Why patients with type 1 diabetes are more likely to spend time in hypoglycemia, and how low carb diets for type 1 patients can help.
Patients with type 1 are left to guess proper insulin meal bolus sizes due to the lack of macronutrient distribution recommendations. Observation studies have shown positive outcomes in those who practice a low carbohydrate diet; however, there is a lack of randomized trials to support proper evidence. These studies have also shown that there is a 20% greater chance of an estimation error in a meal containing a high carbohydrate content versus a low carbohydrate content. This error impacts glycemic variability and the risk of hypoglycemia. By having a meal with lower carbohydrate content, there should be less chance of error, but to make up for the loss of energy intake, fat and protein should be increased. This could lead to potentiate changes in CV risk.
In the study, researchers wanted to determine long-term effects on glycemic control and cardiovascular (CV) risk in patients with type 1 practicing a low carbohydrate diet versus a high carbohydrate diet. The study was a randomized open-label crossover study, including 14 adults with type 1 for more than 3 years. Patients were to undergo 2 12-week intervention periods, with a 12-week washout period in-between. The low carbohydrate diet (LCD) was classified as <100 g carbohydrates per day and the high carbohydrate diet (HCD) was classified as >250 g per day. There were 2 arms, the LCD-HCD arm or the HCD-LCD arm. The researchers determined they needed 10 patients to complete the study to give a power of 80% at a 5% significance level using a two-sided paired t-test.
Patients received individual meal plans to meet proper carbohydrate requirements as well as education on healthy macronutrient sources. They were to document the amount of carbohydrates eaten in their pumps, but there were no requirements to record the type. Outcomes measured were obtained when patients were fasting, on the first and last day of the treatment period. The primary endpoint was the difference in time spent in the range 56 – 180mg/dL (3.9-10.0 mmol/L) assessed by continuous glucose monitoring (CGM) during 12 weeks of LCD and 12 weeks of HCD. Secondary endpoints listed were the difference in glycemic variability, time in glucose ranges, and the variables collected at the beginning and end of each intervention period. 4 patients dropped out, leaving 10 to complete the study.
The results showed that there was no significant difference between the groups in the time spent in the range 56-180mg/dL (3.9-10.0 mmol/L). However, there was a significant difference between the groups in the time spent in hypoglycemia, on average spending 25 minutes less per day below 70mg/dL (3.9 mmol/L) (P < 0.001) and 6 minutes less per day below 56mg/dL (3.0 mmol/L) (P = 0.018). Also, during LCD, glycemic variability was found to be lower (P = 0.004) and there were no reports of severe hypoglycemia throughout the study. Comparing the two arms, during HCD, a significant amount of total daily bolus insulin doses were used (P < 0.001), there was an increased systolic blood pressure (P = 0.007), and weight gain (P = 0.001). Between the two arms, there were no statistically relevant changes in CV risks.
The authors concluded, by decreasing carbohydrate intake to < 100 g per day, there will be a reduction of time spent in hypoglycemia, with decreased glycemic variability and decreased weight, but no effect on CV risk factors. While their data is statistically significant, the patients with type 1 who participated in the study had designed individual meal plans, as well as education and practice with carbohydrate counting skills. These results may not be beneficial for the general population without proper education prior to large reductions in carbohydrate intake.
- Patients with type 1 have a lack of recommendations for proper macronutrient intake, leading to guessing of insulin meal bolus doses and possible hospitalizations for hypoglycemic events
- LCD have previously shown positive results in observational studies, with the need for randomized controlled trials
- Less intake of carbohydrates equals less hypo’s and less glucose variability
References: Low Carb Diets for Type 1:
Schmidt, Signe, et al. Low versus high carbohydrate diet in type 1 diabetes: A 12-week randomized open-label crossover study. Diabetes, Obesity & Metabolism. 2019 March 26.
Emma Kammerer, L|E|C|O|M Bradenton School of Pharmacy, PharmD Candidate