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Fiber is part of a healthy diet, and it turns out it could help prevent breast cancer, too.

The Cancer Prevention Institute of California recently published a report in Cancer Medicine touting the effectiveness of beans in thwarting the disease. They say beans were more effective than fruits and veggies at preventing the disease.

The nutrition community feels strongly that that idea should be debunked.

“Fiber may play an important role in breast cancer reduction in relation to grain and bean consumption in subsets of the population, but the majority of research has shown that when it comes to fruits and vegetables (and bean and whole grain consumption), it’s their phytonutrients, antioxidants, vitamins and minerals that are responsible for slaying cancer cells,” said New York nutritionists Tammy Lakatos Shames and Lyssie Lakatos.

“While fiber may offer protection against cancer, to say a food is better than another because it has more fiber isn’t the case,” they add.

Examining the science

In the recent study, researchers looked at data on fiber intake from 2,135 women with breast cancer and compared it to data on 2,571 women without breast cancer.

The researchers found a 25 percent reduction in breast cancer in those who consumed bean fiber, total beans or total grains. Researchers did not find fiber intake from fruits and vegetables to reduce breast cancer risk.

They found 28 to 36 percent reductions in women with higher bean intake who had estrogen receptor- and progesterone receptor-negative breast cancers compared to women with receptor-positive breast cancer.

“Most currently known risk factors for breast cancer apply to hormone receptor-positive subtypes. This paper adds to the evidence that dietary factors may play a role in ER-PR- breast cancer, which is more frequently diagnosed in African American and Hispanic women,” Esther John, PhD, the lead researcher, said in a statement.

For U.S.-born Hispanics, African Americans, and whites, fruits and vegetables were the primary source of fiber intake.

High grain intake lowered the risk of ER-PR- breast cancer but only among white women.

According to the researchers’ report, fiber intake via fruits and vegetables did not reduce breast cancer risk — a notion that nutrition professionals are questioning.

Beans over fruits and veggies?

Jessica Levinson, a dietitian from New York, was pleased that the study touted beans because they are an important part of a healthy diet.

“But it doesn’t mean fruits and vegetables are not,” she told Healthline.

Levinson pointed out a few flaws in how the study results may be interpreted.

Beans are a staple in the diets of many Hispanics, so that becomes a limitation of the study. The authors note that in the report.

Kim Larson, a nutritionist and health coach at Total Health in Seattle, concurred with Levinson’s thoughts.

“This study was conducted with two-thirds of a Hispanic population and one-third of non-Hispanic whites, which explains why the bean intake and total fiber from beans is so high — much higher than we see in the average mixed representative population,” Larson noted.

Also, the study data was self-reported — another red flag.

“We also must consider this dietary intake was self-reported from only a food frequency questionnaire that groups foods, not daily recorded food records which often give us more specific information — both of which have high errors in accuracy,” Larson told Healthline.

The fiber intake of the women was at least 25 grams a day, but the general population typically doesn’t consume that much on a daily basis.

Fiber facts

In general, fiber has been thought to have an inverse relationship to risk of breast cancer, Larson said.

“The hypothesis is that fiber is thought to lower estrogen by increasing the amount excreted fecal, while also decreasing intestinal reabsorption of estrogen, along with possibly regulating the bioavailability of insulin-like growth factors, which play a role in breast cancer development,” she explained. “All of these things are thought to help lower blood estrogen levels, helping to keep breast cancer development at bay.”

More research is needed on how, exactly, fiber works with regard to breast cancer prevention.

“We do not know enough about how and why fiber is involved in reducing breast cancer risk, but we have evidence that increasing total fiber intake helps protect against various diseases, like heart disease and other types of cancers,” she added.

Beans not only contain a lot of fiber, they also have other cancer-protecting benefits that come from their antioxidants, lignans, saponins, soluble fiber, and phytochemicals.

“That said, we can’t discount the wonderful and known health benefits of consuming a wide range of fruits and vegetables that contain fiber, antioxidants, and numerous vitamins and minerals,” Larson said.