Can young, healthy athletes really be vitamin D deficient? Our son’s basketball coach wants everyone tested. We think it’s a lot of hype. Do you think this is really necessary?


Most likely your son’s coach has heard something about the perils of low vitamin D. Without it, we can suffer low bone mass, decreased immune function, and altered physical performance. Any of those (and especially all in combination) can pose serious problems for athletes.

For example, bone fractures and muscle injuries associated with low vitamin D can sideline athletes for an entire season. Frequent colds, flus, and other more serious illnesses from a compromised immune system can lead to days without practice and poor performance. The athlete may not miss a day but still isn’t at the “top of their game” so-to-speak.

The biggest known risk factors for vitamin D deficiency are: 1) limited sun exposure (based on where athletes live), 2) the use of sunscreen, and 3) athletes with dark skin pigmentation. Does your son fit any or all of these descriptions?

To elaborate just a bit, these factors limit the skin’s absorption of ultraviolent B (UVB) rays from the sun needed for vitamin D production in the body. Living, practicing and playing indoors (especially in the northern latitudes) is a direct cause of low UVB radiation. But living in a sunny climate may be thwarted by the increased use of sunscreen products. We use these to keep UVB rays from contributing to skin cancer.

Before anything can be done about low vitamin D, it is essential to know what the vitamin D levels are. This can be done with a simple blood test. But that’s where simplicity ends because experts say there is no clearly known optimal level of vitamin D to shoot for. Right now, the various levels are determined by measuring total serum 25-hydroxyvitamin D (25(OH)D3) and defined as:

Deficient: 25(OH)D3 is less than 20 ng/mL
Insufficient: level is 20 to 31 ng/mL
Intoxication: blood levels are higher than 150 ng/mL
Sufficient: at least 30 ng/mL up to 50 ng/mL

Having “sufficient” blood levels of vitamin D means the body can absorb calcium from our diet to keep bones healthy. And sufficient levels prevent the cascade of biologic events that occur in the body when vitamin D drops too low. For athletes, the end-result is protection from stress fractures, bone fractures, and soft tissue injuries of muscles, tendons, and ligaments.

Experts in this area do recommend a blood test to determine levels of total serum 25(OH)D3 for at-risk athletes before attempting any vitamin D supplementation. Treatment should be applied to those individuals with low (insufficient or deficient) vitamin D. Taking large (supraphysiologic) doses of Vitamin D supplements is NOT recommended as a way to enhance athletic performance. High levels of vitamin D can lead to kidney (and other tissue) damage.

Talk with your son’s (or your) primary care physician about this recommendation. Your physician can advise you as to the medical necessity of baseline Vitamin D testing. Any deficiencies requiring supplementation must be treated under his or her supervision and guidance anyway.