Encyclopedia of Diets - A Guide to Health and Nutrition

Resources

BOOKS
Kushner, Robert and Nancy Kushner.Dr. Kushner’s Per-
sonality Type Diet.New York: St. Martin’s Press, 2003.
Kushner, Robert.Evaluation and Management of Obesity.
Daniel Bessesen ed.Philadelphia: Hanley and Belfus,
2002.
Kushner, Robert and Marty Becker.Fitness Unleashed!: A
dog and owner’s guide to losing weight and gaining health
together.New York: Three Rivers Press, 2006.
Kushner, Robert and Daniel Bessesen eds.Treatment of the
Obese Patient.Totowa, NJ: Humana Press, 2007.
Shannon, Joyce Brennfleck ed.Diet and Nutrition Source-
book.Detriot, MI: Omnigraphics, 2006.
Willis, Alicia P. ed.Diet Therapy Research Trends.New
York: Nova Science, 2007.

ORGANIZATIONS
American Dietetic Association. 120 South Riverside Plaza,
Suite 2000, Chicago, Illinois 60606-6995. Telephone:
(800) 877-1600. Website:http://www.eatright.org

OTHER
Kushner, Robert. ‘‘Dr. Kushner’s Personality Type Diet.’’
drkushner.com2007.http://www.doctorkushner
.com(March 22, 2007).

Helen M. Davidson

Phytonutrients
Definition
Phytonutrients are a class of nutrients that are
thought to have health-protecting properties. The pre-
fixphytois from the Greek and means plant, and it is
used because phytonutrients are obtained only from
plants.

Purpose
Unlike the macronutrients (proteins,carbohy-
drates,fats) and micronutrients (vitamins, tracemin-
erals) that are needed for growth,metabolism, and
other body functions, phytonutrients are not consid-
ered essential. This is because they can be lacking in
the diet without harmful health consequences. How-
ever, throughout history, plants have been cultivated
and used to prevent and treat various human diseases.
More recently, understanding the chemical role played
by these phytonutrients in plants has provided new
clues as to how they may help humans. When eating
plant-based foods, some of these phytonutrients iden-
tified as protectors in plants are transferred to our

bodies. The herbs and spices used for adding flavors

and tastes to foods are now known to be associated

with a long list of potential beneficial effects on human

health. Phytochemicals derived from the plants to this

day remain the basis of several medications used for

the treatment of a wide range of diseases. Throughout

the world, botanists and chemists actively search the

plant kingdom for new phytochemicals. Over 40% of

medicines now prescribed in the Unites States contain

chemicals derived from plants. For example, ephe-

drine, a phytochemical, is used in the commercial

preparation of pharmaceutical drugs prescribed for

the relief of asthma symptoms and other respiratory

problems. Phytochemicals isolated from plants have

also been a great help for discovering a large propor-

tion of the drugs now available for the treatment of a

wide range of human diseases such as pulmonary dis-

eases, cardiovascular diseases, diabetes,obesity, and

cancers.

Description

There are three broad classes of phytonutrients:

phytochemicals, medicinal plants and herbs and spices.

Phytochemicals

Thousands of phytochemicals have been isolated

and characterized from plants, including fruits and

vegetables. The most well-known include include ter-

penes,carotenoids, flavonoids, limonoids, and phy-

tosterols. In nature the bright green and red pigments

present in cabbages and lettuce, tomatoes and straw-

berries have evolved to help absorb otherwise harmful

ultraviolet radiation from the sun. They include the

yellow, orange, and red carotenoids. Green and leafy

SOURCE: Agricultural Research Service, U.S. Department of

Agriculture

Ways phytonutrients may protect human health

Serve as antioxidants

Enhance immune response

Enhance cell-to-cell communication

Alter estrogen metabolism

Convert to Vitamin A (beta-carotene is metabolized to vitamin A)

Cause cancer cells to die (apoptosis)

Repair DNA damage caused by smoking and other toxic exposures

Detoxify carcinogens through the activation of the cytocrome P450 and

Phase II enzyme systems

More research is needed to firmly establish the mechanisms of action of the

various phytochemicals

(Illustration by GGS Information Services/Thomson Gale.)

Phytonutrients