Plant-derived sterols, known as phytosterols, have been shown repeatedly to lower bad LDL cholesterol in the blood. A combined analysis of existing trials, published in the Journal of Nutrition, now shows the average size of the effect can be estimated from the dose given.
A large number of clinical studies have demonstrated that eating phytosterols or phytosterol-enriched foods leads to reduced blood levels of bad LDL cholesterol. Elevated LDL cholesterol is a major risk factor for coronary heart disease. To see how exactly the phytosterol effect varies with dose, scientists from Unilever and Wageningen University, The Netherlands, combined results from 84 randomised, controlled trials in one dataset and re-analysed them together - a process called meta-analysis.
The average reduction in blood LDL cholesterol across all studies was found to be 9% with a mean daily phytosterol dose of 2.15 g, administered over 21-182 days. This would roughly translate into 10-20% less new cases of coronary heart disease. Absolute reductions were higher in people with higher baseline LDL cholesterol. Furthermore, the meta-analysis revealed a continuous dose-response relationship, enabling researchers to estimate the effect of any given dose of phytosterols on blood LDL cholesterol levels.
A larger effect was observed with solid foods than with liquid foods but only at high phytosterol doses (> 2 g per day), suggesting that this finding may have little practical relevance for phytosterol doses close to the proposed intake of 2 g per day. There was a tendency towards a slightly lower efficacy of single vs. multiple daily intakes of phytosterols, but the LDL cholesterol-lowering effect was significant for both single and multiple daily intakes. Little added benefit was observed beyond 2.5 g per day of phytosterols. The type of phytosterols, i.e. sterols or stanols, and the format of the food (fat-based vs. non fat-based and dairy vs. non-dairy) had no influence on the relationship between dose and response.
Phytosterol-enriched foods and supplements are the only way to achieve intakes high enough to reduce blood LDL cholesterol. Products currently on the market (enriched spreads, fermented milk drinks, etc.) usually contain the proposed daily phytosterol dose of 2 g in 1 to 3 portions.
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