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Onions, Garlic, and Lower Risk of Breast Cancer

Good news for women who really like to eat onions and garlic! A study conducted in Puerto Rico found that women who more frequently consumed garlic and onions, especially  "sofrito", had a lower risk of breast cancer. Both onions and garlic are an important part of the Puerto Rican diet, and sofrito is a raw onion and garlic based condiment or puree that is the base for many Puerto Rican dishes.

This study found that as consumption of garlic and onions increased, there was a decrease in the risk of breast cancer, which was true for women both before menopause or after menopause. There was evidence of a dose-response (the more eaten, the lower the risk). This association was especially strong for women consuming sofrito more than once a day - they had a 67% decrease in breast cancer risk compared to those who never ate sofrito.

The researchers point out that studies show that the more one eats of onions and garlic, the lower the risk of certain cancers, such as the lung, prostate, colon, and stomach. However, the evidence for whether it has a protective effect on breast cancer has been mixed, but with most studies finding a protective effect with frequent consumption of onions and garlic, especially raw onions and garlic. One study in Mexico found a 70% lower risk of breast cancer in those eating one slice of onion per day, compared to those eating less than one slice. The researchers also mentioned that studies find that cooking onions and garlic reduces their anticancer activity.

From Science Daily: Onion and garlic consumption may reduce breast cancer risk  

Onions and garlic are key ingredients in sofrito, a condiment that's a staple of Puerto Rican cuisine. They may also be a recipe for reducing the risk of breast cancer.

"We found that among Puerto Rican women, the combined intake of onion and garlic, as well as sofrito, was associated with a reduced risk of breast cancer," said Gauri Desai, the study's lead author, who is an epidemiology PhD student in UB's School of Public Health and Health Professions.

In fact, those who consumed sofrito more than once per day had a 67% decrease in risk compared to women who never ate it. The idea for the study stemmed from previous scientific evidence showing that eating onions and garlic may have a protective effect against cancer.

Puerto Rico was a perfect place to study, because women there consume larger amounts of onions and garlic than in Europe and the U.S., due largely to the popularity of sofrito, Desai noted. Onions and garlic also are eaten regularly in "guisos" (stews), as well as in bean- and rice-based dishes in Puerto Rican cuisine. In addition, "Puerto Rico has lower breast cancer rates compared to the mainland U.S., which makes it an important population to study," Desai said.

So, why the focus on these two ingredients? "Onions and garlic are rich in flavonols and organosulfar compounds," Desai said. In particular, garlic contains compounds such as S-allylcysteine, diallyl sulfide and diallyl disulfide, while onions contain alk(en)yl cysteine sulphoxides. "These compounds show anticarcinogenic properties in humans, as well as in experimental animal studies," said Lina Mu, the study's senior author, who is an associate professor of epidemiology and environmental health at UB.

Study participants were enrolled in the Atabey Study of Breast Cancer, a case-control study named after the Puerto Rican goddess of fertility. The study was conducted between 2008 and 2014 and included 314 women with breast cancer and 346 control subjects.

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