Supplements can be important if you are deficient in a particular nutrient
When we’re continually presented with information about how vitamins help prevent disease it’s understandable that they’ve attained an almost magical dietary status. One vitamin apparently prevents heart disease, another may halt the progression of dementia but these research studies may not tell the whole story. More often than not a vitamin is essential to prevent or slow the progression of disease, but most of us aren’t so deficient in that vitamin to make taking a supplement worthwhile.
Recently researchers from the University of California decided to examine the relationship between dietary supplements and cancer risk. We’ve all read research about how anti-oxidants, folic acid, vitamin D and other nutrients can help fight the spread of cancer. The science is solid but the observational studies that indicate these links between nutrients and a lower risk of certain cancers are based on people who have diets high in fruit and vegetables, not on those taking supplements. When the researchers looked at data relating to anti-oxidants and cancer risk, for example, they found no clear evidence that supplements had a significant effect. They even warn that taking a supplement could have a negative impact. “Supplementation by exogenous [ie not directly from your diet] antioxidants may well be a two-edged sword; these compounds could serve as pro-oxidants [chemicals that cause oxidative stress] or interfere with any of a number of protective processes,” they say.
The researchers warn against taking dietary supplements for cancer prevention unless advised to do so by your doctor. If, for example, you had been found to be deficient in a particular nutrient and your diet isn’t providing you with enough, it could be extremely important for you to take a supplement. "While most people get enough vitamins through their diet, some nutrients are harder to keep at optimum levels – vitamin D for example," says registered nutritionist Dr Carina Norris. "Also, some people have increased requirements for certain micronutrients (vitamins and minerals), such as pregnant and breastfeeding women, and athletes. And over-65s are recommended to take a 10ug vitamin D supplement, as it's harder for your body to absorb this vitamin than when you're younger. Finally, if you're a vegetarian or vegan, or follow a special diet, for example for coeliac disease, you might find it harder to get enough of particular nutrients from your food, and in this case a supplement could help."
The study was published in the Journal of the National Cancer Institute.