February 12, 2014
Power Athletes Should Be Wary of Vitamin D2 Supplementation

Boone, NC—While debate continues to rage on whether vitamin D supplementation is a panacea or a waste of money, a new study has specific advice for one group of potential users: Power athletes and others looking for an edge to improve their performance should avoid taking vitamin D2.

Appalachian State University researchers found that vitamin D2 supplements decreased levels of vitamin D3 in the body and resulted in higher muscle damage after intense weight lifting. The report was published recently in the journal Nutrients.

“This is the first time research has shown that vitamin D2 supplementation is associated with higher muscle damage after intense weight lifting, and thus cannot be recommended for athletes,” said David Nieman, DrPH, who directed the food industry-funded research.

The study, conducted at the Human Performance Lab at the North Carolina Research Campus in Kannapolis, was designed to measure whether 6 weeks of vitamin D2 supplementation in NASCAR pit crew athletes affected exercise-induced muscle damage and delayed onset of muscle soreness.

For the double-blind study, one group of athletes consumed 3,800 IU a day of a plant-based vitamin D2 derived from Portobello mushroom powder that had been irradiated with ultra-violet light to convert the ergosterol in the mushrooms to vitamin D2 (ergocalcifoerol). The other group of athletes took a placebo.
Despite the hypothesis that the vitamin supplement would improve performance by reducing inflammation and aiding in recovery from exercise-induced muscle damage, researchers instead found that taking the supplement increased exercise-induced muscle damage in the pit crew athletes, the first documented evidence of exercise-induced muscle damage in athletes taking high doses of vitamin D2.

“When the sun hits our skin, it turns into vitamin D3. The body is used to that,“ Nieman said. “High vitamin D2 levels are not a normal experience for the human body. Taking high doses of vitamin D2 caused something to happen at the muscle level that isn't in the best interest of the athletes. Now we need others to test this and see if they come up with the same results.”

Nieman pointed out that restoring vitamin D levels in older people could improve muscle function, but that the same effect hasn’t been documented in younger adults.

“We were interested in seeing if increasing vitamin D in the pit crew athletes who train heavily in the off season would improve their muscle and immune function,” he said. “While vitamin D2 levels in the blood increased, we found that levels of the valuable D3 decreased. And to our surprise, those taking vitamin D2 didn't have just a little more muscle damage, they had a lot more damage.”

U.S. Pharmacist Social Connect