Antioxidants, produced by the body and obtained through foods, are a critical part of the body’s powerful defense system. To understand them, it’s important to know something about oxidation. In cells, oxygen is constantly involved in chemical reactions in which electrons (charged atomic particles) are shifted around. To generate energy, our cells remove electrons from sugars, fatty acids and amino acids and add them to other molecules, especially oxygen. This creates highly reactive, unstable particles known as free radicals, which combine quickly with other elements.
Free radicals are generated during normal cellular processes, but also when we are exposed to ultraviolet rays, air pollution, intense physical exertion and tobacco smoke, for example. Antioxidants help “spare” our cells by becoming oxidized themselves. For the most part, our antioxidant reserves can keep errant oxidation under control. But over time, cellular damage can result if we are exposed to more oxidative stress than the body can handle.
According to current thinking, oxidative stress may play a role in aging and chronic illnesses, such as heart disease, cancer, Alzheimer’s, Parkinson’s and cataracts. For instance, oxidation of low-density lipoprotein (LDL) makes these cholesterol packages more damaging to blood vessel walls, while oxidation of DNA may contribute to cancer.
On the other hand, free radicals sometimes come in handy. For example, certain immune cells, including some types of white blood cells, manufacture them and use them as weapons against infectious agents.
Are more antioxidants better?
There are thousands of different kinds of antioxidants in fruits, vegetables and whole grains, as well as in coffee, tea, chocolate and wine, which operate in different parts of cells and participate in different chemical reactions in the body. As a first line of defense, some antioxidants suppress formation of free radicals, while others “scavenge” to remove them before they do damage, or work to repair damage once it has been done. Some familiar nutrients that act as antioxidants are vitamins C and E, beta carotene, and selenium; many others are phytochemicals, such as quercetin and other flavonoids; still others are enzymes, such as glutathione peroxidase and superoxide dismutase.
You might reasonably think that getting more antioxidants is better. At least marketers pitching “antioxidant-rich” foods and supplements want you to believe this. But no one knows if this will really combat chronic conditions—or how much you need just to stay healthy. It’s not even proven that oxidative stress is a primary factor in the development of disease or whether it is secondary to other factors. It’s possible that the disease-lowering benefits of plant foods seen in many studies are not due to the antioxidant properties of their constituents but rather to something else.
For example, in contrast to previous research, a 2013 study published in Neurology of more than 5,000 people found that those who consumed more antioxidants in their diets did not have a lower risk of stroke or dementia.
What’s more, research has shown that high levels of some antioxidants can have adverse effects (high-dose beta carotene supplements increase lung cancer risk in smokers, for example). Under certain circumstances, antioxidants can turn into pro-oxidants and promote free radical formation. It’s a delicate balance. That’s why you should steer clear of supplements and get your antioxidants instead from whole foods, which have combinations of antioxidants that work together as a team to combat oxidation reactions.
Originally published October 2012. Updated January 2014.