Low-carb diet shows promise against type 2 diabetes
A carbohydrate-reduced high-protein (CRHP) diet is better than an isoenergetic conventional diabetes (CD) diet for patients with type 2 diabetes (T2D), according to a recent study.
“A moderate macronutrient shift by substituting carbohydrates with protein and fat for 6 weeks reduced [glycated haemoglobin (HbA1c)] and hepatic fat content in weight stable individuals with type 2 diabetes,” said researchers.
Twenty-eight T2D patients (mean age, 64±7.7 years; 20 males) were enrolled in the open label crossover study. Fourteen participants received 6 weeks of the CRHP diet followed by another 6 weeks of the CD diet; the remaining 14 patients received the interventions in the reverse order.
At baseline, patients had had diabetes for a mean of 7.0±5.4 years, and the average HbA1c was 7.6±0.8 percent. [Diabetologia 2019;doi:10.1007/s00125-019-4956-4]
Assessments performed at the end of each diet period showed that the CRHP diet elicited a significant drop in HbA1c levels as compared to the CD diet (–6.2±0.8 vs –0.75±1.0 mmol/mol; –0.6±0.1 percent vs –0.1±0.1 percent; p<0.001). The CRHP diet also resulted in significantly lower fasting plasma glucose concentrations (–0.71±0.20 vs 0.03±0.23 mmol/L; p<0.05).
Meal challenges after 6 weeks of intervention likewise revealed that CRHP led to 19.4-percent and 59.7-percent reductions in postprandial plasma glucose area under the curve (AUC) and net AUC, respectively (p<0.001 for both relative to CD).
Liver fat fraction also decreased significantly following the CRHP diet (–2.4 percent vs 0.2 percent; p<0.01). The same was true for pancreatic fat fraction (–1.7 percent vs 0.5 percent; p<0.05), though no such changes were observed for muscle fat fraction and visceral and subcutaneous adipose tissue. Changes in systolic and diastolic 24-hour blood pressure also remained comparable between the diet arms.
“As no differences between diets were found in [the homeostatic model assessment of insulin resistance], and only a modest decrease in fasting plasma glucose was observed on the CRHP diet, the reduction in HbA1c may primarily be due to a persistent reduction in postprandial blood glucose level during the CRHP dietary treatment,” researchers explained.
Other mechanistic explanations may exist as well, they noted, such as the presence of specific food items such as nuts and dairy products. “We further speculate that the higher content of fat in the CRHP diet may slow the rate of gastric emptying and, in turn, decrease the rate of glucose delivery to the circulation.”
“The reduction in fasting and postprandial triacylglycerol concentrations during the CRHP diet may result from reduced de novo lipogenesis due to the persistent reduction in insulin excursions,” contributing to the drops in hepatic fat accumulation observed in the present study, researchers added.
The CRHP dietary intervention was also relatively safe, with only four cases of constipation recorded; one had to be treated with a laxative. There were also reports of vitreous degeneration, paroxysmal atrial fibrillation, sleep disturbances and bursitis during the CRHP arm, though none were deemed related to the intervention.
The results of the present study call “for future studies to elucidate the long-term beneficial effects and feasibility of CRHP diets in a real-life setting,” said researchers.