Rethinking Vitamin D

The scientific community is rethinking the view that Vitamin D can be a powerful tool in preventing disease. Over the last few years, we saw many studies suggesting major benefits from high vitamin D – researchers thought it could reduce the risk of cardiovascular problems by up to 58%, diabetes by up to 38% and colorectal cancer by up to 33%.

Now a systematic review of previously published scientific studies concludes that these findings were not confirmed in 172 randomized trials, which are the gold-standard method for research.

The review in The Lancet Diabetes & Endocrinology found that taking vitamin D supplements had no effect on the occurrence of disease, its severity or course. The lead authors now think low vitamin D levels are a symptom of poor health – not the cause, and that could explain why vitamin D deficiency is reported in a wide range of disorders.

This comes after two other large studies cast doubt on the sunshine vitamin’s efficacy in preventing bone loss or disease.

Meanwhile, evidence is growing that supplements, such as fish-oil capsules, may be less beneficial than food sources of specific nutrients.

Health Canada’s recommended dietary allowance for vitamin D is 800 IU per day, which could be found in foods like fatty fish and egg yolks. In addition, the agency recommends that everyone over the age of 50 take a daily vitamin D supplement of 400 IU. Other authorities have recommended taking 1000 IU daily. Whether this does any good is now an open question and will remain so until large scale clinical trials decide the issue once and for all.