A randomized cross-over trial of the postprandial effects of three different diets in patients with type 2 diabetes

Abstract

Background: In the clinic setting both fasting levels of glucose and the area under the curve (AUC) of glucose, by determination of HbA1c levels, are used for risk assessments, in type 2 diabetes (NIDDM). However little is known about postprandial levels, and hence AUC, regarding other traditional risk factors such as insulin and blood-lipids and how this is affected by different diets.

Objective: To study postprandial effects of three diets, during a single day, in NIDDM.

Methods: A low-fat diet (45-56 energy-% from carbohydrates), and a low-carbohydrate diet (16-24 energy-% from carbohydrates) was compared with a Mediterranean-style diet (black coffee for breakfast and the same total-caloric intake as the other two diets for lunch with red wine, 32-35 energy-% from carbohydrates) in a randomized cross-over design. Total-caloric intake/test-day at the clinic from food was 1025-1080 kCal in men and 905-984 kCal in women. The test meals were consumed at a diabetes ward under supervision.

Results: Twenty-one participants were recruited and 19 completed the studies. The low-carbohydrate diet induced lower insulin and glucose excursions compared with the low-fat diet (p<0.0005 for both AUC). The insulin-response following the single Mediterranean-style lunch-meal was more pronounced than during the low-fat diet lunch (insulin increase-ratio of the low-fat diet: 4.35 ± 2.2, of Mediterranean-style diet: 8.12 ± 5.2, p = 0.001) while postprandial glucose levels were similar. The increase-ratio of insulin correlated with the elevation of the incretin glucose-dependent insulinotropic-polypeptide following the Mediterranean-style diet lunch (Spearman, r = 0.64, p = 0.003).

Conclusions: The large Mediterranean-style lunch-meal induced similar postprandial glucose-elevations as the low-fat meal despite almost double amount of calories due to a pronounced insulin-increase. This suggests that accumulation of caloric intake from breakfast and lunch to a single large Mediterranean style lunch-meal in NIDDM might be advantageous from a metabolic perspective.

Trial registration: ClinicalTrials.gov NCT01522157 NCT01522157.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. CONSORT Flow Diagram.

Abbreviations: LF, low-fat diet; LC, low-carbohydrate diet; M, Mediterranean diet.

Figure 2. Effects of three different diets on glucose, insulin, triglycerides and glucose-dependent insulinotropic-polypeptide (GIP).

Effects of a low-fat diet (open circles, regular lines), low-carbohydrate diet (open squares, dashed lines) and a Mediterranean-type diet (open triangles, dotted lines) with similar total energy intake as the low-fat and low-carbohydrate diets contained for both breakfast and lunch combined but eaten only at lunch paired with a glass of red wine (a, effects on glucose; b, effects on insulin; c, effects on serum triglyceride levels; d, effects on the incretin hormone glucose-dependent insulinotropic-polypeptide). All 19 patients with type 2 diabetes tested the three different diets for breakfast and lunch, *corresponds to Wilcoxon's signed rank paired test in comparison with the control (low-fat diet) at the same time-point (p