Over the past several years, attaching the word antioxidant to any product has become a buzzword meaning “it’s good for you, no matter what the problem,” much like the words natural or organic in previous decades. What exactly are antioxidants, and what do they do for us? To answer that question, we have to understand a little basic biochemistry.
The Old Testament proclaims quite accurately that “the life of a creature is in the blood” (Leviticus 17:11). Blood off course carries oxygen, and any tissue that doesn’t get it for more than a few minutes is doomed. But while a steady supply of oxygen is necessary for basic metabolic operations in every cell, oxygen’s reactions with a variety of compounds generate free radicals: highly unstable molecules containing one or more unpaired electrons, which are definitely not content to live a biochemical “single life.” Instead, free radicals actively seek out other molecules from which they can swipe an electron and regain their stability. Those molecules may in turn become free radicals, stealing electrons from their neighbors and turning them into free radicals, and so on, in a literal chain reaction reminiscent of some horror-movie scenario.
Unfortunately, molecules that have lost an electron to a free radical may be altered or even damaged in ways that can affect their function. Free radicals inflict their electron thievery on all kinds of important compounds: fatty acids, proteins, and even DNA, the complex blueprint containing the genetic information needed to make proteins and new cells. Free radicals no only arise from ongoing reactions involving oxygen within our body, but from other sources as well: polluted air, cigarette smoke, even the food we eat and water we drink.
The totality of this nonstop biochemical onslaught by free radicals is often called oxidative stress, and fortunately our bodies are designed to carry out ongoing repair operations to counter it. Furthermore, a number of enzymes in-activate free radicals. With the passage of time, however, these wondrous mechanisms may become less effective or may simply be overwhelmed. Current research has implicated free radical damage in many of our modern plagues: cardiovascular disease (heart attack and stroke), cancer, eye disorders, and arthritis, not to mention the aging process itself.
Coming to the aid of our cells and biochemical repair mechanisms are the antioxidants in our foods (and, for some, in supplements). These include the antioxidant vitamin C and E and a host of phytochemicals (compounds that are found in plants), including the carotenoid compounds (of which the best known are beta-carotene and lycopene), phytoestrogens, flavonoids, phenols, and polyphenols. Some of these, such as vitamin C and E, work by sacrificially donating an electron to a free radical, thus stabilizing it and preventing it from grabbing an electron from another molecule. What makes these types of antioxidants particularly virtuous is that they remain stable after giving away the coveted electron. Other compounds join in the battle by stimulating the body’s own enzymes that are antioxidants or that repair free radical damage. In addition, certain minerals—notably selenium, manganese, copper, and zinc—while not antioxidants themselves, are necessary for the proper function of antioxidant enzymes.
A growing body of research suggests or demonstrates the benefits of foods containing various antioxidants:
- Laboratory experiments show that various antioxidants can prevent the oxidation of LDL (bad) cholesterol by free radicals, an event widely considered to be a critical step in the development of diseased arteries.
- Large population studies indicate that those whose diets are rich in antioxidants, and to some degree those taking vitamin E supplements, have lower rates of coronary artery disease.
- Similarly, research suggest a link between diets abundant in fruits and vegetables in general, and vitamin C in particular, and lower rates of a number of cancers, including those in the mouth, larynx, esophagus, stomach, pancreas, colon and rectum, lungs, breast, and cervix.
- A number of studies suggest that antioxidants in the diet—especially vitamin C, as well as the carotenoids lutein and zeaxanthin—may reduce the risk of both cataracts and macular degeneration, the leading causes of visual problems among the elderly.
If a number of antioxidants in food have been identified and associated with health benefits, then taking generous amounts of them in supplements should seriously improve one’s health and well-being—right? For years, a multi-billion-dollar supplement industry has been shouting “Amen!” all the way to the bank, but hard rock data to back its enthusiastic claims has been difficult to come by. One notorious example: Beta-carotene, an antioxidant found in deeply pigmented fruits and vegetables, appear to be a prime candidate for supplement superstardom. But in four large randomized controlled studies comparing the health of people given an identical-appearing placebo, the supplement group struck out. Only one study involving a concoction of antioxidants given to a poorly nourished population in rural China, showed some benefit. One study of U.S. physicians found no difference between those who took the supplement and those who didn’t. And two large studies involving smokers showed an increased risk of lung cancer among those taking the beta-carotene supplement.
Indeed, this type of discouraging scenario—where a concentrated supplement of a specific nutrient in a controlled experiment doesn’t seem to work as well as expected—has been rather common. There are several important reasons why this should not come as a big surprise:
- Diseases such as cancer and cardiovascular disease aren’t like scurvy, where a single missing ingredient added to the diet will produce dramatic results. Their causes and prevention involve complex interactions of many variables.
- Similarly, hundreds of antioxidants and antioxidant-enhancing substances work in a variety of ways in different environments within the body, and in turn they interact with one another in complex ways. Attempting to isolate one substance that would prove to be the key antioxidant may prove to be a lost cause.
- Even in well-designed experiments involving supplements, it can be difficult to control the effects of individual dietary choices on a long-term basis. Furthermore, even an experiment lasting for several years may not last long enough to pick up very subtle effect from a supplement.
- Even with antioxidants, it is possible to take too much. For example, with niacin, when large amounts are packed into a pill, it acts as a drug with very different side effects. Some antioxidants perform their appointed tasks when consumed in food, but when they are taken at the much larger dose found in a supplement, they may have the opposite effect, acting as a pro-oxidant—substances that include oxidative stress rather than protect against it.
There is an important take-home lesson here, one that we cannot state often enough: While vitamins and other supplements can be beneficial (and for some, lifesaving), they are not a substitute for wise food choices. As clever as we might become though research and development of nutritional products, no one can duplicate the rich and complex blend of nutrients and phytochemicals in food, especially fruits and vegetables. Remember, the only truly natural products are found in the produce section of the supermarkets. An important corollary: Supplements cannot compensate for a lifetime of poor lifestyle choices (smoking, overeating, abusing drugs and alcohol, refusing to exercise, and so forth). You can’t fill your gas tank with turpentine and then expect the fancy additive to take care of your engine.