Two thousand years ago, Hippocrates is said to have noted, “All disease begins in the gut.” As I see it, he was right: Our intestines contain trillions of microbes of many species that metabolize food and make vitamins accessible to us. Adding up to about 4 pounds of body weight, these good bugs protect us against “bad” microbes like tetanus and E. coli, the culprit behind traveler’s diarrhea. They are central to our health.
“Probably one of the most important services your microbes provide is immunity,” says Martin Blaser, director of the Human Microbiome Program at NYU Medical Center and chair of the Presidential Advisory Council on Combating Antibiotic-Resistant Bacteria. But for decades, researchers say, we’ve been inadvertently annihilating microbes through various behaviors: excessive use of antibiotics, scrubbing ourselves with antibacterial soap, and more. The microbes that live inside us amount to a vast community, Blaser explains, and when its balance is disrupted, the bad guys can flourish.
What can we do to support our beneficial bacteria? The single quickest way to change gut microbes for the better is to be selective about the foods we eat. Certified organic, high-fiber, and fermented ingredients show promise in helping to bolster gut health. But so does plenty of exposure to dirt, like you get through gardening. Conversely, processed foods and products like hand sanitizers include chemicals that harm good bacteria.
1. Eat organic.
In her book The Dirt Cure, pediatric neurologist Maya Shetreat-Klein claims that veggies grown in healthy soil move some of the dirt’s diverse microbes into our bodies, promoting health. As for meat, Blaser writes in Missing Microbes: How the Overuse of Antibiotics Is Fueling Our Modern Plague, “Seventy to 80 percent of all antibiotics sold in the U.S. are used for the single purpose of fattening up farm animals.” The Centers for Disease Control and Prevention (CDC) links these doses to the spread of antibiotic-resistant pathogens, which it calls “an important problem for human health.” Certified organic meat is antibiotic-free (here are 7 ways to eat organic meat on a budget).
2. Go whole grain.
High-fiber, whole-plant foods are rich in oligosaccharides, the complex carbohydrates that microorganisms eat, write nutritionists Gene and Monica Spiller in their book What’s With Fiber? These so-called prebiotics, the Spillers say, make whole grains like quinoa and buckwheat, a bowl of morning oatmeal, and whole wheat pasta and brown rice better for fostering the growth of beneficial microbes than refined grains such as white flour. The USDA recommends an intake of 14 grams of fiber per 1,000 calories consumed. Try supplementing your diet with whole wheat bread (which contains 3 grams of fiber per slice) and high-fiber snacks, such as raw apples (3.5 grams). (Check out this list of the 11 healthiest whole grains you can eat.)
3.Embrace fermented foods.
With an ingredients list that includes live active cultures, yogurt provides billions of microbes per serving. Although some experts aren’t yet convinced, Gary Huffnagle, professor of internal medicine, microbiology, and immunology at the University of Michigan’s Mary H. Weiser Food Allergy Center, says that fermented foods containing live cultures—including unpasteurized kimchi, kefir, sauerkraut, and pickles—help replenish and protect good gut microbes. Find them in the refrigerated section of your grocery or make your own (here's how to make your own sauerkraut in a jar).
According to Andrew Gewirtz of the Center for Inflammation, Immunity, and Infection at Georgia State University, chemicals in these products crowd out good bacteria and may predispose you to diabetes and other obesity-related diseases.
5. Steer clear of commercial emulsifiers.
Many processed ice creams, puddings, salad dressings, and other foods gain their smooth, dense consistency from polysorbate 80 and carboxymethylcellulose (CMC). These chemicals, which you won’t find in organic products, disrupt our gut microbes, creating inflammation, says Gewirtz. He cites them as culprits in the surge in metabolic syndrome—a group of heart-disease risk factors, such as high blood-pressure and blood-sugar levels. (Lower your blood pressure naturally with these 8 simple strategies.)
6. Be judicious with antibiotics.
The statistics track together: In the past 50 years, rates of obesity have gone up 200 percent, diabetes has increased sevenfold, and asthma rates have skyrocketed by 250 percent; in just the last decade, peanut allergies have tripled. Blaser makes a compelling case that carpet-bombing good microbes with antibiotics has contributed to the rise in these conditions. The CDC reports that one-third of all antibiotic prescriptions are prescribed for viruses, which don’t respond to them. If you or your kids get sick, the CDC recommends “watchful waiting” before dosing: Ask your doctor if you can hold off for a few days to see if the infection dissipates on its own without antibiotics.
7. Get dirty.
Studies done in Switzerland in the 1990s and more recently with Indiana’s Amish community suggest that kids growing up on small farms in close proximity to naturally raised livestock have a lower incidence of allergies and asthma, perhaps because the animals diversify human microbes. Research suggests that pets provide similar benefits. So might organic gardening, suggests Shetreat-Klein.
The microbiome is the subject of ongoing research: Dozens of clinical trials and studies are investigating the relationship between our microbes and illnesses. At the University of Michigan, Huffnagle’s studies have shown the dramatic effect that microbes have on the immune system in animals and humans. Rob Knight of the University of California at San Diego has cofounded American Gut, the world’s largest crowd-sourced research project, through which you can have your own microbiome analyzed for a small fee. And, unsettling as it might sound, Fecal Microbiota Transplants (essentially, poop transplants, which are FDA-regulated for some antibiotic-resistant infections) are 90 percent effective in combating bacteria and repopulating the gut with beneficial microbes.
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