Troubling questions have been raised about the quality and safety of vitamins and dietary supplements, in a joint investigation by the New York Times and the PBS Frontline program.

The report asked leading clinicians and researchers for their assessment of whether products actually did consumers any good.

It found that in the multi-billion-dollar industry, some supplements and vitamins could actually be harmful.

“We love the notion of a magic pill. It’s something that makes it all better. It’s just too seductive,” pediatrician Paul Offit, from the Children’s Hospital of Philadelphia, said.

He questioned why people were taking supplements and vitamins in the first place.

“You need vitamins to live. The question is, do you get enough in food? And I think the answer to that question is yes,” Dr Offit said.

“Then you look on the back (of product bottles) and you find that a number of these vitamins are contained in amounts that are much greater than the recommended daily allowance.

“Now there are studies done showing if you take a mega vitamin, you actually can hurt yourself.

“You actually can increase your risk of cancer, increase your risk of heart disease. I think few people know the risks they’re taking.”

The Frontline report, broadcast on Four Corners, also examined the science surrounding vitamin D, vitamin E and fish oil.

Fish oil has been widely taken as a supplement in the belief it could prevent heart attacks and cardiovascular disease.

But after compiling the best studies on fish oil from the world’s most prestigious scientific journals, epidemiologist Andrew Grey, from the University of Auckland, argued differently.

“I think for cardiovascular disease, one has to say there is no compelling evidence that taking fish oil protects against the first heart attack, or a second heart attack,” Dr Grey said.

“People who are advised to do that, or are doing it, are wasting their time and their money.”