The past decade has been good to vitamin D. It’s even been called the “next miracle supplement.” Initial research on vitamin D found that it was vital for bone health and preventing diseases like rickets and osteomalacia. More recently, we’ve found that supplementing vitamin D offers many potential health benefits, beyond bone health.

The Basics

Vitamin D is a fat-soluble vitamin (technically, it’s a prohormone), known for its effects on bone and calcium metabolism. If you’re deficient in vitamin D, bringing your levels back to normal may improve athletic performance. One research review noted that people with low levels of D (less than 50 ng/dl) experienced benefits to physical activity after supplementation. Sedentary individuals can improve their power output with a 4,000 IU daily dosage of vitamin D, paired with resistance training.

Dosing Guidelines

So how much D is enough? Researchers found that a dose of 4,000 IU was used to successfully increase power output in sedentary persons, but it didn’t say that lower doses (such as 2,000 IU) were less effective. Additionally, because vitamin D levels are not lowered by exercise it is thought that this dose applies to both athletes as well as sedentary persons.

A dose 2,000 IU combined should be seen as an “ideal” supplemental dose since the ideal total daily dose (from food and supplements) is somewhere between 2,000 IU and 4,000 IU. While doses slightly higher than 4,000 IU are not by any means harmful to health nor performance – much higher doses are prescribed to those found to be acutely deficient – preliminary evidence suggests it may be slightly pro-adipogenic (fat promoting) in women (no studies in men, but thought to apply to them as well) yet doesn’t confer much additional benefits relative to the 2,000-4,000 IU range. This amount has been shown to be very safe while providing a variety of health benefits. If you want to take more, talk to your doctor about getting your vitamin D levels checked out so that you can lock down the most efficacious dose.

To Dose or Not to Dose 

Is vitamin D a miracle supplement? Not necessarily, but deficient athletes would definitely benefit from boosting their vitamin D intake, either through food, sun, or supplements. Low vitamin D levels correlate with an increased risk of illness and stress fractures in athletes.

T-Booster? Vitamin D has even been called a testosterone booster. Unfortunately, vitamin D only increases testosterone levels in deficient people, and in those cases, only back to normal levels. Taking extra vitamin D will not raise testosterone further.

Greatest D

Which kind of D should you be taking? One study out of Creighton University reported that D3 was about 90% more potent at raising levels of the storage form of vitamin D in the body, 25-hydroxyvitamin D, than vitamin D2. It also increased stored levels of the vitamin three times more than D2 did. So…D3 peeps.

For more information, check out’s page on vitamin D.

Dr. Spencer Nadoksky is the Director of and also a practicing physician in Virginia. As a former Division I NCAA wrestler, Dr. Nadolsky ties his past athletic background in when treating his patients. For more on Dr. Spencer, you can visit his blog at