Low carbohydrate diets are beneficial to the health. In this regard they have been shown to cause weight loss, improve insulin sensitivity, reduce fasting blood glucose levels, reduce fasting triglyceride levels and have beneficial effects on blood lipoprotein cholesterol. The reason that low carbohydrate diets are effective is not because carbohydrates are deleterious to the health. As with all things, the devil is in the detail and to understand the detrimental effects of some high carbohydrate diets, it is necessary to understand the type of high carbohydrate diets that are detrimental to the health. With low carbohydrate diets, it is not the limiting of carbohydrates per se that is beneficial, but the limiting of refined carbohydrates. This point is often missed by those commenting on such matters, but is pivotal to understanding of the problems of carbohydrates. The observation that high carbohydrates diets can be healthy if they also contain high amounts of fibre suggests for example that carbohydrates are not disease causing agents in isolation.
Researchers have investigated the beneficial effects of high carbohydrate high fibre diets on insulin sensitivity and found them to be beneficial. For example, in one study1 researchers fed healthy young and old adults a high carbohydrate diet containing 68 % of energy as carbohydrate and between 68 and 88 grams of fibre per day for 3 to 4 weeks. Other subjects consumed a control diet containing 43 % of energy from carbohydrates and 16 to 19 grams of fibre. The high carbohydrate high fibre diet was effective at lowering fasting blood glucose concentrations and significantly increased blood glucose disposal, when compared to the control diet. In addition, the high carbohydrate high fibre diet decreased fasting blood insulin levels compared to the control diet, suggesting that insulin sensitivity had improved. Total blood cholesterol also decreased following the high carbohydrate high fibre diet, supporting the results from previous studies that have showed cholesterol lowering effects from high fibre diets.
These results suggest that high carbohydrate diets are healthy and can have beneficial effects on blood glucose, insulin and cholesterol. A number of variables differed between the control and treatment diets in this study, and so it is difficult to identify the causative agent of the changes observed. However, these results are consistent with other studies that have shown blood glucose, insulin and cholesterol lowering effects for dietary fibre. This suggests that it was the fibre within the high carbohydrate high fibre diet that was largely responsible for these effects. The beneficial effects of low carbohydrate diets seen in many studies when compared to high carbohydrate diets are therefore likely because the high carbohydrate diets used in such comparisons largely comprise of refined carbohydrates. Low carbohydrate diets are therefore beneficial as they are in effect reducing the refined carbohydrate intake of the diet. Comparing a low carbohydrate diet with a high carbohydrate high fibre diet might not show such benefits.
RdB
