Vitamin D Cold and Flu Fighting Ability Found in Supplements

Vitamin D can protect against the cold, flu and possibly other acute respiratory infections, claimed British researchers who said its additional abilities are available from supplements. Their work was quickly challenged, though.

In the study, published Wednesday in the British Medical Journal, researchers at Queen Mary University of London found that vitamin D had benefits beyond the bone and muscle health it is known for.

Scientists analyzed raw data from nearly 11,000 participants in 25 clinical trials from 14 countries including the United Kingdom, United States, Japan, India, Afghanistan, Belgium, Italy, Australia and Canada.

Lead researcher Adrian Martineau said vitamin D supplements appeared to most effective in those with the lowest vitamin D levels and when supplementation is given daily or weekly rather than in more widely spaced doses.

"This major collaborative research effort has yielded the first definitive evidence that vitamin D really does protect against respiratory infections," said Martineau. "Our analysis of pooled raw data from each of the 10,933 trial participants allowed us to address the thorny question of why vitamin D 'worked' in some trials, but not in others."

"Vitamin D fortification of foods provides a steady, low-level intake of vitamin D that has virtually eliminated profound vitamin D deficiency in several countries. By demonstrating this new benefit of vitamin D, our study strengthens the case for introducing food fortification to improve vitamin D levels in countries such as the U.K. where profound vitamin D deficiency is common."

The researchers said daily or weekly vitamin D supplements could mean 3.25 million fewer people in the United Kingdom would have at least one respiratory infection a year, assuming a population of 65 million, according to The Guardian.

In a British Medical Journal editorial, though, Mark Bolland from the University of Auckland and Alison Avenell from the University of Aberdeen said the Queen Mary research was not good enough to prove vitamin D's effectiveness.

"Current evidence does not support the use of vitamin D supplementation to prevent disease, except for those at high risk of osteomalacia (weak bones and muscles due to low blood vitamin D levels, currently defined as less than 25 nmol/L)," said Bolland and Avendell.

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