Phytochemicals: The Protection Packed in Plant Foods

by Beth Fontenot, MS, RD, LDN

"Eat your fruits and vegetables" is familiar nutritional advice and was no doubt originally intended to encourage people to eat foods that would meet all of their nutritional needs. 

Now, the science of nutrition has unearthed even more reasons why that advice is indeed beneficial: phytochemicals. Fruits and vegetables as well as other whole foods like nuts, legumes, and whole grains contain phytochemicals that have the ability to alter body processes and protect against heart disease, cancer, and many other chronic diseases.

The word phytochemical means plant chemical. In fact, the term "phyto" comes from the Greek word for "plant." Phytochemicals are organic, non-nutritive, naturally occurring chemicals found in plant foods. Even though they are non-essential nutrients, meaning they are not needed to sustain life, they may prolong life because of their health promotion properties.

Protecting Plants and People

Phytochemicals are a plant's way of protecting itself. They help shield tender buds and sprouts from predators, the elements, and pollution. These protective compounds are passed along to us when we eat plant foods.

One of the reasons we may like (or don’t like) certain foods is because of the phytochemicals they contain. These various compounds give foods their color, taste, and smell. They put the hot in habaneras, the gusto in garlic, the bitterness in broccoli, and the color in carrots. For example, carotenoids give foods their deep red, dark orange and yellow color while anthocyanins provide the various shades of red, purple, and blue found in other fruits and vegetables.

Flavonoids are the pigments that are responsible for the many other shades of yellow, orange, and red in foods. Isothiocyanates and indoles are the chemicals in cabbage that give that notorious odor to the kitchen when cabbage is cooked. Capsaicin puts the hot in chili peppers.

How Phytochemicals Help the Body

Phytochemicals appear to have significant physiological effects in the body. Whether they are acting as antioxidants, mimicking hormones, stimulating enzymes, interfering with DNA replication, destroying bacteria, or binding to cell walls, they seem to work to curb the onset of diseases such as cancer and heart disease. Some phytochemicals work alone, others work in combination, and some seem to work in conjunction with other nutrients in food, such as vitamins.

The more brightly colored the food, the more phytochemicals a food contains, perhaps making the food that much more beneficial. However, less colorful fruits and vegetables, like onions and corn, are also rich in phytochemicals. Eating a wide variety of fruits and vegetables is the best way to achieve all the potential benefits that phytochemicals offer.

There are over 1,000 known phytochemicals and probably many more that are yet to be discovered. The table below shows several types of phytochemicals, their possible beneficial effects, and food sources of each.

Table 1.

Chemical Name	Possible Benefits	Food Sources
Allicin	Acts as an antioxidant; antimicrobial; may lower blood pressure and cholesterol	Garlic, onions, leeks, chives
Anthocyanins	Act as antioxidants; may lower blood pressure and improve vision; anti-inflammatory and antimicrobial activity; may provide protection against cancer and heart disease	Blueberries, blackberries, red apples and their skins, red potatoes, black raspberries, black currants, gooseberries.
Capsaicin	May lower blood pressure and cholesterol; may prevent blood clots; may curb inflammation	Chili peppers
Carotenoids (beta -carotene, lycopene, lutein and more)	Acts as an antioxidant; may reduce the risk of cancer, heart disease, and age-related macular degeneration; may enhance the immune system response.	Carrots, sweet potatoes, pumpkins, apricots, peaches, tomatoes, brightly colored peppers, dark leafy green vegetables
Flavonoids	Act as an antioxidant; may protect against heart disease; may protect against peptic ulcers; anti-inflammatory effect; anti-cancer activity.	Onions, curly kale, leeks, broccoli, apples, blueberries, purple grapes, purple grape juice, whole wheat, red wine, dark chocolate, tea
Isoflavones	Inhibit cell replication in the GI tract; may reduce the risk of estrogen-sensitive cancers (breast, ovarian, colon, prostate); may decrease the risk of osteoporosis	Soybeans and soy products, other legumes.
Indoles	May inhibit the action of estrogen; may decrease the risk of cancer	Cruciferous vegetables (broccoli, Brussels sprouts, cabbage, cauliflower, horseradish, mustard greens, turnip greens, kale)
Isothiocyanates	Act as an antioxidant; may increase the activity of enzymes that function in the detoxification and elimination of toxins.	Cruciferous vegetables (broccoli, Brussels sprouts, cabbage, cauliflower, horseradish, mustard greens, turnip greens, kale)
Lignans	May block estrogen activity in the cells and reduce the risk of breast, ovarian, prostate, and colon cancer; reduce the risk of heart disease.	Flaxseed ,sesame seed, whole grains like rye, wheat, oat, and barley, soybeans, cruciferous vegetables, apricots, strawberries, nuts, seeds
Monoterpenes	May reduce the risk of cancer; antibacterial, antiviral, antimicrobial.	Skins and oils of citrus fruits
Phenolic Acids	May protect against oxidative damage diseases, i.e. heart disease, stroke, cancer.	Tea, coffee, berries, oranges, pears, prunes, soybeans, oats, potatoes
Resveratrol	May prevent damage to blood vessels, reduce LDL cholesterol, prevent blood clots.	Grapes, wine, grape juice, peanuts, blueberries, bilberries, cranberries
Tannins	Act as antioxidants; may reduce the risk of cancer.	Grapes, persimmons, lentils, blueberries, tea, , chocolate, wine

