Did you know your gut is home to over four pounds of bacteria, tens of trillions of microorganisms, and over 1,000 different species of bacteria containing more than three million genes? (1) Believe it or not, we all possess an enormous ecosystem of microbes and bacteria in our intestinal tract, otherwise known as the gut microbiome. Diverse and constantly evolving, the gut is responsible for much more than just digestion. In recent years, growing evidence has shown that the gut plays a central role in your overall wellbeing, including supporting a healthy immune system and even affecting your risk for disease and obesity. (1)
The World Within: Getting To Know Your Gut
It sounds counterintuitive, but having a bunch of bacteria in your belly is actually vital to keeping harmful pathogens and "bad" bacteria out. A healthy human intestine is home to thousands of species of bacteria, all of which work together in a network of cooperation and competition to keep the microbiome balanced. (2) One major function of a healthy gut microbiome is colonization-resistance, or your microbiome's ability to fight off pathogens and prevent them from colonizing in the gut. However, with the increased prevalence and exposure to antibiotics, drugs and probiotics and changes in our diet, this delicately balanced microbiome is disrupted, leading to pathogen overgrowth, further susceptibility to infection, and inflammation in the GI tract. (2, 3)
You Are What You Eat: How Diet Affects Gut Balance
Recent studies are indicating that our day-to-day food intake actually has a significant impact on the balance of our gut microbiome and its overall function, namely the high-fat, high-sugar "Western" diet that has grown to become commonplace in the U.S. (4) In a study conducted by the FAS Center for Systems Biology at Harvard University, dieters were either put on a plant-based diet (consisting of grains, legumes, and vegetables) or an animal-based diet (consisting of meats and cheeses) for five consecutive days. The study found that the gut microbiome did indeed respond to a rapidly altered diet. Their research also showed that the animal-based diet increased the abundance of certain bile-tolerant microorganisms, supporting a link between dietary fat, bile acids and the outgrowth of microorganisms capable of triggering inflammatory bowel disease. (4)
In a separate study published in the human nutrition journal Nutrients, researchers conducted an experiment on mice to assess the effect a certain diet had on their gut microbiome. (3) Mice were initially fed a plant-based diet low in fat, then switched over to a high-fat, high-sugar "Western" diet. Researchers noted key gut population changes in their experiments, such as the absence of gut-barrier protecting bacteria. (3) Overall, researchers found that dietary changes explained 57 percent of the total variation in gut bacteria whereas changes in genetics only accounted for 12 percent. (3) Interestingly, the research also showed that a high-fiber vegetarian diet altered intestinal bacteria by increasing the production of short chain fatty acid production, decreasing intestinal pH, and thus preventing the growth of pathogenic bacteria like E. coli. (3)
It can be concluded that diet does indeed have an impact on the wellbeing of the gut, and that certain foods impact the body's overall health and function better than others. What impact does diet have on the development of disease states?
Is A Gut Imbalance Harmful To Your Health?
Growing evidence suggests that the gut microbiome may also be an important factor in the pathogenesis of certain diseases, many of which have shown a rapid increase in occurrence in the past two decades, including type 1 and 2 diabetes, asthma, colon cancer, inflammatory bowel disease and even obesity (5). New research argues that these disease states are related to protective and pathogenic bacteria imbalances in the gut called dysbiosis, which alter the intestinal microbiome both ecologically and functionally, increasing the risk for disease. (6)
In an article published in the journal Molecular Aspects of Medicine, scientists considered the relationship between the gut microbiome, obesity and insulin resistance. Their research was astonishing, and concluded that gut microorganisms do indeed affect functions like ingestion, energy harvest, energy expenditure and fat storage, all of which impact the development and maintenance of obesity (7). Furthermore, significant differences were noted in the metabolic activity of the gut microbiome of lean vs. obese individuals, suggesting that gut dysbiosis could further exacerbate to the development of obesity or diabetes. (7) In another study, researchers found a promising link between the gut microbiome and fat mass development, insulin resistance and low-grade inflammation, all of which are common characteristics of obesity. (8) Many of the key players involved in the control of fat mass development were also linked to the gut, while inflammation was also attributed to dysbiosis of certain plasma levels. (8)
This evidence reinforces the notion that diseases like obesity, diabetes and IBD all relate back to the microbial balance of the gut, and are largely affected by diet, both long and short-term.
A Balancing Act
While the research that's been conducted in the field is promising, there's still much to be learned about the relationship between our gut and our diets. That being said, keeping your gut's microbiome in check is key to maintaining a healthy immune system and optimally functioning digestive system. This is easily attainable through a balanced diet that's rich in fresh vegetables and limited in processed foods. Eating a diet packed with vegetables, legumes and complex carbohydrates while limiting animal products and byproducts and refined sugars will support a healthy gut, maintain a strong immune system and will keep your dietary problems at bay. If you find it difficult to cut meat out of your diet, try going "meatless" one day a week, then increasing the days as often you feel comfortable. Substitute white breads or pasta with complex carbohydrates like quinoa, wild rice and amaranth. Not only does a primarily plant-based diet keep you satiated, but it will also contribute greatly to your gut's health and your immune system's overall wellbeing.
1. "Everything You Always Wanted to Know About the Gut Microbiota..." Gut Microbiota Worldwatch. Gut Microbiota Worldwatch, 2015. Web. 1 Dec. 2015.
2. Stecher B. The Roles of Inflammation, Nutrient Availability and the Commensal Microbiota in Enteric Pathogen Infection. Microbiol Spectr. 2015;3(3)
3. Brown K, Decoffe D, Molcan E, Gibson DL. Diet-induced dysbiosis of the intestinal microbiota and the effects on immunity and disease. Nutrients. 2012;4(8):1095-119.
4. David LA, Maurice CF, Carmody RN, et al. Diet rapidly and reproducibly alters the human gut microbiome. Nature. 2014;505(7484):559-63.
5. Bushman FD, Lewis JD, Wu GD. Diet, gut enterotypes and health: is there a link?. Nestle Nutr Inst Workshop Ser. 2013;77:65-73.
6. Chan YK, Estaki M, Gibson DL. Clinical consequences of diet-induced dysbiosis. Ann Nutr Metab. 2013;63 Suppl 2:28-40.
7. Shen J, Obin MS, Zhao L. The gut microbiota, obesity and insulin resistance. Mol Aspects Med. 2013;34(1):39-58.
8. Cani PD, Delzenne NM. The gut microbiome as therapeutic target. Pharmacol Ther. 2011;130(2):202-12.