Pills millions of us take every day can increase risk of heart attack

Vitamin and mineral supplements taken by millions of people could do more harm than good, actually increasing the risk of heart disease and an early death, according to research. 46% of people in the UK take vitamins and minerals on a daily basis, fuelling an industry worth more than £500 million a year.

But most are a waste of money - offering no protection against illness, according to US scientists. Combining vitamin D with a calcium pill, for instance, made a stroke more, rather than less, likely.

The study, published in the journal Annals of Internal Medicine, analysed 277 previous randomised trials involving almost one million people. It looked at the effects of 16 different nutritional supplements and eight dietary interventions on mortality and cardiovascular outcomes in the adult participants.

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Lead author Dr Safi Khan, of the University of West Virginia in the US, said: "We found out only a few of the 16 nutritional supplements and one of the eight dietary interventions evaluated had some protective effect in cardiovascular risk reduction. In our study the fish oil supplementation we found to be protective against heart attacks and folic acid supplementation was found to be protective against strokes."

But some were associated with substantial harms. Dr Khan said: "A combination of calcium and vitamin D was associated with a higher risk of stroke." He added: "Other supplements did not seem to have significant effect on mortality or cardiovascular outcomes."

These included multivitamins, selenium, vitamin A, vitamin B6, vitamin C, vitamin E, vitamin D alone, calcium alone, folic acid, and iron. When it came to dietary interventions there was even less evidence of benefits.

Dr Khan said: "We examined Mediterranean diet, reduced dietary fat, modified dietary fat and reduced saturated fat intake. We found none of these dietary modifications had any effect on cardiovascular risk."

Only two dietary interventions had notable benefits - but just for specific patients. Reduced salt intake protected against deaths from any cause in participants with normal blood pressure.

Dr Khan added that omega-3 fats found in fish were protective against heart attacks and coronary heart disease. Current US dietary guidelines recommend several healthy eating patterns, including Mediterranean and vegetarian diets.

But they do not recommend routine supplement use to reduce the risk for cardiovascular disease or other chronic diseases. It was not clear if nutritional supplements and dietary interventions play a role in preventing mortality and cardiovascular disease.

Dr Eric Topol, of the Scripps Research Translational Institute, who reviewed the findings for the journal, said they are limited by the quality of the evidence. He said: "For example, geographic considerations among the studies need to be considered.

"The reported benefit of folate seems to be largely driven by the inclusion of one study from China, where a folate-rich diet is not routine. In addition, most studies rely on food diaries, which are based on a person's memory of what they consumed and therefore are not wholly reliable.