Imagine a bustling city on a weekday morning, with sidewalks crowded by people rushing to work. Now shrink that scene to a microscopic scale, and you get an idea of what the microbiome inside your body looks like. This microscopic metropolis is home to trillions of microorganisms, including bacteria, fungi, parasites, and viruses, most of them living in delicate harmony. When this balance is disturbed, it can significantly impact your health.

These “bugs” are largely influenced by what we eat. Processed and fried food can damage the gut equilibrium, while vegetables and fruits help maintain it. Now, researchers found that adding a daily teaspoon of herbs and spices and an ounce of peanuts to the diet can also have a positive impact on your gut.

Microbiome and diets

Research has shown that people who have a lot of different microbes have better health, and a better diet, than those who don’t have much bacterial diversity,” Penny Kris-Etherton, a professor of Nutritional Sciences at Penn University, and one of the researchers behind the two new studies on microbiome health, said in a statement.

The first study compared the effects of eating 28 grams (one ounce) of peanuts daily versus consuming a higher-carb snack, such as cheese bits or pretzels. Over six weeks, researchers found that participants who snacked on peanuts experienced a significant increase in Ruminococcaceae, a type of gut bacterium linked to better liver metabolism.

A total of 50 participants completed the study, with the researchers assessing fecal bacterial diversity. Nuts (including tree nuts, peanuts, and nut butter) are usually recommended as part of healthy dietary patterns. Peanuts are the most consumed nut in the US. But this was the first study to look at their effect on microbiota composition.

In the second study, which looked at herbs and spices, the researchers analyzed the impact of adding blends of herbs and spices (such as ginger, cinnamon, cumin, turmeric, rosemary, oregano, basil, and thyme) to the diets of participants at risk of cardiovascular disease. Herbs and spices have been previously associated with a healthy gut, but not actually investigated.

The researchers looked at three doses — about 1/8 teaspoon per day, a little more than 3/4 teaspoon per day, and about 1 1/2 teaspoon per day. By the end of the four-week experiment, participants had an increase in gut bacteria diversity, including an increase in Ruminococcaceae, especially those eating the highest doses of herbs and spices.

“It’s such a simple thing that people can do,” said Kris-Etherton in a statement. “Everyone could benefit by adding herbs and spices. It’s also a way of decreasing sodium in your diet but flavoring foods in a way that makes them palatable and, in fact, delicious! Taste is really a top criterion for why people choose the foods they do.”

Putting this into context

This is far from the first study to suggest that plant-based foods are beneficial for your gut microbiome.

A systematic review published in the British Journal of Nutrition examined the impact of nut consumption, including peanuts, on human gut microbiota. The review found that while nut intake modestly influenced gut microbiota diversity, certain nuts, particularly walnuts, were associated with significant shifts in bacterial composition. These changes included an increase in genera capable of producing short-chain fatty acids (SCFAs), such as Clostridium, Roseburia, Lachnospira, and Dialister, which are beneficial for gut health.

Another 2024 highlighted in Gastroenterology Insights explored the role of herbs and spices in modulating gut microbiota to promote healthy aging. The review emphasized that commonly consumed herbs and spices, rich in bioactive compounds like polyphenols, can positively influence gut microbiota composition. This modulation may help prevent or manage age-related health declines by promoting a balance between prominent gut bacteria phyla, such as Bacteroidetes and Firmicutes.

As the gut microbiome is showed to be more and more important, incorporating these types of foods into your diet is increasingly looking like a good idea.

Scientists are still learning about the connection between gut microbiota and a range of health factors, from blood pressure to weight. A lot more research is still needed, said Kris-Etherton. In the meantime, we can all start looking at our diets and think of ways to make changes. It’s never too late to start eating a healthier diet.

The two studies were published in the Journal of Nutrition and the Journal of Clinica Nutrition.