Vitamin D is a fat-soluble vitamin essential to maintain healthy bones and muscles in the body. Humans get the majority of their vitamin D from sunlight, which results from a metabolic reaction when skin is exposed to UVB rays. In certain regions, however, reliable sunlight is not always available. And even in the summertime, if runners spend minimal time outside to avoid the heat, they won’t get as much of those vitamin-filled rays. Inadequate vitamin D intake is associated with higher risk of cancer, diabetes, depression, fatigue and hypertension.
To get adequate amounts of vitamin D, experts suggest getting 5-30 minutes of unprotected sun exposure (meaning your face, chest, arms and legs are exposed) each day. The enormous movement towards constant sunscreen usage has also decreased vitamin D formation in humans, since sunscreen partially blocks the rays that metabolize the vitamin. That said, increased sun exposure is unequivocally associated with increased risk for skin cancer—so keep lathering up, and we can figure this vitamin D thing out separately.
Unfortunately, not many foods are great sources of vitamin D. The best sources are fatty fish like salmon, swordfish and tuna—but it’s difficult to consume those every day. In the 1930s, milk became fortified with vitamin D to prevent rickets—a bone malformation caused by severe vitamin D deficiency in children. To this day, fortified milk, orange juice and other dairy products are still main sources of vitamin D.
Here are a few ways to increase vitamin D if you’re spending much of your summer indoors this season:
- Try to get some sun exposure every day, even if it’s only 5 minutes.
- Make an effort to increase your consumption of fatty fish.
- Consume at least two servings of vitamin D fortified products like milk, orange juice or cereal each day.
- Consider taking a vitamin D supplement if you still feel fatigued, depressed or slower than normal this summer.