As a fitness professional, you probably eat cleanly, maintain a regimented workout schedule, get good sleep, and manage stress levels. Here’s the bad news: Even when you’re doing everything correctly, you’re probably not making or getting enough vitamin D. Researchers find vitamin D deficiencies, in fact, quite common among athletes. Signs of deficiencies include stress fractures, musculoskeletal pain, and frequent illness. Even in young, healthy athletes, deficiencies can increase your risk for injury and prolong recovery.(1)

Once considered a vitamin, researchers now see vitamin D as an active hormone that impacts various systems, including musculoskeletal health, immunity, and heart health.(2)

Unfortunately, vitamin D insufficiencies have increased over the last 30 years, and today 77 percent of Americans are considered insufficient in vitamin D.(3)

Studies show athletes have comparable vitamin D levels to those of the general population, meaning you’re either deficient or insufficient in this crucial vitamin. (Vitamin D deficiencies are lower than insufficiencies, but both mean you have lower-than-ideal levels of vitamin D.)

Numerous factors contribute here, including where you live and whether you play indoor or outdoor sports. Practically put, if you do burst training on park stairs in San Diego, you’re probably making more vitamin D than someone in Toronto who spends most of his/her time inside a gym.

Sunlight is the best way to get vitamin D. If you’re avoiding the sun or using lots of sunscreen, your skin probably isn’t optimally synthesizing this vitamin. In fact, wearing a sunscreen with a sun protection factor (SPF) of 30, although it prevents you from getting burned, reduces your skin’s vitamin D synthesis by more than 95 percent.

Skin tone can also impact how much vitamin D you make. People with a naturally dark skin tone require at least three to five times longer exposure to make the same amount of vitamin D as a person with a lighter skin tone.(4)

Compounding the sunlight problem, very few whole foods contain vitamin D. Fortified foods like cereal and milk are a terrible way to get vitamin D, since most come loaded with junk ingredients like sugar or gluten, and contain the inferior form of vitamin D (ergocalciferol or vitamin D2).

Altogether, that spells bad news for your physical performance. Among its duties, vitamin D plays a role in bone growth and maintenance. This workhorse vitamin regulates electrolyte metabolism, protein synthesis, gene expression, and immune function; all crucial aspects for stellar athletic performance.(5)

Research shows optimal vitamin D levels can also prevent stress fractures and muscle injury.(6)

If you want to build muscle, optimize your D: Muscle tissue contains vitamin D receptors, and cross-sectional and longitudinal studies show vitamin D plays a functional role in muscle.(7)

Other research shows optimal levels of vitamin D can reduce inflammation, pain, and myopathy while increasing muscle protein synthesis, ATP concentration, strength, jump height, jump velocity, jump power, exercise capacity, and physical performance.

That’s quite a resume for a vitamin!

Here’s the thing. More is not necessarily better. It’s not about mega dosing on vitamin D supplements, it’s about helping your body achieve those optimum levels of vitamin D. Excess levels may actually be a problem, for some.

“There is a growing concern that the trend to aim for higher blood levels of vitamin D is not supported by the scientific evidence, and over time may contribute to calcification of the arteries, kidney stones and other health problems,” says the Weston A. Price organization.(8)

The first step to optimizing D levels is learning your current level. Ideally, you want vitamin D levels within the 30-80 ng/ml range, equivalent to 75-200 nmol/L. Randomized clinical and placebo controlled trials show vitamin D levels within that range can positively impact numerous health conditions.(9)

To do that, you’ll need the correct combination of sunlight, food, and supplementation. Along with working with your doctor or healthcare professional, these seven strategies can help optimize your vitamin D levels.

  1. Ask your doctor for a 25(OH)D test.Don’t guess your levels; test to find out. According to the Vitamin D council, ask for the 25(OH)D test, not the inferior 1,25(OH)2D test. Alternately, you can do an at-home test where you prick your finger, put a drop of blood on blotter paper, and send it off to a lab to be tested.(10)
  2. Work with your physician to get D levels up to par. If you have deficiencies, researchers suggest a cumulative dose of at least 600,000 IUs administered over several weeks, can replenish vitamin D stores. Never take single large doses at one time, and always work with your physician to replenish those levels.(11)
  3. Find your maintenance dose.Once you’ve hit your optimal level, you’ll want to maintain it. Studies show adults in temperate climates need at least 800 to 1,000 IUs of vitamin D daily to get serum 25-hydroxyvitamin D concentrations of at least 30 ng/mL (75 nmol/L).(12) Talk to your doctor about finding the right dosage to meet optimal D levels.
  4. Buy the right supplement.Look for a professional-quality vitamin D3 or cholecalciferol (not the inferior D2 or ergocalciferol) soft gel or liquid that also contains vitamin K. Beware of inferior ingredients, like soybean oil, common in commercial vitamin D products. Take this supplement with a meal containing fat, since vitamin D is a fat-soluble vitamin.
  5. Easy does it.Like with exercise, too much vitamin D can become counterproductive and lead to problems like arterial calcification, kidney stones, and other health problems.(13) “In general, vitamin D toxicity occurs at 25(OH)D blood levels over 500 nmol/L or at a daily intake exceeding 30,000 IU/day over an extended period of time,” says Canada’s Vitamin D Fact Sheet. “Supplements taken as directed and up to 4000 IU/day for adolescents and adults (age 9 and up) would not lead to toxicity. Individuals with liver and kidney conditions may have a lower threshold for vitamin D toxicity than the general population.”(14) I strongly recommend getting your vitamin D levels checked at least twice a year and emphatically avoid mega dosing on your own.
  6. Get some natural sunlight.Again, too much of a good thing becomes bad. Don’t get carried away basking on the beach for hours, but do, safely, aim for daily direct sunlight in the non-peak hours when you’re not likely to burn.
  7. Eat more fish.Wild-caught fish is a rock-star food among athletes: Besides containing stellar amounts of vitamin D, it contains impressive amounts of protein, important nutrients like selenium, and anti-inflammatory omega-3 fatty acids. If you’re not a fan of cooking fish or find getting enough of this power food a challenge, check out my recipe for salmon patties here – it’s so easy and delicious. Crunchy on the outside, soft and warm on the inside, these patties are great for lunch or dinner, served with a side dish that will make the flavor of the fish the highlight of your meal.

Raised in a holistic family, Dr. B.J. Hardick is an organic food fanatic, green living aficionado, and has spent the majority of his life working in natural health care. In 2009, he wrote his first book, Maximized Living Nutrition Plans, which has now been used professionally in over 500 health clinics. Dr. Hardick regularly blogs healthy recipes and holistic health articles on his own website,, and speaks to numerous professional and public audiences every year. He maintains a private practice as a Doctor of Chiropractic. In his spare time, he invests his keen interest in sustainable living into urban development in his hometown of London, Ontario.