Flaxseeds Influence Gut Microbiome and May Reduce Breast Cancer Risk

• Researchers found a link between the gut microbiome and expression of miRNAs in breast tissue in mice, one influenced by flaxseed lignans.
• miRNAs are molecules that regulate the expression of genes, which affects the kinds and amounts of proteins made in cells.
• Experts caution that while animal studies can help us understand connections like this, the results may not apply directly to humans.

Flaxseeds and other foods rich in lignans may reduce the risk of developing breast cancer, suggest preliminary results from an animal study.

More research is needed, though, including clinical trials in people.

In the study, published Dec. 7 in Microbiology Spectrum, researchers focused on how lignans influenced the relationship between the gut microbiome — bacteria and other microbes living in the gastrointestinal tract — and the generation of microRNAs (miRNAs) in the mammary gland.

miRNAs are noncoding RNAs that regulate the expression of genes in cells, which affects the kinds and amounts of proteins made there.

“If these findings are confirmed, the microbiota becomes a new target to prevent breast cancer through dietary intervention,” study author Elena M. Comelli, PhD, associate professor in the Department of Nutritional Sciences at the University of Toronto in Canada, said in a news release.

Flaxseed’s effects on the microbiome

In the study, researchers examined the effect of flaxseed lignans on the gut microbiome of young female mice. In particular, they looked at the amounts and types of microbes in the cecum, the first part of the colon.

Flaxseeds are the richest dietary source of lignan precursors, but these compounds are also found in other seeds, whole grains, legumes, fruit and vegetables.

When plant lignans are ingested, they can be converted by intestinal bacteria to other compounds that are absorbed into the bloodstream.

Some previousTrusted Source research has found that postmenopausal women who consume higher amounts of lignans in their diet have a lower risk of breast cancer. Another 2010 study found that dietary intake of lignan was associated with a lower risk of dying from breast cancer.

Jo L. Freudenheim, PhD, professor in the Department of Epidemiology and Environmental Health in the University at Buffalo’s School of Public Health and Health Professions, the lead author of 2010 study, said the findings of the new research might provide a potential mechanism for the results seen in her study.

Gut microbiome and gene expression

In the new study, researchers found a relationship between the cecal microbiome and mammary gland miRNA expression, which was altered by a diet containing flaxseed lignan components.

In particular, mice fed lignan components generated specific miRNA responses in the mammary gland, including the production of miRNAs related to the regulation of genes involved in breast cancer.

“[This study] shows changes in the expression of miRNAs in the breast with changes in the gut microbiome, with possible changes in metabolic processes that could be important in breast cancer,” Fruedenheim told Healthline.

“This provides some evidence for another potential mechanism linking the gut microbiome with breast cancer,” she said.

However, she said there are a large number of steps that must occur in the body between the changes in miRNAs and the development of cancer, both in mice and in people.

In addition, “it is not clear to what extent the microbiota profiles that [the researchers] are studying in a laboratory setting are relevant to humans living in a more complex environment,” she said.