Plant steroids are types of natural organic compounds found in plants. Many types of plant steroids exist and play important roles in the biological processes of plants, such as growth and development, cell division, and resistance to damage from environmental stresses like cold weather. Some plant steroids are also useful for their effects when consumed by human beings because their presence decreases the amount of cholesterol in the bloodstream. Plant steroids should not be confused with anabolic steroids used to increase muscle mass, which are a synthetic substance that imitates the effects of human androgenizing hormones such as testosterone.
All steroids have a characteristic chemical structure based around carbon atoms linked by single or double bonds and arranged into four interconnected rings. Additional groups of atoms called functional groups are bonded to the carbon atoms in the rings at various points, which vary from one steroid to another. Different steroids have different properties that vary according to the number of double bonds in the carbon rings and the composition of the attached functional groups.
The most biologically prominent plant steroid is brassinolide (C28H48O6), which is important to the development of plant cells and promoting the plant's growth. It is part of a larger class of plant steroids called brassinosteroids. Brassinolide is synthesized from campesterol (C28H48O), another plant steroid that is part of a group of similar steroid compounds called phytosterols. Other examples of phytosterols, also commonly called plant sterols, include beta-sitosterol (C29H50O) and brassicasterol (C28H46O).
Phytosterols are plant steroids with a chemical structure similar to that of cholesterol (C27H46O), a steroid found in animals. Cholesterol is essential to human biology and is naturally produced in the human body, but excess levels of dietary cholesterol can damage the circulatory system. Phytosterols have a demonstrated ability to reduce cholesterol levels in the human bloodstream because their similar chemical structure allows them to react with chemicals in the digestive tract that normally bond with cholesterol so that the cholesterol can be absorbed by the intestines. When phytosterols are present, they bond with these chemicals and prevent cholesterol molecules from doing so, causing dietary cholesterol in the intestines to be excreted rather than absorbed.
Consequently, phytosterol-rich foods can have a beneficial effect on people with elevated cholesterol levels. The most naturally phytosterol-laden foods are vegetable oils, nuts, and things made from them. Other foods can be artificially enriched with phytosterols, and they can also be taken in the form of tablets or pills. There is also research suggesting that phytosterols consumption can decrease the risk of some cancers, such as lung, breast, and stomach cancer. Excessive phytosterol levels may also interfere with the absorption of some dietary nutrients and can have dangerous effects in people with certain health conditions, such as the metabolic disorder sitosterolemia, so intentionally increasing phytosterol intake for health reasons without first seeking guidance from a physician is not recommended.