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Researchers say onions and garlic contain compounds that have anticarcinogenic properties. Getty Images
  • Researchers report that women in Puerto Rico who eat onions and garlic on a daily basis have a lower risk of breast cancer.
  • They say onions and garlic contain flavonols and organosulfur compounds that have anticancer properties.
  • Experts say women should focus on healthy diets, not just onions and garlic, as well as regular exercise as ways to reduce the risk of breast cancer.

Eating onions and garlic every day may help protect you against breast cancer.

That’s according to a new study published in Nutrition and Cancer.

Onions and garlic contain flavonols and organosulfur compounds.

These compounds show anticarcinogenic properties, according to researchers.

Previous studies have suggested that garlic and onions may have some protective effect on certain cancers, particularly those of the gastrointestinal tract.

So, scientists from the University at Buffalo and University of Puerto Rico investigated the association between garlic and onions and breast cancer.

They chose Puerto Rico for their population-based study because it has a lower breast cancer rate than the United States mainland.

Also, women who live there tend to eat more onions and garlic than women in the rest of the United States or Europe.

One reason is that onions and garlic are key ingredients in sofrito, a popular condiment in Puerto Rican cooking.

The research concluded that the combination of onions, garlic, and sofrito was associated with lower risk of breast cancer.

The study included 314 women with breast cancer and 346 other women between the ages of 30 and 79.

The research took place between 2008 and 2014.

The researchers adjusted for factors such as smoking, family history, and age.

Questionnaires were used to estimate dietary intake of onions and garlic, including sofrito.

Women who reported eating sofrito more than once a day had a 67 percent decrease in risk compared to women who never ate it.

Total intake of garlic and onions is more important than sofrito intake, according to the researchers.

They acknowledge several study limitations. One is its small size. Another is the difficulty of estimating the amounts of onions and garlic actually consumed.

There’s a lot of variation in sofrito recipes. So, it’s hard to say how much onion and garlic a serving contains. In addition, sofrito typically contains a variety of other ingredients, including tomatoes, peppers, and cilantro.

Other studies involving onions, garlic, and cancer have encountered similar problems with estimating amounts.

The 2016 review concluded that there are gaps in the research, especially when it comes to determining healthy amounts and cofounding factors.

Dr. Sangeeta Aggarwal is an oncologist at Sobrato Cancer Center at Santa Clara Valley Medical Center in California.

“In general, we know that a diet high in garlic specifically has been associated with lower cardiac risk and lower risk of lung cancer,” she told Healthline.

“It’s never been associated with breast cancer, so this is a new finding,” said Aggarwal.

She found the study to be well done with carefully chosen “control” participants to match age, geographic area, and other characteristics.

However, she’d prefer to see a larger group of people studied. She also observed that the women were asked about onion, garlic, and sofrito consumption for the previous 12 months.

“In my opinion, 12 months’ exposure is very short to say that it is associated or protective of breast cancer. Nevertheless, it is an intriguing study,” continued Aggarwal.

Kailey Proctor, MPH, RDN, is an oncology dietitian at the Center for Cancer Prevention and Treatment at St. Joseph Hospital in California.

Proctor told Healthline it’s important not to sensationalize these types of findings, since cancer involves so many lifestyle and genetic factors.

For women who have had breast cancer, she encourages maintaining a healthy body weight to reduce the risk of a recurrence or secondary cancer.

Proctor stresses the importance of exercise.

“Being physically active helps you maintain a healthy body weight, which we know reduces the risk of cancer. Find an activity you enjoy and can stick to long term,” said Proctor.

Aggarwal doesn’t necessarily want women to take this study to heart either because there’s so much more to learn.

But she does urge women to pay attention to diet, especially where alcohol is concerned.

“A heavy amount of alcohol, especially more than 7 drinks per week is associated with breast cancer risk,” she explained.

Aggarwal does not recommend that her patients attempt an “overwhelming” organic or vegetarian diet.

“That’s not what caused breast cancer and not what could affect the outcome eventually. What I tell my patients is to be vigilant about excessive sugar and a fatty diet and anything that would raise weight,” she said.

Aggarwal also cautions against use of plant-based estrogen for symptoms of menopause, as this may increase the risk of breast cancer.

When it comes to diet, Proctor advises looking at the big picture.

“Instead of hyper-focusing on a certain nutrient, make sure you are eating balanced meals (vegetable, lean protein, healthy fat, complex carbs) while minimizing intake of added sugar,” she said.

Proctor recommends a diet that includes plenty of fruits and vegetables, plus whole grains.

“I can’t say it enough but add more color to your plate to ensure you are getting a variety of nutrients (vitamins, minerals, antioxidants, and phytonutrients),” she said.

“Garlic and onions are an amazing way to add flavor to more plant-based dishes. You can grill onions in the summer to have with lean protein, like chicken or seafood, or sauté them in a stir-fry with broccoli, peppers, and carrots. So again, it’s about adding more vegetables — and garlic and onions are a great way make them taste better for picky eaters,” said Proctor.

She advises limiting processed sugary foods and drinks that lack nutritional value.

“These foods and beverages are easy to over-consume, which may lead to weight gain. What we do know about cancer and diet is that maintaining a healthy body weight greatly reduces the risk of breast cancer as well as 11 other types of cancers,” said Proctor.