Introduction

Eating more broccoli, tomatoes, citrus fruits, onions, soybeans and other foods from plants may help to protect you against several chronic diseases such as heart disease and cancer.

And it is not just because of the nutrients they contain! It is more likely because of the chemicals found in these foods -- phytochemicals.

Activity

Think about the different colors in a rainbow and where you would place different foods.

What are Phytochemicals?

Phytochemicals (pronounced fi-toe/chemicals) are naturally occurring components in fruits, vegetable, legumes and grains. They are non-nutrients because they are not considered essential at this time; however, phytochemicals have many beneficial functions in the body such as getting rid of free radicals.

The term phytochemicals means chemicals found in plants. They give a plant its color, flavor and smell and are a part of a plant's natural defense system. It is these defense qualities in phytochemicals that have researchers intrigued because those same qualities may also benefit humans. Researchers believe phytochemicals could go a long way in helping to reduce the risk for several chronic diseases including heart disease and cancer.

How do Phytochemicals Work?

There are thousands of different phytochemicals with possible health benefits of which only a fraction have been studied. Much of the research done on phytochemicals has been with animals or in test tubes. Within the last few years, scientists have studied many of the phytochemicals' effects in humans. Many studies have also been done either retrospectively or prospectively. A large group of individuals is studied, data on food intake and disease conditions are assessed and relationships are drawn.

The Nurses' Health Study, established in 1976 by Dr. Frank Speizer, and the Nurses' Health Study II, established in 1989 by Dr. Walter Willett, are among the largest prospective investigations into the risk factors for major chronic diseases in women. The studies have grown to include a team of clinicians, epidemiologists and statisticians at the Harvard Medical School, Harvard School of Public Health, Brigham and Women's Hospital, Dana Farber Cancer Institute, Boston Children's Hospital and Beth Israel Deaconess Medical Center. Many of the conclusions drawn based on these studies support increased intake of photochemicals for combating chronic diseases.

For example, when it comes to heart disease, some studies suggest certain phytochemicals called flavonoids may inhibit LDL cholesterol production, and this will lead to reduced cholesterol levels, (LDL, the bad cholesterol involved in depositing fat inside your arteries). Flavonoids are found in broccoli, grapefruit, onions, citrus fruit, tea and soybeans. They may also help prevent blood clotting, which can reduce the risk for a heart attack or a stroke. More than 4,000 different flavonoid substances have been found; about 900 are present in human diet.

Other phytochemicals, known as sulfur compounds, are believed to reduce cholesterol production in your body, make platelets in the bloodstream less sticky and even help keep your blood pressure down. Sulfur compounds are found in garlic, leeks and onions.

The cancer connection occurs when phytochemicals work to keep healthy cells in your body from being damaged. Protected cells are less susceptible to an attack by a cancer-causing agent. Ellagic acid, found in grapes, is believed to be one such bodyguard to your cells. Several phytochemicals, such as limonene and caffeic acid, may help to reduce cancer risk by shuttling cancer-causing elements out of your body before they can cause damage.

Where Can You Find Phytochemicals?

Fruits, vegetables, legumes and whole grains are full of phytochemicals. In fact, orange juice has 59 known phytochemicals; broccoli has at least 40, and the herb tarragon has 70. Some of the plant foods you find these chemicals in are:

Cruciferous Vegetables

Cruciferous vegetables are one of the most important groups of vegetables from health perspective. The cruciferous vegetables are broccoli, cauliflower, cabbage, brussels sprouts, bok choy and kale. They contain many phytochemcials that have been linked to lower cancer risk, such as glucosinolates, crambene, indole-3-carbinol and isothiocyanates.

Cruciferous vegetables may help to regulate enzymes that defend against cancer. Compounds in cruciferous vegetables can stop the growth of cancer cells in various cells. They help against cancers of breast, endometrium, lung, colon, liver, colon and cervix.

Soy Foods

Soy Foods

Soybeans contain several types of phytochemicals. Soy contains several different phytochemicals that have been associated with relief of symptoms of menopause, decreasing bone resorption and decreasing risk of developing certain types of cancers and kidney and cardiovascular diseases. In the United States, we have a range of soy products to choose from. The popularity of soy has grown since the health benefits of soy have become widely known.

