Phytonutrients are disease-fighting molecules found in plants. In humans, phytonutrients interact with our DNA to turn on health enhancing genes. Fruits, vegetables, grains, legumes, nuts and teas are rich sources of phytonutrients. They serve as antioxidants, enhance immune response, alter estrogen metabolism, convert beta-carotene to vitamin A, and can help repair DNA damage caused by smoking and other toxic exposures.
a day. Furthermore, some of the most nutrient dense, the dark green vegetables and deep yellow vegetables, each represent less than one of the daily servings consumed. In addition, less than half the population consumes the minimum number of fruit servings recommended per day.
Some of the more common classes of phytonutrients are carotenoids and flavonoids (polyphenols) including isoflavones (phytoestrogens).
Carotenoids make up the red, orange and yellow pigments in fruits and vegetables. Fruits and vegetables that are high in carotenoids appear to protect humans against certain cancers, heart disease and age-related macular degeneration.
| Carotenoid | Common Food Source |
| alpha-carotene | carrots |
| beta-carotene | leafy green and yellow vegetables (e.g. broccoli, sweet potatoes, pumpkin, carrots) |
| beta-cryptoxanthin | citrus, peaches, apricots |
| lutein | leafy greens such as kale, spinach, turnip greens |
| lycopene | tomato products, pink grapefruit, watermelon, guava |
| zeaxanthin | green vegetables, eggs, citrus |
Food sources rich in polyphenols include onion, apple, tea, red wine, red grapes, grape juice, strawberries, raspberries, blueberries, cranberries, and certain nuts.
Polyphenols can be classified as non-flavonoids and flavonoids. The flavonoids quercetin and catechins are the most extensively studied polyphenols relative to absorption and metabolism.
| Nonflavonoids | Sources |
| ellagic acid | strawberries, blueberries, raspberries |
| Flavonoids | Sources |
| anthocyanins | fruits |
| catechins | tea, wine |
| flavanones | citrus |
| flavones | fruits and vegetables |
| flavonols | fruits, vegetables, tea, wine |
| isoflavones | soybeans |
Population studies have linked fruit and vegetable consumption with lowering the risk for chronic diseases including specific cancers and heart disease. Phytonutrient research is experiencing remarkable growth. Hopefully, more specific information on phytonutrient consumption and human health will rise. For now, it appears that an effective strategy for reducing risk of cancer and heart disease is to increase consumption of phytonutrient-rich foods including fruits, vegetables, grains and teas.
