Microbiome - Feed It Healthy

Every time you eat, you are feeding trillions of bacteria, viruses, and fungi that live inside your gut. But are you feeding them the right foods?

Scientists used to know very little about these communities of microbes that collectively make up the gut microbiota, also known as your gut microbiome. But a growing body of research suggests that these vast communities of microbes are the gateway to your health and well-being — and that one of the simplest and most powerful ways to shape and nurture them is through your diet.

Studies show that our gut microbes transform the foods we eat into thousands of enzymes, hormones, vitamins, and other metabolites that influence everything from your mental health and immune system to your likelihood of gaining weight and developing chronic diseases.

Gut bacteria can even affect your mental state 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 can even play a role in how well you sleep.

However, the wrong mix of microbes can churn out chemicals that flood your bloodstream and build plaque in your coronary arteries. The hormones they produce can influence 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 behaviors, appear to play a much larger role in shaping your gut microbiome than genetics. In fact, genes have a surprisingly small effect. Studies show that even identical twins share just one-third of the same gut microbes.

Eating a wide variety of fiber-rich plants and nutrient-dense foods seems especially beneficial, said Tim Spector, a professor of genetic epidemiology at King’s College London and the founder of the British Gut Project, a crowdsourced effort to map thousands of individual microbiomes.

Even if you already eat a lot of fruits and vegetables, Spector advises increasing the variety of plant foods you eat each week. One fast way to do this is to use more herbs and spices. You can use a variety of leafy greens rather than one type of lettuce for your salads. Adding a variety of fruits to your breakfast, adding several different vegetables to your stir fry, and eating more nuts, seeds, beans, and grains is good for your microbiome.

These plant foods contain soluble fiber that passes through much of your gastrointestinal tract largely unaffected until it reaches the large intestine. There, gut microbes feast on it, metabolizing and converting the fiber into beneficial compounds such as short chain fatty acids, which can lower inflammation and help to 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 who had the highest levels of microbial diversity also consumed higher levels of fiber. And they even gained less weight over the 10-year study, which was published in the International Journal of Obesity

The microbiome is the collection of all microbes, such as bacteria, fungi, viruses, and their genes, that naturally live on our bodies and inside us. Although microbes are so small that they require a microscope to see them, they contribute in big ways to human health and wellness. They protect us against pathogens, help our immune system develop, and enable us to digest food to produce energy.

Because the microbiome is a key interface between the body and the environment, these microbes can affect health in many ways and can even affect how we respond to certain environmental substances. Some microbes alter environmental substances in ways that make them more toxic, while others act as a buffer and make environmental substances less harmful.

How can the microbiome affect health?

The critical role of the microbiome is not surprising when considering that there are as many microbes as there are human cells in the body. The human microbiome is diverse, and each body site – for example, the gut, skin, and oral and nasal cavities – has a different community of microbes.

A person’s core microbiome is formed in the first years of life but can change over time in response to different factors including diet, medications, and environmental exposures.

Differences in the microbiome may lead to different health effects from environmental exposures and may also help determine individual susceptibility to certain illnesses. Environmental exposures can also disrupt a person’s microbiome in ways that could increase the likelihood of developing conditions such as diabetes, obesity, cardiovascular and neurological diseases, allergies, and inflammatory bowel disease. For example, specific changes in the gut microbiome have been linked to liver health. NIEHS-funded researchers and collaborators developed a rapid, low-cost tool that uses stool samples to detect microbial changes that can accurately diagnose liver fibrosis and cirrhosis.

Dietary fiber can only be broken down and fermented by enzymes from microbiota living in the colon. Short chain fatty acids (SCFA) are released as a result of fermentation. This lowers the pH of the colon, which in turn determines the type of microbiota present that would survive in this acidic environment. The lower pH limits the growth of some harmful bacteria like Clostridium difficile. Growing research on SCFA explores their wide-ranging effects on health, including stimulating immune cell activity and maintaining normal blood levels of glucose and cholesterol.

Foods that support increased levels of SCFA are indigestible carbohydrates and fibers such as inulin, resistant starches, gums, pectins, and fructooligosaccharides. These fibers are sometimes called prebiotics because they feed our beneficial microbiota. Although there are supplements containing prebiotic fibers, there are many healthful foods naturally containing prebiotics. The highest amounts are found in raw versions of the following: garlic, onions, leeks, asparagus, Jerusalem artichokes, dandelion greens, bananas, and seaweed. In general, fruits, vegetables, beans, and whole grains like wheat, oats, and barley are all good sources of prebiotic fibers.

Be aware that a high intake of prebiotic foods, especially if introduced suddenly, can increase gas production (flatulence) and bloating. Individuals with gastrointestinal sensitivities such as irritable bowel syndrome should introduce these foods in small amounts to first assess tolerance. With continued use, tolerance may improve with fewer side effects.

If one does not have food sensitivities, it is important to gradually implement a high-fiber diet because a low-fiber diet may not only reduce the amount of beneficial microbiota, but increase the growth of pathogenic bacteria that thrive in a lower acidic environment.

Probiotic foods contain beneficial live microbiota that may further alter one’s microbiome. These include fermented foods like kefir, yogurt with live active cultures, pickled vegetables, tempeh, kombucha tea, kimchi, miso, and sauerkraut.