Intake of dietary plant sterols is inversely related to serum cholesterol concentration in men and women in the EPIC Norfolk population: a cross-sectional study

Phytosterols and vascular disease

Phytosterols or plant sterols have long been known to lower serum cholesterol concentrations by competing with dietary and biliary cholesterol for intestinal absorption. Food products containing phytosterols and phytostanols are now available to assist in lowering blood cholesterol levels. In contrast to these possibly beneficial effects of plant sterols, a rare genetic condition called sitosterolemia, an autosomal recessive disorder also known as phytosterolemia, is characterized by over absorption of phytosterols and premature coronary artery and aortic valve disease. Phytosterols have also recently been identified in atheromatous plaque obtained from individuals with apparently normal absorption of plant sterols raising the possibility that phytosterols are a novel atherosclerotic risk factor. This article reviews phytosterols and their relationship to vascular disease.

High-performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry determination of cholesterol uptake by Caco-2 cells

A simple, sensitive and selective liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometric method (LC/APCI-MS/MS) was developed and applied to quantitative determination of uptake of cholesterol by Caco-2 human intestine cells. Caco-2 cells were cultured in medium containing cholesterol-3,4-13C2 and phytosterols from nutritional supplements after in vitro digestion. Cellular cholesterol (cholesterol-3,4-13C2) and endogenous cholesterol were extracted using methanol/chloroform (1:2, v/v) and directly analyzed using LC/APCI-MS/MS with selected reaction monitoring (SRM), using cholesterol-2,2,3,4,4,6-d6 as an internal standard. Detection and quantification limits were 2.2 and 7.2 pmol, respectively. This method provides an effective tool for rapid determination of cholesterol uptake by cells with increased selectivity and sensitivity in comparison to previously reported LC/APCI-MS analysis using selected ion monitoring (SIM).

High serum phytosterol levels in short bowel patients on parenteral nutrition support

BACKGROUND & AIMS

Patients with short bowel syndrome (SBS) are often depending on parenteral nutrition support (PNS), sometimes complicated by liver dysfunction. Phytosterols in parenteral lipid emulsions have been suspected to be responsible for cholestasis in paediatric nutrition support. The aim of the present study was to evaluate phytosterol intake and serum phytosterol levels in adult SBS patients.

METHODS

We quantified serum levels of phytosterols, cholesterol, and markers for bile acid and cholesterol synthesis, by gas or liquid chromatography in 21 healthy controls, and in 24 adult SBS-patients, 8 with and 16 without PNS. Phytosterols and cholesterol in parenteral lipid emulsions were also quantified.

RESULTS

Serum levels in SBS-patients without PNS; with PNS; and in controls, were on average for phytosterols 11; 63; and 23 micromol/l (P<0.05 for differences), cholesterol 4,2; 3,8; and 5,1 mmol/l, lathosterol 808; 824; and 228 micromol/100 mmol cholesterol, and 7alpha-hydroxy-4-cholesten-3-one 207;191; and 18 nmol/l, respectively (P<0.05 between controls and SBS). Phytosterols in lipid emulsions ranged from 591 to 958 micromol/l.

CONCLUSIONS

SBS-patients on PNS have higher serum levels of phytosterols than other SBS-patients and controls, possibly because of phytosterols in lipid emulsions. Patients with SBS, regardless of nutrition support, have lower serum levels of cholesterol but higher cholesterol and bile acid synthesis compared to controls.

Micellar Phytosterols Effectively Reduce Cholesterol Absorption at Low Doses

BACKGROUND

The objective of this study was to evaluate the effects of micellar phytosterols on cholesterol absorption in humans.

METHODS

24 healthy adults (mean age 37 years, 16 women and 8 men) underwent four cholesterol-absorption tests to compare the effects of micellar phytosterols supplement containing 500, 300, 200 mg phytosterols and placebo on cholesterol absorption in a cross-over design. Individual absorption tests were separated by 2 weeks. Using the single oral isotope method, inhibition of cholesterol absorption was determined by gas-chromatography mass spectrometry measurement of the differences in plasma hexadeuterated cholesterol enrichment 4 days after test meals with or without phytosterols. Each test meal provided 500 kcal and 89 mg cholesterol including 40 mg tracer cholesterol. We used a general linear mixed model with SAS to test the significance of treatment effect.

RESULTS

Micellar phytosterols had a significant overall effect on cholesterol absorption (p = 0.0002), reduced cholesterol absorption by 23.3% at a dose of 300 mg phytosterols (p = 0.0004) and by 32.0% at a dose of 500 mg phytosterols (p = 0.0001) compared with the placebo. The effect of 200 mg treatment did not reach statistical significance but there was a tendency (p = 0.052).

CONCLUSION

Water-dispersible, micellar phytosterols reduced cholesterol absorption effectively at very low doses.

Rapeseed oil, olive oil, plant sterols, and cholesterol metabolism: an ileostomy study

OBJECTIVE

To study whether olive oil and rapeseed oil have different effects on cholesterol metabolism.

DESIGN

Short-term experimental study, with controlled diets.

SETTING

Outpatients at a metabolic-ward kitchen.

SUBJECTS

A total of nine volunteers with conventional ileostomies.

INTERVENTIONS

Two 3-day diet periods; controlled diet including 75 g of rapeseed oil or olive oil.

MAIN OUTCOME MEASURES

Cholesterol absorption, ileal excretion of cholesterol, and bile acids. Serum levels of cholesterol and bile acid metabolites. Differences between diets evaluated with Wilcoxon's signed rank sum test.

RESULTS

Rapeseed oil diet contained 326 mg more plant sterols than the olive oil diet. Rapeseed oil tended to decrease cholesterol absorption by 11% (P = 0.050), and increased excretion of cholesterol, bile acids, and their sum as sterols by 9% (P = 0.021), 32% (P = 0.038), and 51% (P = 0.011) compared to olive oil. A serum marker for bile acid synthesis (7alpha-hydroxy-4-cholesten-3-one) increased by 28% (P = 0.038) within 10 h of consumption, and serum cholesterol levels decreased by 7% (P = 0.024), whereas a serum marker for cholesterol synthesis (lathosterol) as well as serum levels of plant sterols remained unchanged.

CONCLUSIONS

Rapeseed oil and olive oil have different effects on cholesterol metabolism. Rapeseed oil, tends to decrease cholesterol absorption, increases excretion of cholesterol and bile acids, increases serum marker of bile acid synthesis, and decreases serum levels of cholesterol compared to olive oil. This could in part be explained by different concentrations of natural plant sterols.

SPONSORSHIP

Supported by the Göteborg Medical Society, the Swedish Medical Society, the Swedish Board for Agricultural Research (SJFR) grant 50.0444/98 and by University of Göteborg.