Long-term administration of inulin-type fructans has no significant lipid-lowering effect in normolipidemic humans

Short-term studies have shown that the addition to diet of inulin-type fructans, a nondigestible carbohydrate, may have a plasma lipid-lowering effect in humans. Whether this beneficial effect persists during long-term administration has not been determined. The study was aimed at determining whether a prolonged (6 months) administration of inulin-type fructans to healthy subjects has a lipid-lowering action. In a double-blind, randomized, placebo-controlled study, 17 healthy subjects were studied before and after 6 months of daily administration of placebo (8 subjects) or 10 g of a mix of inulin and oligofructose (9 subjects). During this 6-month period, they consumed their usual diet and did not modify their everyday way of life. We measured plasma lipid concentrations; cholesterol synthesis and hepatic lipogenesis; and adipose tissue and circulating mononuclear cell messenger RNA concentrations of key regulatory genes of cholesterol metabolism. Compared with the administration of placebo, the administration of inulin-type fructans had no effect on plasma triacylglycerol concentrations and hepatic lipogenesis and induced only a nonsignificant trend for decreased plasma total and low-density lipoprotein cholesterol levels and increased high-density lipoprotein cholesterol concentration. Cholesterol synthesis was not significantly modified. Of all the messenger RNA concentrations measured, none was significantly modified by the administration of inulin-type fructans. In conclusion, contrary to what was observed in short-term studies, we observed no significant beneficial effect of a long-term (6-month) administration of inulin-type fructans on plasma lipids in healthy human subjects.