Guar gum, locust bean gum and other viscous legume fibres may have beneficial effects at lowering levels of plasma lipids. The reason for this is not known, but may relate to the ability of the fibres to slow the absorption of glucose to the blood and therefore they may have beneficial glycaemic effects. Alternatively, the fibres may be utilised as a source of energy by gut bacteria, and these gut bacteria may in turn produce short chain fatty acids that are absorbed from the lower intestine where they pass to the liver and favourably modify lipoprotein and cholesterol metabolism. It is also thought that such viscous fibres may sequester bile acids from recirculation and thus increase cholesterol excretion. Legume gums are therefore an effective way to modulate plasma lipoprotein levels and legume consumption is associated with favourable health outcomes partly for this reason. Researchers have therefore tried to use legume gums in order to modulate cholesterol levels in hypercholesterolaemic individuals with some success.
For example, in one study1, researchers fed hypercholesterolaemic and healthy individuals 8 to 30 mg per day of locust bean gum in order to assess its effects on lipoprotein plasma levels. The locust bean gum is a white tasteless powder that is very similar to guar gum in its appearance and structure. It was incorporated into a number of foods including bread, crackers, cookies and potato slices. The subjects were split into groups and each group received food with and without locust bean gum in a crossover design study. In the hypercholesterolaemic subjects, total cholesterol levels decreased by 10 and 17 % and low density lipoprotein levels (LDL) decreased by 11 and 19 % following 4 weeks of locust bean consumption in the two groups, respectively. In the normal healthy subjects total cholesterol levels decreased by 6 and 11 % and low density lipoprotein levels (LDL) decreased by 10 and 6 % in the two groups, respectively. In both groups the improvement in plasma lipoprotein levels were greater in the hypercholesterolaemic individuals as might be expected.
The beneficial effects of legume fibres are not limited to humans. In fact many animal studies have also shown the cholesterol modifying effects of legumes in rodents. For example, researchers have also tested the effects of various legumes and legume products on rats2. Tender cluster bead pods are a common food consumed in South India, and they contain around 20 % guar gum. One group of researchers fed rats either cluster bean pods, fibre from the cluster beans or cluster bean pods with their fibre partially removed, and reported that all treatments exerted cholesterol lowering effects in rats fed a hypercholesterolaemic diet. However, adding the pods with the fibre partially removed and the isolated pod fibre together did not produce an additive effect as great as the whole cluster bean pods. This adds further weight to the suggestion that fibre in its whole food form, consumed as whole plant material may be more beneficial to the health that isolated components such as individual supplementary dietary fibres.
Dr Robert Barrington’s Nutritional Recommendation: There is little doubt that dietary fibre is an important component of a healthy diet. When carbohydrates are present in the diet fibre is likely an essential nutrient. Consuming fibre in its whole form as found in whole foods is the best way to take advantage of its health benefits. Isolated fibre supplements are beneficial in some circumstances but evidence continues to accumulate that they are not as effective as the fibre present in whole plants. In addition, the viscous nature of many of these fibre makes their isolation and addition to other foods problematic in terms of detrimental texture. They are therefore best enjoyed in their original whole food state.
RdB