What are the Health Benefits of Soy?

Recent research suggests that soy protein and its phytochemical compounds may help to prevent some of the major chronic diseases, including heart disease, cancer and osteoporosis, as well as reduce the symptoms of menopause. Researchers speculate that the synergistic effect of the soluble fiber, phytoestrogens, saponins, phytate and other components may be responsible for the health benefits of soy foods.

What are Some Soy Foods?

Soybeans and soy products, such as soybean oil, soy flour and soy protein, are used extensively in a variety of foods found in a typical supermarket. Soy beverages, tofu, textured soy protein and soy flour can be used as foods or incorporated into many dishes, baked goods and other foods. The soybean and its components give foods sound nutrition, good taste, a long shelf-life and a competitive price. Many of the products available are listed below.

Soy oil accounts for 79% of the edible fats and oils used annually in the United States. Soybean oil contains 61% polyunsaturated and 24% monounsaturated fatty acids, totaling 85% unsaturated fatty acids. Soybean oil is particularly rich in linoleic and linolenic fatty acids. Soybean oil is a chief component of mayonnaise, margarine, salad dressing and vegetable shortening.

Soy flour is the simplest form of soy protein. The flour is produced by grinding and screening defatted soy flakes. Soy flour is about 50% protein. Soy flour can be found in baked goods, noodles, cereals, pancake flour, frozen desserts and instant milk drinks.

Soy isolates are developed through a chemical process in which most of the protein is withdrawn from the defatted flake. The resulting product contains about 90% protein and little moisture. Soy isolates are the chief component of many dairy-like products, including processed cheese, soy milk, infant formula, nondairy frozen desserts and coffee whiteners. They are used to add texture to meat products and are valued for their emulsifying properties.

Soy concentrates contain about 65% protein and retain most of the bean's dietary fiber. Concentrates also add texture and help foods retain moisture. Surimi, protein drinks, soup bases and gravies contain soy concentrates.

Soybeans, especially the outer hull, are an excellent source of dietary fiber (six grams fiber per one cup cooked). When soybeans are processed, the hull is removed and then processed further to create a fiber additive for breads, cereals and snacks. Soybeans contain both soluble and insoluble fiber. Soluble fiber may help lower serum cholesterol and control blood sugar. Insoluble fiber increases stool bulk, may prevent colon cancer and can help relieve symptoms of some digestive disorders.

Whole soybean foods such as full-fat flour are made from whole soybeans and therefore have the same fat, protein and dietary fiber content as the whole bean. Full-fat flour is used for doughnut mixes, pie crusts, pancake batters and other baked goods.

Soy milk is made from ground soybeans that are mixed with water to form a milk-like liquid. It is consumed by dairy-sensitive individuals as well as strict vegetarians who eat no animal proteins. Soy milk is an excellent source of protein, B-vitamins and iron, and, if fortified, provides adequate calcium. It has low levels of saturated fat and no cholesterol.

Textured soy protein (known commonly as TSP or TVP) is made from defatted soy flour which is compressed and dehydrated into a product rich in protein and fiber and low in fat and sodium. TSP is used as a meat enhancer, extender and substitute.

Mainstays of healthy diets throughout the East for centuries, Asian whole-soybean foods are slowly gaining acceptance in the United States as a unique source of nutrition that can help reduce saturated fat in the diet. Whole-soybean foods are high in protein, fiber and unsaturated fat, and rich in vitamins and minerals. They also show many anticarcinogenic properties related to the unique benefits of soy isoflavones.

Tofu (soybean curd) is a bland, cheese-like cake formed from soy milk by adding a coagulant (typically calcium sulfate) to the milk to form curds that are then shaped and pressed into cakes. Depending on the coagulant used, tofu is rich in minerals and is an excellent source of high-quality protein, polyunsaturated fats (including linoleic and linolenic acids), B vitamins and iron. Versatile and nutritious, tofu can be used in soups, salads, pastries, sandwiches and spreads. It can also be used as an alternative to yogurt or soft cheese.

