Writing in the BMJ, the team says the effect of vitamin and mineral supplements on the risk of non-communicable diseases in “generally healthy” populations is controversial.
They point to randomised trial evidence that does not support use of vitamin, mineral, and fish oil supplements to reduce the risk of these diseases, such as cardiovascular disease, cancer, or T2 diabetes.
“To date, randomised trials have largely shown no benefit of vitamin, mineral, and fish oil supplements on the risk of major non-communicable diseases in people without clinical nutritional deficiency,” says the team led by Dr Fang Fang Zhang, associate professor at the Friedman School of Nutrition Science and Policy at Tufts University.
“These results contrast with findings from observational studies, where supplemental nutrient intakes are often associated with a reduced risk of these diseases.
“The apparent associations from observational studies may result from unknown or unmeasured confounding factors such as socioeconomic status and lifestyle factors, including a better overall diet.”
The team points to a review of 15 randomised trials that appears to confirm the lack of benefits of supplements on cardiovascular events, mostly among patients with risk factors.
This review, along with others focuses on vitamins, minerals and omega-3 fatty acid intake, which has shown some benefits, namely a reduction in myocardial infarction (heart attack) cases.
This result is largely consistent with findings from meta-analyses that fish oil supplementation did not have substantial effects on the primary or secondary prevention of cardiovascular disease.