A handful of peanuts and a few pinches of herbs and spices could possibly give your gut a healthy boost, according to two separate studies from Penn State University in the US.

There are trillions of individual microorganisms living in the human stomach and intestines, comprising hundreds to thousands of species of bacteria, viruses, and fungi. Collectively, they are known as the gut microbiome, and their importance is so great to our health, scientists think of it as a supporting organ.

Diet, exercise, and medication are just some of the factors that can influence the makeup of a person's gut, which means each individual's gut community is unique.

If your gut microbiome isn't fed and appropriately nurtured, harmful microbes can proliferate, while symbiotic ones have more trouble with tasks such as dealing with our immune system and breaking down our food.

Scientists are still trying to figure out what features mark the healthiest gut communities, but as research progresses, they are starting to get a better idea.

"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," explains nutritional scientist Penny M. Kris-Etherton.

While we commonly think of diets in terms of their fundamentals, like greens and meats, a considerable amount of variation in our cultural and personal preferences come down to the way we add some zing to our meals.

Kris-Etherton and her colleagues at Penn State are among the first to study the effect of herbs and spices on the composition of the human gut.

In their study, 54 adult participants at risk of cardiovascular disease took part in a four-week randomized controlled-feeding experiment.

During the trial, everyone stuck to the same general menu, which was designed to reflect the average American diet. Some participants were asked to add 0.5 grams (about 0.2 ounces) of spices to their meals, while others were asked to add 3.3 grams or 6.6 grams.

The spice blend included cinnamon, ginger, cumin, turmeric, rosemary, oregano, basil, and thyme. A control group, meanwhile, were asked to put none of these spices on their food.

Fecal samples taken before and after the experiment reveal that diets with more spices tend to show greater bacterial diversity.

"It's such a simple thing that people can do," says Kris-Etherton.

"The average American diet is far from ideal, so I think 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!"

The new findings support recent research that suggests herbs and spices are a natural prebiotic that feeds healthy bacteria in the human gut.

In 2019, a randomized, placebo-controlled, double-blinded pilot study found that a 5-gram capsule of a spice blend, containing cinnamon, oregano, ginger, black pepper, and cayenne pepper, triggered changes to the gut microbiome that were seen within weeks.

In the more recent study, however, the spice blend was slightly different and was directly incorporated into participants' daily meals.

Those who ate meals with medium and high amounts of spice, equivalent to about a 3/4 teaspoon per day and about 1 1/2 teaspoon per day, showed a greater abundance of gut bacteria called Ruminococcaceae. This family of microbes is generally found in higher numbers in healthier human adults, although its exact role in the gut is uncertain.

Those participants who ate spices in the study also showed lower numbers of proinflammatory molecules in the gut, indicating a possible anti-inflammatory effect.

More research is needed to figure out exactly which spices are affecting gut microbes and why, but that's not the only dietary supplement that seems to boost certain gut bacteria.

A recent randomized controlled trial, also from Penn State, recently investigated the effect of peanuts on the microbiota for the first time.

The study took place over six weeks and included 50 adults all on the same daily diet. At the end of each day, after dinner but before bed, participants ate either 28 grams of dry roasted, unsalted peanuts, or they ate a small sample of cheese and crackers.

In the group snacking on nuts, as with the spices in the previous study, Ruminococcaceae bacteria were significantly more abundant in the gut of participants at the end of the study.

There's still so much about the gut microbiome that scientists don't understand, but for now, adding a pinch of spice to your diet probably won't hurt and it might even help. If nothing else, it'll add some flavor.

The spice study was published in The Journal of Nutrition, and the peanut study was published in Clinical Nutrition.