Specific phytonutrients called
flavonoids are thought to
enhance selected biological
functions in humans. Tea,
oranges, and mint have
high amounts of flavonoids.
What do citrus, berries, onions, teas, and red wine have in common?
They all contain considerable amounts of specific phytonutrients called
flavonoids. These foods and many others are included in a new supplemental
database soon to be released by scientists from the Beltsville Human
Nutrition Research Center (BHNRC) in Beltsville, Maryland. The center
also developed and manages USDA's National Nutrient Database for Standard
Reference, which is the major authoritative source of food composition
information in the United States. Other specialty databases include
those for carotenoids and isoflavones. These compilations may be found
on the World Wide Web by going to www.nal.usda.gov/fnic/foodcomp.
Flavonoids make up the largest subgroup of phytonutrients or phytochemicals,
now widely studied by the scientific community because of purported
health benefits. Phytonutrients are beneficial compounds found in plant-based
foods, including fruits, vegetables, nuts, seeds, roots, certain teas
and wines, and even in some chocolate.
Work on the database began when ARS
scientists with the Nutrient Data Laboratory (NDL) in Beltsville and
the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts
University in Boston, Massachusetts, undertook an extensive search of
existing scientific literature and a review of information supplied
by food producers. NDL researchers evaluated the existing flavonoid
data and screened it with a USDA-developed data-quality-evaluation system.
Then, a quality score was assigned to each value for each food.
"These confidence codes, lettered A, B, C, or D, appear
in a column alongside the values posted," says Joanne Holden, who
heads the NDL. "This column gives users a handle on the quality
of the data provided. By knowing the flavonoid content of foods, researchers
can assess dietary intakes of flavonoids and perhaps one day identify
relationships between those intakes and various chronic-disease risk
Dietary flavonoids fall mainly into five subclasses: flavonols, flavones,
flavanones, flavans, and anthocyanidins. A plant produces more flavonoids
as a protective response when it undergoes stress, such as exposure
to ultraviolet radiation or attack by fungi or bacteria. Increased flavonoid
levels are thought to enhance certain biological functions in humans.
Indeed, some flavonoids have antioxidative, antimicrobial, and possibly
anticarcinogenic and cardioprotective effects.
Soon to be launched, the new ARS Flavonoid Database will provide analytical
values for selected compounds in about 220 foods. An update will also
appear containing new data on 59 food items that are now being analyzed
by BHNRC's Food Composition Laboratory. Scientists there developed a
new analytical method that simultaneously separates and measures the
five major flavonoid classes. The samples of fruits, nuts, and vegetables
used were collected as part of NDL's National Food and Nutrient Analysis
Program, developed in collaboration with the National Institutes of
Health to improve the quality and quantity of data in USDA's National
Nutrient Database.By Rosalie Marion Bliss,
Agricultural Research Service Information Staff.
This research is part of Human Nutrition, an ARS National Program
(#107) described on the World Wide Web at www.nps.ars.usda.gov.
Joanne M. Holden is
with the USDA-ARS Nutrient
Data Laboratory, 10300 Baltimore Ave., Bldg. 005, Beltsville, MD
20705-2350; phone (301) 504-0630, fax (301) 504-0632.