The uptick in microbiome research and awareness we’re seeing is crucial—but an important question we also need to be asking is, why does gut health seem to be under attack now more than ever? With the help of some prominent gut experts, mbg explored an array of modern-day gut saboteurs—and what you can do to counter them: Fiber—found in vegetables, fruits, and a variety of whole grains—promotes gut microbial biodiversity and feeds beneficial bacteria in the GI tract. In fact, these “good” bugs use fiber food to produce gut-healthy, anti-inflammatory compounds called short-chain fatty acids (SCFAs). But the average American gets just 15 grams of fiber per day, when we should be getting at least 25 to 30 grams. “Part of the problem we’re seeing today could be due to three to four generations of progressively diminished fiber consumption,” says gastroenterologist Will Bulsiewicz, M.D., author of Fiber Fueled, referencing a groundbreaking 2016 study1 in Nature by Stanford University microbiome researcher Justin Sonnenburg, Ph.D. For the study, researchers fed mice a low-fiber diet over multiple generations. After one generation, there was a decline in microbial biodiversity in the gut, which was reversible when fiber-rich foods were returned to the diet. But with each subsequent generation, there was a progressive loss of biodiversity that was harder to reverse (and impossible to completely reverse). “Compared to the Hadza of Tanzania2, some of the last remaining communities of hunter-gatherers, people in the U.S. have about 40% less microbial diversity in the gut,” says Bulsiewicz. “This leads us to believe that we’ve essentially lost 40% of what we’re supposed to have as humans. To an extent it’s reversible, but this study shows that we might be in a place where we’re impaired from the get-go.” Excessive consumption of animal products (particularly in the absence of fiber-rich foods) may also have a negative impact on the gut microbiome. This was illustrated in a 2014 study by Harvard researchers in which they put the same group of people on two drastically different diets—an animal-based diet3 of foods like bacon, eggs, salami, and pork rinds; and a vegan diet of foods like rice, tomatoes, lentils, squash, and fruit—and measured the effects of each. What they found: On the animal-based diet, there were significant increases in the bile-tolerant gut microbes, which are necessary for breaking down fat but also associated with inflammatory processes. Additionally, excessive refined carbohydrate and sugar intake has been shown to reduce the microbial biodiversity and feed bad microbes. “Someone who’s eating way too much sugar is going to become a fertile ground for yeast to grow in their gut,” a form of gut imbalance, says Vincent Pedre, M.D., integrative physician and author of Happy Gut. That’s because antibiotics don’t just act on the bad bacteria that cause us issues; they also affect your resident, good microbes. For example, a 2008 study found that treatment with the antibiotic ciprofloxacin5 “influenced the abundance of about a third of the bacterial taxa in the gut, decreasing the taxonomic richness, diversity, and evenness of the community.” And while many of these bacterial groups recovered by four weeks post-treatment, some didn’t—even after six months. But even if you’ve managed to avoid an antibiotic prescription recently—there’s still a possibility that you’re being exposed. A 2018 paper featuring findings from the American Gut Project—an ongoing project in which researchers at U.C.–San Diego analyze fecal samples from individuals around the country to gain insight into the gut microbiome—revealed how scientists detected agricultural antibiotics in samples from people who hadn’t taken any antibiotics the year prior. Not-so-fun fact: “Around 80% of the antibiotics in our country are actually being administered to livestock as a part of animal agriculture,” says Bulsiewicz. Much more research is needed to determine the implications of this discovery, but it could mean the antibiotics given to animals could end up in human bodies and affect the gut. That said, at this point, there’s no study defining the likelihood of being exposed to antibiotics via food. “What we’ve come to learn about [the Hadza] through the American Gut Project is that their gut is really an extension of their greater environment,” says Bush. “They actually have bacteria in the gut that are specific to zebra skin—they’re really touching nature all the time and therefore reinforcing this extremely diverse microbiome. There’s also an enormous amount of skin-to-skin contact—they’re wearing no clothes much of the time, children are always on the