It is bizarre to imagine, but there are trillions of microbes currently residing throughout our entire bodies. Though the majority of them are harmless, each one plays a key role in maintaining the functions of the body.

According to a report from Time, a new study has shown that the bacteria living in our guts have more to do with regulating metabolism than previously thought. Microbes help digest food and keep invasive pathogens at bay, but it also turns out that they have a significant effect on blood cholesterol levels.

The study, led by Jingyuan Fu from the University Medical Center Groningen in the Netherlands, was published in the journal Circulation Research. It revealed how the makeup of the different types of bacteria in the intestines can influence weight and cardiovascular health.

The study examined blood and fecal samples from 893 people and genetically sequenced the bacterial colonies present in each. They discovered 34 different microbial sequences that appeared to influence body mass index, or BMI, and lipid levels in the blood.

After the scientists controlled for factors like age, gender, and genetics, they found that gut bacteria were responsible for up to 6 percent of the discrepancies between patients’ triglyceride and HDL levels.

Triglycerides are connected to an increased risk of diabetes and cardiovascular disease, whereas HDL cholesterol is linked to a decreased risk of these conditions.

The gut bacteria accounted for 26 percent of HDL level differences after the scientists looked at the results in light of the entire microbiome in the digestive tract.

The numbers reveal a pattern, but there will need to be more studies conducted to paint a clearer picture of the way microbes affect cholesterol and overall cardiovascular health.