Two New Studies Reveal How Diet Influences Cholesterol Through Genetics and Gut Microbes

Two new studies provide fresh insights into how diet affects cholesterol levels, with one highlighting the role of genetic factors in low-carbohydrate diets and the other linking microbe-rich foods to better metabolic markers.

The first study, based on data from the randomized controlled DIETFITS trial, found that genetic predisposition significantly influences how low-carbohydrate diets impact LDL cholesterol. Among 431 participants with available genetic data, those on a healthy low-carb diet who had a higher polygenic score for elevated LDL cholesterol experienced greater increases in LDL when they consumed more saturated fat. This interaction was not observed in individuals following a healthy low-fat diet, indicating that the LDL-raising effect of saturated fat is amplified in genetically susceptible people only in the context of carbohydrate restriction.

The findings, presented at NUTRITION 2026, suggest that polygenic scores could eventually help clinicians identify individuals likely to experience adverse cholesterol responses to low-carbohydrate diets. The lead researcher, a postdoctoral scholar at Stanford University School of Medicine, noted that these results explain why some people see their LDL cholesterol spike on low-carb diets while others do not. General dietary guidance recommends limiting saturated fat to less than 10% of daily calories and favoring unsaturated fats from sources like nuts, seeds, olive oil, and avocado.

A separate cross-sectional study published in Nutrition Research examined dietary intake of live microbes and metabolic health in 58 Australian adults. Researchers developed a database categorizing foods into low, medium, or high levels of live microbes based on estimated colony-forming units per gram. They found that higher intake of foods with medium or high live microbe content—such as raw fruits, vegetables, and fermented products—was associated with improved markers of insulin sensitivity and cholesterol profiles, including lower LDL cholesterol and higher HDL cholesterol. The analysis adjusted for gender, smoking status, and energy intake, but the authors caution that residual confounding is possible given the observational design and small sample size.

Both studies emphasize the complexity of diet–health interactions. While genetics can modulate how saturated fat from low-carb diets affects LDL cholesterol, the presence of live microbes in the diet may independently influence cardiometabolic risk factors. The researchers behind the genetics study stressed the importance of monitoring individual responses to dietary changes rather than assuming uniform outcomes.