Diabetes Takes Guts: 5 Reasons to Care about your Microbiota

Ryan Bradley, ND, MPH     January, 2015


Did you know that only about 10% of the cells in your body are human? The other 90% belong to the bacteria in and on your body - your “microbiota”! Although the concept of gut “dysbiosis” has been an element of natural medicine theory and practice for many decades, science is now catching up and demonstrating more and more intricate connections between the bacteria living in our guts and our health. Why should you care? The short answer is that your microbiota impacts a lot more than just your digestive health, but also your insulin sensitivity, mood, and risk for atherosclerosis and cardiovascular disease. Why else should you care? You can do something about it! 


1. Your Microbiota Impacts Your Insulin Sensitivity and Weight

The potentially causative role of gut-based organisms in the regulation of human weight gain was supported by the revolutionary research by Backhed et al. which demonstrated the induction of weight gain and obesity in lean animals by transferring bacteria from the gut of obese animals to the guts of lean animals 1. Does this relationship apply in humans? It seems so. The research of Vrieze et al. took samples of gut bacteria from lean donors and infused them into the guts of male participants with the metabolic syndrome 2. The result? Increased levels of a short-chain fatty acid called “butyrate” and increased insulin sensitivity. 


2. Your Microbiota Impacts your Heart Disease Risk including Inflammation

As discussed in the Healthy Living Article, Diet, Stress, and the Obese Gut, there is a potent interaction between dietary choices and inflammatory compounds produced by gut bacteria. Specifically, the consumption of animal fats increase blood concentration of a chemical called trimethylamine-N-oxide (TMAO), which has been linked to increased risk of cardiovascular events 3-6. Additionally, high fat, low fiber diets may promote increased gut absorption of a compound from the cell walls of bacteria called lipopolysaccharide (LPS). LPS induces inflammation in the liver, which also leads to insulin resistance and weight gain 7,8. 


3. Your Microbiota Impacts your Mood

Recent research compared the bacteria in the gut of people with and without depression, and found differences in the amounts of certain organisms 9. Specifically, those with depression had less Bacteroidetes species, and relatively more Alistipes and Oscillibacter. Providing a potentially mechanistic link, Alistipesspecies have been linked to chronic inflammation, and Oscillibacter produces a compound called valeric acid, which may bind neurotransmitter receptors for GABA (which is considered a calming, inhibitory neurotransmitter). 


4. Your Microbiota Interacts with your Diet

Diets rich in plant foods are rich in fiber, antioxidants, and polyphenolic compounds - all of which have been linked to lower heart disease risk. Historically our understanding of the relationship between diet, diabetes, and heart disease has been overly simplistic often including erroneous assumptions about “antioxidants” reducing systemic “oxidative stress”, fiber binding up fat (which is partially true but not the whole story), and polyphenols (like the popular supplement resveratrol also found in red wine) serving as antioxidants. We are learning the impact of diet may be more a function of the types of bacteria that we feed in our gut, and the effects of their byproducts of our diet. For example, recent research suggesting coffee protects from diabetes 10,11 may be attributable to the effects coffee has on gut bacteria. Specifically, the polyphenol compounds in coffee reduced potentially harmful species bacteria in the gut, and increased the blood concentrations of insulin sensitizing short chain fatty acids 12. 

As fascinating, the health benefits of resveratrol may also be mediated through interactions with gut bacteria. Research by Queipo-Ortuno et al. demonstrated that feeding healthy humans red wine polyphenols impacted the types of bacteria in the gut, which was then associated with changes in cardiovascular risk factors and inflammation 13. Specifically, red wine polyphenols increased the number ofEnterococcus, Prevotella, Bacteroides, Bifidobacterium, Bacteroides uniformis, Eggerthella lenta, and Blautia coccoides-Eubacterium rectale groups. Changes in cardiovascular risk factors were numerous and included changes in blood pressure, triglyceride, total cholesterol, HDL cholesterol, and C-reactive protein (a measure of inflammation). Changes in cholesterol and inflammation were most closely correlated to changes in the number of Bifidobacteria . 


5. Supplementing Prebiotics and Probiotics May Improve Glucose Control & Heart Disease Risk

All of the above interactions between the gut microbiota, insulin resistance, inflammation and heart disease risk are fascinating, but the really convincing evidence of the importance of these interactions is that supplementing prebiotics (the fibers and other carbohydrates that support the growth of certain bacteria in the gut) and probiotics (the organisms themselves) actually translates into improvement in risk factors and lower inflammation. In addition to the research of Vrieze et al. mentioned above, a clinical trial by Asemi et al. randomly assigned participants to taking a combination prebiotic/probiotic mixture containing the organism Lactobacillus sporogenes and inulin as prebiotic for 6 weeks. Compared to the control group, the participants receiving the mixture had reductions in their C-reactive protein and increases in concentrations of a potent antioxidant called glutathione 14. Similar results were found in their earlier research on a multi-species supplement (containing Lactobacillus acidophilus, L. casei, L. rhamnosus. L. bulgaricus, Bifidobacterium breve, B. longum, Streptococcus thermophilus, and fructo-oligosaccharide ) as a prebiotic 15. Further evidence of a beneficial effect of probiotics in type 2 diabetes is provided by Ejtahed et al. in their study using probiotic-enriched yoghurt (containing Lactobacillus bulgaricus, Streptococcus thermophiles, Bifidobacterium lactis and L. acidophilus ) in humans with type 2 diabetes 16. In addition to improvements in antioxidant status, they also measured improvements in fasting blood sugar and small, but significant, reductions in hemoglobin A1c (compared to changes in the control group in which hemoglobin A1c actually increased). 


What’s the Bottom Line?

We are not separate from the organisms that populate our gastrointestinal tracts - in fact our fates are intricately linked. Modifying our diet modifies the types and numbers of organisms in our gut but modifying their diet (by changing our diet) and their metabolism of our diet - directly impacts our risk of developing diabetes, heart disease, and depression. What’s the most important ingredient in a microbiota-friendly diet? Plants!! Vegetables, fruits, beans/legumes, nuts, seeds, herbs and spices… any and all types of plants. 

So… if you can’t make dietary changes for yourself, consider doing it to help all the critters living in your gut. They will thank you for it by lowering your blood sugar, cholesterol, oxidation and inflammation! 

In health, Ryan Bradley, ND, MPH




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