In that the human body contains billions of microorganisms, and microbial cells found in the human gut are estimated to outnumber human cells by ten-to-one in healthy adults, Ece Mutlu, from Rush University Medical Center (Illinois, USA), and colleagues have embarked on a research study, funded by the U.S. Department of Defense, to chart the presence of microorganisms found within the gut and to explore how microbial imbalances may impact diseases like breast cancer.  While about 20 to 25% of the risk of developing breast cancer is related to family history, the known breast cancer susceptibility genes such as BRCA2 and BRCA 2 explain less than 5-10% of the total breast cancer cases attributable to familial factors.  Researchers are thus exploring the possibility that the gut microbiome passed on from mother to child may be another familial factor previously never accounted for in the genetic risk models.  Explains Dr. Mutlu:  “The currently recognized environmental risk factors are estimated to account for only 40 % of the variance in breast cancer incidence.  There is a large body of evidence implicating that dietary factors such as alcohol, high fat foods are also possible breast cancer risk enhancers, and fruits and vegetables are protective.  If we are able to find the microbes responsible for particular diseases, it may increase the likelihood of developing new diagnostic tests and treatments for diseases like breast cancer.”