Nutrient Spotlight for Runners – Are you getting enough Vitamin D?

By Elizabeth (Beth) Mansfield, PhD, MSc, RD

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 runners who train outside between the months of April and November, between the hours of 10 am and 4 pm. Why?

  1. In Canada, for most of the winter months, there is insufficient UVB radiation from sunlight to have an effective amount of vitamin D production.
  2. Throughout the summer months, the time to get some UVB radiation is during the day – and many runners train early in the morning or late in the afternoon/early in the evening.
  3. Most Canadians do not get enough dietary vitamin D. It is found in the skin of fatty fish, some mushrooms, fluid 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.
  4. 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 runners are at greatest risk for inadequate vitamin D?

  • Runners over 50 years of age. 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.
  • Runners with lactose intolerance. The inability to digest milk sugar means that the main dietary source of vitamin D – that found in milk – is absent from the diet.
  • Runners 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?

  • Runners over 50 years of age should take 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 foods with vitamin D added to them. In Canada, milk, margarine, and some yogurts are fortified with vitamin D. Some foods are also supplemented with Vitamin D, such as some ready to eat cereals and orange juices
  • Fish and eggs are other good sources of vitamin D.

Listed below are common sources of vitamin D.

Food/Fortified Foods   IU’s
Fortified soy beverage* 250 mL (1 cup) 120
Margarine 5 mL (1 tsp.) 60
Milk 250 mL (1 cup) 100
Yogurt made with fortified milk   (175 mL) 80
Egg yolk, large 40-50
Supplemented Foods:
Ready to eat cereal supplemented with Vitamin D 40
Orange juice supplemented with Vitamin D 120-140
Fish:
Mackerel 90 g (3 oz.) 310
Salmon, canned 90 g (3 oz.) 650
Sardines, 1 can 100 g (3.75 oz.) 250
Tuna 90 g (3 oz.) 236
Supplements:
Cod liver oil (1 Tbsp) 1360

 

About Beth Mansfield and Peak Performance 
Dr. Elizabeth (Beth) Mansfield, PhD, RD is a Registered Dietitian, Sport Nutrition Specialist, and Certified Exercise Physiologist with Peak Performance in Ottawa. Beth educates Canadian athletes on sport nutrition for health and performance.

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