Elevated levels of blood lipoproteins are caused by poor quality diets. Low quality foods containing refined cereal grains and refined crystalline fructose induced insulin resistance and this raises plasma levels of fasting insulin. Insulin is the primary anabolic hormone, and in its presence catabolic pathways are inhibited. This makes sense biochemically because during periods of anabolism, catabolic pathway flux would lead to futile cycles, wasting energy. The pathological consequences of raised levels of fasting insulin is weight gain, as oxidation of fatty acids are a catabolic process. Further, the shift in the metabolism of the liver to one of anabolism is likely the reason that plasma levels of cholesterol increase. It is the very low density lipoprotein (VLDL) that exports fatty acids from the liver and these are degraded to low density lipoproteins (LDL) in the blood as triglycerides are passed to the tissues. High insulin levels therefore stimulate the export of energy to tissues, raising plasma VLDL and LDL levels.
Statins are HMG-CoA reductase inhibitors that inhibit the synthesis of cholesterol by the liver, which in term reduces the amount available for export to tissues. Individuals who take statins can experience a reduction in plasma low density lipoprotein (LDL) cholesterol level of around 25 %. However, as elevated lipoprotein levels are caused by poor quality diets, which have other health consequences, statins do nothing to improve health. In fact, taking statin drugs is associated with serious side effects because cholesterol is required by all cells for normal regulation of activity. While the risk of cardiovascular disease does drop when taking statins (although it is a very small amount, often using relative risk to inflate the appearance of the figure; here), the risk of other forms of death increase, such that total mortality risk is not altered. Individuals who are fat and unhealthy and choose to take statins to lower cholesterol remain fat and unhealthy. They may however take a different path to the grave.
The observations from the nutritional literature that many foods can lower plasma LDL levels to a similar extent as statins, while producing no side effects is interesting. Very little reporting of the effects of these foods makes it to the mainstream arena for obvious reasons. Legumes are one such food that have shown to be as effective as any pharmaceutical at lowering LDL blood levels. This may relate to the soluble dietary fibres present in the legumes. For example, in one study1, researchers investigated the effects of guar gum on the lipoprotein levels of healthy volunteers. Guar gum is a galactomannan fibre from the guar bean (Cyamopsis tetragonoloba) and is similar to many other bean fibres in its chemical and physical properties. Subjects who received 9 grams of guar gum per day in a capsule for 4 weeks experienced a 16.6 % reduction in total cholesterol and a 25.6 % reduction in LDL cholesterol, compared to the placebo group. The greatest reductions in cholesterol levels occurred in the first two weeks of the study.
Therefore 9 grams of guar gum was effective at lowering plasma levels of total and LDL cholesterol. What is more, the magnitude of the fall in cholesterol levels is similar to that seen by the statin drugs. However, in the case of the guar gum, no side effects are reported for ingestion, as would be expected from a component of food. Interestingly the decrease in plasma cholesterol levels were seen without any other modifications to the diet. However, had a high quality diet been adhered to during the study period, the magnitude of the changes may have increased. Further, the subjects in this study were all healthy and therefore the magnitude of the fall in cholesterol levels may have been greater for subjects with hypercholesterolaemia. The reason that soluble fibres such as guar gum are effective at lowering plasma cholesterol levels may relate to the ability of the fibre to increase the excretion of bile acids, which in turn are synthesised from cholesterol. Eating whole legumes has been shown to have similar effects.
RdB
