New Review: Are Too Many Antioxidants Bad for the Body?

July 26, 2011

"This may mean reexamining the health implications of adding large amounts of antioxidants to foods," the researchers wrote.

A new review on antioxidants published in the Journal of Agricultural and Food Chemistry questions whether reducing oxidative stress too much, through the use of antioxidants, may in fact be harmful to the body.

The study does not relate to antioxidants added to foods as preservatives.

Researchers from the USDA and multiple U.S. universities looked at recent  published science  on antioxidants and reactive oxygen species (ROS), the molecules antioxidants are intended to remove.

While some antioxidants are capable of inhibiting oxidative stress---a condition linked to chronic disease---recent studies have suggested potentially harm from antioxidant supplementation. One example cited by the researchers is a 2005 study in which vitamin E supplementation was linked to increased risk of all-cause mortality.

Aside from the notion that antioxidant supplementation may not always be beneficial to the human body, the researchers also state that ROS "may be essential, because at low levels ROS may function to trigger antioxidant responses."

In fact, previous research has shown that exercise and exercise-generated ROS may be vital to numerous biological mechanisms, including the expression of immune-response proteins like chemokines and cytokines.

"Available scientific evidence does not necessarily support the assumption that all ROS present health risks and should be reduced to as low level as possible," wrote lead author and USDA researcher John W. Finley. "This has implications for the fortification of foods with antioxidants, as well as for the consumption of many dietary supplements. A corollary is that supplemental doses of some antioxidants may block beneficial actions of other physiological processes, and at high doses some antioxidants may be toxic."

The conclusions drawn up in this study have something to say about the widespread marketing use of the word antioxidants, a term which is now forbidden from products marketed in the European Union.

Nutritional Outlook thanks Harry Rice, PhD, for the tip.