The gut microbiome, the ecosystem of bacteria and other microbes in our digestive system, has demonstrated its significant influence on human health. The relationship we have with our microbiomes is transactional, though. If we take care of the microbes in our guts, then they will take care of us. As proof, researchers from the University of South China’s Department of Gastroenterology found that when people had diets that favored their microbiomes, their odds of being diagnosed with hyperlipidemia (high cholesterol) were lowered.

The microbiome plays a crucial role in numerous human biological processes. Studies have shown it plays a role in cholesterol synthesis, bile metabolism, and pro-inflammatory signaling, to name a few. One reason the microbiome is a pivotal player in these roles is our relationship with it. Whatever we eat, the gut microbiome also eats. While we can digest most of the food we eat, some foods, like fiber, are not digested by us because we lack the enzymes needed to break them down.

Unfortunately, those fibers have sugars and nutrients that we do need for our health, and that’s where the microbiome comes in. The bacteria in our guts have the enzymes required to break down fiber, and we then absorb the resulting products. This relationship is the perfect example of symbiosis, as the gut microbiome can digest foods we can’t while we provide it with protection and food sources.

The gut microbiome is established upon birth and nurtured through our diets. For example, human breast milk contains a sugar used by a specific bacterium found in human infants. So, mothers’ milk selects for those bacteria to provide support for the baby instead of potentially harmful bacteria in the baby’s gut. As we move from milk to solid food, our diets have a greater influence on the composition of our microbiome. When we change our diets, the microbiome's byproducts and its effects on our biological processes also change.

To assess how a diet affects the microbiome, the Dietary Index for Gut Microbiota (DI-GM) was developed to quantify how a diet aligns with microbiome-supporting patterns. This index focuses on specific components of a diet that can either promote or impair the diversity and metabolic output of the microbiome, making it a more tailored and effective tool than other dietary indexes. Using the DI-GM, the researchers from the University of South China found that a diet that supports the microbiome enhances its role in regulating cholesterol levels in the human body.

Hyperlipidemia is a significant factor that contributes to cardiovascular diseases globally. Thankfully, it is one factor that is easy to modify through medications and lifestyle changes. Unfortunately, even with these interventions, the global prevalence of high lipid profiles in patients continues to rise due to dietary transitions and dysfunctional metabolisms. With the microbiome playing a significant role in human metabolism, the researchers examined patients who shifted their diets to better support their microbiome to assess the effects on their cholesterol levels.

The researchers analyzed 21,352 participant responses from the CDC’s National Health and Nutrition Examination Survey (NHANES) from 2010 to 2020. From these responses, the researchers used two 24-hour dietary recall surveys and the DI-GM to categorize diets as promoting or not promoting microbiome health.

They also examined patients’ lipid profiles from NHANES to determine hyperlipidemic status. As for medications, the researchers found that the primary lipid-lowering medication used was a statin, with a small number using other types, such as fibrates or niacin.

After adjusting their analysis to include demographics, lifestyle, nutrition, and clinical variables, people with higher DI-GM scores (promoting the gut microbiome) had lower odds of high cholesterol. Their findings suggest that diets rich in fermentable fibers, which are accessible food sources for gut microbes, can contribute to healthier lipid profiles. This also makes their results the first to relate high cholesterol and hyperlipidemia to the DI-GM.

The researchers also note that participants who were classified with hyperlipidemia reported a lower daily intake of total calories, protein, fat, and carbs. While this may sound counterintuitive, it may reflect reporting bias, as participants restricted their diets after a high-cholesterol diagnosis and before completing the survey.

Another reporting bias that could have occurred was that participants with health conditions might under-report their food intake as they incorrectly perceive certain foods as unhealthy. The researchers advise interpreting their findings with caution and suggest longer studies to determine dietary patterns before disease diagnosis. They recommend having longer studies following patients over many years to determine a more concrete correlation between a microbiome-focused diet and cholesterol maintenance.

Despite these biases, the findings still highlight the gut microbiome as a promising and modifiable factor for improving cholesterol health. By emphasizing diets rich in fiber and other microbiome-supporting foods, people could influence lipid metabolism in meaningful ways.

While the researchers caution that self-reported dietary data and study design limit definitive conclusions, the results reinforce the growing view that nurturing gut health can have far-reaching effects on cardiovascular risk. As future studies further clarify this relationship, dietary strategies that prioritize the microbiome may become an increasingly important component of cholesterol management and preventive care.