The hypolipidaemic effect of inulin: when animal studies help to approach the human problem.

The paper by Jackson et al. (1999) in the present issue of the British Journal of Nutrition is devoted to the analysis of the effect of inulin on blood lipids in moderately hyperlipidaemic men and women. The hypolipidaemic effect of dietary inulin-type fructans has been suggested by many animal studies, in which either a hypotriacylglycerolaemic, or a hypocholesterolaemic effect was observed when animal diets were enriched with such non-digestible, fermentable carbohydrates (for review, see Roberfroid & Delzenne, 1998). Jackson et al. (1999) show in their human study the occurrence of a rather punctual hypotriacylglycerolaemic effect, which is observed after 8 weeks of treatment with 10 g inulin/d and is preceded by decreased insulinaemia, observed after 4 weeks. They also suggest an inter-individual variability in the response to inulin, which is dependent on the plasma triacylglycerol level at the beginning of the treatment. Interestingly, they present a table in which several human studies are reported, and indicate clearly that in some experiments, inulin-type fructans decrease cholesterolaemia and/or triacylglycerolaemia, whereas in some other studies, no effect can be seen, as recently shown in hyperglycaemic patients (Alles et al. 1999). The data obtained in animals could help to clarify those discrepancies. First, in animals, the type of diet in which inulintype fructans are incorporated influences the metabolic response.