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In 2008, the National Institutes of Health began the Human Microbiome Project, a 5-year international research initiative to identify the associations between bacteria and human health and disease. Bacteria inhabit every nook and cranny of every surface of our body—inside and out. Termed the “microbiome”, these thousands of bacterial species that are associated with the human body are responsible for a healthy immune response, protection against unhealthy or “pathogenic” bacterial and viral invasion, the production of vitamins, and the digestion and absorption of the food we eat.

Of the trillions of cells that make up a human, ninety percent are bacteria, viruses and other microbes. That’s right. You are more bacteria than human! In fact, the Human Genome Project has found that we have only about 22,000 genes while the bacteria associated with each of us totals 8 million genes! This finding has profound implications for human health.

It is now understood that there exists complex interactions between bacteria and the cells that line the wall of the intestine. Some bacteria communicate with intestinal cells in a way that damages the intestine, thereby increasing its permeability and thus the movement of toxins and food allergens into the body. When this occurs, the immune system of the digestive tract, known as the GALT (Gut Associated Lymphatic Tissue) increases its production of inflammatory chemical mediators. These mediators of inflammation have the ability to modify immune system activity and inflammation throughout the entire body. Other bacteria, the species most commonly found in probiotic supplements, have the ability to heal the lining of the intestine as well as to decrease inflammation. Thus, there is an ongoing competition between species of bacteria that are beneficial to our health and species which are detrimental. This competition has far-reaching consequences, largely owing to the modulation of systemic immunity and inflammation. Research has found a connection between the intestinal microbiome and the following conditions:

Breast Cancer: Lactobacillus acidophilus, a commonly used probiotic, has been found in a recent study to improve immune function, decrease inflammation, and reduce tumor growth patterns in breast cancer-bearing mice.

Asthma: A 2011 study summarized findings that demonstrate a direct correlation with the disruption of healthy gut bacteria and asthma. This paper presents evidence for the perinatal programming of asthma via the intestinal microbiome. Numerous factors can modify the dominant species of intestinal bacteria and include perinatal stress, breastfeeding, probiotics and antibiotics.

Obesity: In a 2012 paper entitled “The Role of the Manipulation of the Gut Microbiota in Obesity,” the authors summarize findings that show that the manipulation of gut bacteria by diet, antibiotics, or probiotics could promote, prevent or reverse obesity.

Colon Cancer: An October 2012 study in Nutrition and Cancer found that two different species of Lactobacilli bacteria were able to inhibit gastric and colorectal cancer cells as well as induce cancer cell death. What is also noteworthy about this study is that cancer inhibition was accomplished with both live and dead bacteria. Traditionally it has been believed that only live probiotics confer health benefits.

Human Papilloma Virus (HPV) and Cervical Dysplasia: A study in the European Journal of Cancer Prevention found that women who consumed a daily probiotic drink for 6 months were twice as likely to cure their dysplasia compared to the control group who did not consume the probiotic. Additionally, the virus was cleared in about 50% more women using the probiotic. This finding was confirmed in another study of Bifidobacter on human papillomavirus type 16.

The aforementioned conditions are only a sampling of the wide range of illnesses for which a connection is being discovered with the microbiome. It is likely that a relationship between all illnesses and intestinal bacteria will be uncovered owing to the ability of bacteria to modify immunity and inflammation throughout the entire body. This can be stated with reasonable certainty because research has shown that inflammation is at the core of all disease.

It is my recommendation that everyone take a probiotic. More importantly, however, is the need to eat in a manner that will support populations of beneficial bacteria. My next posting will discuss this in greater detail.