Why Are Phytochemicals Better Found in Food Than Supplements?

by Bridget Coila

Plant compounds called phytochemicals serve a protective function for plants, but can also affect the bodies of people who consume those plants. Some of these phytochemicals seem to offer protection against diseases such as cancer, cardiovascular disease and neurodegenerative diseases. As scientists discover more and more valuable health benefits of phytochemicals, supplement manufacturers race to put them in pill form and offer them for sale. But phytochemicals removed from the plant foods where they originated don't seem to work as well as eating the whole food.


A wide variety of foods carry phytochemical components, including fruits, vegetables, nuts, seeds, whole grains, legumes and soy products. Some of these have been widely researched, while others are not yet well understood. Some well-known phytochemicals that are currently under study include soy isoflavones, resveratrol in red wine, sulfurous compounds in garlic and onions, and flavonoids and carotenoids in fruits and vegetables.


Whole foods provide more than just a single phytochemical, while supplements typically contain only one type. In addition, whole foods have vitamins and minerals that a phytochemical supplement lacks. Fiber is another beneficial component found in whole foods that isn't present in supplements. By eating whole foods, your body can take advantage of all the nutrients provided and boost health throughout your body, not just in the area targeted by that phytochemical.


The complex mixture of compounds in plants often work together in ways that are not fully understood. Because supplements separate out these beneficial components from other chemicals in the food, this can reduce or change the way a specific phytochemical works in the body. For example, flavonoids and carotenoids work better when they are in the same food than when taken separately as supplements. A study conducted by the Department of Food Science at Cornell University in Ithaca, New York, which was published in December 2004 in the "Journal of Nutrition," found that there are thousands of phytochemicals in any given fruit or vegetable and that these compounds work together in ways that are not possible to replicate using supplements.


Consuming phytochemicals in whole food form may be safer than taking supplements. The doses supplied by supplements are typically much higher than what is found in food, increasing the risk of toxicity. Few studies have been done on megadoses of phytochemicals in humans, so it is possible that these compounds could be harmful when taken in large amounts. The phytochemicals in foods are perfectly balanced with other nutrients and compounds in the plant and have an unsurpassed safety record of having been eaten by millions of people worldwide with few, if any, documented side effects.

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