Glycemic Control with High-Protein/Low-Carbohydrate Diets

A recent study looked at how different diets such as high-protein and low-carb can affect blood glucose levels in patients with type 1 diabetes.

Carbohydrate counting remains a vital strategy for glycemic control in patients with diabetes mellitus. Various dietary plans can be recommended for patients to aid in glycemic control, such as the Mediterranean diet or a high-protein/low carbohydrate diet (HPD). Ajala et al. saw that these dietary patterns, especially the Mediterranean diet, led to improvements in glycemic control in patients with type 2 diabetes. However, few studies have compared the efficacy of these patterns on glycemic control in patients with T1DM. As carbohydrate counting is essential to determine insulin needs, these patients may require additional dietary considerations. A recent study by Dimosthenopoulos et al. sought to answer which diet provided the most benefit in patients with T1DM. 

This latest study was a randomized crossover study that assessed the differences between a Mediterranean diet (40% carbs), high-protein/low carb (20% carbs), and reference diet (50% carbs) on glycemic control in patients with T1DM. All patients were on a basal-bolus regimen which included using the insulin-to-carbohydrate ratio (ICR) and insulin sensitivity factor (ISF) to adjust their doses. Diets were similar in caloric value and created using predetermined macronutrient specifications. The investigators asked patients to record a food diary before the study to change the interventional diets based on patient-specific habits to improve compliance. Patients would eat their randomly assigned dietary pattern for three separate weeks with a seven-day washout period when transitioning. During that washout period, patients would eat their regular diet as they usually would. Patients recorded everything consumed in a food diary for the duration of the study. Before and after each dietary intervention, patients would be interviewed about their experience and level of adherence. In addition to manual blood glucose (BG) monitoring, patients were set up with a continuous BG monitor for each 7-day interventional period. The primary outcome was to see how these diets affect glycemic control. To assess this, they measured the percentage of time in the euglycemic range (70-140 mg/dL), time spent below and above this range, and time spent in other consensus recommended ranges. Secondary outcomes included the daily average number of times above or below the euglycemic range, mean BG level, glycemic variability, and insulin needs. Investigators used the Shapiro-Wilk test for all outcomes to assess for normal distribution. Based on the normality, they evaluated the outcomes using repeated measures ANOVA or Friedman tests. The investigators also did a post-hoc pairwise analysis via repeated measure t-test or Wilcoxon signed-ranked test. They defined significance as p<0.05 and p<0.017 with the Bonferroni adjustment.

In total, fifteen patients with T1DM participated in the study. Macronutrient consumption showed that adherence was high for all three diet plans (>90%). Overall, the HPD and Mediterranean diet were comparable and did not significantly differ in outcomes. There was no difference in the percentage of time spent in the euglycemic range between the three interventions (p=0.105). The pairwise analysis did show a significant difference between HPD and reference diet (p=0.018) until adjusted with Bonferroni correction. Furthermore, there were substantial differences in the time spent below 70 mg/dL between the three diets (p=0.008). HPD showed improvements in residual time compared to a reference diet (median 12% vs. 14%, respectively; p=0.007). When increasing the range to 70-180 mg/dL, the HPD also performed significantly better in percent time spent in range than a reference diet (74.33% ± 2.85% vs. 67.53% ±12.73%; p=.012). For secondary outcomes, patients on an HPD also had less glycemic variability (p=0.016) and lower mean insulin (p=0.041; not significant when adjusted for Bonferroni) and postprandial doses (p=0.016) compared to reference diet. There was no significant difference in mean BG level or insulin correction.

Based on these results, eating a high-protein/low carb diet may help patients with type 1 diabetes with glycemic control. Specifically, patients following this diet spent more time within a BG range of 70-180 mg/dL, had lower glycemic variability, required less postprandial insulin, and had less time in hypoglycemia. It is essential to distinguish that these benefits were only seen when comparing an HPD to a diet that consists of 50% carbohydrates. Because of the small sample size and length of the study, it isn’t easy to ascertain how clinically significant these results are, especially in the long term. More research with larger samples is needed to verify these findings.

Practice Pearls:

• High-protein/low-carbohydrate diets may offer some benefit for glycemic control to patients with type 1 diabetes.
• Effects were comparable between high-protein/low-carbohydrate diets and the Mediterranean diet.
• High attrition rates and a small sample may have hampered the findings of this study.

Dimosthenopoulos, Charilaos et al. “The beneficial short-term effects of a high-protein/low-carbohydrate diet on glycaemic control assessed by continuous glucose monitoring in patients with type 1 diabetes.” Diabetes, obesity & metabolism vol. 23,8 (2021): 1765-1774. doi:10.1111/dom.14390

Ajala, Olubukola et al. “Systematic review and meta-analysis of different dietary approaches to the management of type 2 diabetes.” The American journal of clinical nutrition vol. 97,3 (2013): 505-16. doi:10.3945/ajcn.112.042457

Andy Dao, PharmD Candidate, University of South Florida Taneja College of Pharmacy