Over the last several years, a slew of evidence has come to light that we are experiencing a worldwide epidemic of vitamin D insufficiency. Some studies suggest that half of the world’s population is not receiving an optimal daily dose of this vital nutrient.

It is difficult to overstate the importance of vitamin D for overall health. A deficiency in vitamin D has been linked to osteoporosis, obesity, diabetes, depression, Alzheimer’s disease, and various autoimmune conditions. A lack of vitamin D has also been shown to play a role in the development of colon, breast, and prostate cancers, which, along with lung cancer, are the three most commonly diagnosed forms of the disease.

People who are highly fit may think that they don’t need to worry about vitamin D, since their lifestyle will largely mitigate their risk for diseases, such as diabetes and osteoporosis as well as their risk factors for cancer and cardiovascular disease. While that is a valid point, evidence shows that fit people should be even more interested in vitamin D. 

• Vitamin D Boosts Testosterone: A study published in the journal Hormone and Metabolic Research showed that men who were given extra daily vitamin D for a year enjoyed higher testosterone levels than the placebo group who did not receive the vitamin.
• Vitamin D Improves Muscle Recovery: In one recent study, scientists examined the difference in exercise-induced injury between a group of men with low vitamin D levels, and another group who received supplemental vitamin D. The men who took the extra vitamin D experienced enhanced muscle repair and hypertrophy, and returned to full strength more quickly after an intense workout than the men who were deficient in vitamin D.

Vitamin D is scarce in food, even fortified ones like milk or cereals. The sun is the best source of the vitamin. To get an adequate amount of vitamin D, experts recommend spending 15 to 20 minutes a day in sunshine with 40 percent of the skin surface exposed.

If that sounds like a tall order considering where you live, your work schedule, and a desire to prevent premature aging of your skin from UV rays, you’re not alone. (Incidentally, sunblock prevents your skin from absorbing vitamin D.)

Additionally, older people, dark-skinned individuals, and overweight or obese people do not absorb the vitamin very effectively. That’s why vitamin D supplementation is crucial. 

Experts recommend at least 600 IU of vitamin D3 (known as cholecalciferol) a day, at a bare minimum for health.⁶ However, a more effective dose for active people is closer to 2000 IU (about 50 mcg) a day. The upper limit for safety is about 10000 IU a day, so a daily dose of 2000 IU is completely reasonable. Be sure to take your daily vitamin D with some fat-containing food to ensure optimal absorption.