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Athletes who play indoor sports at risk of vitamin D deficiency, study finds

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Basketball players and others who enjoy indoor sports may be at risk of vitamin D deficiency, researchers have said.

Vitamin D is necessary for building and maintaining healthy bones. The body creates vitamin D from direct sunlight on the skin when outdoors, which means that if you spend a lot of time indoors you may not get enough.

In a study published in the journal Nutrients, researchers at George Mason University in Virginia and the Mayo Clinic Health System Sports Medicine Research in Wisconsin assessed vitamin D status among basketball players from the university’s men’s and women’s teams.

The findings showed that the majority of the athletes had insufficient levels of vitamin D but a daily vitamin D supplement of 10,000 IU improved their status.

During the 2018-2019 season, players were allocated a high dose of vitamin D3 supplement (10,000 IU), low dose (5,000 IU) or none, depending on their circulating 25-hydroxyvitamin D levels at the start of the study. The objective was to identify the dosage of vitamin D3 supplementation required for optimal status.

The researchers gathered data on each player’s body composition, skin pigmentation, sun exposure, dietary intake and blood, and the participants were monitored regularly during the study.

Athletes with darker skin pigmentation had a heightened risk of vitamin D insufficiency at baseline, while none of the participants with fair or very fair skin fell into the insufficient category at baseline.

“Overall, our findings showed that 13 of the 20 (65%) participants were vitamin D insufficient at baseline,” said Dr Margaret Jones, professor in the university’s School of Kinesiology. “This result is consistent with a recent systematic review and meta-analysis wherein 56% of a total sample of 2,000 athletes residing in nine different countries including the United States had inadequate levels of vitamin D.”

In follow-up assessments about five months later, the greatest change was seen in the 10,000 IU group — although only one participant reached optimal status in this group.

“A daily dosage of 10,000 IU vitamin D3 supplementation mitigated the high prevalence of vitamin D deficiency among collegiate basketball players but was insufficient for all to reach sufficient levels,” the researchers concluded.

As well as sunlight and supplements, Vitamin D is found in a small number of foods, including oily fish, red meat, egg yolks and fortified foods.