Diets high in phytosterols, such as vegetarian diets, have long been linked to lower risk of heart disease and diabetes by lowering low-density lipoprotein (LDL) cholesterol but food surveys, questionnaires, and diaries are not reliable enough to make clinical determinations while in mouse experiments the doses were too human to be relevant in the real world.

New correlation from the Harvard T.H. Chan School of Public Health presented at the annual meeting of the American Society for Nutrition looked at metabolites present in blood samples from over 11,000 study participants and other metabolic biomarkers in blood samples from over 40,000 participants combined with food-frequency questionnaires led the authors of the new EXPLORATORY results to estimate each participant’s intake of total phytosterols and three individual phytosterols: β-sitosterol, campesterol and stigmasterol. Participants in the top quintile for phytosterol intake consumed about 4-5 servings of vegetables, 2-3 servings of fruit, two servings of whole grains and half a serving of nuts per day.

Those are all possible under a normal human diet.



None of the gathered data was by Harvard, they instead analyzed pooled data from three studies that collectively involved over 200,000 U.S. adults. All of the study participants were nurses or other health professionals, and almost 80% were women. During the follow-up period of up to 36 years, over 20,000 study participants developed type 2 diabetes and nearly 16,000 developed heart disease.

Compared with those in the bottom quintile for phytosterol intake, those in the top quintile were 9% less likely to develop heart disease and 8% less likely to develop type 2 diabetes. Similar associations were observed for β-sitosterol, but not for campesterol or stigmasterol. The researchers also examined the makeup of the gut microbiome and associated enzymes in a subset of 465 study participants. They identified several microbial species and enzymes associated with higher phytosterol intake that may influence the production of metabolites associated with a lower risk of diseases.

“Our clinical biomarker and metabolomic results suggest the involvement of insulin activity, inflammation and the metabolism of metabolites associated with type 2 diabetes and cardiovascular disease,” said Dr. Fenglei Wang, PhD, research associate at the Harvard T.H. Chan School of Public Health. “This suggests that phytosterol might reduce risk by alleviating insulin resistance and inflammation.”