Effects of a traditional African diet on the metabolic control of black patients with type II diabetes mellitus

Abstract

Diabetes mellitus has become more prevalent in developing cultures and takes an enormous human and monetary toll each year. Previous research has indicated that the traditional African diet may possibly be the optimal dietary treatment of westernised black non-insulin-dependent diabetes mellitus (NIDDM) subjects. The main hypothesis tested in this study was therefore that the traditional African diet, compared to the westernised diabetic diet as followed by local black people with NIDDM, improves metabolic control, reduces weight, and minimises the risk for macro-vascular complications. The study consisted of three phases. Firstly, a pilot study was undertaken to develop a suitable food frequency questionnaire and to determine the food and nutrient intakes of the local black NIDDM population. It was found that these patients followed a three-meal-per-day pattern. The distribution of dietary energy was 17 % from protein, 35 % from fat and 48 % from carbohydrate. It became clear that the eating habits of these NIDDM patients were in a process of westernisation. Vitamin and mineral intakes were relatively low. Nutrition education and dietary counselling were recommended. In the second phase, the acute or short-term effects of a traditional African meal on blood glucose responses were examined. The glycaemic index (GI) and second meal response of a traditional African meal, consisting of maize meal porridge, soya mince and "morogo" (cooked green leaves) were measured in 14 black NIDOM subjects. A standard reference meal of white bread plus tea, was used as control. The GI of the traditional meal was significantly lower in the women than in the men. In the women, it resembled predicted values based on published GI values of individual foods optained in healthy subjects. A true Staub-Traugott effect (a facilitated glucose disposal during the second meal) was present in both men and women. A second meal response was only observed when the GI of the first meal was low.

Lastly, the long-term effects of a traditional African diet on the metabolic control of black patients with NIDDM were determined. A control group of eight men and 13 women followed an adapted, westernised diabetic diet and a test group of eleven men and 19 women followed a low GI African diet, rich in maize meal porridge, soya and green leafy vegetables for a period of five months. Results showed that the patients could follow the diet success= fully. The test diet resulted in statistically significant, but not clinically significant weight loss. It did not, however, influence either glycated haemoglobin, nor fructosamine values. It was concluded that dietary intervention will improve glycaemic control possibly only if accompanied by substantial weight loss in these obese NIDDM subjects. Lipid profiles were normal to slightly high, in contrast with the high values reported for white NIDDM patients. The weight loss in the test group was accompanied by small but statistically significant decreases in plasma triglycerides, apolipoprotein B, fibrinogen and total cholesterol (in men). It is possible that the lower GI of the test diet contributed to the improvement in lipoprotein profiles. It is recommended that: * a reducing diet with a low energy content as well as a low GI combined with moderate exercise, should be prescribed for overweight black NIDDM patients; * the high prevalence of hypertension and overweight in these patients should get attention; and * the energy needs of black obese NIDDM patients, and the relationship between weight and glycaemic control should be investigated further. From the results of this study it is clear that the dietitian should be an integral part of the medical team and that he/she can play an important role in improving and maintaining quality a£ life for the NIDDM patient. The insight of the dietitian in the nutritional problems of the OM patient should enable him/her to provide education, motivation and attention, form diagnosis of diabetes, throughout the course of the disease.