The Overselling of Antioxidants

Why the current craze over antioxidant-rich foods shows a serious misunderstanding of how nutrients actually work

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Paul Sutherland / National Geographic / Getty Images

We want to be healthy. We diligently strive to control our health in every way we possibly can. We have learned that we should eat low-fat, high fiber diets with lots of antioxidant-rich vegetables and fruits. We load up on salmon and blueberries and drink green tea because we are told they will prevent cancer, heart disease or Alzheimer’s. We are drawn, like moths to a flame, to new lines of yogurt, packaged cereal, even blue corn tortilla chips because they boast high levels of antioxidants. In a world where so many aspects of our environment are out of our control, we find comfort in the world of food; we can say no to French fries and Twinkies, drink some pomegranate juice and feel good about ourselves.

But here’s the deal. Scientists studying the interior life of cells know that metabolic pathways can be driven by the presence or absence within the cell of key compounds, such as nutrients. We, however, will read a provocative nutrition headline and make the jump — out of context — that in consuming those extra nutrients we are flipping cellular switches as in a physiological game that score us extra points and prolong our life. For example, the B vitamins riboflavin and niacin are critical to every chemical step in releasing the energy potential in food. But consuming a surplus of these vitamins cannot drive metabolism and give you more energy. The only people who will benefit from an increase in nutrients in this way are those who are actually deficient in them.

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An excellent case study in the ways we misunderstand how nutrients work is the current craze over antioxidants. For some decades, science has known that many chronic diseases, including heart disease, stroke, diabetes, Alzheimer’s, Parkinson’s and cataracts, among others, are associated with damage caused by very destructive compounds called free radicals. Free radicals are extremely unstable and avidly seek to stabilize themselves by oxidizing neighboring cell components (proteins, lipids, DNA,) in turn causing these chemicals to become damaged. Free radicals are everywhere — they occur naturally whenever we use oxygen — and are also triggered by environmental ills, such as air pollution, radiation, ozone and tobacco smoke, but they’re not always bad. Their wrecking ball qualities are often needed by cells and tissues to remove what is no longer useful and make way for the new.

Within our cells, we have a highly effective system that uses antioxidant compounds to control and counteract free radical damage. There is not just one antioxidant, there is a dizzying array of them at work in living organisms. Antioxidants are not interchangeable — one cannot step in and function in place of another — so for every specific free radical reaction, a specific antioxidant is required. Some antioxidants are essential nutrients (notably vitamin C, vitamin E, beta-carotene, selenium). A great many are phytochemicals, chemical components of plants, many of which also function as color pigments (carotenoids, anthocyanins, lycopene, lutein, polyphenols, flavonoids.) Antioxidant chemicals are even added to food products to prevent color changes and increase shelf life (BHA, BHT, citric acid.)

All manner of foods have been shown to have high antioxidant capacity in the artificial environment of a test tube, which is to say, outside of a living organism. But the relationship between this antioxidant capacity and any actual health benefits in our bodies cannot be corroborated because of a myriad of confounding factors, from digestion and absorption into the blood and cells, to interactions with other cellular chemicals or events. Even Barry Halliwell, a pioneer in antioxidant research, has concluded in the American Journal of Clinical Nutrition that “despite the enormous interest in [antioxidants] as potential protective agents against the development of human disease, the real contributions of such compounds to health maintenance and the mechanisms through which they act are still unclear.”

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There is no doubt about the health benefits of eating vegetables and fruits, of all types. Vegetables and fruits are nutrient dense, high in fiber and tend to displace other less healthy foods and eating them is undeniably linked to a reduced risk of disease, although we cannot yet describe the chemical basis for these correlations. So by all means, reach for the blueberries, but don’t do it in the name of antioxidants — or any other specific nutrient, for that matter.