Evidence continues to mount that dietary carbohydrate restriction can be beneficial for improving blood sugar control, including reversing type 2 diabetes (T2D) and prediabetes. A study published late last year in the journal Nutrients showed that a low-carb diet led to reversal of T2D and normalization of hemoglobin A1c in a significant number of subjects.
Study data came from a retrospective clinical audit of three primary care practices in New Zealand, encompassing 106 patients with T2D or prediabetes (mean age 54 years). The intervention called for dietary carbohydrate reduction, contact with a health coach trained in nutrition, behavior change and motivational interviewing, plus community- or peer-based initiatives, such as weekly meetings (in person or online), cooking classes, Facebook groups, and educational videos. Patients were advised to keep carb intake below 130 grams per day, but specific targets were not prescribed or tracked.
Findings showed that at a median follow-up of 19 months, 32% of patients with T2D at baseline achieved reversal and 44% of those with prediabetes attained normoglycemia. (This analysis used a slightly more generous definition of “reversal” than is usually used. A broadly accepted definition is HbA1c < 6.5% with or without metformin, but a cutoff of < 6.7% was used here, which is consistent with New Zealand guidelines.)
Apart from improving blood sugar, significant decreases were seen in median body weight and alanine aminotransferase (ALT). Changes in triglycerides and blood pressure were not significant, which is unusual for a low-carb study, as these measurements tend to decrease when carbohydrate intake is reduced.
An obvious limitation to this analysis is that detailed dietary intakes were not collected, so the degree of compliance couldn’t be assessed, nor could dose-response relationships be identified. The authors noted that very-low-carb and ketogenic diets (typically ≤ 50 g carbs/day) tend to yield larger effects compared to more modest carbohydrate reduction, but this analysis shows that even a general reduction can yield benefits, particularly when patients have access to support.
A strength of the analysis is that it demonstrates the efficacy of carbohydrate reduction in “the real world,” with within “the constraints, diversity, and competing pressures of routine care,” as opposed to the tightly regulated conditions of a randomized controlled trial. This particular audit is also noteworthy because a significant number of patients were of Māori ethnicity (indigenous peoples of New Zealand), a group that is disproportionately affected by T2D, and in whom the condition tends to progress rather than improve.