Will Saw Palmetto Raise Cholesterol?

Saw palmetto is a small North American palm tree that Native Americans used to enhance fertility in women and address urinary complaints in men. Saw palmetto is used in contemporary herbal medicine to treat benign prostatic hyperplasia, or enlarged prostate. While these benefits are due to chemicals in the plant that promote hormonal effects, another compound structurally similar to cholesterol may increase the risk of heart disease in certain people.

The botanical name for saw palmetto is Serenoa repens, although some older texts still use Sabal serrulatum, by which the plant was formerly known. An interesting aspect about this change in nomenclature is that it makes saw palmetto the only species residing in the Serenoa genus.

Saw palmetto berries contain palmitic, cis-linoleic, stearic and other fatty acids. Various flavonoids, including isoquercitin, kaempferol and rhoifolin, are also present in the fruits, as well as water-soluble polysaccharides. The herb is an abundant source of phytosterols, plant steroid compounds chemically similar to cholesterol. Of particular significance in terms of potential effects on cholesterol metabolism in humans is the plant steroid beta-sitosterol and its related esters and glycosides.

Phytosterols like beta-sitosterol are not readily absorbed in the gut on their own, but their chemical structure allows them to compete with dietary cholesterol in the intestinal tract, in effect displacing “real” cholesterol molecules and facilitating their elimination from the body. A review published in "The Journal of Nutrition” in 2009 concludes that plant-based phytosterols reduce total and LDL cholesterol levels in a dose-dependent manner. A subsequent review published in “Prostaglandins, Leukotrienes and Essential Fatty Acids” in 2011 indicates that high intake of the stanol form of plant phytosterols may be more effective at lowering cholesterol than the sterol form.

The Prospective Cardiovascular Münster (PROCAM) study completed in 2005 followed 156 men at high risk for heart disease for 10 years to learn that elevated levels of plasma sitosterol levels are associated with an increased likelihood of a major coronary event. The study objective was based on the finding that a rare genetic disorder called sitosterolemia, which is characterized by extremely high levels of sitosterol concentrations, is associated with higher incidence of atherosclerosis in some people. It is not clear, however, if sterols from saw palmetto or other plant sources directly raise cholesterol and heart disease risk. A review of the Ludwigshafen Risk and Cardiovascular health (LURIC) study published in the “Journal of Lipid Research” in 2009 suggests that an increased risk of cardiovascular disease from plant phytosterols in the absence of sitosterolaemia is unlikely and has more to do with the ratio of the absorption and metabolism of individual plant sterols.

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