Background

Type 2 diabetes is a common disease and the prevalence has increased in large parts of the world. In treatment of diabetes the type of diet is of great importance considering metabolic factors such as glucose level and blood lipids. Which diet that is most beneficial to avoid diabetic complications has been heavily debated in recent decades. This thesis is based on two clinical studies designed to compare the effects of different macronutrients.

Methods

A clinical trial was designed to compare a low-carbohydrate diet (LCD) to a low-fat diet (LFD) in treatment of patients with type 2 diabetes. Sixty-one patients at two health care centres were included and randomized to get advice to eat a LCD or a LFD. The LCD had an energy content where 50 energy percent (E%) where from fat, 20 E% from carbohydrates and 30 E% from protein. For the LFD the nutrient composition was similar to what is traditionally recommended for treatment of type 2 diabetes in Sweden. Metabolic factors, anthropometrics and questionnaires were analysed.

To study postprandial effects a trial was designed to compare three different diets. Twentyone patients with type 2 diabetes were included to in randomized order test the three types of diets on separate test days. On each test day the patients were served breakfast and lunch and blood samples were taken at six times these days. Glucose, lipids and hormones were analysed.

Results

There were equal weight reduction in the two groups in the first trial during the two-year study period. At six month when compliance was good according to diet-records, the glucose level (HbA1c) was lowered and the HDL-cholesterol was increased in the LCD group. The inflammatory markers IL-6 and IL-1Ra were significantly lower in the LCD group than in the LFD group. At 12 months the physical function, bodily pain and general health  scores improved within the LCD group only.

In the second trial the postprandial glucose and insulin levels were lower on the LCD compared to the LFD. However, the LCD resulted in a tendency to higher postprandial triglyceride levels. The Mediterranean type of diet with all energy intake at lunch resulted in a more pronounced insulin response and a glucose level at lunch similar to that of the low-fat diet. The increase-ratio of insulin correlated to the elevation of the incretin glucose-dependent insulinotropic peptide (GIP).

Conclusions

In the two-year study we found benefits for the LCD group regarding glucose control and insulin doses. Furthermore, only the LCD was found to improve the subclinical inflammatory state and there were some aspects of improved well-being in this group. Aiming for 20% of energy intake from carbohydrates is safe with respect to cardiovascular risk factors  compared with the traditional LFD and this approach could constitute a treatment alternative.

In the postprandial state, the LCD induced lower insulin and glucose excursions than the LFD but at the same time a tendency of higher triglycerides. The long-term significance needs to be further examined. The accumulation of caloric intake from breakfast to lunch to a single large Mediterranean-style lunch-meal in type 2 diabetes might be advantageous from a metabolic perspective.