With regard to cancer, several studies have specifically explored the links between onion and garlic consumption and the risk of colorectal, stomach and prostate cancer. In general, these studies have found that the more you consume, the lower the risk of developing these types of cancer.
However, less extensive research led by Gauri Desai of the University at Buffalo (USA) has focused on the link to breast cancer.
The experts set out to investigate this issue further, observing a population of women in Puerto Rico. The reasons for choosing this population were two: first, “Puerto Rico has lower rates of breast cancer compared to the United States, which makes it an important population to study,” Desai explains; second, a condiment called “sofrito”, which consists mainly of garlic and onion, represents a traditional Puerto Rican sauce – although also very popular in Spain – that is widely consumed throughout the island.
The researchers used hospital and clinic records to identify 314 women ages 30 to 79 who had breast cancer between 2008 and 2014. They also included 346 control participants who were matched for age and residential area. Control subjects had no history of cancer. They used a food frequency questionnaire to ask about dietary patterns and total onion and garlic intake, which included the consumption of sofrito.
The team used unconditional logistic regression to examine the association between onion and garlic intake and the development of breast cancer, adjusting for factors such as age, education, family history, body mass index, smoking, and others.
The benefits of stir-fry
The researchers found an inverse association between moderate and high total consumption of onion and garlic and cases of breast cancer, compared to low consumption of these vegetables. Their findings were consistent after the researchers had stratified the results according to menopausal status, suggesting that “high consumption of onion and garlic is protective against breast cancer in the [studied] population.”
“Sofrito intake, when tested alone, was inversely associated with breast cancer; for those who consumed sofrito more than once a day, there was a 67% decreased risk, compared to those who never consumed. We found that Among Puerto Rican women, the combined intake of onion and garlic, as well as sofrito, was associated with a lower risk of breast cancer, “says Desai.
Why can onions and garlic reduce the risk of cancer?
Although the study was observational and cannot explain the mechanisms behind the findings, the researchers suspect that the flavanols and organosulfur compounds abundant in onion and garlic may be responsible for the anticancer effects.
In particular, the S-allylcysteine, diallyl disulfide, and diallyl sulfide in garlic, for example, have shown “anticancer properties in humans, as well as in experimental studies in animals,” comments Lina Mu, leader of the work that publishes the journal Nutrition and Cancer.
Study limitations
The authors also acknowledge some limitations in their research. For example, “ the study size was small, particularly for stratified analyzes on menopausal status,” the experts write. Second, the number of people who had never consumed garlic or onion was too small to use as a reference group. Therefore, the low exposure group still consumed some onion and garlic. For this reason, the results “may have underestimated the true association between garlic and onion consumption and breast cancer.”
“In addition, there is no standardized recipe for sofrito, a condiment that is usually homemade and, therefore , the recipe varies a bit from cook to cook, ” add the authors. “Therefore, we could not estimate the amount of onion and garlic in the sauce either.”
“Although the recipe for stir-fry varies somewhat, other ingredients are generally added, such as bell peppers, tomatoes, coriander, and black pepper. Since we did not adjust our models for these ingredients, we cannot be sure that our results were due to the sole effect of onion and garlic “, conclude the experts.
Referencia: Onion and Garlic Intake and Breast Cancer, a Case-Control Study in Puerto Rico. Gauri Desai, Michelle Schelske-Santos, Cruz M. Nazario, Rosa V. Rosario-Rosado, Imar Mansilla-Rivera, Farah Ramírez-Marrero, show all. Received 19 Apr 2019, Accepted 29 Jul 2019 DOI: https://doi.org/10.1080/01635581.2019.1651349
