Low-carb diets may improve renal, CV risk factors in T2D patients

In individuals with type 2 diabetes (T2D), low-carbohydrate diets (LCDs) may improve renal and cardiovascular (CV) risk factors, suggests a review from the UK.

“People with T2D are at significantly increased risk of CKD* … Improving hyperglycaemia for T2D patients is key to avoiding CKD; reducing dietary carbohydrates for those with T2D is one effective way to do this,” said the researchers. LCDs, which have been recently recommended by the ADA**, may be an effective approach for managing metabolic conditions including T2D. [Diabetes Care 2020;43(Suppl):S1-S2; Metab Clin Exp 2021;116:154591; Nutr Metab 2005;2:31]

A retrospective analysis was conducted using data from a single practice in the north of England. LCD was offered to 485 patients with a diagnosis of T2D with normal renal function or mild CKD. Of these, 143 (median age 61 years, 64 percent male) continued the diet and had complete data by end of March 2020. [Curr Opin Endocrinol Diabetes Obes 2021;28:469-479]

Among those who followed the LCD for over an average of 30 months, serum creatinine significantly dropped by a mean 4.7 mmol/L. According to the researchers, this was the most significant improvement, translating to a p value of 0.0000054.

Other measures of renal function that improved significantly were eGFR*** (from 85.5 to 88.0 mL/min/1.73 m²; p=0.003) and urine ACR*** (from 1.02 to 0.61 mg/mmol; p=0.002). “In the context of T2D and DKD*, anticipating an even greater rate of decline in eGFR would not be considered unreasonable. This makes mean eGFR improvement of 2.4 mL/min/1.73 m² BSA^# over [the] evaluation period all the more remarkable,” the researchers noted.

Glycaemic control

Hb_A1c improved from a median 65 to 47 mmol/mol (p<0.001) despite a net ‘deprescribing’ of 35 diabetes drugs. This appears to support the LCD approach of reducing dietary sugar and refined carbohydrate intake, said the researchers.

However, the risk of hypoglycaemia remains with intensive glycaemic control. [Lancet 1998;352:837-853] “[Nonetheless, having a] mean Hb_A1c improvement of 21.5 mmol/mol, [with] nearly half [achieving] drug-free T2D remission … minimizes the risk of iatrogenic hypoglycaemia,” the researchers said.

Improved blood glucose is key

Taken together, the improvements are remarkable, considering the average age of participants and average T2D at baseline of 5 years and 3 months, the researchers explained.

“Whatever the underlying reasons for the significant improvements in renal function [in our study], there seems to be a good physiologic argument for putting improved blood glucose central to the care of people with T2D, hypertension, and DKD. It is likely that reducing hyperglycaemia improves T2D control in addition to hypertension and renal function in this vulnerable group,” they said.

“[F]or those interested in safely improving blood glucose to achieve these potential benefits, our method of advising and supporting a reduction in dietary sugar and starchy carbohydrate [appears to be] a sensible approach. After 8 years of experience in providing this service, we find this approach to be clinically effective, patient-friendly, and sustainable,” they continued.

“At least, for those with normal renal function or mild DKD, this review offers healthcare professionals using an LCD intervention some reassurance that this dietary approach may improve multiple aspects of cardiometabolic health, whilst posing little risk to renal function for people with T2D,” they said. “What remains to be shown is the effect of the approach on individuals with T2D and moderate/severe CKD.”

Further exploration is warranted to validate the current observations and shed light on mechanisms by which LCDs influence renal function. It would also be imperative to look into factors responsible for maintaining drug-free T2D remission, and exact dietary patterns and macronutrient compositions to ascertain diet regimens that would deliver the most benefit in this patient population.