Phytosterols

Phytosterols, also known as phytosterols or plant sterols, are secondary plant substances. They chemically belong to the group of plant steroids (sterols). Phytosterols chemically differ from zoosterols (zoosterols) and the mycosterols occurring in fungi (fungal sterols e.g. ergosterol) by a double bond to C-22 and C1- or by aliphatic side chains to C-24.

Phytosterols are found in the fat-rich parts of plants, such as oils, nuts and seeds. They are particularly abundant in pumpkin seeds, sunflower seeds, wheat germ, sesame and soya beans, and in .

The most common plant sterols are: stigmasterol, beta-sitosterol and campesterol. Phytosterols are structural components in the cell membranes of plants. In this function they are comparable to animal cholesterol, which is present in the cell membranes of animal cells.

With a normal diet, 160-360 mg of phytosterols are ingested daily. Vegetarians get about 2 times this amount. The phytosterol concentrations in serum are between 0.3 and 1.7 mg/dl with a normal diet.

Phytosterols are used therapeutically to lower cholesterol and for the symptomatic treatment of benign prostatic hyperplasia. Phytosterols are also used to treat atopic eczema.

When phytosterols are administered orally, a competitive inhibition of cholesterol absorption in the intestine is assumed. However, since cholesterol is produced by the organism itself to about 90 % independently of the diet, an increased endogenous synthesis occurs as a result of phytosterol intake. Nevertheless, there is an overall slight reduction in total and LDL cholesterol (partial compensation). Phytosterols lower total and LDL cholesterol regardless of whether the individual has normal or elevated blood fat values.

With external application phytosterols are used in skin care products especially for dry skin. Phytosterols improve the skin barrier function. Mostly mixtures of different phytosterols like beta-sitosterol, campesterol and brassicasterol are used.

Phytosterols are considered as novel specific foods. As such, they must undergo an authorisation procedure in the European Union before they are placed on the market. In the European Pharmacopoeia, on the other hand, "phytosterol" is monographed as a substance defined by content (at least 70% beta-sitosterol) and origin (only hypoxis, Pinus and Picea plant genera).