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Glutathion helpt met vis tegen borstkanker.*
Dat het eten van vis, speciaal
vette vis (zoals zalm, makreel,..) gezond is was reeds bekend. De
hierin aanwezige omega3 vetzuren worden verantwoordelijk gehouden voor de kanker
beschermende eigenschappen. Door veel vis te eten daalt de kans op borstkanker
met wel 35%. Uit onderzoek onder 63.000 Chinezen in Signapore is nu gebleken dat
vrouwen waarbij bepaalde Glutathiongenen (genen die de aanmaak van Glutathion
regelen ) meer actief zijn tot wel 74% minder kans hebben op borstkanker.
Researchers who found that fish
oils appear to reduce breast cancer risk have now discovered that the oils may
especially benefit women with particular genetic makeups.
The protective effects of fish
oils, called marine n-3 or omega-3 fatty acids, are linked to the
cancer-fighting properties of the oil's byproducts, propose investigators from
the Keck School of Medicine of the University of Southern California and the
National University of Singapore. The study in Carcinogenesis was published
early online through the journal's Web site.
Moreover, researchers believe
that women whose bodies do a poor job of getting rid of the fish oils'
byproducts are the ones who benefit most from consuming the oils. That may help
scientists better understand exactly how fish oils deter cancer.
"In this study, we found
that women with certain common DNA patterns experienced more breast cancer
protection from marine n-3 fatty acids than women with other common
patterns," explained Manuela Gago-Dominguez, M.D., Ph.D., assistant
professor of preventive medicine at the Keck School of Medicine of USC and the
study's lead author.
Findings came from the Singapore
Chinese Health Study, a prospective investigation of diet and cancer risk in
more than 63,000 Chinese men and women in Singapore.
"Through this study, we have
identified a novel gene-environmental interaction between certain genotypes and
omega-3 fatty acids on breast cancer development," says Mimi C. Yu, Ph.D.,
professor of preventive medicine at the Keck School and principal investigator
of the Singapore Chinese Health Study.
The researchers had already found
that among postmenopausal women in this group, those who ate the most n-3 fatty
acids (from fish such as salmon and mackerel) were 34 percent less likely to be
diagnosed with breast cancer than women who ate the least n-3 fatty acids from
fish. They suspected that lipid peroxidation products-that is, substances
produced when the fatty acids break down-were behind the protection.
Gago-Dominguez explains that
certain enzymes in the body known as glutathione S-transferases (GSTs, for
short) help the body flush out and get rid of these lipid peroxidation products.
Each person has certain genes that carry the recipe for making GST. But
interestingly, these genes can be found in slightly different varieties-called
polymorphisms-in the population. The differences between the genes can mean the
difference between GST that clears substances efficiently out of the body and
GST that works a little slower.
The researchers looked at the
genetic makeup of study participants and grouped them according to which
polymorphisms they had. They found that postmenopausal women who had
low-activity versions of genes associated with GSTs (known as GSTM1, GSTT1 and
GSTP1) had a lower risk of breast cancer. Women with a combination of the
lowest-activity forms of GSTM1 and GSTP1 had 64 percent lower risk of the
cancer, and women with a combination of the lowest-activity forms of GSTT1 and
GSTP1 had a 74 percent lower risk of the cancer.
Among women with high-activity
versions of GST-related genes, though, they saw no evidence that fish oils
reduced breast cancer risk. That held true for both pre- and postmenopausal
women.
Interestingly, laboratory studies
have shown that cancer growth is suppressed by n-3 fatty acid byproducts, and
the suppression is enhanced by drugs that increase lipid peroxidation. When
antioxidants are introduce to battle the effects of peroxidation, though, the
cancer continues to grow.
"Our findings may have
practical implications in treatment and prevention strategies for breast
cancer," says Gago-Dominguez. "Marine n-3 fatty acids have been shown
to enhance the cancer-killing effect of certain chemotherapy drugs and
radiotherapy in experimental studies. Since these anti-cancer agents may act, at
least in part, through similar oxidative mechanisms as n-3 fatty acids-which is
why patients under chemotherapy are advised not to take antioxidant vitamin
supplements-understanding the anti-cancer effect of marine n-3 fatty acids may
be important to finding the mechanisms for killing cancer cells."
Manuela Gago-Dominguez, J. Esteban Castelao, Can-Lan Sun, David Van Den Berg, Woon-Puay Koh, Hin-Peng Lee, and Mimi C. Yu, "Marine n-3 fatty acid intake, glutathione S-transferase polymorphisms and breast cancer risk in postmenopausal Chinese women in Singapore. Carcinogenesis, published early online; doi:10.1093/carcin/bgh230. (Okt. 2004)