Last reviewed by Faculty of Harvard Medical School on August 28, 2012
By Linda Antinoro, R.D., L.D.N., J.D., C.D.E.
Phytonutrients are powerful and healthy substances to include in your diet. While technically not "nutrients" (which include carbohydrates, protein, fat, vitamins and minerals, and which are deemed essential to life), there is growing evidence that phytonutrients play a crucial role in helping to maintain health and prevent a number of diseases, such as macular degeneration and some cancers. These protective compounds are part of an emerging area of nutritional science, with new compounds being continually discovered.
"Phyto" comes from the Greek word for "plant," and that's primarily where you can find phytonutrients in plant foods such as fruits, vegetables, whole grains, dried beans and nuts.
There are numerous classes of phytonutrients, which in turn contain hundreds of different phytonutrients within. It is estimated that upwards of 900 phytonutrients have been identified as components of food. Some of the more well-known phytonutrients are isoflavones (in soy); lignans (in flaxseed and whole grains); carotenoids, such as beta-carotene, lutein and lycopene (in brightly colored fruits and vegetables); and flavonoids (in red-blue tinted fruits). Below is an additional sampling from the plethora of phytonutrients:
Choosing colorful foods (M&Ms dont count) helps to ensure that you get as many protective phytonutrients as possible. Typically the deeper the color, the more phytonutrients present in the food. Notable exceptions are cauliflower, garlic and onions. They contain these healthful substances as well. When it comes to fruits and vegetables, think citrus and cruciferous. Examples are oranges, grapefruits, tangerines, broccoli, Brussels sprouts, cabbage, cauliflower and kale. These are especially packed with an array of phytonutrients.
While whole grains may not be as vivid as deep red, orange, yellow and dark-green produce, they dont lack in phytonutrients. Whole-grain breads, cereals, rice and pasta are excellent sources of lignans and saponins. Though darker grains can be whole-grains, color alone may not always be an accurate gauge. Some breads are simply darkened by molasses or other sweeteners.
It is best to check the ingredient label to determine if it is a whole grain. Aim for all the grain in the product to be 100-percent whole wheat or 100-percent whole grain. At the very least, the whole grain should be the first ingredient. Best breads, for example, are those in which all the flours listed are whole-grain varieties. Other whole-grain choices include: oatmeal, whole corn meal, whole-wheat bulgur, whole-wheat couscous, triticale, teff, kamut and spelt.
The burgeoning interest in phytonutrients has created a vast supply of supplemental products lining store shelves. A pill just cant do what diet can, however. For instance, in one study lutein was much more available to the body from the food source rather than the supplement version. It appears that other substances in the food enhance lutein uptake. This is probably the case for other phytonutrients as well. Reliance on plant-based foods better ensures diversity and synergy of the phytonutrients present. For example, a single serving of vegetables may provide more than 100 different phytonutrients. This crucial synergistic interaction is generally lost when you rely on only isolated substances in a pill. Attempting to single out one element is not a wise or prudent thing to do, since optimal and safe doses have yet to be established. Case in point is the past beta-carotene bust. Research in the 1990s showed that for some individuals, taking beta-carotene supplements was actually harmful.
To maximize your intake of these promising substances:
Linda Antinoro, R.D., L.D.N., J.D., C.D.E is a senior nutritionist at Brigham and Womens Hospital. She is also a certified diabetes educator. In addition to counseling ambulatory patients at the Nutrition Consultation Service, she serves as a group nutritionist/facilitator for the Womens Health Initiative, which is a landmark research study involving postmenopausal women.