DEAR DR. BLONZ: I read that orange-, pink- or red-fleshed fruits and vegetables contain beta carotene, but I wonder just what it is and how it got its name. I also recall you mentioning another antioxidant category with which I am completely unfamiliar: the "flavonoids." What are they, where did they get their name, and what foods contain them? -- S.H., Poway, California
DEAR S.H.: The naming of chemical compounds is a recipe of science and folklore. The root, or family name, of compounds is often taken from the name of the plant in which it was first discovered. From that point on, naming variations tend to be based on how the structure differs from the parent compound.
In the case of beta carotene, the parent compounds are the carotenes -- a group of yellow-red pigments widely distributed in plants, but most notably present in carrots (hence the name). The "beta" is the Greek letter designation for the fact that a key structure is in the second, or beta, position. (Alpha and gamma carotene have their identifying structures in the first and third positions, respectively.)
What's unique about these colorful compounds is that oxygen tends to combine with them in preference to other compounds and bodily tissues. The fact that beta carotene is a more attractive target means that its presence can "spare" other bodily substances and tissues from being oxidized, and possibly damaged in the process. That is the essence of what it takes to be called an antioxidant.
Please understand that oxidation is not a bad thing: It is entirely essential for life, and is used to release the energy from the foods we eat. After all, we breathe to get oxygen into our body. But when oxidation takes place at the wrong place and at the wrong time, it can lead to tissue damage that causes aging and can increase our risk of heart disease, cancer, certain forms of arthritis and a host of other ailments. A diet that is rich in whole-food antioxidants can help stave off unwanted damage due to errant oxidation. Nutrients that function as antioxidants include vitamin C, beta carotene, vitamin E and selenium. And manganese, copper and zinc are constituents of superoxide dismutase, an enzyme that plays an important role in the body's antioxidant defense system.
The flavonoids are compounds that contain a particular structure called a flavone. They, like the carotenes, are color compounds and strong antioxidants. The flavonoids are widely distributed in plants, and include such compounds as quercetin (found in onions), rutin (buckwheat), the bioflavonoids (citrus fruits) and the isoflavones (soybeans).
Through the discovery of antioxidant compounds and how they work, science has provided a detailed explanation of yet another reason why whole foods are so good for us.
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