Who knew that collectively, a group of tiny life forms in our intestines could have such an impact on our health? The gut microbiome, made up of trillions of microorganisms such as bacteria, fungi, and viruses (and their genes), not only plays a role in the digestion and absorption of our nutrients but actually may help to ensure the integrity of our gut lining, protect against pathogens, support immune function, aid in detoxification, and synthesize a variety of vitamins. It also might help to determine how much energy we burn and how much fat we store, and more research is emerging on the significant effect it has on brain function and mood. In addition, we’re beginning to understand and connect the dots between dysbiosis (an imbalance of microbial populations in the gut) and common chronic conditions such as inflammatory bowel disease, diabetes, obesity, CVD, and Alzheimer’s disease.
Of particular concern these days is the possible connection between microbial diversity and a host of autoimmune diseases. One of the ways the gut may play a role is through maintaining a strong and resilient intestinal barrier, which keeps unhealthful microbes and other large molecules from escaping the digestive tract and making their way into the bloodstream. The integrity of this wall relies on the ability of a healthy microbial community nourished by a fiber-rich diet to create short-chain fatty acids (SCFAs), which nourish the cells of the intestine and strengthen the gut barrier.
As dietitians know from countless dietary recalls, most Americans are significantly lacking fiber in their diets. If that intestinal barrier breaks down as a result of bacterial starvation, imbalances or ongoing exposure to toxic compounds, foreign bodies are more able to cross from the inside of the intestines to the bloodstream and potentially cause an overactive immune response. In addition, SCFAs produced in the gut have significant effects on other bodily processes, including supporting healthy cholesterol levels, helping us to feel full, potentially increasing calorie burning, and promoting microbial diversity, which keeps the healthy cycle going.
If you haven’t already guessed, what plays a significant role in shaping this internal ecosystem? Diet! For patients who may be struggling with some of the aforementioned conditions, working with them to support a healthy and resilient microbiome may be a key piece to help them address some of these imbalances. Below are five potential dietary microbiome supporters and five possible disruptors for you to consider as part of your assessment and recommendations for a healthier and more resilient microbiome.
5 Supporters of Optimal Microbial Health
1. Fiber: Ensuring sufficient amounts of this key nutrient found in beans, grains, nuts, seeds, fruits, and vegetables is one of the best ways to keep those gut bugs well fed and able to carry out their numerous functions. Variety may be an essential factor, though; the American Gut Project out of the University of California San Diego found that participants who consumed at least 30 different plant foods per week had more diverse microbiomes than those who consumed fewer than 10 different plant foods.
2. Phytochemicals: These are beneficial and colorful compounds, such as polyphenols, found in plants that have been shown to inhibit the growth of pathogenic bacteria, stimulate beneficial bacteria, and reduce inflammation in the gut, a hallmark of numerous diseases. Produce grown in healthy soil that’s teeming with its own microbes is going to provide additional exposure to friendly microorganisms. Once again, diversity may be key here. Encourage a plate that’s as polychromatic as possible.
3. Probiotic-rich foods: This includes both cultured foods such as yogurt and kefir but also unpasteurized fermented foods like sauerkraut, kimchi, kvass, and a variety of fermented veggies, from beets and carrots to radishes. These foods not only provide the host with beneficial microorganisms, but they also may help to reduce the presence of less favorable gut bacteria. In addition, fermentation also has been suggested to increase the antioxidant activity and availability of the nutrient content of many foods.
4. Prebiotics: These are the undigestible components of foods that essentially feed probiotics and help them to thrive. Obviously, there’s some crossover with the fiber category, but certain types of fiber worth highlighting include inulin and fructooligosaccharides found in foods such as onions, garlic, maple syrup, and bananas. Studies have suggested that regular inclusion of this food group helps to improve cardiovascular and joint inflammation issues.
5. Beta-glucans: Some emerging research has shown that beta-glucans, compounds in mushrooms and grains such as oats or barley, may have both immune-building and prebiotic properties that enhance the growth of some gut bacteria as well as protect the gut lining. It’s pretty easy to get most patients to enjoy a bowl of oatmeal or toss some mushrooms in their salad, soup, or stir-fry periodically. Added benefit: Consumption of beta-glucans also has been linked to lower cholesterol levels.
5 Detractors of Optimal Microbial Health
1. Refined sugar and carbohydrates: Higher consumption of this type of carbohydrate is associated with lower gut microbe diversity, and unhealthful bacteria thrive on these foods. High-fructose corn syrup in particular has been suggested in mouse studies to alter SCFAs, damage the intestinal wall, and drive inflammation. Steer your patients towards fiber-rich versions of foods they love and help curb sweet cravings with new flavors, such as those found in herbs and spices, which may offer an additional anti-inflammatory and digestive boost.
2. Red and processed meats: High intake of these foods is associated with less favorable alterations to the gut microbiome, feeding unhealthful bacteria and possibly encouraging intestinal inflammation. They’ve been associated with lower levels of SCFAs and with higher levels of trimethylamine N-oxide in the bloodstream, which can increase the risk of heart disease.
3. Pesticides: Numerous animal and in vitro studies suggest that these chemicals significantly alter the gut microbiome. If organic or pesticide free produce isn’t available to those with whom you work, suggest peeling or thoroughly washing to reduce the residues as much as possible.
4. Nonnutritive Sweeteners: Also known as “artificial sweeteners,” these sugar replacements may alter the composition and function of the microbiota. Ironically, as with sugar, consuming these sweeteners also may result in dysbiosis. Encourage patients to add a touch of honey or maple syrup instead.
5. Stress: This isn’t food, but it’s key; not mentioning it would be a disservice. I can’t call myself a true integrative dietitian if I don’t bring at least one lifestyle component into this conversation. The production of the hormone cortisol under chronically stressful circumstances (know anyone with those?) can negatively affect the makeup of the microbiome and reduce the production of SCFAs. Interestingly, a disruption of microbiome status has been associated with stress-related disorders.
As dietitians, we’re already a part of ensuring a healthful diet to promote optimal health. Hopefully these tips can help us go the extra mile with our patients to help address and resolve underlying imbalances, while at the same time promoting plant foods that are more environmentally friendly.
— Mary Purdy, MS, RDN, serves as adjunct faculty at Bastyr University where she earned her master’s degree. She has provided clinical nutrition counseling for the past 12 years, hosts the podcast Mary’s Nutrition Show, and speaks regularly at a variety of conferences.
(Editor’s Note: Some portions of this article were taken from Mary Purdy’s book The Microbiome Diet Reset. The full article is reprinted with permission from the Greater Seattle Dietetic Association.)