According to Universal Nutrition, its Natural Sterol capsules can enhance the body's ability to increase muscle mass and density; boost performance and recovery; and intensify energy levels and strength. It is intended to work like an anabolic steroid for bodybuilders. The company claims that the plant sterols present in its supplements are chemically similar to testosterone and can bind to estrogen receptor sites, reducing the likelihood of estrogen conversion.
Jerry Brainum of Iron Man magazine explains that sterols function similarly in plants to cholesterol's role in humans. Both materials are present in the membranes of plants and animal cells. Plant sterols are called phytosterols and animal sterols are called zoosterols, according to Wikipedia. Cholesterol in humans is a precursor to the synthesis of hormones like testosterone, estrogen, cortisol, progesterone and dehydroepiandrosterone, or DHEA, notes Brainum.
The U.S. Food and Drug Administration has approved phytosterols for use as a food additive. As a nutritional supplement, phytosterols have been shown in clinical trials to block cholesterol absorption sites in the human intestine, says Wikipedia. This helps to reduce cholesterol levels and the risk of atherosclerosis, which is the buildup of fatty deposits in artery walls, according to the American Heart Association. The AHA has expressed concern over the safety of phytosterols as they relate to cardiac health and notes that the compounds' modes of action are not yet established. More research is needed before they are considered safe for regular use.