The study, published in Clinical Nutrition, suggests that the reduced cholesterol absorption that is characteristic of metabolic syndrome (MetS) may interfere with the mechanisms of phytosterols cholesterol lowering action – thus reducing their efficacy as a cholesterol lowering agent.
The team of Spanish scientists found that whilst phytosterol enriched foods were able to efficiently lower blood lipid profiles of healthy volunteers, they had no effect on the lipid profiles of volunteers with metabolic syndrome.
“The results of this study demonstrate that MetS subjects with hypercholesterolaemia who consume phytosterols […] do not exhibit any improvement in their lipoprotein profile, suggesting that phytosterol therapy is of little value,” said the authors, led by Dr Antonio Hernandez-Mijares from the University of Valencia, Spain.
Metabolic syndrome (MetS) is a combination of metabolic disorders that promote the development of cardiovascular disease.
“The core components of dyslipidemia in MetS, which are likely to provoke atherosclerosis, are the ‘lipid triad’ of high plasma triglycerides, low levels of high-density lipoprotein cholesterol, and a preponderance of small, dense low-density lipoprotein particles,” explained Hernandez-Mijares and colleagues.
They noted that nutritional modification and lifestyle changes are “the cornerstone of dyslipidaemia therapy.”
Previous research has suggested daily consumption of foods rich in phytosterols may reduce the plasma concentration of LDL-cholesterol.
“Phytosterols are known to reduce intestinal cholesterol absorption, which leads to a significant reduction of serum LDL-cholesterol concentrations (about 10%) without altering HDL-cholesterol or triglycerides when administered at a dose of 2 g/day,” said the authors.
However the effect of the daily consumption of phytosterols for metabolic syndrome is yet to be established, they added:
“There is a lack of relevant data, and the few studies carried out to assess the impact of phytosterols supplementation on MetS subjects are contradictory.”
Hernandez-Mijares and co-workers explained that people with metabolic syndrome often have higher levels of cholesterol, which is accompanied by reduced cholesterol absorption. They suggested that the lower absorption of cholesterol observed in people with metabolic syndrome may interfere with phytosterols’ mechanism of action, therefore reducing their efficacy as cholesterol reducing agents.
The new research investigated whether the addition of low-fat milk enriched with phytosterols in the diet improved cardiovascular risk factors in a group of 24 people with moderately high cholesterol levels and MetS.
Hernandez-Mijares and colleagues reported that neither a dietary intervention nor enrichment of foods with phytosterols brought about any improvement in the serum lipoprotein profile of metabolic syndrome patients.
In contrast, non-metabolic syndrome participants were found to have reduced levels of total cholesterol, LDL-cholesterol, non-HDL-cholesterol and Apolipoprotein B-100 after both a dietary intervention and enrichment of foods with phytosterols.
“Supplementation produced a significant increase in phytosterol levels only in the non-MetS population,” said the authors.
“The results of the present study show that neither dietetic guidelines nor enrichment with phytosterols improved lipid profile in a hypercholesterolaemic population with MetS. This lack of response appears to be associated with low intestinal cholesterol absorption,” explained Hernandez-Mijares and co-workers.
“This suggests that the cholesterol-lowering effect of phytosterol was undermined when cholesterol absorption was low,” they added.
Source: Clinical Nutrition
Published online ahead of print, doi: 10.1016/j.clnu.2011.03.00
“Low intestinal cholesterol absorption is associated with a reduced efficacy of phytosterol esters as hypolipemic agents in patients with metabolic syndrome”
Authors: A. Hernández-Mijares, C, Bañuls, A, Jover, E, Solá, L. Bellod et al