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Miso soep en Soja vermindert kans op borstkanker.*
Vrouwen in Japan eten ongeveer 700 keer meer isoflvanonen
(hoofdbestanddeel van soja) dan vrouwen in het westen. De kans op borstkanker is
in Japan zeer klein.
Japanese women who are
frequent eaters of miso soup, a soy-filled staple of Japanese cuisine, and soy
ingredients called isoflavones appear to be less likely to develop breast cancer, researchers reported Tuesday.
Women in Asian countries have
only a fraction of the risk of breast cancer seen in Western countries, and the
current findings add to a growing body of evidence that suggests isoflavone
intake might help explain why.
In Japan, for instance, women
typically consume approximately 700 times more isoflavones than U.S. whites.
Still, more studies are needed
to determine whether the soy ingredient does, in fact, reduce breast cancer
risk, study author Dr. Seiichiro Yamamoto of the National Cancer Center Research
Institute in Tokyo told.
"The evidence level of
isoflavone/soy and breast cancer is elevated from 'possible' to 'probable' by
our study," Yamamoto said. "But it is still not convincing."
However, eating a little extra
soy couldn't hurt, the researcher added.
"Because no harmful
evidence about soy intake is reported and Asian people eat a lot of soy, it is
not bad to recommend to eat soy and isoflavone in Western countries,"
Yamamoto said.
Many researchers have
investigated the link between eating soy and developing breast cancer, but
previous studies have shown mixed results, with some suggesting that soy and
isoflavones offer no benefits in protecting women against breast cancer,
according to the Journal of the National Cancer Institute report.
In the new study, the
researchers asked more than 21,000 middle-aged women living in Japan how much
soy and soy-containing products they ate, then followed them for 10 years and
noted who developed breast cancer.
During the study period, 179
women developed breast cancer, the authors write. Women who reported eating miso
soup and foods that contain isoflavones were less likely to be diagnosed with
the disease than others.
Those women who consumed the
most isoflavones typically drank at least two to three cups of miso soup daily
and also ate soy-containing foods such as soybeans and tofu almost every day.
These soy-containing foods
alone, however, did not influence breast cancer risk in the same way as miso
soup or total isoflavone amount.
Interestingly, women who ate
the least amount of isoflavones still consumed around 250 times more of a type
of isoflavone called genistein than U.S. white women.
And the highest rate of breast cancer -- seen in women who ate the least amount of isoflavones -- was still lower than that seen in similarly aged women living in Western countries, the authors report.
Yamamoto and colleagues
suggest that conflicting reports of the influence of isoflavones on breast
cancer risk may have resulted from errors in measuring how much of the compound
women ate, or from comparisons involving non-Asian women, who may show only
small differences in the amount of isoflavones consumed by breast cancer
patients and those who are cancer-free.
SOURCE: Journal of the
National Cancer Institute 2003;95:906-913.