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Late summer and early fall are the time of year to take full
advantage of a wide variety of fruits and vegetables available to
Consumers. Phytochemicals are found in all plant foods including
grains and beans, but simply eating a variety of fresh fruits and
vegetables guarantees an intake of some of the most intriguing
members of the phytochemical family. Stocking up on broccoli,
cabbage, garlic, grapes and berries provides you with an array of
potential disease-fighting phytochemicals. Peppers, tomatoes and
corn round out a high-phytochemical diet.
Flowers on plants belonging to the cruciferous family
cluster in groups of four, a pattern suggestive of a crucifix.
Cruciferous vegetables include broccoli, cauliflower, cabbage,
brussels sprouts, kale, collards, rutabaga, and kohlrabi, bok
choy and turnips. Also in this family are the more pungent
relatives of broccoli including mustard and mustard greens,
horseradish, radish, watercress, and arugula. These vegetables
are rich in isothiocyanates and indoles, phytochemicals that have
been examined for their role in cancer prevention.
Isothiocyanates appear to interact with a series of enzymes
in the liver important in detoxifying and excreting potential
carcinogens. Indoles increase the conversion of estrogen to its
inactive form, a mechanism that may protect reproductive tissues
from exposure to estrogen. Cumulative overexposure to estrogen is
thought to be a risk factor for certain types of cancer. Indeed,
experimental studies so far suggest indoles have a protective
effect against breast cancer.
Garlic, onions, shallots and leeks all belong to the allium
family. Relatives of the lilly, these plants contain compounds
called allyl sulfides. These sulfur-containing compounds give
this family of foods their characteristic pungency, making them a
favorite in Italian, Chinese and Mediterranean fare. Allyl
sulfides have been recognized as potent inhibitors of
carcinogenesis. They work by activating enzymes that break down
certain cancer-causing substances and increase the body's ability
to excrete them.
Berries including strawberries, cranberries and
blackberries, along with grapes, contain ellagic acid. This
important phytochemical appears to reduce damage to DNA caused by
carcinogens like tobacco smoke and air pollution. One study has
shown it inhibits tumors of the esophagus in rats.
In addition to ellagic acid, purple grapes also contain
flavonoids. Flavonoids are a diverse group of phytochemicals
found in many types of fruits, grains and vegetables. The
particular types of flavonoids in grapes have splashed red wine
across media headlines recently, but purple grape juice deserves
just as much attention. The flavonoids in grapes appear to make
blood less likely to clot, a mechanism important in the
prevention of certain types of heart disease.
A few more summer sources of phytochemicals worth noting
include peppers, tomatoes and corn. Hot peppers, and spices
derived from them (chili powder, paprika) provide capsaicin, a
compound that appears to block carcinogens and prevent them from
binding to DNA.
Lycopene, a relative of beta-carotene, is found in tomatoes
and watermelon. It is a potent antioxidant, featured in studies
of prostate cancer prevention.
Zeaxanthin, another relative of beta-carotene, is
responsible for the yellow color of corn. It is also found in
most of the dark leafy vegetables. Zeaxanthin has strong
antioxidant properties and has been studied for its role in
enhanced immune function, giving it status as a potential anti-
cancer player.
The study of phytochemicals as they pertain to human health
is a new field. Before any definitive recommendations can be made
as to intakes of specific types and amounts of phytochemicals,
more studies need to be completed. In the meantime, it is safe to
say, once again: "Eat your fruits and veggies." Most scientists
agree it's likely the synergistic effects of phytochemicals as
they coexist naturally with other phytochemicals and nutrients
that gives them their unique properties. There is overwhelming
agreement that the best way to obtain potential benefits of
phytochemicals is by eating a wide variety of plant foods.
To optimize the phytochemical content of foods, follow the
same storage and handling recommendations made for retaining
vitamins in foods. Specifically, try to obtain fruits and
vegetables in season; limit peeling, as some phytochemicals are
concentrated in the skin; and steam, broil or microwave them,
using minimal amounts of cooking liquid to preserve
water-soluble phytochemicals.
For more information, contact your local
Colorado State University Extension office.
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