Phytosterols, "naturally occurring plant sterols", have a long history of research documenting both safety and efficacy in promoting heart health by affecting cholesterol.  The American Heart Association published a scientific advisory in its official publication, Circulation, advocating the use of phytosterols in cholesterol control.  In addition, the FDA has approved a health claim for the relationship between diets that include plant sterol/stanol esters and a lower risk of CHD.

The molecular structure of phytosterols is practically identical to that of cholesterol.  Therefore, cholesterol receptors known as micelles accept phytosterols as though it were cholesterol.  This results in the blockage of dietary cholesterol, inhibiting absorption into the bloodstream.  Additional cholesterol controlling benefits may take place by interference with bile, which is made by the liver from cholesterol.

New research is also under way to confirm positive effects of phytosterols and sterolins on Chronic Fatigue Syndrome, fibromyalgia, tuberculosis, sinusitis, HIV, Hepatitis C, and other infectious diseases, whereby beta-sitosterol in particular is said to modulate immune function, inflammation and pain levels through its effects on controlling the production of inflammatory cytokines.

Research has also shown that phytosterols such as beta-sitosterol may help normalize the function of
T-helper lymphocytes and natural killer cells following stressful events.