Nutritional Management of Diabetes Mellitus and Dysmetabolic Syndrome

The metabolic syndrome is a common metabolic disorder that results from the increasing prevalence of obesity. It also refers to a clustering of specific cardiovascular disease risk factors whose underlying pathophysiology is thought to be related to insulin resistance with an excessive flux of fatty acids implicated. Opinions have varied as to whether the metabolic syndrome should be defined to indicate mainly insulin resistance, the metabolic consequences of obesity, risk of cardiovascular disease, or simply a collection of statistically related factors. Based on these different viewpoints 4 definition sets of the metabolic syndrome are formulated. The pros and cons of each of them are extensively discussed. A major role in the etiology of the metabolic syndrome is ascribed to the occurrence of insulin resistance. Data are provided that insulin resistance can worsen the expression of this syndrome, but cannot have a primary role. Therefore, insulin resistance is not the main player of the metabolic syndrome, but central obesity is. Free fatty acid induced insulin resistance is found and induced by central obesity. The metabolic syndrome is a cluster of abnormalities in which each of them deserves its own (maximal) treatment to diminish the risk for cardiovascular disease.

This review focuses on the efficacy and safety of Chinese medicine in the treatment of type-2 diabetes. Included were 84 controlled clinical studies of type-2 diabetes treated with Chinese medicine for at least 1 month. Reported outcomes were: symptom relief; improvement in glycemia, insulin resistance and secondary failure, and adverse events. Symptom relief was achieved in most (80%) of the patients receiving Chinese medicine. Compared with orthodox drugs, Chinese medicine had a 1.2-fold (95% CI 1.2–1.3) increase in symptom relief. The relative risk of achieving a fasting blood glucose of 7.3 mmol/l or a postprandial blood glucose of 8.2 mmol/l was: 3.0 (95% CI 1.4–6.5) for Chinese medicine plus diet versus diet; 2.0 (95% CI 1.4–3.0) for Chinese medicine versus placebo; 1.8 (95% CI 1.4–2.3) for combined Chinese medicine and orthodox drugs versus Yuquan Wan (a classic Chinese herbal formula for diabetes), 1.5 (95% CI 1.4–1.7) for combined Chinese medicine and orthodox drugs vs. orthodox drugs, and 1.3 (95% CI 1.2–1.5) for Chinese medicine versus orthodox drugs. A fasting blood glucose of 8.2 mmol/l plus symptom relief was observed in 71–100% of the patients with secondary failure to oral anti-diabetic drugs. Serious adverse events including hypoglycemic coma and death were caused by adulteration with orthodox drugs, erroneous substitution, self-meditation, overdoses, and improper preparation. Chinese herbal medicine should be used cautiously with doctors’ prescription and follow-up. Long-term clinical studies may disclose the effectiveness of Chinese medicine in reducing the mortality and morbidity of diabetic complications.

The increasing prevalence of diabetes is reaching epidemic proportion worldwide. Because of the associated morbidity and mortality, it is exerting major pressure on the healthcare system. With a better understanding of the pathophysiology of type-2 diabetes, the concept of primary prevention has emerged. A number of studies have confirmed that intensive lifestyle modification was very effective in the prevention of diabetes in the impaired glucose tolerance (IGT) population. However, maintaining long-term lifestyle modification is a major challenge. It is, therefore, important to have other strategies, either pharmacological or surgical, that can be used as an adjunct or alternative to lifestyle modification. The Chinese study showed that metformin and acarbose could reduce the risk of diabetes by 65 and 83%, respectively, in IGT subjects. The efficacy of metformin was confirmed by the Diabetes Prevention Program (31% risk reduction) and that of acarbose by the STOP-NIDDM trial (36% risk reduction) in a similar high-risk population. The TRIPOD study showed that troglitazone could reduce the risk of diabetes by 55% in Hispanic women with a history of gestational diabetes. And more recently, the XENDOS study showed that orlistat could reduced the risk of diabetes by 37% in obese subjects when used as an adjunct to an intensive lifestyle program. Three studies have suggested that bariatric surgery in morbidly obese subjects could reduce the risk of diabetes to near zero.

The glycemic index concept owes much to the dietary fiber hypothesis that fiber would reduce the rate of nutrient absorption and increase the value of carbohydrate foods in the maintenance of health and treatment of disease. However, properties and components of food other than its fiber content contribute to the glycemic and endocrine responses postprandially. The aim of the glycemic index classification of foods was therefore to assist in the physiological classification of carbohydrate foods which, it was hoped, would be of relevance in the prevention and treatment of chronic diseases such as diabetes. Over the past two decades low glycemic index diets have been reported to improve glycemic control in diabetic subjects, to reduce serum lipids in hyperlipidemic subjects and possibly to aid in weight control. In large cohort studies, low glycemic index or glycemic load diets (glycemic index multiplied by total carbohydrate) have also been associated with higher levels of high-density lipoprotein cholesterol, reduced C-reactive protein concentrations and with a decreased risk of developing diabetes and cardiovascular disease. More recently, some case-control and cohort studies have also found positive associations between the dietary glycemic index and the risk of colon, breast and other cancers. While the glycemic index concept continues to be debated and there remain inconsistencies in the data, sufficient positive findings have emerged to suggest that the glycemic index is an aspect of diet of potential importance in the treatment and prevention of chronic diseases.

