Deep Dive: Low carb diets for type 2 diabetes: beneficial but difficult to maintain

Nutrition is central to the management of type 2 diabetes mellitus (T2DM), but the guidelines for T2DM diet composition have changed over time. Early in the 20th century, prior to the development of injected insulin, people with T2DM were encouraged to restrict carbohydrate intake to 10 grams per day^[1]. Later, once injected insulin was widely available and reductions in fat^[2] and total energy were adopted for improved cardiovascular health, management of T2DM with the standard recommended diet (45–60% of total calories from carbohydrate, 20–35% from fat, 15–20% from protein) became routine. Now, low carbohydrate (LC) diets (less than 45% of total calories from carbohydrate) are making a comeback.

Armed with a focus on protein to replace the reduction in carbohydrates (rather than mostly fat), LC diets are cycling back^[3] into focus for T2DM management. Recent^[4] meta-analyses^[5] have demonstrated improvements in blood glucose markers following short-term (three to six months) LC diets, but meta-analyses investigating the effects of long-term interventions (longer than 12 months), as well as safety considerations regarding higher protein intake and kidney health, are lacking.

Although higher protein intake in healthy individuals^[6] appears to be consistent with normal kidney function, diabetes is a major risk factor^[7] for kidney disease and some observational evidence^[8] suggests that higher protein intake is associated with decreased glomerular filtration rate (GFR, an estimate of kidney function usually calculated based on how well kidneys filter creatinine, a waste product of muscle) in people with diabetes.

The authors of the study under review conducted a meta-analysis to determine the long-term influence of low carbohydrate diets on glycemic control, weight loss, and kidney function in participants with T2DM, when compared to standard higher-carbohydrate diets.

Low carbohydrate diets for T2DM management have been changing over time, with a mostly fat diet being replaced with higher protein content. This has sparked concerns about kidney health and the long-term impacts of the diet. The authors of the study under review conducted a meta-analysis to evaluate the long-term safety and efficacy of modern low carbohydrate diets in people with T2DM.