Breast Cancer and Probiotic Link Largely Untapped

Guest BloggerClinical Corner

breast cancer

With breast cancer a leading cause of death among woman globally, it’s no surprise that billions of dollars are spent searching for better outcomes. Much of the largess is poured into cancer drugs and other treatments. Relatively little is spent exploring a microbiome connection.

That’s a shame because breast microbiota may be fertile ground for intervention.

How so?

First, microbial composition is linked to cancer risk. And we know that breast milk, rich in lactic acid bacteria, counters some cancer-causing species. That may be one reason why breastfeeding reduces cancer risk for mother and child.

Second clue: healthy breast tissue microbes differ from that of tissue taken from women with breast tumors. One novel study showed that higher relative abundances of bacteria that had the ability to cause DNA damage in vitro were detected in breast cancer patients, as was a decrease in some lactic acid bacteria, known for their anti-carcinogenic properties.

Of course, saying that certain bacteria can cause cancer is premature. Nevertheless, many studies show that pathogenic bacteria are inextricably linked by various means: damaging DNA, producing carcinogenic metabolites, encouraging new tumors and interfering with tumor suppressors.

Probiotics and breast cancer

We know that consuming probiotics and fermented products containing lactic acid bacteria was linked to reduced breast cancer risk in some epidemiological studies.

For an excellent review of probiotic research on breast cancer read “Modification in the diet can induce beneficial effects against breast cancer” from Felix Aragón and colleagues in San Miguel de Tucumán, Tucumán, Argentina. The work appeared in World Journal of Clinical Oncology.

A few studies supporting the link:
  • Long-term consumption of beverages containing L. casei Shirota and soy isoflavone was inversely associated with the incidence of breast cancer in a study with Japanese women.
  • Milks fermented by B. infantis, B. bifidum, B. animalis, L. acidophilus and L. paracasei inhibited breast cancer cell line growth in vitro in another older study.
  • Yogurt consumption in one study was negatively correlated with breast cancer.
  • Fermented milks produce metabolites that contribute to anti-tumor activities.
  • Kefir feedings in mice diminished tumor growth most likely due to metabolites.
  • A strain of L. casei  decreased the growth rate of tumor and prolonged the survival of the animals with invasive ductal carcinoma.

There are other studies but mostly in mice and not nearly as many as the possibilities would suggest. Bolstering the immune response appears to be a key strategy of these isolated strains of probiotics.

Probiotics are just one part of the cancer puzzle. Fermented foods including yogurt, kefir, kombucha, and cultured vegetables absolutely should be part of everyone’s diet, male or female.

Changes in dietary patterns are related to less risk of cancer. There’s more: patients diagnosed and treated for breast cancer who adopt better diets can improve survival.

Together with a healthful cancer-fighting lifestyle (no tobacco, alcohol, ideal body weight, exercise and lots of fruits and vegetables), probiotics may add another potent tool to the arsenal against cancer.