Fiber for a Strong Defense
GUT TALK
TIPS FOR A HEALTHY MICROBIOME by Melinda Hemmelgarn
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t’s hard to imagine surrendering control of our minds and bodies to trillions of microorganisms, but an ever-growing body of research from the Human Microbiome Project shows how microbes living in and on our bodies affect and even predict our physical and mental health. The majority of these microorganisms, or microbiota, live within our large intestine. According to Kelly Tappenden, Ph.D., a registered dietitian and head of the Department of Kinesiology and Nutrition at the University of Illinois–Chicago, we have more microbial cells within our gut than we have human cells in our body. These microbes help digest food, regulate appetite, produce certain vitamins, synthesize chemicals such as serotonin, metabolize carcinogens and regulate our immune
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system. She suggests that we think of them collectively as an organ that develops and changes as we age. “A huge proportion of your immune system is actually in your GI tract,” says Dan Peterson, assistant professor of pathology at the Johns Hopkins University School of Medicine. Taking care of our gut microbes is paramount during times of stress and risk of infection. In their book, The Good Gut: Taking Control of Your Weight, Your Mood, and Your Long-Term Health, Stanford researchers Justin and Erica Sonnenburg explain how healthy gut bacteria are essential for both metabolic health and strong immunity, adding that the chemicals our gut microbes synthesize behave like drugs—they are absorbed into our bloodstream and influence our biology. Seattle-based biologist Ann Bikle re-
The Sonnenburgs define a microbiotafriendly diet as rich in plant-based, high-fiber foods and limited in meat and saturated animal fats. Low-fiber diets contribute to a decline in gut microbe diversity, resulting in a weakened immune system. “Fiber is fuel for the gut,” says Joanne Slavin, Ph.D., a registered dietitian and professor of food science and nutrition at the University of Minnesota-St. Paul. It’s naturally found in fruits, vegetables, beans, peas, whole grains, nuts and seeds. Fermentable fibers such as fruit pectin, beta-glucans in barley and oats, and oligosaccharides in beans are metabolized by gut bacteria to produce short-chain fatty acids that provide energy to cells in the colon. Many fermentable fibers are called “prebiotics” because they promote the growth of beneficial gut bacteria. Inulin, for example, is a prebiotic fiber found naturally in onions, garlic, leeks, asparagus, wheat and oats. Teresa Martin, a registered dietitian based in Bend, Oregon, who researches gut health and disease prevention, recommends 35 to 50 grams of fiber per day to promote diverse, abundant and resilient gut microbes. For those over 50 years of age, the Institute of Medicine recommends 30 grams of dietary fiber per day for men and 21 grams for women. Most Americans get half the recommended amounts because highly processed, lowfiber foods are ubiquitous. Plus, popular gluten-free, keto and paleo diets limit whole grains. When buying packaged foods, check labels carefully and choose those providing at least three grams of fiber per serving.
A Healthy Microbiome for Life Martin shares the following strategies for developing and preserving gut health:
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fers to the colon as an “onboard medicine chest”. Unfortunately, warns Sonnenburg, physicians too often prescribe antibiotics, which wreak havoc on our microbiota, leaving us susceptible to disease-causing organisms.
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