Oral phytosterols reduce total and LDL cholesterol without affecting HDL cholesterol, meta-analysis shows

Summary

This meta-analysis was performed to investigate the effect of supplements or foods enriched with phytosterols (PS) on the blood level of PS (as measured by campesterol and sitosterol) and on total, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol levels.

Inclusion criteria included randomized, placebo-controlled trials published through June 2012 with oral intake of supplements or foods enriched with typical PS forms (e.g., no ferulated PS) as the active treatment and sufficient data on blood PS levels. Treatment was limited to PS compositions containing at least 80% plant sterols and no more than 20% plant stanols.

Exclusion criteria included trials with confounding co-interventions and trials with colectomized patients, patients with hetero- or homozygous sitosterolemia or patients taking ezetimibe. Trials of less than 2 weeks duration or using more than 10 g/day of PS were also excluded.

Data on blood levels of campesterol, sitosterol, and cholesterol were extracted and net effects were calculated using a random-effects models. Heterogeneity was assessed with I-squared (I²) and Q-statistics. Publication bias and subgroup analyses were also performed.

A total of 41 trials with 2,084 participants met the criteria and were included in the analysis. The average age of the participants was 49 years (range 10 to 60 years) and the average BMI was 26 kg/m² (range: 19 to 35 kg/m²). The average dose of PS from supplements or enriched foods was 1.6 g/day (range 0.3 to 3.2 g/day). The median duration of studies was 28 days (range 21 to 315 days).

Results indicate that, compared to control, PS significantly increased average blood levels of sitosterol and campesterol by 2.24 μmol/L (31%) and 5.00 μmol/L (37%), respectively, and reduced average total and LDL cholesterol by 0.36 mmol/L (5.9%) and 0.33 mmol/L (8.5%), respectively. PS intervention had no effect on HDL cholesterol level.

Subgroup analyses indicate that the increase in blood levels of sitosterol and campesterol correlated with the dose of PS, the baseline PS level and the PS composition of the test products. In the highest PS dose category (2.0 to 3.2 g/day), increases in sitosterol and campesterol were, on average, 3.56 and 7.64 μmol/L, respectively.

The authors report heterogeneity among the studies, more for circulating sitosterol and campesterol than for LDL cholesterol and total cholesterol levels. They attribute this, in part, to differences in PS dose, baseline PS level and PS composition of test products. Publication bias was reported for sitosterol and campesterol analyses, but not for LDL cholesterol and total cholesterol analyses.

These findings indicate that the oral intake of PS as supplements or in enriched foods increase the blood level of PS (total level remains below 1% of total sterols circulating in the blood). In addition, oral PS (1.6 g/day on average) reduces total cholesterol by 5.9% and LDL cholesterol by 8.5%, on average, without affecting HDL cholesterol.