Phytosterols are plant sterols structurally similar to cholesterol. They include mainly campesterol, sitosterol, stigmasterol, and their respective stanols (5 alpha-saturated derivatives), which chemically resemble cholesterol. They are present in a normal diet bur less than 0.1% of serum sterols are plant sterols. A phytochemical-rich, plant-based diet is of importance in reducing risks of hormone-related neoplasms.
Examples of Phytosterols
There are a number of phytosterols including
beta sitosterol, stigmasterol,
campesterol, and
brassicasterol.
Certain herbs have a high concentration of phytosterols, for instance,
saw palmetto.
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Benefit of Stigmasterol and
Phytosterols
Epidemiologic and experimental studies suggest that dietary phytosterols
may offer protection from the most common cancers in Western societies, such as
colon, breast and prostate cancer. The reasons may include the effect of phytosterols
on membrane structure and function of tumor and host tissue, signal transduction
pathways that regulate tumor growth and
apoptosis, immune
function of the host and cholesterol metabolism by the host.
Phytosterols and
Cholesterol
Phytosterols inhibit intestinal cholesterol absorption, and fat-soluble
plant stanol esters were introduced as a functional food for lowering
serum cholesterol in the early 1990s; plant sterol esters entered the
market at the end of the 1990s. Inhibition of the intestinal absorption of
cholesterol stimulates cholesterol synthesis, a factor which limits serum
cholesterol lowering to about 10% with phytosterols. Enrichment of the
diet with plant stanol esters reduces absorption and serum concentrations
of both cholesterol and plant sterols, whereas enrichment of the diet with
plant sterol esters, especially in combination with statins, lowers serum
cholesterol but increases serum plant sterol levels. Long-term cholesterol
lowering, needed for the prevention of coronary heart disease, may be
successful with plant stanol esters, which lower serum cholesterol in both
genders over at least a year.
Stigmasterol and
Cholesterol
Plant sterols compete with cholesterol for intestinal absorption to
limit absorption and lower plasma concentrations of cholesterol.
Stigmasterol (24-ethyl-cholesta-5,22-dien-3beta-ol; Delta(22) derivative
of sitosterol [24-ethyl-cholest-5-en-3beta-ol]), but not campesterol
(24-methyl-cholest-5-en-3beta-ol) and sitosterol, is reported to inhibit
cholesterol biosynthesis via inhibition of sterol Delta(24)-reductase in
human Caco-2 and HL-60 cell lines. Researchers studied the effect of
feeding 0.5% stigmasterol on plasma and liver sterols and intestinal
cholesterol and sitosterol absorption in 12 wild-type Kyoto (WKY) and 12
Wistar rats. After 3 weeks of feeding, cholesterol and sitosterol
absorption was determined in 6 rats from each group by plasma dual-isotope
ratio method. After 3 more weeks, plasma and hepatic sterols and hepatic
enzyme activities were determined in all rats. After feeding stigmasterol,
baseline plasma cholesterol was 1.3 times and plant sterols 3 times
greater in WKY compared with Wistar rats. Stigmasterol feeding lowered
plasma cholesterol by approximately 11%, whereas plasma campesterol and
sitosterol levels were virtually unchanged in both rat strains, and
stigmasterol constituted 3.2% of plasma sterols in WKY rats and 1% in
Wistar rats. After 6 weeks of feeding, cholesterol and sitosterol
absorption decreased 23% and 30%, respectively, in WKY, and 22% and 16%,
respectively, in the Wistar rats as compared with untreated rats. In
conclusion, stigmasterol, when fed, lowers plasma cholesterol levels,
inhibits intestinal cholesterol and plant sterol absorption, and
suppresses hepatic cholesterol and classic bile acid synthesis in Wistar
as well as WKY rats. However, plasma and hepatic incorporation of
stigmasterol is low.
Phytosterol complex 350 mg
beta sitosterol 140 mg
campersterol 70 mg
Stigmasterol 60 mg
Brassicasterol 5 mg