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Vitamin D Megadose Bad Side Effects?

Vitamin D is good for our bones and muscles but too much of it may not be a good thing according to a study by Australian scientists at the University of Melbourne.

From Time Magazine:

Encouraged by previous studies showing that 500,000 IU of vitamin D, given over multiple doses over a short period of time, and a single injection of 300,000 IU improved balance and strength and reduced fractures, Australian scientists at the University of Melbourne expected that a walloping single oral dose of 500,000 IU would also be effective. The study, led by Geoffrey Nicholson and Kerrie Sanders, involved 2,256 women, ages 70 years or older, who were considered to be at high risk of fracture. They were randomly assigned to receive 500,000 IU of cholecalciferol (a form of vitamin D) or placebo once a year for up to 5 years.

To the researchers’ surprise, women who received vitamin D actually suffered more falls and fractures than women who got the placebo pill. The trial participants experienced a total of 5,404 falls over the course of the study; compared with the placebo group, women taking the vitamin D megadose experienced 15% more falls and 26% more fractures.

Although women in the treatment group did have higher blood levels of vitamin D throughout the year than their placebo-taking counterparts, the added vitamin offered no protection again broken bones. “People have been exploring what is the upper limit of dosing that can be given,” says Nicholson, head of the department of clinical and biomedical sciences at the University of Melbourne. “And I think we inadvertently exceeded it. I think the take home message is that megadoses are not safe; that’s certainly going to be our approach until we have evidence to the contrary.”




1 comment

1 John { 01.08.11 at 9:43 am }

Studies like this one are VERY confusing. The Mega dose used was 500,000 IUs once a year. The other study referred to were 300,000 IUs injected 4 times a year which was common practice for 35 years in East Germany (USSR.) This practice was done because of the phenomenal results. The FDA recommends only 600 IU per day which is a reason why so many are sick in America today. If you are not actively increasing your vitamin D levels from sun UV exposure (includes indoor tanning) or supplementation then you are vitamin D deficient.

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