By Russell H. Greenfield, MD Clinical Assistant Professor of Medicine UNC Chapel Hill School of Medicine
I want to believe that antioxidant supplements are good for me, for my family and for you. I have long been a believer, and maybe you have been, too. After all, we are long past the point of questioning whether vegetables and fruits are good for us – we accept that they are on the basis of remarkably consistent research results accumulated over decades that show how eating a variety of brightly colored produce on a daily basis helps reduce the risk for chronic illness such as heart disease, diabetes and even cancer. Our confidence in this concept is unshakable, even today.
Part of the reason that vegetables and fruits are believed to be so good for us, maybe even the primary reason, is that they contain important antioxidants. Our bodies need an adequate supply of antioxidants to limit the buildup of compounds called reactive oxygen species (ROS) that are normally produced as a byproduct of cellular energy production. ROS also accumulate when we are exposed to toxins such as tobacco smoke and radiation. When an excess amount of ROS exists, there is said to be a state of oxidative stress, a condition linked to the development of numerous health problems. It only makes sense then that adding more antioxidants to our systems should help lessen the chance for oxidative stress to occur and, by extension, help prevent illness.
Eating 5-9 servings of vegetables and fruits each day as is generally recommended can be hard. On the surface it would seem so much easier, even more efficient, to take high doses of the antioxidants found in produce in supplement form.
Linear thinking is comforting. To top it off, a large number of research trials suggest wide-ranging benefits from antioxidant supplementation. But more often than not, the human body does not behave in linear fashion and unintended consequences from what we assume to be healthy actions can occur.
A disturbing string of research results in recent years have suggested that high-dose antioxidant supplementation may have a dark side in select circumstances. At first, it was all too easy to dismiss these studies as outliers in the face of the overwhelming evidence of the benefits of antioxidant intake from food. Then studies were published strongly suggesting that high-dose supplementation with beta carotene, a type of provitamin A normally found in much lower concentrations in yellow/orange vegetables and fruits, increased the risk of cancer in people who smoke. More recent studies point to a heightened risk of prostate cancer among otherwise healthy men taking high-dose vitamin E, and to a possible association between high-dose selenium supplementation and an increased risk of skin cancer. The operative words are “high-dose” – not the naturally low concentrations found in food but the supernormal amounts present in many supplements, even some multivitamins.
ROS have long been portrayed as the enemy of good health but it now appears that we need them for the proper functioning of our immune systems, including the ability to rid ourselves of invading microbes and the rogue cells that, left to divide and multiply, can turn into cancer. We need the proper balance of ROS and antioxidants to maintain the body’s defenses and innate healing systems. And it is possible that in our desire to optimize health through the ingestion of high-dose antioxidant supplements, we may be doing more harm than good.
The topic of antioxidants is complex and the jury is still out, but it seems the time is right for a collective deep breath to reconsider our need for high-dose antioxidant supplementation. Another concern is when the umbrella term “antioxidants” is applied to a host of compounds that are not one in the same – they function in different capacities, might enhance our health or protect us from harm in some circumstances, and in high doses could paradoxically lead to harm in other situations. We need to better understand which situation is which.
The antioxidants found in vegetables and fruit, however, exist in naturally low concentrations alongside other nutrients that can also promote good health. Even those who do their best to follow a healthy diet could likely benefit from taking a multivitamin as insurance against nutritional gaps in their diet, but a basic multivitamin containing a reasonable range and amount of nutrients should be adequate. Others may need additional targeted supplementation based on their unique health circumstances, but the focus for most of us should be on dietary sources of antioxidants until we have clarity regarding safety.
My confidence in antioxidants has been shaken by the recent data calling high-dose supplementation into question, and they should give you pause as well. But keep in mind that it is the pills that have many experts concerned, not the produce.