Adapted from Why low carb diets for type one patients? Jun1 2019 by Emma Kammerer Pharmacy Doctorate Candidate Bradenton School of Pharmacy originally published in Diabetes in Control.
Both Dr Jorgen Neillsen and Dr Richard Bernstein have shown that insulin users have fewer attacks of hypoglycaemia and that the attacks are less severe. A new randomised controlled study by Schmidt et al confirms this finding.
Studies have shown that when a high carb diet is consumed there 20% greater error in carbohydrate estimation compared to when a low carb diet is chosen. This then affects the insulin dose administered, and thus the resulting blood sugars.
Schmidt wanted to look at the long term effects on glycaemic control and cardiovascular risk in type one patients on a low carb diet compared to a high carb diet.
The study was a randomised open label crossover study involving 14 adults who had had diabetes for more than 3 years, to eliminate the honeymoon effect. The patients went on one diet for 12 weeks, had a washout period of another 12 weeks, and then took up the other diet. This was done so that the glycated haemoglobin levels would not be carried over from one diet to the next.
A low carb diet was defined as less than 100g carb a day and a high carb diet as over 250g per day.
Patients were given individualised meal plans and education on how to eat healthy carbs, fats and proteins. They all were experienced insulin pump users. They were asked to record total carbohydrate eaten but not the food eaten. Measurements were taken on fasting days on the first and last day of the study periods.
Blood glucose levels were downloaded from continuous glucose monitoring devices.
Four patients dropped out of the study so ten completed the test which was considered satisfactory by the statistician involved.
Results showed that the time spent in normal blood sugar range 3.9 to 10 mmol/L ( USA 56-180) was not significantly different for each diet.
The time spent in hypoglycaemia, below 3.9 (USA 70) was 25 minutes less a day on the low carb diet, and six minutes less a day below 3.0 (USA 56).
On the low carb diet glycaemic variability was lower and there were no reports of severe hypoglycaemia.
On the high carb diet, significantly more insulin was used, systolic blood pressure was higher and weight gain was more.
There was no relevant changes in factors for cardiac risk between the two study arms.
The study showed that a low carb diet can confer real advantages to type one patients but education on how to conduct a low carb diet and manage the lower doses of insulin is required.
Schmidt, Signe et al. Low versus high carbohydrate diet in type 1 diabetes: A 12 week randomised open label crossover study. Diabetes, Obesity and Metabolism. 2019 March 26.