Abusing dietary supplements could increase risk of cancer
Nearly one in two Americans and one in four Frenchwomen use dietary supplements today. And yet, according to this study, exceeding the daily recommended dose increases the risk of developing cancer.
Dietary supplements have developed and diversified considerably in recent years. Used to fight fatigue or stimulate memory, to ready skin for sun or boost the immune system, they are essentially made up of vitamins, minerals, trace elements, proteins, fatty and amino acids, plants (or plant preparations) and excipients.
Dietary supplements: a real social phenomenon
According to the latest Nutrinet health study by the French Agency for Food, Environmental and Occupational Health & Safety (ANSES), more than 25% of Frenchwomen and 15% of Frenchmen use them regularly. One in ten children also take some at least once a year.
In the US, where the phenomenon is similar and spreading, Tim Byers, an expert in cancer prevention and a scientist at the University of Colorado, has led a group study on the subject for more than 20 years.
His conclusions were just presented at the American Association for Cancer Research's annual conference, where he showed how these products, if taken in excess of their daily recommended dose, increase the risk of cancer.
Tested on animals, then people
The study, which began 20 years ago, was based on the observation that trace elements, fibers and nutrients present in fruits and vegetables protected from cancer if they were consumed regularly. Tim Byers and his team then wanted to know if that was also the case with dietary supplements that contained similar substances.
"When we first tested dietary supplements in animal models we found that the results were promising," says the author of the study. Once the scientists started testing on humans, "We found that the supplements were actually not beneficial for their health."
Over the course of several years, thousands of volunteers consumed dietary supplements while others were taking placebos. The team led several random clinical trials in Finland and the USA.
At the conclusion of these trials, the scientists observed that beta-carotene, an antioxidant used in these products, increased the risk of lung cancer by 18% (in Finland) and by 28% (in the USA).
Byers also refers to other studies in the same vein that indicate that vitamin E increases the chance of prostate cancer by 17% while selenium raised the risk of squamous cell skin cancer by 25%.
Only excessive consumption can be dangerous
Byers concludes that people who take more dietary supplements than they need to tend to run a higher risk of cancer, though he remains reassuring, adding that "This is not to say that people need to be afraid of taking vitamins and minerals. If taken at the correct dosage multivitamins can be good for you. But there is no substitute for good food."
Link to the study: www.ncbi.nlm.nih.gov/pmc/articles/PMC3352833
