Phytonutrients Take Center Stage
Thanks to research, carrots, onions, garlic and cucumbers taste better and
contain more nutrients. And better crop yields and disease resistance make more
of these favorite foods available.
0n the cusp of the millennium, researchers are
busily uncovering a host of beneficial compounds in plant foods. While these
phytonutrients aren't essential by traditional definitions, they apparently
reduce risks of diseases of aging.
For example, the isoflavones in soy products may reduce the risk of heart
disease, osteoporosis, and several types of cancer. Certain flavonoids in
blueberries may actually reverse nerve cell aging. And a wide array of
compounds in fruits and vegetables may protect cell components against
oxidative damage as well as vitamins C or E.
Indeed, cancer, heart disease, and Alzheimer's disease may plague the
middle-aged and elderly because of our limited knowledge of phytonutrients.
Research in this arena, now less than two decades old, may relegate some of
today's ills to the history booksjoining scurvy and pellagra.
Phytonutrients have provided the impetus for plant and nutrition scientists
to work together because foods will continue to be the primary source of these
compounds. While a few visionary plant scientists have improved the nutritional
quality of foods, breeders have focused on increasing yields or warding off
insects or diseases.
That is changing. Projects have sprouted up to screen germplasm for specific
phytonutrients or to find ways to increase or preserve them in cultivated
varieties. Following are just a few examples of this new wave:
Genetic engineering has produced tomatoes with up to three
times more lycopenethe cancer-preventing red pigmentthan normal and
a shelf life several weeks longer. Autar K. Mattoo and colleagues at the
ARS Vegetable Laboratory in Beltsville,
Maryland, inserted a gene that retards plant aging, or senescence, along with a
promoter that is triggered by ripening. The engineered tomatoes accumulate more
lycopene and other antioxidants during the longer ripening stage. This novel
approach should work in other fruits and vegetables.
Tissue culture at the ARS Western Regional Research Center
in Albany, California, is producing tomatoes with 10 times more lycopene than
store-bought tomatoes. Betty K. Ishida and colleagues grow tomatoes in test
tubes kept at cooler temperatures, which triggers certain genes to produce the
enzymes that increase lycopene production, she says. She is searching for the
specific genes responsible and other ways to activate them.
Environmental and genetic factors also make a difference.
Cantaloupes grown at the ARS Subtropical Agricultural Research Center in
Weslaco, Texas, differed in beta carotene levels by 500 percent, depending on
the soil, the cultivar, and fruit size, says Gene E. Lester. Now Lester and
colleagues are embarking on a project to understand the postharvest storage
factors, as well as the environmental and genetic factors that affect
phytonutrient levels in a variety of fruits and vegetables.
Breeding will be central to putting produce with enhanced
phytonutrients on the table. Broccoli is a good source of compounds that may
inhibit cancer. But there's good potential for increasing the crop's potential
anticancer punch. Mark W. Farnham in the ARS Vegetable Research Unit at
Charleston, South Carolina, and Jed Fahey at Johns Hopkins University in
Baltimore, Maryland, found that the supposed anticancer
precursorglucoraphaninexhibits a thirtyfold difference in Farnham's
inbred broccoli lines.
Storage can affect phytonutrient levels, says Irwin Goldman
of the University of Wisconsin. Onions that have been in cold storage up to 90
days show more antiplatelet activity. This can reduce cardiovascular disease
risk by interfering with the clumping of blood plateletsthe first stage
in clot formation.By Judy
McBride, Agricultural Research Service Information Staff.
This research is part of Human Nutrition, an ARS National Program (#107)
described on the World Wide Web at
Beverly A. Clevidence heads
the USDA-ARS Phytonutrients
Laboratory, Bldg. 308, 10300 Baltimore Ave., Beltsville, MD 20705-2350;
phone (301) 504-8367, fax (301) 504-9098.
Tracing Elements and Vitamins
A Chinese document dating back 5,000 years described goiteran enlarged
thyroid glandand recommended that afflicted people eat seaweed and burnt
spongeboth good sources of iodine. The element, however, was not
recognized as dietarily essential until 1850.
Anemia, another deficiency disease, was treated around the 4th century B.C.
by giving patients water used to quench heated iron swords. Iron itself was
used to treat anemia as early as the 17th century. But the discovery of other
essential elements didn't occur until the start of the 19th century. Sodium and
potassium were soon followed by the other major mineralscalcium, sulfur,
magnesium, and chlorine.
Except for iron and iodine, the essential trace elementsthose needed
in milligram or microgram quantity dailyremained unknown until the early
20th century. In the 1950s and 1970s, four elements considered toxic food
contaminantsselenium, chromium, fluorine, and silicongained new
respect when found to have a function in the body. And other trace elements are
gaining essential status.
Vitamins, like minerals, had been hinted at for millennia. Diseases like
beri beriknown in the Orient as early as 2600 B.C.and
scurvythe sailors' cursewere long believed to be due to toxins from
pathogens in the digestive tract. In 1747, British naval surgeon James Lind
cured scurvy with lime juicethus the term "limey" was coined to
mean an English sailor.
Hippocrates advocated liver as a remedy for night blindness around the 4th
century B.C., but the active component, vitamin A, was not chemically defined
until 1913. The 1920s and 30s were ripe for vitamin discovery, accounting for
11 of the 15 vitamins. Now there's a new surge of discovery around
health-enhancing compounds in plant foods known as phytonutrients.
"Phytonutrients Take Center Stage" was published in the
issue of Agricultural Research magazine.