Beta-sitosterol. Phytosterols (PS) are fats present in plants–mostly in plant oils, nuts and seeds. Because the human body cannot produce PS, they must be obtained through the diet. Epidemiologic studies suggest that phytosterol intake supports good health 1. Processing of plant oils typically reduces their PS content 1. The average consumption of PS in industrialized Western countries is low, about 78 mg/day. Asian countries consume an average of 4 times that amount, about 400 mg/day 2.