There is debate among professionals regarding the use of the glycemic index (GI) for meal planning. In type-1 diabetes, there are 4 studies (average duration 4 weeks) comparing high versus low GI diets; none reported improvements in HbA1c, and although 2 reported improvements in fructosamine, 2 reported no differences. In type-2 diabetes, there are 12 studies (average duration 5 weeks); 3 reported improvements in HbA1c and fructosamine, 5 reported no differences in HBA1c, and 3 reported no differences in fructosamine. In adults, there is limited evidence that a low GI diet is beneficial for weight loss or satiety. Three epidemiologic studies reported that a low GI/glycemic load (GL) is associated with a reduced risk of developing diabetes or prevalence of insulin resistance; however, 5 studies report no association between GI/GL and the risk of developing diabetes, fasting insulin or insulin resistance, or adiposity. In general, the total amount of carbohydrate in a meal is the primary meal-planning strategy for people with diabetes. The GI can be used as an adjunct for the fine tuning of postprandial blood glucose responses. Other food/meal-planning interventions have been shown to be more effective than the use of the GI. Copyright

There is a large bulk of evidence that using low glycemic index (GI) foods has a very significant impact on the amelioration of metabolic disturbances observed in diabetic and/or hyperlipidemic patients and in subjects affected by the metabolic syndrome. Studies bringing convincing evidence against this concept are very rare if any. Improvement is observed not only in postprandial blood glucose and insulin variations but also in circulating plasma lipid levels and the morphology and function of adipocytes. Using the concept of low GI foods in diet counseling of diabetic patients is not exclusive of other measures to improve postprandial and overall blood glucose control. On the contrary, the use of low GI foods should be considered as one of other means and tools available to improve diabetes control (such as other dietary modifications, use of specific and nonspecific drug therapy altering postprandial blood glucose). Among these therapies, the most promising ones are -glucosidase inhibitors, glynides, rapid insulin analogues and in the near future the GLP1 analogue. Again, all these classes of drugs could be associated with one another in order to obtain a postprandial delta excursion target of not below 20 and not above 40–50 mg/dl blood glucose.

Fructose is a monosaccharide which is abundant in nature. It is the sweetest naturally occurring carbohydrate. The availability of fructose increased substantially when it became possible in the 1960s to economically produce high fructose syrups from corn starch and other starches. Such high fructose syrups are now used to sweeten soft drinks, fruit drinks, baked goods, jams, syrups and candies. The most recent data available suggest that fructose consumption is increasing worldwide. Fructose presently accounts for about 10% of average total energy intake in the United States. Studies in both healthy and diabetic subjects demonstrated that fructose produced a smaller postprandial rise in plasma glucose and serum insulin than other common carbohydrates. Substitution of dietary fructose for other carbohydrates produced a 13% reduction in mean plasma glucose in a study of type-1 and type-2 diabetic subjects. However, there is concern that fructose may aggravate lipemia, particularly in men. In one study, daylong plasma triglycerides (estimated by determining the area under response curves) in healthy men was 32% greater during a high fructose diet than during a high glucose diet.

Concentrations of glucose and lipids in the blood have important health implications and are influenced by dietary intake. Dietary intake and energy expenditure regulate body weight, which is also an important determinant of health. Thus it would be important to determine the optimal diet for affecting blood glucose and lipids and body weight. Many professional health organizations in different countries have made dietary recommendations that include caloric restriction when needed to prevent or reverse overweight or obesity, limitation of saturated and trans fat, and emphasis on fruits and vegetables. These professional groups have not recommended extremely low carbohydrate or extremely low fat diets, despite much popular interest and recent research in these approaches. In several clinical trials, diet and exercise interventions prevented or delayed the development of type-2 diabetes. These trials showed the value of diet interventions, but did not attempt to determine which dietary approach was optimal. Clinical trials attempting to determine the optimal diet suffer from small sample sizes, short follow-up, and poor follow-up of participants. Therefore, the optimal balance between the total fat and carbohydrate contents and the optimal types of fats and carbohydrates remain unknown.

The nutrition recommendations of 6 major scientific organizations (the American Diabetes Association, the Diabetes and Nutrition Study Group of the European Association for the Study of Diabetes, the Canadian Diabetes Association, the Joslin Diabetes Center and Joslin Clinic, the American Association of Clinical Endocrinologists and Diabetes UK) are reviewed. They all agree that weight loss (with reduction in energy intake and increase in physical activity) is an important therapeutic strategy in all overweight/obese individuals who have or are at risk of type-2 diabetes. Very low carbohydrate diets are not considered appropriate. The recommended proportion varies slightly (from 40 to 65%). The concept of the glycemic index is stressed as important in nearly all guidelines. Fiber intake is advised, up to 50 g/day, if tolerated. Protein intake (for normal kidney function) is advised to range from 10 to 20% of total energy. A low fat diet (30–35%) is recommended by all.

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