Studies show that our gut microbes convert the food we eat into thousands of enzymes, hormones, vitamins, and other metabolites that affect everything from your mental health and immune system to your likelihood of gaining weight and developing chronic diseases develop.
Gut bacteria can even affect your state of mind by producing mood-altering neurotransmitters like dopamine, which regulates pleasure, learning, and motivation, and serotonin, which plays a role in happiness, appetite, and sexual desire. Some recent studies suggest that the composition of your gut microbiome may even play a role in how well you sleep.
But the wrong mix of microbes can release chemicals that flood your bloodstream and build up plaque in your coronary arteries. The hormones they produce can affect your appetite, blood sugar levels, inflammation, and your risk of developing obesity and type 2 diabetes.
The foods you eat — along with your environment and lifestyle — seem to play a much bigger role in shaping your gut microbiome than genetics. In fact, genes have a surprisingly small effect. Studies show that even identical twins share only a third of the same gut microbes.
Your “good” microbes feed on fiber and variety
In general, scientists have found that the more diverse your diet, the more diverse the gut microbiome. Studies show that high levels of microbiome diversity are correlated with good health, and that low levels of diversity are associated with higher rates of weight gain and obesity, diabetes, rheumatoid arthritis, and other chronic diseases.
Eating a wide variety of high-fiber plants and nutrient-dense foods appears to be particularly beneficial, said Tim Spector, professor of genetic epidemiology at King’s College London and founder of the British Gut Project, a crowdsourcing effort to map thousands of individuals’ microbiomes.
Even if you already eat lots of fruits and vegetables, Spector recommends increasing the variety of plant-based foods you eat each week. A quick way to do this is to use more herbs and spices. You can also use different types of leafy vegetables for your salads instead of one type of lettuce. Adding a variety of fruits to your breakfast, adding different types of vegetables to your stir-fries, and eating more nuts, seeds, beans, and grains is good for your microbiome.
These plant-based foods contain soluble fiber, which passes through much of your gastrointestinal tract largely unaffected until it reaches the large intestine. There, gut microbes feed on it, metabolizing it and converting it into beneficial compounds like short-chain fatty acids, which can reduce inflammation and help regulate your appetite and blood sugar levels.
In one study, scientists followed more than 1,600 people for about a decade. They found that people with the highest microbial diversity also consumed more fiber. And they gained even less weight over the 10-year study published in the International Journal of Obesity.
Build-up of “bad” microbes thrive on junk food
Another important measure of gut health is a person’s ratio of beneficial to potentially harmful microbes. In a study of 1,100 people in the United States and Britain published last year in Nature Medicine, Spector and a team of scientists at Harvard, Stanford and other universities identified clusters of “good” gut microbes that protect people from cardiovascular disease. Disease and obesity protected and diabetes. They also identified clusters of “bad” microbes that promote inflammation, heart disease and poor metabolic health.
While it’s clear that eating lots of fiber is good for your microbiome, research shows that eating the wrong foods can tip the balance in your gut in favor of disease-causing microbes.
The Nature study found that “bad” microbes were more common in people who ate lots of highly processed foods that were low in fiber and high in additives like sugar, salt and artificial ingredients. This includes soft drinks, white bread and pasta, processed meats, and packaged snacks like cookies, candy bars, and potato chips.
The findings were based on an ongoing project called the Zoe Predict Study, the largest personalized nutrition study in the world. It’s run by a health sciences company that Spector and his colleagues founded called Zoe, which allows consumers to have their microbiomes analyzed for a fee.
Add more spices, nuts, plants, and fermented foods to your diet
Once you start increasing the variety of plant-based foods you eat on a daily basis, set a goal of eating about 30 different plant-based foods per week, says Spector. That might sound like a lot, but you’re probably already eating a lot of these foods.
The sample menu shows how you can easily consume 30 different plant-based foods in just three meals throughout the week.
- One day, start your morning with a bowl of plain yogurt with sliced bananas and strawberries, a pinch of powdered cinnamon, and a handful of mixed nuts (with almonds, pecans, cashews, hazelnuts, and peanuts). Meal list: 8 plant-based foods
- On another day, eat a leafy salad with at least two mixed leafy greens, tomatoes, carrots, broccoli, and bell peppers. Add Herbes de Provence, a condiment that usually contains six herbs, to grilled chicken or fish. Meal list: 12 plant-based foods
- Later in the week, tuck into pesto-seasoned chicken (it contains basil, pine nuts and garlic) and enjoy a bowl of brown rice with onions and kidney beans and a side of roasted vegetables with green and yellow squash, mushrooms and shallots. Meal list: 10 plant-based foods
Another way to nourish your gut microbiota is to eat fermented foods like yogurt, kimchi, sauerkraut, kombucha, and kefir. The microbes in fermented foods known as probiotics produce vitamins, hormones and other nutrients. When you consume them, they can increase the diversity of your gut microbiome and boost your immune health, said Maria Marco, a professor of food science and technology that studies microbes and gut health at the University of California, Davis.
In a study published last year in the journal Cell, researchers at Stanford found that when people ate fermented foods every day for 10 weeks, it increased microbial diversity in the gut and lowered their levels of inflammation.
“We’re increasingly developing a very comprehensive understanding of why microbes are so good for us,” Marco said.
Do you have a question for Anahad about healthy eating? E-mail [email protected] and we may answer your question in a future column.