There have been question marks about taking supplements to prevent health problems ever since research into beta-carotene in the 1990s dropped a bombshell. Back then beta-carotene, the red-orange pigment that colours plant foods like mango and carrots, was a rock star of the nutrient world, with studies suggesting that a beta-carotene-rich diet reduced lung cancer risk. But research giving beta carotene to smokers in the form of supplements, not food, delivered a nasty shock – these supplements appeared to increase lung cancer risk, not reduce it.
There was another surprise last year when US researchers linked a high intake of fish oil from both fish and fish oil supplements to a higher risk of prostate cancer. Until then fish oil had one of the shiniest haloes of any supplement on the shelf – along with evidence that it could help protect the heart and reduce inflammation in rheumatoid arthritis, it was considered generally safe.