Updated on August 31, 2015
The Gut Microbiome by Alexandra Weinstein, RD CDN
Gut health has been a hot topic lately. The buzz-worthy word “gut” refers to the alimentary canal, including the intestine and stomach: essentially the entire Gastrointestinal Tract or digestive tract. New research has revealed that the bacterial content (or “microbiome”) of your gut may impact overall health, particularly the risk of certain chronic diseases. The human gut contains a vast number of microorganisms known collectively as the “gut microbiota.” Factors including age, genetics, environment and diet may influence the makeup of this microbiota. Each of us has a unique combination of healthy microflora (bacteria) living in our digestive tracts. Our unique microflora is affected by certain factors such as how we were born (vaginal delivery vs. caesarian section), whether or not we were breastfed, what antibiotics we may or may not have been exposed to in childhood, illness, diet, and other environmental factors. The microbiome becomes more stable with age, meaning less subject to change. The microbiome community carries out a range of useful functions for the host, including digesting foods we cannot easily digest including some fibers, stimulating the immune system, and blocking the growth of harmful microorganisms. Though the research is quite young and there is little to put into practice at this time, the goal is that treatment for some diseases can be tailored to each person based on their unique microbiome.
The exact content, meaning types of bacteria, in our microbiome and how that affects our risk of chronic disease has been the subject of recent research. Researchers have been looking into the gut microbiome for how it relates to Inflammatory Bowel Disease, Irritable Bowel Disease, obesity, insulin resistance, Type 2 Diabetes, and other chronic health conditions. For example, researchers have found a reduction in diversity of the microbiome which is associated with Inflammatory Bowel Disease. Regarding obesity, recent research in mice has highlighted an increased ratio of a class of microbes called Firmicutes to Bacteroidetes in obese mice relative to their lean counterparts. (SOURCE: The gut microbiota and its relationship to diet and obesity: New insights. Siobhan F. Clarke, Eileen F. Murphy, Kanishka Nilaweera, Paul R. Ross, Fergus Shanahan, Paul W. O’Toole, and Paul D. Cotter. Gut Microbes. 2012 May 1; 3(3) 186-202.) Researchers have shown that long-term dietary patterns affect the ratios of Bacteroides, Prevotella, and Firmicutes, and that short-term changes may not have major influences. In addition, researchers have studied the impact of a strict vegan or vegetarian diet on the microbiota, and found a significant reduction in Bacteroides spp., Bifidobacterium spp., and the Enterobacteriaceae, while total bacterial load remain unaltered (SOURCE: The Microbiome in Inflammatory Bowel Diseases: Current Status and the Future Ahead. Aleksandar D. Kostic,1 Ramnik J. Xavier,1,2 and Dirk Gevers. Gastroenterology. 2014 May; 146(6): 1489-1499.). The implications of these changes in microflora have yet to be fully discovered, but stay tuned!
What can we do to improve our gut health? Foods that support gut health include fermented foods (lactic acid bacteria have acted on the food pre consumption to break down the sugars into lactic acid, making the food easier to digest) such as sauerkraut, pickles, olives, tempeh, Kimchi, Kefir, yogurt, miso, cultured non-dairy alternatives such as some soy, almond, or coconut milk-based yogurt products, soy sauce. These foods contain probiotics, or live bacteria, that can potentially improve our population of these healthy microflora. Probiotics are live microbial organisms present in food or supplement form. On the flip side, it would be advisable to avoid animal products treated with antibiotics, as these might destroy healthy gut flora.
In addition to eating foods that contain probiotics, they are also available in supplemental form. With the supplement market so flooded, how do we choose a probiotic? Look for an expiration date- this will help guarantee that the pill does actually contain live cultures, because a probiotic is no good if the bacteria are not live. Probiotics are filled with living microorganisms that if not properly made, shipped or stored, may not actually contain what they were manufactured with. Look for a probiotic with multiple different strains of bacteria. Look for at least 1 billion or more live organisms. Consumerlabs.com is a great resource for information on whether products actually contain what they say they contain, and what contaminants might be present. Store probiotics in a cool, dry place out of sunlight. Some probiotics require refrigeration. Generally, studies have indicated that probiotics are safe, however caution should be taken in a person who is very young, very old, or immunocompromised, and particularly in the critically ill population.
A prebiotic is “a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microflora that confers benefits upon host well being and health”. (SOURCE: Probiotics, Prebiotics, and Synbiotics. Michael de Vrese, J. Schrezenmeir. Food Biotechnology. Advances in Biochemical Engineering/Biotechnology Volume 111, 2008, pp 1-6607 May 2008). They are nondigestible or partially digestible food ingredients that stimulate the growth of healthy bacteria in the colon. Food sources of prebiotics include inulin and chicory root (nondigestible fructo- oligosaccharides), which can be added to foods to increase fiber content, or can be found in Jerusalem artichoke, onions, asparagus, leeks, dandelion root, burdock, and artichoke. Of note, prebiotic foods may be poorly tolerated in those with Irritable Bowel Syndrome due to their propensity to be fermented by gut microflora and produce gas.
To close, the subject of the gut microbiome is fascinating, and we have just broken the surface in the world of research on this subject. The best advice for now would be to consume both pre-and probiotic foods as tolerated, as part of a healthy, “clean” diet, and to avoid pesticides, hormones and antibiotics in food as possible. I look forward to learning more about what our unique microbiome means!
Alexandra Weinstein, RD CDN, is a Manhattan based Registered Dietitian. Alex graduated from New York University and went on to complete her Dietetic Internship at Brigham and Women’s Hospital in Boston. Alexandra has worked for New York City teaching hospitals for the last five years, both in inpatient and outpatient settings. Alex’s expertise is focused around Digestive Disorders.