Trillions of bacteria, fungi, and viruses live on and inside us, and maintaining a good, balanced relationship with them is to our advantage. Together they create a gut microbiome, a rich ecosystem that performs a variety of functions in our bodies. The bacteria in our guts can break down food the body cannot digest, produce essential nutrients, regulate the immune system, and protect against harmful germs. We don't yet have the blueprint for exactly which good bacteria a robust needs, but we do know that ist important for a healthy microbiome to have a variety of bacterial species. Many factors affect our microbiome, including our environment medications like antibiotics, and whether we are delivered by C-section or not. Diet too is emerging as one of the leading influences on the health of our guts. And if we can`t control all of these factors, we can manipulate the balance of our microbes by paying attention to what we eat. Dietary fibers from food like fruits, vegetables, nuts, legumes, and whole grains are the best fuel for gut bacteria.

When bacteria digest fiber, they produce a short chain of fatty acids that nourish the gut barrier, improve immune function, and can help prevent inflammation which reduces the risk of cancer. And the more fiber you ingest, the more fiber-digesting bacteria colonize your gut. In a recent study, scientists exchanged the regular high-fiber diets of a group of rural south Africans, with high-fat meat-heavy diets, of a group of African-Americans. After just two weeks on the high-fat, low-fiber, western-style diet, the rural African group showed increased inflammation of the colon, as well as a decrease in butyrate. That`s a short chain of fatty acids though to lower the risk of cancer. Meanwhile, the group that switched to a high-fiber, low-fat diet had the opposite result. So what goes wrong with our gut bacteria when we eat low-fiber processed foods? Lower fiber means less fuel for the gut bacteria, starving them until they die.
 This results in less diversity and more hungry bacteria. In fact, some can even start to feed on the mucus lining. We also know that specific food can affect gut bacteria. In one recent microbiome study, scientists found that fruits, vegetables, tea, coffee, red wine, and dark chocolate increased bacterial diversity. These foods contain polyphenols, which are naturally occurring antioxidant compounds. On the other hand, foods high in dairy fat, like whole milk, and sugar-sweetened sodas were correlated with decreased diversity. How food is prepared also matters. Minimally processed, fresh food generally has more fiber and provides better fuel. So lightly steamed, sauteed, or raw vegetables are typically more beneficial than fried dishes. There are also ways of preparing food that can actually introduce good bacteria, also known as probiotics, not your gut. Fermented foods are teaming with probiotic bacteria, like lactobacillus and bifidobacteria. Originally used as a way of preserving foods before the invention of refrigeration, fermentation remains a traditional practice all over the world. Foods like kimchi, sauerkraut, tempeh, and kombucha provide variety and vitality to our diets.
 Yogurt is another fermented food that can introduce helpful bacteria into our guts. That doesn`t mean that all yogurt is good for us, though. Brands with too much sugar and not enough bacteria may not actually help. These are general guidelines. More research is needed before we fully understand exactly how any of these foods interact with our microbiome. We see positive correlations, but the inside our guts are difficult places to make direct observations. For instance, we don`t currently know whether these foods are directly responsible for the changes in our diversity, or if something more complicated is happening. While we`re only beginning to expire the wilderness inside our guts, we already have a glimpse of how crucial our microbiomes are for digestive health. The great news is we have the power to fire up the bacteria in our bellies. Fill up on fibers, and fresh and fermented foods, and you can trust your gut to keep you going strong.