Grape
The compound found in the
skins of red grapes (resveratrol) is being studied
to see how it affects the development and progression of heart disease
and cancer.
Resveratrol is found in 70 different plants, including mulberries
and peanuts, but grapes and grape products are the richest source.
All wines have some resveratrol, but the highest concentration is
in red wine. (Jang M, et al. Cancer chemopreventive activity of resveratrol,
a natural product derived from grapes. Science 1997;275(5297):218-20.)
Resveratrol was discovered after hundreds of tests in search of anti-cancer
compounds. The compound has been tested only in cell cultures and
laboratory animals. In an 18-week study of mice, doses of resveratrol
reduced the number of skin tumors by up to 98 percent compared with
skin cancers on control mice.
It occurs in the vines, roots, seeds, and stalks, but its highest
concentration is in the skin, which contains 50-100 micrograms (µg)
per gram. Resveratrol is a phytoalexin, a class of antibiotic compounds
produced as a part of a plant's defense system against disease.
Resveratrol is being studied to see how it affects the initiation,
promotion, and progression of cancer. With regard to tumor initiation,
it has been shown to act as an antioxidant by inhibiting free radical
formation, and as an anti-mutagen in rat models. Resveratrol appears
to decrease tumor promotion activity by inhibiting cyclooxygenase-1
(COX-1), an enzyme that converts arachidonic acid to pro-inflammatory
substances that stimulate tumor-cell growth. Studies related to progression
have found that resveratrol induced human promyelocytic leukemia cell
differentiation and inhibited ribonucleotide reductase, an enzyme
needed for DNA synthesis in proliferating cells. One appealing characteristic
of resveratrol's anti-cancer potential is its minimal toxicity to
blood-forming cells. More studies using both cellular and animal models
are needed before any such data would be applicable to human use.
The similarity in structure between resveratrol and diethylstilbestrol
(a synthetic estrogen) has prompted investigations into resveratrol's
potential as a phytoestrogen (a plant compound that produces estrogen-like
effects). However, these properties also stimulate the growth of human
breast cancer cells. This finding seems contrary to its other anticancer
activities, and is a cause for concern.
Fresh, preserved, and dried grapes are used in the form of liquid
extracts, tinctures, gargles, enemas, douches, and compresses. Grape
skins are used to make wine. Grape seed extract and resveratrol are
available in tablets and capsule supplements. The dosages vary depending
on the manufacturer. Because there havent been any clinical studies,
the optimal therapeutic dosage hasnt been established for resveratrol.
Based on animal studies, a reasonable therapeutic dosage of resveratrol
might be about 500 mg daily.
The complete grape diet begins with a period of fasting and eating
only grapes for 1 or 2 weeks. Then, fresh fruits and sour milk can
also be consumed. The next stage of the diet includes raw vegetables,
salads, nuts, dairy products, honey, and olive oil. During the final
stage of the diet, if a person is doing well, they may be given one
cooked meal per day.
An exclusive grape diet is unhealthy and does not supply the body
with adequate amounts of protein and important nutrients, such as
vitamin B 12. Grape seed extract is believed to be safe, but additional
research is needed for confirmation.
The amount of resveratrol in red wine varies greatly, and increased
consumption of wine to increase resveratrol intake poses certain health
risks. Alcohol is associated with increased risks of cancers of the
mouth, esophagus, pharynx, larynx, and liver in both men and women,
and of breast cancer in women. Cancer risk also increases with the
amount of alcohol consumed. However, the cardiovascularand the
anticarcinogenic benefits of moderate drinking may outweigh
the risk of cancer in men over age 50 and in women over age 60.
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