Sorry got is wrong way round it seems that the incidence of breast cancer among the immigrant population increased after moving to America and other countries from what it had been, this was possibly linked to a change in their diet after moving from Poland to a new country.
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Polish Women in the Midwest
To sort out which factors might affect breast cancer risk among such migrant populations, Dorothy Rybaczyk Pathak , Ph.D., from Michigan State University in East Lansing, and the University of New Mexico in Albuquerque, and colleagues turned to the Polish migrant communities around Chicago and Detroit. Breast cancer incidence in these communities tripled within one generation, reaching the high rates of U.S.-born women. The rapid change in rates pointed to diet as a possible risk factor. Pathak presented the work at the American Association for Cancer Research's prevention meeting in Baltimore in October."
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In a case–control study among women within these communities, the researchers found that raw- or short-cooked cabbage and sauerkraut consumption (more than three servings per week) during adolescence and adulthood was associated with a 72% reduced risk of breast cancer compared with those who consumed 1.5 or fewer servings per week. Consumption of long-cooked traditional Polish dishes, such as hunter's stew, cabbage rolls, and pierogies, had no effect on risk.
The inverse association was strongest when consumption occurred in adolescence, even if the women did not continue to consume large amounts during adulthood. High consumption during adulthood was also associated with reduced breast cancer risk, even for women who ate intermediate or small amounts during adolescence.
“This is a unique population,” said Pathak, herself a Polish-born American. “Poles consume cabbage in many forms, and a lot of it—three times more than Americans. Working with the migrant population allowed us to study the effect of a wide range of exposures to cabbage that can't be found in the U.S. population.”
Cabbage is a cruciferous vegetable, which includes broccoli, Brussels sprouts, kale, collard greens, and cauliflower. These plants contain glucosinolates that break down in the body into products with anticarcinogenic properties. Cooking decreases the bioavailability of these agents, which have been shown to reduce the risk of various cancers in both animal and human studies.
“Observing the effect for only the raw or lightly cooked [vegetables] fits well with the bioavailability of these compounds in our diet,” Pathak said."
https://academic.oup.com/jnci/article/98/7/436/2522057
Not the original article but similar.