Every year when winter rolls around, there seems to be a renewed interest in Vitamin D among athletes. This is for good reason. Perhaps more than any other vitamin, this one has permeated the nutrition and sports science literature for the past decade. The reasons are many, but we know that one’s levels of this crucial nutrient are directly impacted by sun exposure. Even the most active of us receives less sunlight in the winter months, which can negatively impact our Vitamin D status.
In a 2009 article published in the Annals of Internal Medicine, it was estimated that 77% of Americans are deficient in Vitamin D, and that is using the relatively conservative reference ranges for general population norms. In this measure, the otherwise healthy and active athletic population seems to be no better off. For those interested in performance, this is a problem.
As additional studies on Vitamin D are conducted, we are learning more about what it can do to optimize health and performance. On many topics though, the data is not yet conclusive. We learn more every year on this subject, and the sports medicine community is certainly keeping a close eye on the literature.
What does Vitamin D do?
- Acts as a hormone in the body, which means it travels to multiple tissues and is involved in many physiologic functions. There are receptors on nearly every type of tissue in the body, and even gene expression is regulated by this vitamin.
- Enhances calcium absorption, which impacts bone health. Studies have demonstrated a higher risk of stress fractures in athletes who are deficient in Vitamin D.
- Impacts protein synthesis and muscle recovery.
- Crucial for hormone production.
- Regulates some components of immune and inflammatory response. Some studies suggest that maintaining appropriate Vitamin D levels may protect against viral illness such as colds and flu.
- Impacts muscular strength, possibly due to an influence on muscle fiber type and size.
- Higher levels of Vitamin D are associated with a higher VO2max in some studies.
How can you test your Vitamin D level?
- A simple blood test at the lab can tell you your level. You’ll want to test 25-OH-Vitamin D, or 25-hyroxy Vitamin D.
Should you supplement?
- Reference ranges are generally reported as “deficient” (<10), “insufficient” (~20-30), and “sufficient” (>30). However, these levels are based on preventing disease states. It is generally accepted that optimal physiologic performance for athletes may require higher stores. In fact, Vitamin D does not start to be stored in the fat and muscle until a patient’s level is greater than 40. For this reason, many physicians who work in sport will recommend levels closer to 60 for athletes.
- Every person is different and has their own health history and risk profile. You should discuss supplementation with your doctor.
- I believe that anyone supplementing with Vitamin D should undergo blood work to determine their requirement and their response to treatment. It’s easy and cheap to do, and it takes out the guess work!
Whether winter or summer, a person’s Vitamin D status can be very influential with regard to their health and performance. Testing your level is easy and highly recommended! If you are trying to be a healthy, strong, resilient athlete who performs at your max and recovers well, you need to know where you stand on this metric. Deficiency is common in athletes and it’s easy to address.