Miso is a thick, high-protein paste made from soybeans, salt and a fermenting agent (usually an Aspergillus mold culture) that is similar in taste and color to soy sauce. Sometimes a grain, such as rice and barley, is fermented with the soybeans for additional flavor. Miso is popular as a soup and breakfast drink in Japan. The fermenting yeast in miso makes it a rich source of vitamin B-12. In addition, research has shown that antioxidant components in miso may inhibit formation of oxidized cholesterol that forms plaque in the arteries (Santiago et al., 1992).

Natto is made of fermented, cooked, whole soybeans and offers nutritional values similar to those found in miso. It has a sticky, viscous coating and is strong-smelling, with a cheesy texture. It is used as a spread or in soups.

Tempeh is made of whole, cooked soybeans infused with a culture to form a dense, chewy cake. It is a good source of fiber protein, polyunsaturated fats and lecithin, as well as useful amounts of calcium, iron, magnesium, potassium and some B vitamins.

Soybean sprouts are rich in vitamins A, B and C and are eaten raw in salads or cooked.

Soy sauce, the most widely recognized of soybean foods, is fermented from a mixture of whole soybeans, wheat flour and fermenting agents, such as yeast, for about 18 months. Then the liquid is extracted and processed. Soy sauce adds sodium and flavor to the diet.

Tomato Products

Tomatoes contain a chemical, lycopene, which is a carotenoid without any vitamin A activity. It is an antioxidant and removes reactive oxygen species as they develop. Reactive oxygen species are thought to cause degenerative changes seen in chronic diseases of aging such as hypertension, heart disease and cancer.

Lycopene causes the red color of tomatoes. Lycopene is also in other fruits such as guava and watermelon. Tomatoes are the best source of lycopene in the American diet. About 80% of dietary lycopene comes from tomato products. Cooking increases lycopene bioavailability, possibly by breaking the cell walls; cooked tomato products such as tomato sauce and paste are the best sources. Carotenoids are fat-soluble, and availability of lycopene is increased with some added fat. Foods such as pizza, red pasta sauce and marinara are good sources of lycopene. Lycopene is less available in raw tomato products.

According to the USDA Food Guide, the recommendation is to consume 1 ½ to 2 cups of fruit and 2 ½ to 3 cups of vegetables daily, depending on age and gender Higher consumption of fruits and vegetables results in reduced incidence of chronic diseases of aging. Include tomatoes as part of your healthy diet to reduce the risk of prostate and other cancers.

Lycopene has many beneficial effects. In particular, lycopene is thought to help prevent prostate cancer. The American Cancer Institute studied 50,000 health professionals for lycopene intake. There was 16% reduction in the incidence of prostate cancer in those who had the highest lycopene intake compared with those who had much lower lycopene intake. Higher lycopene intake resulted in reduction of other cancers as well. In terms of dietary intake of lycopene containing foods, this translates into consuming tomato products more than twice a week in the high intake group compared to those who consumed tomato products less than once a month.

Onions and Garlic

Garlic has chemopreventive, antibiotic, antihypertensive and cholesterol-lowering properties. Even garlic, onion, celery, endive, chives and white wine contain chemicals that fight cancer such as allyl sulfides allicin. Onion and garlic are also thought to lower blood pressure and reduce blood clotting.

Berries

Berries are nutritionally excellent and contain significant amounts of dietary fiber, vitamin C (ascorbic acid), vitamin A (beta carotene), B vitamins and minerals. They are also a good source of both soluble and insoluble fiber. Raspberries and blackberries, for example, contain 4-6 grams of fiber per 100 grams. High fiber intakes are believed to help in the prevention of heart disease and colon cancer.

All vegetables with deep red, blue and purple color contain anthocyanins that act as antioxidants. Flavonoids are a category of phytochemicals. There has been a lot of interest in flavonoids because of their beneficial effects. All red and blue berries contain flavonoids. Raspberries are a good source of the flavonoids quercetin and kaempferol.

Quercetin is an anticarcinogenic and it acts as an antioxidant to inhibit LDL oxidation. Quercetin and kaempferol prevent lipid peroxidation by several mechanisms. These are: 1. scavenging lipid peroxidation-initiating radicals, 2. binding metal ions, 3. scavenging lipid peroxyl radicals and 4. inhibiting enzymatic systems responsible for free radical production. Quercetin may also block the release of histamine and may therefore be beneficial for those suffering from allergies.

