Government regulators and scientific experts need to do a better job providing clear guidance on the health benefits, as well as the risks, of certain dietary supplements.
In a commentary published in the Journal of the National Cancer Institute, health experts with the University of California-San Diego Moores Cancer Center and colleagues noted evidence from animal, laboratory and observational studies in people has suggested taking certain dietary supplements may lower a person’s cancer risk.
But others have also shown that some supplements have no health benefit and others may actually increase risks.
To examine the connection between dietary supplements and cancer risks and benefits, lead researcher Maria Elena Martinez and colleagues analyzed studies of several supplements, including anti-oxidants, folic acid, vitamin D, and calcium. Several found that diets high in fruits and vegetables were associated with lower risk of certain cancers, including respiratory and gastrointestinal, likely because of antioxidants they contain.
But what is unclear is whether supplements are as effective as diet in delivering those nutrients and vitamins, researchers noted. In addition, some antioxidant studies have suggested supplements may increase cancer risks at high doses.
The researchers said more clinical trials — spanning many years and involving more patients — are needed to verify the effect of nutritional supplements.
They noted the nation’s supplements industry reports estimated annual sales of $30 billion.