backs, bellies, or shoulders and passed around from person to person.” All of this, of course, is in stark contrast to how many of us in the U.S. live our lives today (personally, I’m lucky if I get out for a hike once a week), and “as we narrow our contact with nature, animals, and other humans, we get a more narrow microbiome,” says Bush. For a crazy example of just how protective contact with the natural world can be for the gut, consider this: When the Hadza were being studied by the American Gut Project, a missionary group came and gave them boxes of antibiotics in case they got sick. Not really being familiar with the concept of infection, they sat around that night and ate all the antibiotics, thinking it was candy from the West. The crazy part? In the genomic studies of their gut, scientists found that the very next morning—and in the months following—there was no change in their microbiome. “So what that shows you is that if you’re in touch with your environment adequately, you’re pretty impervious to damage because the ecosystem is constantly reinforcing your recovery,” says Bush. “If we stop touching nature, then something like an antibiotic becomes really damaging because we can’t recover.” Of course, many experts debate what all this means for gut health and the extent to which glyphosate (and other herbicides and pesticides) affect the gut microbiome, but according to Bush and Pedre, there is some cause for concern. “Glyphosate acts by chelating minerals—it starves crops of nutrients by chelating minerals in the soil, and it does the same thing if it gets into the gut,” says Pedre. “It can kill bacteria by chelating essential nutrients that they need to replicate and consequently cause dysbiosis.” Research by Stephanie Seneff of MIT supports this idea and proposes that glyphosate is a major driver of the gut-related autoimmune condition celiac disease. A 2013 study authored by Seneff states that “Deficiencies in iron, cobalt, molybdenum, copper, and other rare metals associated with celiac disease can be attributed to glyphosate’s strong ability to chelate these elements7,” and that “Fish exposed to glyphosate develop digestive problems that are reminiscent of celiac disease.” Even more experts are concerned about glyphosate’s effect on soil quality—which can indirectly affect the gut and overall health by stripping our crops of nutrients. “Human health is proportional to soil health,” says Bulsiewicz. “There are interesting studies comparing foods of today to the same foods 70 years ago, and they were more nutrient-dense 70 years ago.” Keep in mind, though, food may not be the most direct way you’re exposed to glyphosate and other pesticides. “The third-largest ‘crop’ grown in the U.S., behind corn and soybeans, is lawn,” says Bush. “So backyards, schoolyards, and other green spaces cover 40 million acres, and many are heavily sprayed with Roundup. That can be public enemy No. 1 within an urban community.” (Bush recommends talking to your town and school district about their Roundup spraying practices, and, if you’re up for some advocacy, asking them to stop.) Bulsiewicz believes the effects of stress can be huge. “As a gastroenterologist, the most challenging patients that I take care of are the patients who have been victims of trauma or have dealt with an eating disorder,” he says. “You can sleep, you can exercise, but if you’re not properly managing your stress or something traumatic that happened to you, you’re not going to have a healthy gut.” As for how sleep affects gut health, it has to do with circadian rhythms. “Circadian rhythm disturbances cause alterations in the gut microbiome,” says Pedre. “I see a lot of people who fly long distances, and they can’t lose weight; it really does a number on the gut.” In fact, in a 2014 study8, researchers induced artificial jet lag in mice (simulating the changes in sunlight that would occur on a flight from Tel Aviv to San Francisco) and found that the gut very quickly transitioned to a type of microbiome that promotes insulin resistance and weight gain. And while staying up until midnight scrolling Instagram probably won’t affect your gut to the same extent as a trans-oceanic flight, it’s still disrupting your body’s ideal circadian rhythm. There are also other lifestyle practices to help support your gut microbiome, like eating more plants, opting for organic produce, exercising regularly, spending time with animals, meditating to ease stress, getting plenty of sleep, and supporting sustainable agricultural initiatives. You won’t be able to change your gut overnight, but taking these small steps may help reinforce a healthier, better microbiome in time.
