"Lack of vitamin puts 30 million Britons at risk," proclaimed the Sunday Telegraph this week. A few private moments with a calculator and I reckoned there was a one-in-two chance it meant me. "Cancer risk in low vitamin D levels," warned the Observer. I shifted uncomfortably in my seat and read on. At this week's European Congress of Endocrinology in Glasgow, the articles said, Belgian professor Roger Bouillon had stressed the dangers of not getting enough vitamin D - osteoporosis, falls and fractures, tuberculosis and an increased risk of colon, breast and prostate cancer. We weren't eating enough oily fish or getting enough sunlight, he said, and taking vitamin D supplements was probably the only realistic way to solve the problem.

Before rushing out to stock up on vitamin pills, something struck me. Surely vitamin D must have been studied as a treatment? I soon discovered that in February, the New England Journal of Medicine published two trials on it, the biggest and most reliable ever. One trial looked at vitamin D and broken bones. Forty thousand women spent seven years randomly assigned with either vitamin supplements or a placebo. Those taking vitamin D suffered a higher rate of kidney stones - but their fracture risk was unchanged. The second study, of about 36,000 women, again randomly allocated them vitamin D or a placebo. This time, it looked at rates of colorectal cancer. Again, there appeared to be no benefit.

And as for the other ailments? Can vitamin D supplementation really help prevent TB or breast and prostate cancers? No idea - nobody appears to have conducted quality research proving a definitive link.