THE LIPID-LOWERING EFFECTS OF RHUBARB STALK FIBER - A NEW SOURCE OF DIETARY FIBER

Dried and ground rhubarb stalk fiber containing, on a dry weight basis, 74% total dietary fiber (66% insoluble and 8% soluble) was prepared from rhubarb plants grown in the province of Alberta, Canada. Effect of this fiber source on the plasma and liver concentrations of cholesterol and triglycerides as well as the hepatic microsomal activities of beta-hydroxy beta-methyl coenzyme A reductase (HMGR) and acyl CoA: cholesterol acyl transferase (ACAT) were examined in mice receiving ad libitum a semi-synthetic diet containing 0.5% cholesterol. Feeding the cholesterol-enriched diet for 4 weeks in the presence of 5% rhubarb stalk fiber resulted in significantly lower plasma concentrations of cholesterol and triglycerides as well as hepatic concentrations of total cholesterol than those of animals receiving the diet where rhubarb fiber was substituted by 5% cellulose fiber. Dietary cholesterol supplementation accelerated ACAT activity. In the presence of 5% rhubarb fiber in the diet, this activity was restored to the level found in animals fed a cholesterol-free diet. On the other hand HMGR activity was inhibited by cholesterol supplementation and remained unaffected by addition of rhubarb fiber. These results indicate that rhubarb stalk fiber has a lipid-lowering effect which may not be mediated via alterations in the synthesis and metabolism of cholesterol.