Ellagic acid is another phytochemical present in berries. Ellagic acid is a phenolic compound that gives a food its mouth-puckering feeling. It can act as a flavorant and a colorant while it is also an antioxidant. Ellagic acid may protect plants against microbial infections.

Ellagic acid is an anticarcinogenic by blocking metabolic pathways associated with the development of cancer cells. It is particularly effective in blocking hormone related cancers. Ellagic acid is found in many fruits, but it is exceptionally high in raspberries and blackberries.

Cranberries have been used to treat urinary tract infections, but recent research shows that they may also be useful for preventing breast cancer and reduce stomach ulcers. Cranberries may be useful in lowering LDL cholesterol levels.

Strawberries are high in antioxidants and vitamin C. They are known to fight heart disease and provide a number of vitamins and minerals that support overall human health. Strawberries have 7-75 mg/100 g phytochemicals by weight.

Raspberries are known for their ability to fight cancer because of the phytochemical content and abundant supply of vitamins and minerals. The anthocyanin content ranges between 20-60 mg/100 g of red raspberries.

Other berries such as black raspberries have 214-428 mg/100 g of phytochemicals; blackberries 83-326 mg/100 g; and boysenberries have over 160 mg/100, cranberries 45-100 mg/100 g, and blueberries 25-495 mg/100 g.

Citrus Fruits

Deep yellow and orange vegetables provide alpha and beta carotenes -- antioxidants that help fight cancer.

Fruits that are yellow/orange provide anthoxanthins that protect against cancerous changes. Citrus fruit are full of antioxidants -- flavonoids -- that have anti-inflammatory and antitumor activity. The flavonoids inhibit tumor cell growth and can activate important detoxifying enzymes. These polyphenols, called limonoids, inhibit tumor formation by stimulating a detoxifying enzyme that catalyzes the formation of less toxic and more water-soluble compounds that can be easily excreted from the body. Polyphenols are the molecules that provide the bitter taste in citrus fruits and tanginess in many fruits and teas.

Can I Just Take a Phytochemical Pill?

Phytochemicals are rapidly becoming available for consumers to purchase. Taking these supplements containing phytochemicals will provide only selected components in a concentrated form, but not all of the compounds that occur naturally in the foods. It is important to eat fruits, vegetables and grains instead of simply taking a pill.

How Can I Get More Phytochemicals in My Diet?

Here are some easy ways to increase your intake of phytochemicals:

1. Eat more whole grains. Don't limit your choices to bread, rice and pasta. Try barley, bulgur and wild rice for variety.

2. Eat a variety of vegetables. Broccoli, carrots, greens, winter and summer squashes, green and red peppers, snow peas and red cabbage all are great choices.

3. Eat more fruits and berries. Research shows the average American eats only one serving per day. A glass of juice at breakfast is a good start, but you might want to try bananas or berries on top of your cold cereal as well. Berries make a great dessert.

4. Don't forget herbs and spices. Even though you do not eat much of them, they also contain phytochemicals. Learn to use them more in your cooking.

5. Explore new foods and new recipes.

According to the Journal of Agricultural Food Chemistry (2004), the 20 most antioxidant-rich fruits and vegetables are:

• Small red beans (dried).
• Wild blueberries.
• Red kidney beans.
• Pinto beans.
• Blueberries (cultivated).
• Cranberries.
• Artichokes (cooked).
• Blackberries.
• Prunes.
• Raspberries.
• Strawberries.
• Red Delicious apples.
• Granny Smith apples.
• Pecans.
• Sweet cherries.
• Black plums.
• Russet potatoes (cooked).
• Black beans (dried).
• Plums.
• Gala apples.

There are other easy methods for increasing fruits, vegetables and grains in your diet. Search the following websites to learn more about phytochemicals and for recipes and tips on increasing phytochemicals in your diet:

Summary

The best way to get phytochemicals in your diet is to eat a wide variety of fruits, berries, vegetables, legumes, beans and whole grains.

Following the recommended number of servings from the Food Guide is the best way to get all of the nutrients and phytochemicals you need.