High-protein diet in diabetic nephropathy: what is really safe?

Protein supplementation changes gut microbial diversity and derived metabolites in subjects with type 2 diabetes

High-protein diets are promoted for individuals with type 2 diabetes (T2D). However, effects of dietary protein interventions on (gut-derived) metabolites in T2D remains understudied. We therefore performed a multi-center, randomized-controlled, isocaloric protein intervention with 151 participants following either 12-week high-protein (HP; 30Energy %, N = 78) vs. low-protein (LP; 10 Energy%, N = 73) diet. Primary objectives were dietary effects on glycemic control which were determined via glycemic excursions, continuous glucose monitors and HbA1c. Secondary objectives were impact of diet on gut microbiota composition and -derived metabolites which were determined by shotgun-metagenomics and mass spectrometry. Analyses were performed using delta changes adjusting for center, baseline, and kidney function when appropriate. This study found that a short-term 12-week isocaloric protein modulation does not affect glycemic parameters or weight in metformin-treated T2D. However, the HP diet slightly worsened kidney function, increased alpha-diversity, and production of potentially harmful microbiota-dependent metabolites, which may affect host metabolism upon prolonged exposure.

Long-Term Effects of High-Protein Diets on Renal Function

Chronic kidney disease (CKD) has a prevalence of approximately 13% and is most frequently caused by diabetes and hypertension. In population studies, CKD etiology is often uncertain. Some experimental and observational human studies have suggested that high-protein intake may increase CKD progression and even cause CKD in healthy people. The protein source may be important. Daily red meat consumption over years may increase CKD risk, whereas white meat and dairy proteins appear to have no such effect, and fruit and vegetable proteins may be renal protective. Few randomized trials exist with an observation time greater than 6 months, and most of these were conducted in patients with preexisting diseases that dispose to CKD. Results conflict and do not allow any conclusion about kidney-damaging effects of long-term, high-protein intake. Until additional data become available, present knowledge seems to substantiate a concern. Screening for CKD should be considered before and during long-term, high-protein intake.