It may seem implausible, but there’s a correlation between our personalities and the types of microorganisms living in our digestive tracts. At least that’s the conclusion of one new study.

The human microbiome is composed of trillions of bacteria, viruses, fungi, and protozoa — a population of foreign cells that exceeds the number of human cells in the body. The organisms in the gut have been shown to impact not only our physical health, but our mental health as well. Prior research has demonstrated the connections between the microbiome and stress, anxiety and depression.

Recently, Oxford University researcher Katerina Johnson focused on broad personality traits in relation to the composition and diversity of the gut microbiome. She found that certain species of bacteria are more abundant in subjects who scored higher in sociability, and that generally the people with more diverse microbiomes tend to have larger social networks. In contrast, those living with a less diverse microbiome reported more stress, anxiety, poor sleep and neuroticism.

The Oxford study claimed only a correlation between some personality traits and gut environment. It did not conclude whether the microbiome shapes behavior — or vice versa, whether behavior modifies the microbiome.

Interestingly, the study did find that intake of naturally-occurring probiotics, such as that found in yogurt, correlated with the diverse, healthy microbiome. But use of probiotic supplements didn’t show the same effect. Here are some other suggestions for improving your own digestive flora:

• Eat more fiber-rich foods. especially legumes and potatoes.
• Eat a wide variety of fruits and vegetables, especially those in season.
• Include in your diet fermented foods that contain live microorganisms, such as kefir, sauerkraut, kimchi, raw milk cheeses, soy sauce, tempeh and natto.
• Consume foods high in polyphenols: nuts, seeds, berries, olive oil, brassicas (plants in the mustard family), coffee and green tea.
• Avoid artificial sweeteners like aspartame, sucralose and saccharine, which tend to reduce microbiome diversity.
• Avoid using antibiotics if you don’t really need them. They will disrupt the microbiome for weeks.
• Spend time in nature, garden and indulge in other outside activities.
• Hang around animals. Research suggests that living with dogs can increase human gut diversity,
• Exercise. Research indicates that lactate produced by activity is beneficial to the gut.

It’s good to remember that our internal bodily environment has as much influence on our mental health as our external environment. So keep those gut critters happy!