'Inflammatory Diet' May Boost Breast Cancer Risk

Eating an "inflammatory diet" as a teen may increase a woman's risk of breast cancer, a new study suggests.

Researchers studied women who, as high schoolers, had consumed diets thought to increase levels of inflammation in the body. Results showed that these women were more likely to develop breast cancer as adults prior to menopause, compared with women who ate a different type of diet as high schoolers

Women who consumed inflammatory diets during their 20s, 30 and 40s were also at increased risk of breast cancer before menopause.  

An inflammatory diet is one that's low in vegetables and high in sugar-sweetened and diet soft drinks, refined sugars and carbohydrates, red and processed meats, and margarine, said study researcher Karin B. Michels, an epidemiology professor at the University of California, Los Angeles Fielding School of Public Health. Consuming these foods has been linked to higher levels of markers of inflammation in the body, Michels said. [6 Foods That May Affect Breast Cancer Risk]

"Our results suggest that a habitual diet that promotes chronic inflammation when consumed during adolescence or early adulthood may indeed increase the risk of breast cancer in younger women before menopause," Michels said in a statement.

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Many factors affect a woman's risk of breast cancer, including her genetic predisposition to the disease, as well as other demographic and lifestyle factors. The new study suggests that an inflammatory diet may be another factor that affects women's risk of the disease, Michels said.

For the study, the researchers analyzed information from more than 45,000 female nurses who began the study when they were ages 27 to 44, and were followed for 22 years. Every four years, the women answered questions about their current diets. In addition, when they were ages 33 to 52, they were asked to complete a survey about the types of food they ate in high school.

The researchers gave each woman's diet an "inflammatory score," with higher scores indicating diets that, in previous studies, have been linked with higher levels of inflammation in the body.

Women were then divided into five groups based on the inflammatory scores for their high school diets. Those in the group with the highest score were 35 percent more likely to develop premenopausal breast cancer, compared with those in the group with the lowest score.

The researchers also performed a similar analysis using the women's inflammatory scores for their diets in adulthood (when the women were ages 27 to 44). This analysis found that those women with the highest scores were 41 percent more likely to develop premenopausal breast cancer, compared to those with the lowest scores. [7 Tips for Moving Toward a More Plant-Based Diet]

The researchers did not find a link between an inflammatory diet and the risk of breast cancer after menopause.

It's important to note that the study found only an association between an inflammatory diet and the risk of breast cancer, and cannot prove that this type of diet caused the women's breast cancer. In addition, the study asked women to recall the diets they ate in high school, and some people may not have remembered their diets very well, which could affect the results, the researchers said.

The study was published today (March 1) in the journal Cancer Research
.