Comparative gastrointestinal and plasma cholesterol responses of rats fed on cholesterol-free diets supplemented with guar gum and sodium alginate

Abstract

The present study investigated the digestion and cholesterol-lowering effects of the watersoluble NSP guar gum (GG) and sodium alginate (SA) in laboratory animals. Groups of five male Wistar strain rats were fed semi-purified cholesterol-free diets containing 0, 50 or 100 g NSP source/kg for 21 d which comprised a 14-d adaptation period followed by a 7-d balance period. Weight gain over the balance period and food conversion ratio decreased linearly with increasing NSP intake (P 0´006 and P 0´07 respectively). DM digestibility decreased with increasing NSP intake P 0´001 and this effect was greater for SA-containing diets compared with GG-containing diets P 0´001X At the lower inclusion rate, 0´9±1´0 of the additional NSP was digested, but this value fell to 0´8 for both NSP sources at the 100 g/kg inclusion rate, implying that the capacity for near complete digestion of the test NSP had been exceeded. Intestinal tissue mass was increased in response to inclusion of both NSP sources. Caecal digesta pH decreased linearly with additional GG, but increased slightly with consumption of SA. Total caecal short-chain fatty acid concentrations (mmol/g caecal contents) increased markedly with 50 g GG/kg but did not increase further with 100 g GG/kg, and were slightly lower than control values in rats consuming SA. Plasma cholesterol concentration fell linearly P 0´03 with increasing NSP in the diet and the effect was similar for both GG and SA. Total output of faecal bile acids rose in rats fed 50 g GG/kg and 50 g SA/kg (59 mmol/7 d v. 24 mmol/7 d for control rats) with no further increase at the higher inclusion rate. These results show that SA has a strong hypocholesterolaemic effect in rats which is similar to that of GG, and that this effect is most likely to be mediated through an interruption in the entero-hepatic circulation of bile acids and not through increased hepatic supply of propionate from fermentation of the NSP in the large bowel.

Alginate reduces the increased uptake of cholesterol and glucose in overweight male subjects: a pilot study

“…Populations with high fibre intakes have lower serum cholesterol. The reduced uptake of cholesterol [3] increased excretion of lipids as faecal bile acid [4,5], coupled with reduced absorption of glucose -leading to altered insulin secretion and therefore lowered cholesterol synthesis -have all been presented as potential candidates for the mechanism of action of fibre in relation to cholesterol lowering.…”

“…There is an inverse linear relationship between supplementary dietary fibre intake and plasma cholesterol for alginate and an associated increase in total faecal bile levels [5]. Kimura et al [18] examined a range of alginate formulations in rats, showing increased cholesterol excretion and improved glucose tolerance.…”

Nutrition Discussion Forum

“…The plasma cholesterol-lowering properties of DF such as b-glucan, psyllium (Romero et al 2002), guar gum (Fernandez et al 1995;Seal & Mathers, 2001), pectin (Fernandez et al 1994), algal polysaccharides (Dvir et al 2000;Seal & Mathers, 2001) or special DF sources such as rhubarb stalk fibre (Goel et al 1999) seem to be mostly related to their macromolecular state. The plasma cholesterol-lowering effects are found especially in hypercholesterolaemic human subjects or animals, and are connected directly or indirectly with the metabolism of bile acids (BA) and neutral sterols (NS) in the intestinal tract and liver.…”

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“…SA also shows a strong hypocholesterolemic effect in rats which is similar to that of GG, and that this effect is most likely to be mediated through an interruption in the enterohepatic circulation of bile acids. [11] GA after fermentation showed energy losses from volatile and gaseous fermentation products but a less utilizable energy 0-4 kcal/g releases in controlled conditions. [12,13] Gum was extracted from some lesser known tropical legumes -Afzelia africana, Detarium microcarpum, and Mucuna flagellipes.…”