Soy and Genistein
Genistein is a substance found in unfermented
soy products, most notably in tofu.
Many beneficial effects have been reported for
Genistein, most significantly as an anticancer
agent and as a protection against cancer.
While there is controversy over its exact
properties and its risks and benefits, it is
certainly one of the most promising substances
now under investigation.
There appear to be a number of other beneficial
effects as well: notably there are reports that
it reduces platelet aggregation and in this
gives some protection against heart disease.
Chemically Genistein is an “isoflavone”.
It is also what is know as a phytosteroid:
that is a plant substance with steroid-like
properties. Genistein imitates, in some manner,
estrogen (and other sexual hormones).
It is thought that it “competes for estrogen
receptors” and thus protects against the
negative effects of estrogen. (Though there
is some controversy about this) it does not seem
to block the necessary functions of the sex
hormones (though one paper speaks of a
lengthening of the menstrual cycle, others argue
this is a normalising and not a surpression).
Genistein seems to be particularly helpful in all
the “hormone responsive cancers”
- breast, ovarian, uterine, prostate -
and also with colon cancer.
In all propability Genistein has more than one
mode of action.
It is reported to also have “angiostatin”-like
activity, that is, to surpress the production
of new blood vessels like shark cartilage or
Folkman’s much vaunted angiostatin and
endostatin “cure”.
Doses of 60 gm (of tofu) per day
(45 mg of isoflavones/day) causes reduction of
gonadotrophic hormones (LH and GSH) as well as
lengthening (or normalising?) the menstrual cycle.
These therefore would seem to be around the
therapeutic dose range.
60 grams is roughly half a cup of tofu.
Some quotations from the scientific literature:
- Isoflavones may bind to the estrogen receptors
without eliciting a large estrogenic response and
may therefore inhibit the stronger endogenous
estrogenic agonists from binding”
- Protective effects against certain cancers,
including lung, colon, stomach, prostate and
breast cancer have been noted with one serving
of soy equal to ½ cup cooked soybeans, tofu, tempeh
or 1 cup of soy milk.
Tofu products are highest in isoflavones
such and genestein”
- Isoflavones exhibit a multitude of biological
effects that influence cell growth and regulation,
and, thus, may have potential value in
the prevention and treatment of cancer.
Isoflavones are weak estrogens and can function
both as estrogen agonists and antagonists
depending on the hormonal milieu
and the target tissue
and species under investigation.”
“High concentration of isoflavones,
may be a safe and effective means
of reducing cancer risk.
In Vitro Hormonal Effects
of Soybean Isoflavones .”
Journal of Nutrition 125: 751S-756S, 1995
- In two-thirds of studies on the effect
of genistein-containing soy materials
in animal models of cancer, the risk of cancer
(incidence, latency or tumor number)
was significantly reduced”
J. Nutr. 125: 777S-783S, 1995
75 and 150 mg/kg gave protection
against colon cancer in rats
- International variations in cancer rates
have been attributed, at least in part,
to differences in dietary intake.
Recently, it has been suggested that
consumption of soyfoods may contribute
to the relatively low rates of breast,
colon, and prostate cancers in countries
such as China and Japan.
Soybeans contain a number of anticarcinogens,
and a recent National Cancer Institute workshop
recommended that the role of soyfoods
in cancer prevention be investigated.
In this review, the hypothesis that soy intake
reduces cancer risk is considered
by examining relevant in vitro, animal,
and epidemiological data.
Soybeans are a unique dietary source
of the isoflavone genistein,
which possesses weak estrogenic activity
and has been shown to act in animal models
as an antiestrogen.
Genistein is also a specific inhibitor
of protein tyrosine kinases;
it also inhibits DNA topoisomerases
and other critical enzymes involved
in signal transduction.
In vitro, genistein suppresses the growth
of a wide range of cancer cells,
with IC50 values ranging from 5 to 40 microM
(1-10 micrograms/ml).
Of the 26 animal studies of
experimental carcinogenesis
in which diets containing soy
or soybean isoflavones were employed,
17 (65%) reported protective effects.
No studies reported soy intake
increased tumor development.
The epidemiological data are
also inconsistent, although consumption
of nonfermented soy products,
such as soymilk and tofu,
tended to be either protective
or not associated with cancer risk;
however, no consistent pattern was evident
with the fermented soy products,
such as miso.
Protective effects were observed
for both hormone and nonhormone
related cancers.
While a definitive statement that
soy reduces cancer risk
cannot be made at this time,
there is sufficient evidence
of a protective effect
to warrant continued investigation.
Messina MJ; Persky V; Setchell KD; Barnes S
Soy intake and cancer risk:
a review of the in vitro and in vivo data.
National Cancer Institute,
National Institutes of Health, Bethesda, MD.
Nutr Cancer, 21(2):113-31 1994
I have not yet tracked down
a definative source for the products.
It is available from:
Blue Moon Shopping Mall
Attention: Sherry Hall
3741 E. Ocean View Ave. Apt. 13
Norfolk, VA 23518 USA
Telephone: (757) 412-0308
By e-mail: bluemoon@pinn.net
who have available
Genistein 1000 mg. (Item #: SN050)
120 tablets....Retail Value $18.98
and they say that
there is no problem shipping to Canada
or you can ask at your local health food shop
see Medical Papers menu
|