Vitamin D3: The Quiet Multiplier Behind Strength, Recovery, and Reaction Time

You train for hours, spend hundreds and thousands of dollars on equipment but if your level of this one powerful substance are not optimal you will not get the benefits of all your hard work and money. I am not talking about a new supplement with fancy packaging or high-end marketing but a substance that our body has relied on for thousands and thousands of years.

The substance is vitamin D. And I want to emphatically state that optimizing your vitamin D3 level may be the single, most important thing you can do for your health and performance.

It is important to know that Vitamin D really isn’t a vitamin that you get from dairy but rather, a hormone-like substance that your skin manufactures when exposed to UV-B rays of the sun (cutaneous synthesis overview). For background physiology, forms, and metabolism see the NIH fact sheet (NIH ODS).

Vitamin D contributes to peak athletic performance by directing the physical processes involved with muscular function, strength and recovery. In addition, it drives physical reaction time, balance and coordination. In order to understand how vitamin D can impact your athletic performance, it’s important to understand that it functions—much like a steroid hormone (due to its highly-anabolic ability to promote growth, repair and recovery). Reviews link vitamin D status to skeletal muscle function, fiber composition, and neuromuscular performance (muscle function review; performance & supplementation overview). Evidence is mixed across sport contexts, but low 25(OH)D consistently associates with poorer power, sprint metrics, and increased injury risk in several cohorts.

What is even more interesting is that the connection between vitamin D and athletic performance has long been known. During the 1960’s and 70’s, the Germans and Russians won many Olympic medals, attributing their success to vitamin D. Historical reports from the early to mid-20th century described performance improvements with ultraviolet exposure and “heliotherapy” in athletes and patients (history of heliotherapy). While protocols and study designs from that era differ from modern trials, the through-line—light-driven vitamin D biology influencing muscle and nervous system performance—remains compelling.

Yet as powerful of a nutrient for health and performance, 95% of the athletes we have assessed—even those who train regularly outdoors—have less than optimal levels (less than 55 ng/ml) of vitamin D. And even more importantly, those who have restored their vitamin D3 to an optimal level have been able to measurably improve their performance, recover from hard efforts faster and depend on the support of a stronger, more responsive immune system. For clinical ranges and testing methodology, see Endocrine Society guidance (Endocrine Society) and an overview of the 25-hydroxyvitamin D lab test (MedlinePlus).

So the take home point here is... if you truly care about your health and performance, assess your vitamin D3 levels (a simple finger-stick is all that is needed) and then use a combination of sun when possible with a low-cost, highly-absorbable form of vitamin D3 to raise your D levels between 55 and 75 ng/ml. It is the best performance and health decision you can make! For evidence-based sun safety basics see the CDC page on UV and skin (CDC Sun Safety), and for dosing considerations and upper limits review NIH ODS guidance (NIH ODS consumer).