NFI - SISA

Time- and dose-dependent effect of psyllium on serum lipids in mild-to-moderate hypercholesterolemia: a meta-analysis of controlled clinical trials

Wei ZH, Wang H, Chen XY, Wang BS, Rong ZX, Wang BS, Su BH, Chen HZ.
Eur J Clin Nutr. 2009 Jul;63(7):821-7.

E’ ormai noto che livelli di assunzione elevati di fibre solubili, comprese quelle ottenute dallo psillio, aumentano l’effetto ipocolesterolemizzante di una dieta ipolipidica, contribuendo alla riduzione del rischio cardiovascolare. Tuttavia rimane da chiarire se tale effetto si prolunghi anche nel lungo periodo e se il meccanismo con cui lo psillio in particolare riduce la colesterolemia, sia di tipo dose-risposta.
Questa metanalisi ha valutato i risultati di 21 studi controllati condotti su più di 1000 soggetti che hanno assunto psillio per non meno di due settimane, come lassativo o come integratore alimentare, a dosaggi variabili tra 3 e 20 g al giorno. Il confronto con circa 700 soggetti che assumevano placebo ha evidenziato che la supplementazione con psillio non ha prodotto effetti significativi sui livelli di HDL e trigliceridi, ma ha ridotto mediamente la colesterolemia totale ed LDL di 14 e 10 mg/dL rispettivamente. Tale effetto è risultato essere dose dipendente soprattutto per il colesterolo LDL: 5, 10 e 15 g/die di psillio lo hanno ridotto del 5,6, 9,0 e 12,5% rispettivamente. A dosi superiori non si è osservato un ulteriore beneficio, ma un aumento degli effetti indesiderati (diarrea).
Questa metanalisi conferma quindi l’utilità della supplementazione con psillio di una dieta controllata mirata alla riduzione della colesterolemia nei soggetti moderatamente ipercolesterolemici.

OBJECTIVES: Evidences from randomized clinical trials and meta-analysis have claimed an association between the use of soluble dietary fiber from psyllium and a cholesterol-lowering effect. However, there is still uncertainty as to the dose-response relationship and its long-term lipid-lowering efficacy. This meta-analysis was primarily conducted to address the dose-response relationship between psyllium and serum cholesterol level and time-dependent effect of psyllium in mild-to-moderate hypercholesterolemic subjects. METHODS: Twenty-one studies, which enrolled a total of 1030 and 687 subjects receiving psyllium or placebo, respectively, were included in the meta-analysis. The studies were randomized placebo-controlled trials, double blinded or open label, on subjects with mild-to-moderate hypercholesterolemia. The dose of psyllium was between 3.0 and 20.4 g per day and intervention period was more than 2 weeks. Any type of diet background was permitted. Diet lead-in period was between 0 and 8 weeks. RESULTS: Compared with placebo, consumption of psyllium lowered serum total cholesterol by 0.375 mmol/l (95% CI: 0.257-0.494 mmol/l), and LDL cholesterol by 0.278 mmol/l (95% CI: 0.213-0.312 mmol/l). With random-effect meta-regression, a significant dose-response relationship were found between doses (3-20.4 g/day) and total cholesterol or LDL cholesterol changes. Regression model of total cholesterol was -0.0222+0.2061 x log (dose+1), and that of LDL cholesterol was 0.0485+0.1390 x log (dose+1). There was a time effect of psyllium on total cholesterol (equation: 6.3640-0.0316 x treatment period) and on LDL cholesterol (equation: 4.3134-0.0162 x treatment period), suggesting that psyllium reduced serum total cholesterol more quickly than LDL cholesterol. CONCLUSIONS: Psyllium could produce dose- and time-dependent serum cholesterol-lowering effect in mild and moderate hypercholesterolemic patients and would be useful as an adjunct to dietary therapy for the treatment of hypercholesterolemia