A new analysis from the Harvard T.H. Chan School of Public Health suggests that diets high in phytosterols—plant-based compounds found in vegetables, fruits, grains, and nuts—may help lower the risk of heart disease and type 2 diabetes.
The findings were presented at the annual meeting of the American Society for Nutrition. Researchers examined blood samples from more than 11,000 participants and metabolic biomarkers from over 40,000 people. These were combined with food-frequency questionnaires to estimate each person’s intake of total phytosterols, as well as three specific types: β-sitosterol, campesterol, and stigmasterol.
Participants with the highest phytosterol intake typically ate 4–5 servings of vegetables, 2–3 servings of fruit, two servings of whole grains, and about half a serving of nuts daily. This diet is achievable for most people without supplements or extreme restrictions.
The Harvard team did not collect new data but instead analyzed pooled results from three long-term U.S. studies involving more than 200,000 adult health professionals—nearly 80% of whom were women. Over a follow-up period of up to 36 years, more than 20,000 participants developed type 2 diabetes and nearly 16,000 developed heart disease.
Compared to participants in the lowest intake group, those with the highest phytosterol intake had a 9% lower risk of heart disease and an 8% lower risk of type 2 diabetes. The strongest associations were linked to β-sitosterol. Campesterol and stigmasterol did not show the same consistent benefits.
In a smaller subset of 465 participants, researchers also analyzed gut microbiome data. They identified several types of bacteria and enzymes tied to higher phytosterol intake. These microbes may help produce metabolites that support lower disease risk.
“Our clinical biomarker and metabolomic results suggest the involvement of insulin activity, inflammation, and the metabolism of compounds related to diabetes and heart disease,” said Dr. Fenglei Wang, a research associate at the Harvard T.H. Chan School of Public Health. “This suggests that phytosterols may reduce risk by improving insulin sensitivity and lowering inflammation.”
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