October 12, 2011 | 3 minute read

When studies are continuously finding evidence of how a vitamin, mineral or phytonutrient can help our health, it’s tempting to assume more is better. But no, suggests a growing body of evidence. The past few days have seen a flurry of studies on the possible harms linked to supplements, with one of the largest focused on cancer.

The new cancer-supplement study looked at vitamin E and selenium’s link to prostate cancer.

Years ago, researchers hypothesized that these two supplements would protect against prostate cancer — and other diseases. A large study of almost 35,000 men turned up no reduction in risk but a hint of an increase in risk with vitamin E. That study began a decade ago and the results were published in 2008.

This new study continued to follow the 35,000 men though July of this year. The men had taken daily supplements for three years beginning in 2001. They were randomly assigned to take either vitamin E, selenium, both, or a placebo. Compared to those who had taken a placebo, the men who had taken vitamin E had a 17 percent increased risk of developing prostate cancer. No link was found with selenium.

The findings suggest the health effects can continue even after men stop taking the supplement.

The study was published in JAMA; here’s the abstract.

Another large new study focused on older women. Here, researchers found that several commonly-used supplements linked to an earlier death.

The study looked at dietary supplement use among almost 39,000 women — the women reported what supplements they took. After tracking the women for 22 years, researchers found that women who took multivitamins, vitamin B6, folic acid, iron, magnesium, zinc and copper were more likely to die during the study period compared to those who did not take the supplements. The association was strongest for iron supplements. Also, calcium supplements appeared to reduce risk of earlier death.

And in yet more new research, a study found that giving patients with lung problems omega-3 fatty acids and other antioxidant supplements may do more harm then good. This study lasted about a month.

There are certainly individuals who need supplements and those who are unsure should check with their doctor.

AICR recommends not to use supplements to lower cancer risk. For overall lower cancer risk, AICRs expert report and its updates clearly show that  a healthy diet — filled with foods containing vitamins, minerals, and phytochemicals —  physical activity, and a healthy weight are the way to go.