Adherence to low carbohydrate diet reduces blood sugar and HbA1c in Prediabetics: JAMA

Louisiana: Researchers at Tulane University have found in a randomized clinical trial that sticking to a low-carbohydrate diet helped people with prediabetes bring down their HbA1c in just a few months. The results of the study suggest that following a low-carbohydrate diet may help individuals with elevated HbA1c levels who are not taking drugs to decrease their blood sugar levels and achieve better glycemic control.

The new study has been recently published in JAMA Network Open.

Type 2 diabetes (T2D) prevention is a foremost public health priority due to the illness's rising prevalence and high disease burden. Although low-carb diets are frequently advised for those who are receiving diabetes treatment, there is little information that cutting back on carbohydrates has any effect on blood sugar levels in those with diabetes or prediabetes who aren't receiving medication.

The authors set out to investigate the impact of a behavioral intervention promoting a low-carb diet on 6-month reductions in HbA1c among those with increased untreated HbA1c in comparison to regular diet.

As the study's lead author and assistant professor of epidemiology at Tulane University School of Public Health and Tropical Medicine, Kirsten Dorans, ScD, said in a statement, "We by now know that a low-carbohydrate diet is one dietary strategy used among people with Type 2 diabetes, but there is not as much evidence on implications of this diet on blood sugar in people with prediabetes.

"Future research could be conducted to see whether this dietary strategy could replace others in the fight against Type 2 diabetes".

To this intent, researchers planned their trial to contrast a low carbohydrate diet intervention with the regular diet in a group of patients with an untreated HbA1c of 6.0–6.9% who were between the ages of 40 and 70. From September 2018 to June 2021, volunteers for the trial were sought out from an academic medical center in New Orleans, Louisiana. According to the trial protocol, participants who were randomly assigned to a low-carb diet intervention were required to consume fewer than 40 net grams of carbohydrates during the first three months and fewer than 60 net grams from months three through six.

For possible inclusion, a total of 2722 participants were identified. 962 of them received screening, and 150 were randomly assigned; 75 were given the low-carb dietary treatments, and 75 were given the standard diet. 6-month data at the time of analysis.

Conclusive points of the trial:

• At month 6, fasting plasma glucose significantly decreased in those who consumed a low-carb diet and had an untreated, high HbA1c (-10.3 mg/dL, 95% CI -15.6 to -4.9).
• HbA1c decreased by 0.23% more in those following the low-carb diet—those who also received dietary counselling—at this point (95% CI: -0.32 to -0.14).
• Additionally, those following a low-carb diet spent more time in the target glucose range (70-120 mg/dL).
• After following the low-carb diet for half a year, low-carb dieters also saw a larger weight loss of 5.9 kg (95% CI -7.4 to -4.4) (or 13 lb) from their body weight.
• By month 3, the low-carb group's HbA1c decreased by 0.16% more, their fasting plasma glucose decreased by 8.0 mg/dL more, and their body weight decreased by 4.1 kg (around 9 lb).

The study does not establish that a low-carb diet protects diabetes, the researchers said in their conclusion. However, it does pave the way for additional study on how to lessen the health risks associated with prediabetes and diabetes in those who are not taking medication to treat them.

REFERENCE

Dorans KS, Bazzano LA, Qi L, et al. Effects of a Low-Carbohydrate Dietary Intervention on Hemoglobin A1c: A Randomized Clinical Trial. JAMA Netw Open. 2022;5(10):e2238645. doi:10.1001/jamanetworkopen.2022.38645