The buzz about vitamins and minerals has lately been re-placed by the buzz about phytochemicals. Phytochemicals are non nutritive substances in plants. Thousands exist, and every plant food contains them. What can they do for us? Knowing what they do for plants may shed some light on the question.
Some phytochemicals protect plants from invaders of all kinds. Predators like leaf-munching insects and animals, bacteria, viruses, and fungi can all be put off by the action of phytochemicals, whether that action comes in the form of an unpleasant taste, a repugnant smell, a startling color, or a poisonous effect. Also, the antioxidant action of certain phytochemicals protects plants against an oxygen-rich environment (remember, plants “breathe” carbon dioxide, not oxygen).
What happens when we consume phytochemical-laden vegetables? Only some of the thousands of phytochemicals have been found (to date) to have an effect on the human body, but these few apparently have enough of an effect to make a difference. (The thousands of phytochemicals as yet uninvestigated represent great research potential. The field of phytochemical research is still in its infancy and may well reveal many other benefits to human health.)
When humans consume certain phytochemicals, we appear to enjoy protective effects similar to those plants receive. Phytochemicals, in many ways, seem to defend the human body against free radical damage (see below) and age-related degeneration, not to mention viruses, bacteria, and fungi.
The phytochemical-cancer connection has been widely researched, and results suggest that phytochemicals may disrupt cancer in more ways than one. Phytochemicals may protect DNA or repair damaged DNA, helping to prevent cancer from developing. They may prevent cancerous cells from multiplying and/or spreading through the body. Phytochemicals may help the body to help itself, giving carcinogen-blocking enzymes a boost.
Much cancer research has focused more generally on vegetable and fruit consumption, which implicates phytochemicals by association. Raw and green vegetable consumption appears to reduce the risk of stomach, lung, mouth, esophageal, colon, rectal, breast, and bladder cancers. Research in other areas has supported general vegetable and fruit consumption as well, suggesting that a diet rich in vegetables and fruits may lower the risk of heart disease and stroke, and boost the effectiveness of the immune system. Some of the phytochemicals more relevant to humans include the allium compounds (in onions and garlic); carotenoids (in dark green and deep orange vegetables), including lycopene (particularly rich in tomatoes and red grapefruit); glucosinolates (in cruciferous vegetables such as broccoli); and flavonoids (in many foods including tomatoes).
Allium compounds, also called organosulfides, exist in onions, garlic, leeks, shallots, and chives. These compounds give these vegetables their unique smell and pungent taste. They also appear to increase the effectiveness of the body’s own cancer-fighting enzymes, halt the production of nitrates into carcinogens, lower cholesterol and blood pressure, and reduce the tendency of the blood to clot. Allium compounds appear to be most potent in raw vegetables, and may be de-stroyed by the cooking process.
Carotenoids are potent antioxidant phytochemicals that fight free-radical cellular damage in the body, possibly guarding against a wide range of chronic diseases. They are the substances in plants that provide their bright red, orange, or deep yellow colors. More than six hundred carotenoids are known, but fewer than fifty have been found to be active in the human body. Examples of beneficial carotenoids found in vegetables are as follows:
Alpha-carotene is a substance that the body converts to vitamin A. Research has linked alpha-carotene to a reduced risk of lung cancer. Carrots are full of it.Beta-carotene (as discussed previously) is another substance the body converts to vitamin A. Well publicized for its anticancer benefits, beta-carotene may also prevent cataracts, slow the progression of heart disease, and boost the immune system. Good sources include most red, orange, and yellow fruits and vegetables, as well as dark, leafy greens.Gamma-carotene is just starting to get attention as an anticancer agent, and research with gamma-carotene is just beginning. The best sources of gamma-carotene are tomatoes and apricots. The above three carotenoids—alpha-carotene, beta-carotene, and gamma-carotene, are thought to be powerful allies against cancer.Lycopene, the carotenoid that gives tomatoes, watermelon, and red grapefruit their rosy hues, has been linked to decreased risk of prostate and breast cancer, and may also protect skin from the damaging effects of ultraviolet radiation.·Lutein and zeaxanthin have been found in the eye and may help prevent age-related macular degeneration by protecting the retina from potentially harmful light exposure, and also by neutralizing the effects of free radicals formed by the negative effects of sunlight on the retina. One study demonstrated a lower incidence of macular degeneration in people who ate increased amounts of spinach and collard greens, both of which contain lutein and zeaxanthin.
Flavonoids include a huge class of compounds (more than four thousand) called phenolic compounds and are found in plants of all types. Flavonoids give plants color, have anti-fungal properties, slow or prevent damaging oxidation, lower cholesterol, prevent the clotting of blood, and protect cells from carcinogens. The most studied flavonoid is quercetin, abundant in onions, wine, and tea. Unlike the allium compounds, quercetin remains intact and available after cooking, and may have an anticancer effect in the body.
Other flavonoids available to the human body from food include isoflavones, found primarily in soybeans (although soybeans aren’t part of a traditional Mediterranean diet, they should be consumed in the Mediterranean spirit of eating). Isoflavones are thought to have an estrogenlike effect on the body, possibly guarding against hormone-related cancers like breast cancer. Catechins are another type of flavonoid, which may be responsible for the anticancer properties apparently inherent in green tea. Flavonoids may also be a factor in the heart-protective benefits of red wine.
One of the most intriguing qualities of phytochemicals, and the most convincing argument for receiving your phytochemicals from food rather than from supplements, is their synergistic nature. Science has only begun to understand the effects of individual phytochemicals on the body. The combined nature of phytochemical interactions in the body—of eating a whole plant, rather than a supplement of artificially produced or isolated single compound—is still largely a matter of speculation, but many experts assert that eating plant foods in a form close to their original state (minimally processed) is the best way to ensure receiving the health benefits, both those understood and those not yet understood.
Even if the term phytochemical was unknown in the Mediterranean during the time when the traditional Mediterranean diet was the pervasive way of eating, phytochemical benefits were at a premium in this diet of locally grown, seasonally consumed, minimally processed plant foods. Understanding the nature of phytochemicals provides one more good reason to return to more traditional dietary practices.
