Get a blood Vitamin D analysis done in the summer to see how your UVB exposure is regulating your own production of Vitamin D and repeat this test at the end of the winter to know if your dietary intake is sufficient to maintain optimal levels. Then work with your Doctor and/or Sport Dietitian to determine need for supplementation.
- Master athletes over 50 yrs of age should consider taking a supplement containing a minimum of 600 IU of vitamin D.
- Include food sources of vitamin D in your diet to help you get the vitamin D your body needs.
- Look for fortified foods (foods with vitamin D added to them). In Canada, milk, margarine, and some yogurts are fortified with vitamin D.
- Fatty fish such as salmon and lake trout, as well as eggs are other good sources of vitamin D.