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ABSTRACT:
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Incidences of breast, colorectal and prostate cancer are high in
the Western world compared to countries in Asia. We have postulated
that the Western diet compared to the semivegetarian diet in some
Asian countries may alter hormone production, metabolism or action
at the cellular level by some biochemical mechanisms. Our interest
has been focused on two groups of hormone-like diphenolic phyto-oestrogens
of dietary origin, the lignans and isoflavonoids abundant in plasma
of subjects living in areas with low cancer incidence. The precursors
of the biologically active compounds detected in man are found in
soybean products, whole-grain cereal food, seeds, and berries. The
plant lignan and isoflavonoid glycosides are converted by intestinal
bacteria to hormone-like compounds. The weakly oestrogenic diphenols
formed influence sex-hormone production, metabolism and biological
activity, intracellular enzymes, protein synthesis, growth factor
action, malignant cell proliferation, differentiation, cell adhesion
and angiogenesis in such a way as to make them strong candidates
for a role as natural cancer-protective compounds. Their effect
on some of the most important steroid biosynthetic enzymes may result
in beneficial modulation of hormone concentrations and action in
the cells preventing development of cancer. Owing to their oestrogenic
activity they reduce hot flushes and vaginal dryness in postmenopausal
women and may to some degree inhibit osteoporosis, but alone they
may be insufficient for complete protection. Soy intake prevents
oxidation of the low-density lipoproteins in vitro when isolated
from soy-treated individuals and affect favourably plasma lipid
concentrations. Animal experiments provide evidence suggesting that
both lignans and isoflavonoids may prevent the development of cancer
as well as atherosclerosis. However, in some of these experiments
it has not been possible to separate the phyto-oestrogen effect
from the effect of other components in the food. The isoflavonoids
and lignans may play a significant inhibitory role in cancer development
particularly in the promotional phase of the disease, but recent
evidence points also to a role in the initiation stage of carcinogenesis.
At present, however, no definite recommendations can be made as
to the dietary amounts needed for prevention of disease. This review
deals with all the above-mentioned aspects of phyto-oestrogens.
(356 Refs)
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