Plant sterols have beneficial effects on hypercholesterolemia, but are they an alternative to statins?

Hypercholesterolemia is an important, independent risk factor for cardiovascular disease, according to a generally accepted wisdom. Measures to normalise elevated blood lipids include diet, exercise and drugs, of which statins are the most widely prescribed. But many people have become somewhat sceptical about the wide-spread use of statins: Traditionally, doctors have viewed statin drugs as the most effective way to lower high LDL cholesterol. But today researchers are starting to believe that statins may not be the magic bullet they’ve always been made out to be. Statins can cause severe adverse effects and some experts have questioned whether they generate more benefit than harm and suggested that ‘BIG PHARMA’ are pushing statins not for the benefit of public health but for maximising profit.

This begs the question: is there an alternative?

This RCT tested the efficacy of a dietary supplement providing 1.8 g/day esterified plant sterols and stanols to improve the fasting lipid profile of men and women with primary hypercholesterolemia. Repeated measures analysis of covariance was used to compare outcomes for sterol/stanol and placebo treatment conditions using the baseline value as a covariate. Thirty subjects were randomized and all of them completed the trial.

Baseline (mean±standard error of the mean) plasma lipid concentrations were: total cholesterol 236.6±4.2 mg/dL (6.11±0.11 mmol/L), high-density lipoprotein (HDL) cholesterol 56.8±3.0 mg/dL (1.47±0.08 mmol/L), LDL cholesterol 151.6±3.3 mg/dL (3.92±0.09 mmol/L), non-HDL cholesterol 179.7±4.6 mg/dL (4.64±0.12 mmol/L), and triglycerides 144.5±14.3 mg/dL (1.63±0.16 mmol/L). Mean placebo-adjusted reductions in plasma lipid levels were significant (P<0.01) for LDL cholesterol (-4.3%), non-HDL cholesterol (-4.1%), and total cholesterol (-3.5%), but not for triglycerides or HDL cholesterol.

The authors conclude that these results support the efficacy of 1.8 g/day esterified plant sterols/stanols in softgel capsules, administered as an adjunct to the National Cholesterol Education Program Therapeutic Lifestyle Changes diet, to augment reductions in atherogenic lipid levels in individuals with hypercholesterolemia.

These findings are encouraging but certainly not rock solid. The study was too small, and the effect sizes were less than impressive. A brand-new systematic review, however, provides much more convincing data.

Its aim was to quantify the LDL-cholesterol-lowering effect of plant sterols/stanols as supplements. Eight eligible clinical trials were identified. Among the trials with a duration between 4 and 6 weeks, plant sterol/stanol dose ranged from 1.0 to 3.0 g/day administrated mainly with the main meals (2 or 3 times/day). Intake of plant sterol/stanol supplements decreased LDL-cholesterol concentrations by 12 mg/dL (0.31 mmol/L) compared with placebo. Further analysis showed no significant difference between the LDL-cholesterol-lowering action of plant sterols/stanols supplements vs foods enriched with plant sterols/stanols. The authors concluded that plant sterol/stanol supplements as part of a healthy diet represent an effective means of delivering LDL-cholesterol-lowering similar to plant sterols/stanols delivered in various food formats.

Crucially, this positive verdict does not stand alone. Another recent review included 5 trials and concluded that a dose-effect relationship of plant stanols in higher doses than currently recommended has been demonstrated by recent clinical studies and a meta-analysis.

Plant sterols seem to be not just effective but also safe: none of the trials published to date reported significant adverse effects. The only concern is the potential decrease in the concentrations of lipid-soluble antioxidants and vitamins, including β-carotene, α-tocopherol, lutein, and α-carotene. It is currently not clear whether these effects are clinically relevant.

The relative merits of phytosterols versus statins are not easy to evaluate. We have hundreds of studies of statins but just a few of sterols. This means our knowledge in this area is incomplete. Statins can cause serious adverse effects but their effects on blood lipids is about one order of magnitude larger that those of sterols. There is plenty of evidence to show that statins lower the risk of cardiovascular disease, while such data are missing for phytosterols.

The choice between statins and plant sterols is thus not easy, particularly considering the often emotional arguments and hype used in the ‘cholesterol-debate’. Phytosterols offer one more alternative therapy for lowering LDL-cholesterol levels. They seem safe and have the added attraction of being ‘natural’ – but the lipid-effects are relatively small, the impact on cardiovascular morbidity and mortality is uncertain, and fairly high doses are required to see any lipid-lowering at all.