It is ingrained in the psyche of the Western population that dietary saturated fat and cholesterol are the causes of cardiovascular disease. It is also ingrained in the psyche of Western populations that dietary fat will make you fat. This has lead many people to avoid high fat foods and instead adopt low fat processed alternatives, that often contain high amounts of added sugar. However, the evidence supporting the accusations against fat and cholesterol is very weak and circumstantial, and we should really consider them fallacies. In fact if we look at the nutritional literature we actually find far more evidence that dietary carbohydrates (particularly sugars) are the cause of both obesity and cardiovascular disease than either fat or cholesterol. It has been known for some time for example that feeding animals high fructose diets causes insulin resistance. In fact insulin resistance in such models can develop in as little as two weeks in rats fed fructose (here). Refined grains too can cause insulin resistance in humans and animals.
The ability of fructose and refined grains to cause insulin resistance relates to their ability to overload the liver with nutrients and increase production of fatty acids. If the rate of digestion and absorption is high, the liver switches its metabolism to one of fatty acid production through the de novo lipogenesis pathway. Some of these fatty acids are synthesised into triglycerides and then exported from the liver in very low density lipoprotein (VLDL) particles. If fatty acid production becomes excessive, the de novo lipogenesis pathway produces more triglycerides than are required for energy and other metabolic functions, and as a result they begin to accumulate in tissues. Under such circumstances triglycerides are deposited in skeletal muscle and the liver and here they interfere with the action of insulin through inhibition of the insulin signal cascade in cells. This is thought to be a leading driver of insulin resistance, which in turn is a driver of obesity and may be required for the development of cardiovascular disease.
The ability of starch to cause an increase in plasma triglycerides is well recorded in the nutritional literature. For example in one study1, researchers fed a group of eight individuals a 3000 kcal diet containing 72 % carbohydrate, 13 % fat and 14 % protein for four days. The carbohydrate content of the diet was composed of refined grains including ready to eat breakfast cereal, white bread and white rice, with some orange juice and noodles. At a different time point the same subjects were also fed a high fibre diet consisting of high fibre ready to eat breakfast cereal, wholemeal bread, brown rice, beans and oranges. The results of the study showed that the the low fibre diet cause a significant increase in plasma triglycerides suggesting that the liver had become overloaded with nutrients. In contrast, the high fibre diet did not cause elevations in triglycerides. Also the low fibre diet caused a significant fall in high density lipoprotein (HDL) cholesterol levels, but this effect was not as pronounced for the high fibre diet.
These results suggest that triglyceride levels can become elevated with as little as four days of feeding a high carbohydrate diet composed mainly of refined starch sources. That carbohydrates are converted to fat in the liver often comes as surprising news to the layman, many having being taken in by the clever marketing surrounding low fat foods by unscrupulous food manufacturers. However such pathways are clearly present in basic nutritional biochemistry textbooks and it is a testament to the poor education systems of the West and the propaganda models of the corporations that such information is not widely known and understood. It should not be surprising that high intakes of grains are able to cause an increase in fatty acid production as it is grains that are used to fatten livestock and increase the saturated fat content of the meat. Feeding the cattle grass is not able to cause the same increases in saturated fat because the grass is less energy dense and contains much higher concentrations of fibre.
Dr Robert Barrington’s Nutritional Recommendation: Eating a high grain diet is a great way to get fat. Particularly if the grains are refined of their fibre content. In contrast eating a high bean diet is a great way to lose weight. The difference in these two approaches to modifying body weight related to the glycaemic effects of the two food groups. Grains tend to have high glycaemic indices and beans tend to have very low glycaemic indices. While grains are therefore digested and absorbed very quickly (overloading the liver with nutrients), beans are the antithesis of this phenomenon. Those wishing to gain body weight should therefore consume high grain diets while those wishing to lose body weight should substitute the grains for beans. As well as raising plasma levels of triglycerides, high grain diets can also lower plasma HDL levels. The detrimental lipoprotein changes seen with high grain diets are reversed once grain intake is reduced. Beneficial lipoprotein changes are therefore often seen on high fat high protein diets such as the Atkin’s diet.
RdB
