According to research, the rhythms of gut microbes are affected by what and when we eat. A study using mice found that when they ate a healthy diet, they generated more beneficial gut microbes, and that the collective activity of microbial life in the gut followed a daily — or diurnal — rhythm. That rhythm in turn supported circadian rhythms in the animal. Mice that were fed a high-fat, stereotypically “Western” diet, on the other hand, produced less optimal microbial life. The gut microbes of these mice did not adhere to a daily rhythm themselves, and also sent signals that disrupted circadian rhythms. These mice gained weight and became obese, while the mice that ate healthfully did not.

Scientists bred a third group of mice without any gut microbes at all. Because they lacked a gut microbiome, there were no bacteria to send signals to the rest of their bodies. Circadian disruption occurred in these mice, but they did not gain weight or suffer metabolic disruption, even when fed the high-fat diet.

This suggests a couple of important conclusions. First, microbial activity is key to normal circadian function and, therefore to sleep. Second, that the microbiome is a key player along with diet in the regulation of weight and metabolism.

Research in humans has returned similar results. The human microbiome appears to follow daily rhythms influenced by timing of eating and the types of foods consumed, and to exert effects over circadian rhythms. Research has also found that the relationship between these different biological rhythms works both ways. Scientists have discovered that disruptions to circadian rhythms — the kind that occurs through jet lag, whether through actual travel or from “social” jet lag — disrupts microbial rhythms and the health of the microbial ecosystem. People who experience these changes to microbial rhythms as a result of circadian disruption suffer metabolic imbalance, glucose intolerance, and weight gain, according to research.

We’ve known for some time about the relationship of sleep, circadian rhythms, and metabolic health. Disrupted sleep and misaligned circadian rhythms have been strongly tied to higher rates of obesity, and to metabolic disorders including type 2 diabetes. This emerging knowledge of the microbiome and its relationship to circadian function may in time deliver to us a deeper understanding of how health is influenced by sleep and circadian activity.

But have you heard of prebiotics? According to the official definition, a prebiotic is any substance used by microorganisms inside the body that confers health benefits. Translation: prebiotics are beneficial microbes’ food. While researchers are still learning about their full potential to boost overall health or even treat disease, one thing is for certain—adding more prebiotics to your diet can give you a happier gut.

How prebiotics work

Most prebiotics are types of dietary fiber, which is a kind of carbohydrate that human enzymes can’t digest. Not every fiber is a prebiotic, however, because there are two categories of dietary fiber: soluble fiber, which is fermented by gut bacteria, and insoluble fiber, which is not fermented. The soluble fibers that are metabolized by beneficial gut microbes are considered prebiotics. Inside your gut, prebiotics stimulate beneficial gut microbes to grow, improving gut health—and other areas of health, too.

Some prebiotics come from sources besides food and impact parts of the body beyond the gastrointestinal tract, but most of the ones we know about are found in food.

Which foods contain prebiotics?

Plants like Jerusalem artichoke, chicory root, apples, bananas, asparagus, onions, leeks, and garlic contain small amounts of prebiotics; and some yogurts, cereals, and breads contain prebiotic additives, like galacto-oligosaccharides (GOS), fructo-oligosaccharides (FOS), and inulin.

While it’s no longer on the menu for us adults, breast milk contains oligosaccharides, a prebiotic that has been found to increase the population of healthy bifidobacteria and discourage the growth of pathogens in babies’ guts. In fact, several types of infant formula are now supplemented with oligosaccharide prebiotics.

What are the major health benefits of prebiotics?

The health effects of prebiotics include improved gastrointestinal health (inhibition of pathogens and immune system stimulation), reduced blood lipid levels, and improved brain function.

Recent research has found that prebiotics may help prevent and treat Type 2 diabetes and cardiovascular disease, lower cholesterol, and positively impact metabolism. Researchers have also found that a healthy gut microbiome fed by prebiotics has positive effects on bone density and strength.

A 2017 study published in the American Journal of Clinical Nutrition found that children who tried prebiotics felt more satisfied after a meal, which could help children with obesity regulate their appetites. A 2017 study at the University of Colorado published in Frontiers in Behavioral Neuroscience was the first research to demonstrate that a prebiotic diet provides protection from stress and positively impacts sleep.

Prebiotics represent an exciting new area of scientific research, and many organizations are funding projects to study how they work, what they can do, and how they might be used to prevent or treat disease.

What do we still need to learn about prebiotics?

The National Institutes of Health (NIH) is funding new research on prebiotics that may include investigations into how prebiotics could be used to help manage inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), or other conditions. Other organizations are funding research on new microbiome-based therapies, methods for analyzing the effects of prebiotics on gastrointestinal tract microbiota, and microbiome-based strategies for the prevention of lifestyle-related chronic diseases.

How can I use prebiotics to improve my health?

Fruits, vegetables, and whole grains contain prebiotics, so your healthcare provider’s usual advice about including a variety of fruits, veggies, and grains in your diet is certainly sound. Eating plenty of fiber-rich foods will also help you take in prebiotics, as well as vitamins and minerals. If you’re following the dietary guidelines for fiber intake, you’d want to eat 25 grams of fiber for every 2,000 calories you consume each day. The bonus is that by eating healthy, plant-based, fiber-rich foods, you’ll gain other health benefits, too.