The Effects of Vitamin D Supplementation on Muscle Strength

A new study suggests when it comes to supplementing with vitamin D, the source makes all the difference.

A systematic review of the effect of Vitamin D supplementation on strength levels in athletes was published in the Journal of Strength and Conditioning Research this week.

Vitamin D2 was found to be ineffective at impacting muscle strength, though vitamin D3 was shown to have a positive impact on muscle strength. There were significant improvements in strength where vitamin D3 was administered, ranging from 1.37% to 18.75%.

Vitamin D is a fat-soluble vitamin that has been proven to bolster your immune function, bone health, reducing hypertension, and even faciliate weight loss. Sunlight is a key source of vitamin D absorption in humans, with deficiency being rife in the Northern territories that are deprived of sunlight in the winter months.

Supplementation has enjoyed a rise in popularity in recent years among athletic populations, with research concluding that vitamin D can have positive effects on everything from your body composition to your testosterone levels. Vitamin D3 is the preferred form for supplementation as it has been proven to be absorbed 500 times faster and 87 percent more effective than its counterpart, vitamin D2, in raising vitamin D levels in the body.

This review shows, as with most supplements, that a period of at least a month is needed to see significant strength increases, and effective dosages can vary. In all of the vitamin D trials reviewed, supplementation lasted from 4 weeks to 6 months and dosages ranged from 600 IU to 5000 IU per day. In general, recommendations vary between 4,000-8,000 IUs/day to supplement a vitamin D deficit and then maintain a healthy level going forward. It’s advisable to check your levels before you attempt to supplement them.

Though strongly advocated by many coaches, it has been difficult to draw definitive conclusions for performance gains from vitamin D supplementation from previous studies, and indeed, the researchers of this review note that additional studies are needed to confirm the associations to strength gains found here. But in the meantime, the review may lead the way to a more definitive association between this vitamin and athletic performance in future.

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