Skip to: Content | Navigation | Sub Navigation

Current Opinion

Health Benefits of Phytonutrients Found in Colorful Fruits and Vegetables


By David Heber, M.D., Ph.D.

The evolution of human dietary patterns was driven by hunger in ancient jungles, then by economics during the last few hundred years when food production was industrialized, and in the last 50 years by the careful design of processed foods advertised on the basis of taste, cost, and convenience with little regard for their nutritional and health value.[1]

Colorful fruits and vegetables provide essential nutrients such as vitamins, minerals, and antioxidants and also other natural plant nutrients. Scientists refer to these plant nutrients by the tongue-twisting names of phytochemicals or phytonutrients. The “phyto” of the word phytochemicals is derived from the Greek word phyto, which means plant. Therefore, phytochemicals are the plant chemicals. These are bioactive plant compounds found in fruits, vegetables, grains, and other plant foods. It is estimated that more than 5000 phytonutrients have been identified out of the more than 150,000 edible plants on the earth, but a large percentage still remains unknown and need to be identified. And, modern humans eat only a fraction of edible plants – about 150–200 varieties worldwide.[2]

More and more convincing evidence suggests that the benefits of phytochemicals in fruits and vegetables may be even greater than is currently understood, since oxidative stress induced by free radicals is involved in the etiology of a wide range of various chronic diseases, and many phytochemicals have antioxidant activity.[2,3] Humans are oxygen-breathing organisms, and oxidative processes that take place within the cells of the body as part of everyday metabolism can lead to the formation of oxygen free radicals which can potentially cause damage to body cells and tissues. However, as long as there are antioxidants available as part of the body’s antioxidant defense system, the process is kept in check.

Population studies have consistently shown that diet plays a crucial role in the health maintenance.[4,5] Consumption of fruits and vegetables, as well as whole grains, has been strongly associated with reduced risk of many common diseases of aging. [4-6] In addition, the overall effects of increasing fruit and vegetable intake on obesity is positive, since most fruits and vegetables have fewer calories per bite than snack foods with hidden fats and sugars This convincing evidence suggests that a change in dietary behavior towards increased consumption of colorful fruits and vegetables, combined with a reduction in refined grains that are mostly brown or beige, may be a practical strategy for significantly reducing the risk of obesity and age-related disorders.[7]

The U.S. National Academy of Sciences has identified about 35 plant foods that can reduce disease risks. Foods and herbs having these activities include garlic, soybeans, cabbage, ginger, licorice root, and the umbelliferous vegetables (including carrots, celery, coriander, parsley, and parsnips) [5]. Additional foods with preventive activity include onions, flax, citrus, turmeric, cruciferous vegetables (broccoli, Brussels sprouts, cabbage, and cauliflower), tomatoes and sweet peppers, brown rice, whole wheat, oats, barley, various herbs (such as mints, rosemary, thyme, oregano, sage, and basil), cucumber, cantaloupe, and berries.[7,8]

Given the history of the diverse intake of plant foods by mankind, it is sensible to encourage a diverse intake. The exact amounts of fruits and vegetables needed each day to reduce disease risks are not known but the evidence of the benefits of fruits and vegetables suggest that it is not premature to advise increased intake of a variety of colorful fruits and vegetables. Consumers need a simple way to organize this collection of beneficial colorful fruits and vegetables and I have designed a color code which groups fruits and vegetables according to the nature of the predominant phytonutrients and as indicated by their visible colors [ 9]. Plant-eating animals naturally use color as an identifying marker of edible plant species. The changing color of ripening fruits and vegetables signify that they are at the peak of their taste and nutritive value. Many of the phytonutrients are actually the pigment molecules that lend ripe fruits and vegetables their distinctive hues. Pigments provide color to food and can enhance the pleasure of eating.

There are over 2,000 known plant pigments in foods [7] and the different colors in fruits and vegetables can indicate their unique physiological roles and health benefits. For example, lutein found in green vegetables such as spinach and avocado localizes to the retina in the area that receives the most ultraviolet light. All the colored phytochemicals that absorb light in the visible spectrum have antioxidant properties. Colorful fruits and vegetables can be recommended for increased diversity of intake for the consumer. For example, the antioxidant lycopene is found as a family of chemically related compounds (phytoene, phytofluene, beta carotene, and tocopherol) in tomatoes and tomato products but also in watermelon which is red in color. Both carrots and sweet potatoes are orange in color and contain beta-carotene an orange antioxidants.

A color-coded system can help consumers change dietary patterns to include more fruits and vegetables by including one serving from each of the seven color groups each day as shown in the table below.

COLOR PHYTOCHEMICALS FRUITS AND VEGETABLES
Red Lycopene Tomatoes and tomato products such as juice, soups, and pasta sauces
Red Purple Anthocyanins and Polyphenols Grapes, blackberries, red wine, raspberries, blueberries
Orange Alpha and Beta- Carotene Carrots, mangos, pumpkin
Orange – Yellow Beta-Cryptoxanthin and Flavonoids Cantaloupe, peaches, tangerines, papaya, oranges
Yellow – Green Lutein and Zeaxanthin Spinach, avocado, honeydew melon
Green Glucosinolates and Indoles Broccoli, bokchoi, kale
White – Green Allyl sulfides Leeks, garlic, onion, chives

REFERENCES

  1. Heber D, Bowerman S. Applying sciences to changing dietary patterns. J Nutr 2011;131:3078S-81S.
  2. Chu YF, Sun J, Wu X, Liu RH. Antioxidant and antiproliferative activities of vegetables. J Agric Food Chem 2002;50:6910-6.
  3. Liu RH. Health benefits of fruits and vegetables are from additive and synergistic combination of phytochemicals. Am J ClinNutr 2003;78:517S-20S.
  4. Temple NJ. Antioxidants and disease: more questions than answers. Nutr Res 2000;20:449-59.
  5. Willett WC. Diet and health: what should we eat? Science 1994;254:532-7.
  6. National Academy of Sciences, Committee on Diet and Health, National Research Council. Diet and Health: Implications for Reducing Chronic Disease Risk. Washington, DC: National Academy Press; 1989.
  7. Craig WJ. Phytochemicals: guardians of our health. J Am Diet Assoc 1997;97(10 Suppl 2):S199-204.
  8. Caragay AB. Cancer-preventative foods and ingredients. Food Technol 1992;46:65-8.
  9. Heber D. and Bowerman S. What Color is Your Diet? New York: Harper Collins, 2001.

Featured

 

Recent studies in mice have indicated an interrelation between energy balance, diet, and the composition of the gut bacteria.
Read More

The Fitness Textbook will teach you the basic principles of human performance nutrition, including muscle metabolism and fuel utilization before, during and after exercise.
Read More