In 1977, the select committee on nutrition and human needs of the US senate recommended increasing carbohydrates intake to 55-60% of the total caloric intake, while reducing fat consumption from approximately 40% to 30% of the total daily calories. The aims of these recommendations were to reduce health care costs and to maximize the quality of life of Americans as stated by George McGovern, the chairman of that committee. The proposed cost saving was related to the possible reduction in the in incidence of heart disease, cancer, stoke among other killer diseases. Despite being controversial recommendations based on weak scientific evidence, the United States Department of Agriculture (USDA) created in 1980 a food pyramid and placed carbohydrates at its base. This national nutritional experiment contributed, as we know now, to the increased prevalence of obesity. In contrary to the main aims of the recommendations, the prevalence of type 2 diabetes and cardiovascular disease went significantly up. Physiologically, this was explained by the increased insulin response to carbohydrates, which through its fat-storage promoting action increases obesity. It was later shown that accumulation of fat inside the belly (visceral fat) is associated with chronic inflammation that is directly related to type 2 diabetes and heart attacks. Before these recommendations and from the turn of the twentieth century, diabetes was predominantly defined as a carbohydrate intolerance disease and was mainly treated by reducing carbohydrates intake. Thus it was absurd that several medical societies, at that time, recommended increasing carbohydrates intake for patients with diabetes. Carbohydrates restriction was particularly successful in treating diabetes before the discovery of insulin, where Elliot P. Joslin and Fredrick Allen, the fathers of diabetes science, successfully treated their patients diagnosed with fatty diabetes (later known as type 2 diabetes) with a diet very low in carbohydrates. Their eccentric diet, by our current standard, was reincarnated later as Atkins diet. Such extreme reduction of carbohydrates, despite being very successful in treating type 2 diabetes before insulin discovery, was shown to be associated with some side events like constipation, headache, bad breath and muscle cramps. Although the amount of carbohydrates intake was significantly relaxed after insulin discovery in 1922, it never exceeded 40% of the daily caloric intake, an amount that was shown to reduce blood glucose and triglycerides. Since 2003, many clinical trials confirmed that reducing carbohydrates was superior to reducing fat in decreasing body weight and improving glucose control. It was later shown that reducing carbohydrates for patients with diabetes improves their sensitivity to their own insulin; reduces belly fat and triglycerides and increases good cholesterol (HDL-cholesterol). More recently an analysis of several studies (meta-analysis) showed that reducing carbohydrates load (amount) and glycemic index (the effect of particular carbohydrates-containing food on blood glucose) was associated with reduced risk of developing type 2 diabetes. After weight reduction, maintaining a diet lower in glycemic index and higher in protein was shown to maintain weight loss for longer duration more than any other dietary composition. Now, it is obvious that increasing carbohydrates load in diabetes diet increases what is called glucose toxicity and consequently increases insulin resistance, triglycerides level and reduces HDL-cholesterol. From 2005, Joslin Clinic has been recommending reduction of carbohydrates intake to 40-45% of the total daily calories and reducing the glycemic index of carbohydrates (see glycemic index table). Its 2005 guidelines for overweight and obese patients with type 2 diabetes or those at risk to develop type 2 diabetes, which was revised in 2011, continue to recommend reducing carbohydrates intake to prevent and treat patients with type 2 diabetes and weight problems. Recently, most medical societies departed from the recommendation of high carbohydrates intake and recommended individualization of the nutrition needs. Joslin has been using these dietary recommendations in its weight management program (Why WAIT), which helped 44 groups of patients since 2005 to shed a total of 10,000 lbs and improve their diabetes control and cut their medications significantly down. Now, it is clear that we did a major mistake in the late seventies of the last century in recommending carbohydrates increase to >40% of the total daily calories. This era should come to an end if we seriously want to reduce obesity and type 2 diabetes epidemics. Such move may also improve diabetes control and reduce risk of heart disease. Unfortunately, many healthcare providers and dietitian across the nation sill recommend high carbohydrates intake for patients with diabetes, a recommendation that may harm their patients than benefiting them.
Copyright Osama Hamdy, MD, PhD