A third study, which controversially found the often-disparaged practice of chelation therapy (ridding the body of heavy metals to treat conditions such as autism) may have some benefit, found multivitamins had no discernible effect on heart disease.
These are large-scale trials done by reputable scientists. They may not slow an industry worth more than US$11 billion ($12.7 billion) in America, or deter the one in two Americans who take vitamins and minerals (let alone the rest of the global population). But these damning studies and the thundering editorials they inspired give sceptics more fuel for their attacks on the sector's often over-the-top claims.
Despite this apparent knockout blow, conventional medical science keeps trying to prove the efficacy or otherwise of isolated vitamins and minerals, unshackled from their original natural source. Some of these have made it into the general shopping basket: even if we don't pop multivitamins like we do M&Ms, we might drop by the health shop for folic acid when we are pregnant, iron tablets when we are tired, and St John's Wort when we feel strung out - all on a doctor's recommendation.
I myself have relatives who swear on their lives that they feel much better thanks to glucosamine supplements, "women's" multivitamins and even that ZB favourite, the magnetic underlay, despite being otherwise sensible souls.
Some scoff, but science continues to take notice. Boston scientists are undertaking a study to see if the nutrients in everybody's favourite "superfood" - dark chocolate - can be taken in capsule form to help reduce the chances of heart attacks and strokes. A second part of the study will take a crack at multivitamins, this time to test whether they lower cancer risk in the general population.
The researchers warn that trying to steal a march on science and hoovering up chocolate bars in a vain attempt to circumvent cancer is unlikely to work. But whether the results are conclusive or not, one thing we do know is that the Mars company - maker of Snickers and Mars bars - should be a winner either way. The company is one of the funders of the study, with the US National Heart, Lung and Blood Institute, and has already patented a way of extracting the magic ingredient, flavanols, from the cocoa bean so it can be sold in capsule form. It already does so but this study may give the trade further legitimacy.
With luck, the flavanol capsule might even help the company undo some of the damage it has done to the world's arteries over decades of successful commerce.
