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United States Department of Agriculture

Agricultural Research Service

The Power of Produce!
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Fariba K. Roughead

From A to Zinc, vitamin and minerals like vitamin D, vitamin C, iron and calcium are household terms. We all know that to have a healthy diet we should consume adequate amounts of these nutrients. But what about isothiocynates, terpenes, indoles, flavonoids, polyphenols, sulfides, etc? Although they sound like the ingredients on your shampoo bottle, these strange sounding compounds, collectively called phytochemicals, are the newest arrival in the field of nutrition. Phytochemicals are found in fruits, vegetables, grains and other plant foods. For example, isothiocynates, flavonoids and indoles are found in cruciferous vegetables like broccoli, brussel sprouts, cabbage and cauliflower. Polyphenols are found in tea and terpenes are in citrus fruits and the oil from caraway seeds. Sulfides are found in garlic and onions.

These naturally occurring compounds may be potent inhibitors of certain cancers and have many other beneficial effects on the body. They seem to perform these beneficial roles by blocking or suppressing the action of cancer-causing agents on tissues. These exciting discoveries have led to a flurry of scientific research focused on learning more about the "power of produce."

Unfortunately, while the knowledge about these compounds is still in its infancy, various phytonutrient supplements have already hit the market. In other words, the technology is way ahead of the science. We can put them into a pill, but we don't have a clue as to how much and in what combination they impart their health-giving effects. In fact, some phytochemicals are quite toxic when intakes are too high. In small amounts, as present in our food supply, they may keep our immune system Awarmed-up@ and on the alert for infectious agents. Another caveat is that while a phytonutrient may combat one disease, it could have adverse effects on other aspects of health. For example, licorice, a plant root, has been used for treatment of peptic ulcer but can cause high blood pressure.

In addition to safety issues, there is the possibility that phytochemicals interact with essential nutrients--vitamins and minerals--in ways yet to be defined. For example, in a recent study at the Grand Forks Human Nutrition Research Center, my colleague Janet Hunt found that higher intakes of phytic acid, a phytonutrient, decreased the absorption of iron in young women.

The tenets of a good diet are adequacy, balance, calorie control, moderation and variety. Although taking supplements is sometimes advisable, such as taking extra iron to treat anemia, taking unnecessary supplements not only gives us a false sense of security about our diet but also can perturb the balance of nutrients. And it's hard on the pocket book, too! So while science attempts to define what our body does with the food we eat, the safest route is to follow the USDA Food Pyramid by eating plenty of fruits, vegetables, and grains.

Last Modified: 4/4/2007
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