The Western diet is increasingly being seen as a primary driver of Western lifestyle diseases. There are a number of reasons why the diet is a poor choice and these include the high red and processed meat content, the poor omega 6 to omega 3 ratio, the high content of refined carbohydrates and the low content of essential nutrients. Traditional diets are not associated with Western lifestyle diseases because they rely more heavily on unprocessed sources of food and this lowers the metabolic damage they are able to cause. In particular traditional diets on the whole contain high amounts of plant material which may be one reason for their health effects. Plant foods provide phytonutrients that have been shown to have health promoting effects that can include reductions in the risk of cancer and cardiovascular disease. In addition, plant foods are excellent sources of fibre, and increasingly the low fibre content of the Western diet is being shown to be a cause of disease. Plant foods are also rich in protein and this can allow reductions in red meat consumption.
Legumes are one plant foods that have highly beneficial effects on health. Those who consume more legumes tend to be leaner, have better blood sugar control and also tend to have lower risk of developing Western lifestyle diseases. Legumes are healthy foods because they may may reverse the metabolic damage caused by the typical Western diet and a number of studies have shown beneficial effects in this regard. In particular legume consumption can alter plasma lipoprotein levels, which may be reflective of their protective effects against insulin resistance and non-alcoholic fatty liver. For example, research has shown that the addition of soybean to the diet in place of red meat and dairy sources of protein may provide beneficial effects at increasing the turnover of the very low density lipoprotein in hypercholesterolaemic men1. In this study levels of plasma triglycerides were not lowered in the high soybean diet, but their catabolism and their synthesis in the liver were increased, such that total pools of VLDL were unchanged.
In addition to the increased turnover of VLDL, there were also trends to increased turnover of low density lipoprotein and intermediate density lipoprotein. Because the VLDL particle is a precursor to both LDL and IDL, this is suggesting of an increase turnover in lipoprotein metabolism as a whole. The increased LDL blood levels seen with hypercholesterolaemia are indicative of increased VLDL production in the liver, the latter being catabolised in the plasma to form the IDL and then the LDL particle. The higher synthesis of the VLDL particle may originate from increased de novo lipogenesis, or the synthesis of fat from carbohydrates. In particular, it is the over consumption of fructose and refined carbohydrates that causes an increased flux through this de novo lipogenesis pathway which may increase plasma VLDL (triglyceride) levels. Therefore soybeans, and perhaps other legumes, may increase both lipoprotein catabolism and lipoprotein synthesis rates. Exercise also causes improvements in VLDL turnover, and this may be one way that health is improved through consumption of soybeans.
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