The recent research into the potential health benefits of phytochemicals has uncovered numerous possibilities. Anthocyanins and other flavonoids appear to improve vision health.(1) Resveratrol is being studied for the prevention of prostate cancer. The isoflavones in soybeans may reduce inflammation and the risk of heart disease.(2) Lignans have shown promise in reducing the growth of cancerous tumors, particularly in the breast and prostate.(3)

Cranberries contain a diverse composition of phytochemicals, and research shows promise that they may help to limit cancer and other diseases of aging.(4)Phytochemicals in apples were shown to reduce cardiac risk factors in obese rats with metabolic syndrome.(5) Whole grain foods contain a wide variety of unique phytochemicals that are thought to be responsible for the health benefits of whole grain consumption.(6)

Vegetarians naturally consume higher levels of carotenoids, flavonoids, and other phytochemicals and tend to have lower cancer rates, lower blood cholesterol levels, lower risk of heart disease, lower blood pressure, and a lower risk of hypertension and type 2 diabetes. Their diets also tend to be higher in dietary fiber, magnesium, potassium, and vitamins C and E, and folate. (7)

The value of phytochemicals is one reason why the USDA's Dietary Guidelines for Americans encourage the consumption of at least five cups of fruits and vegetables and three ounces of whole grain foods every day. On average, Americans eat less than two cups of vegetables per day and only one cup of fruit a day. Less than 5 percent of Americans consume the recommended amount of whole grains with most eating less an one serving a day. Clearly, Americans are lacking in their intake of plant foods and not reaping the health benefits provided by the phytochemicals they contain.

It's Easy to Up Your Intake

The only way to increase the intake of phytochemicals is to eat more plant foods. Here are some tips for incorporating more plant foods in your diet:

• Make a conscious effort to eat at least five portions of fruits and vegetables every day.
• Use catsup on your burgers instead of mayonnaise. Not only is catsup fat-free and lower in calories, but it is rich in the phytochemical lycopene.
• Add shredded peppers, radishes, onions, or broccoli steams to a shredded cabbage and carrot salad.
• Choose dried apricots, pineapples, apples, or tropical mix for snacks instead of candy.
• Eat the white part of citrus fruit, the albedo. While the flesh and juice of citrus fruits are loaded with vitamin C and other nutrients, the albedo is very rich in phytochemicals.

• Add artichokes, onions, sliced tomatoes, or spinach to your pizza.
• Keep jars of chopped garlic, ginger, and basil in your kitchen to speed up meal preparation.
• Drink more tea. Both ordinary and green teas contain beneficial phytochemicals.
• Add grated zucchini, carrots, or apples to plain muffin mix.
• Make spaghetti using less meat and more vegetables. Onions, peppers, squash, zucchini, and carrots can all be incorporated into spaghetti sauce
• Keep frozen vegetables on hand to add to casseroles and soups.
• Eat the whole fruit instead of drinking fruit juice.

• Be liberal in your use of spices when cooking. Basil, oregano, parsley, sage, thyme, turmeric, garlic, and ginger all contain phytochemicals.
• Toss a handful of nuts into a salad.
• Learn to cook with whole grains like brown rice, whole oats, whole wheat, amaranth, barley, buckwheat, and quinoa.
• Experiment with soy products like tofu and vegetable protein meat substitutes.
• Designate one or two meals a week as meat-free meals. Use legumes to create main dishes.
• Be adventurous. Use the resources at your fingertips on the Internet to search for recipes that incorporate fruits, vegetables, whole grains, nuts and seeds in ways you may not have tried before.