Can Eating Garlic and Onions Protect Against Breast Cancer?

The findings of a new study of women in Puerto Rico suggest that consuming high amounts of onion and garlic may have a protective effect against breast cancer. The results were published online in August in Nutrition and Cancer. ¹

“Findings regarding the association of onion and garlic consumption with breast cancer have been inconsistent,” wrote study authors led by Gauri Desai, a PhD student in epidemiology at the University of Buffalo.

This joins other evidence that these foods may protect against prostate, lung, and gastric cancers as well. Studies in several countries including France, Mexico, and China found inverse associations between consumption and breast cancer risk, but others conducted in the Netherlands, Italy, and again in China found no such association.

Onions and garlic contain flavonols and organosulfur compounds which could contribute to anti-carcinogenic effects. These foods are important in the Puerto Rican diet, and are most commonly consumed in the form of a seasoning condiment known as sofrito.

The researchers conducted a population-based case-control study comparing garlic and onion intake, including in the form of sofrito, in 314 women with breast cancer and 346 controls.

Women with breast cancer were slightly older than controls at 58.7 years versus 54.1 years (P < 0.01). Compared to the controls, the women with breast cancer had a higher degree of education (P < 0.01), a lower BMI (P < 0.01), and fewer children on average (2.6 vs 2.9 children; P < 0.01). They also had a higher family history of breast cancer (P < 0.01).

For total garlic and onion intake, women in the highest tertile of consumption had an adjusted odds ratio (OR) for breast cancer when compared to the lowest tertile of 0.51 (95% CI, 0.30-0.87). For those in the medium consumption category, the OR was 0.59 (95% CI, 0.35-1.01). The trend across these groups was significant (P = 0.02).

When the cohort was stratified by menopausal status, some differences emerged. The OR for the highest consumption group compared with the lowest group among premenopausal women was 0.52 (95% CI, 0.19-1.40; P for trend = 0.17). Among postmenopausal women, though, the OR among the highest consumption group was 0.47 (95% CI, 0.24-0.91), and in fact the medium consumption group also had a significantly lowered risk compared to the lowest group, with an OR 0.49 (95% CI, 0.25-0.94; P = 0.07 for trend). The authors noted, though, that the study’s size does limit any interpretation of the stratified results.

 “Our study provides evidence that the consumption of onions and garlic is associated with reduced risk of breast cancer,” the authors concluded. “Further prospective studies and clinical trials are necessary to evaluate the use of onions and garlic in breast cancer prevention.”