Doubt has been cast over the use of vitamin and mineral supplements, with new research finding they don't protect the heart against disease.

Not only are vitamin and mineral supplements a waste of money, they can in some instances actually harm the body, an international study has concluded.

Researchers at the University of Toronto conducted a meta-analysis of all published randomised controlled trials that looked at the effects of vitamin and antioxidant supplements on the risk of heart disease and stroke.

They found the most commonly used supplements --multivitamins, vitamin D, calcium and vitamin C-- provided "no consistent benefit" for the prevention of cardiovascular disease or stroke.

Folic acid alone and B-complex vitamins, which contained folic acid, did show a reduction in stroke.

However, niacin (vitamin B3) and antioxidants (vitamins A, C and E) were associated with an increased risk of all causes of death, according to the findings published in the Journal of The American College of Cardiology.

The Canadian and French scientists say the best way to look after the heart is by getting vitamins and minerals from a healthy diet which includes lots of fruit and vegetables.

Dr Ian Musgrave from the Faculty of Medicine, School of Medicine Sciences at the University of Adelaide said the findings were "neither unexpected nor surprising".

"While vitamins are essential for our health and diseases like scurvy almost banished from developed countries, people have assumed that if a bit of vitamin is good for you a lot is much better," said Dr Musgrave.

"The latter sentiment has turned out not to be true."

According to leading nutritionist and dietician Dr Rosemary Stanton too many Australians have swallowed the line that it's good to take supplements.

But the new research shows it's not a good idea, said Dr Stanton

"This review concluded that money spent on vitamin and antioxidant supplements is not only wasted, but could occasionally be harmful," she said.