A new clinical study suggests that diets high in protein, independent of caloric intake, improve metabolic health.
High-protein diets in type 2 diabetes patients are controversial. Such diets have been linked to increased risk of heart disease and certain cancers. However, these diets have also been praised because they result in less carbohydrate intake and weight loss. A clinical study conducted by researchers in Germany studied the effects of two high-protein diets on patients. The diets were isocaloric, with the only difference being the source of protein: animal or plant (pulses).
The study included 30 type 2 diabetes patients. The average age of participants was 65 years, the average BMI was 30.5, and average HbA1c was 7.0%. Both diets were 30% protein, 40% carbohydrates, and 30% fat. Length of the trial was 6 weeks. The study authors analyzed different metabolic and molecular parameters before and after the diet.
Both subject groups saw an improvement in liver health with reductions AST, ALT, and GGT. The fat content of the liver and Hba1c levels also improved in all subjects. The animal protein diet reduced liver fat content by 43.6% whereas the plant diet reduced liver fat content by 37.1% (p < 0.001). Hba1c levels were reduced by 0.58% in the animal protein diet group and 0.41% in the plant diet group (p < 0.001). Insulin sensitivity, derived from hyperinsulinemic euglycemic clamps, improved significantly only in the animal protein diet group with a change of 0.88 mg/kg BW/min (p < 0.05).
The plant protein diet group saw an improvement in kidney function, which was not found in the animal protein diet group. The serum creatinine reduction was 7.79 micromols per liter (p < 0.01). Glomerular filtration rate also improved in the plant protein diet group. This finding could have important implications for diabetes patients, considering that renal damage is a typical complication of the disease. It is also important to note that the animal protein diet did not have an adverse effect on kidney markers.
Overall, this study suggests that a high-protein diet with controlled carbohydrate and caloric consumption may be beneficial for diabetes patients. Animal and plant sources of protein seem to give different benefits. This study needs to be replicated on a larger scale to more accurately analyze the effect of high-protein diets on diabetic patients. This study was also flawed due to a lack of a true control diet.
- Patients with protein from animal sources had more improvements in liver fat content than patients with protein from plant sources.
- Subjects consuming the plant-protein based diet saw improvements in renal function (creatinine levels and GFR) that patients eating the animal-protein based diet did not have. The animal-protein based diet did not cause a decrease in renal function.
- This clinical trial was small (n=30) and did not have a control diet. Further research is needed to accurately gauge the benefits or disadvantages of a high-protein diet.
Markova M, Hornemann S, Sucher S, et al. Metabolic and molecular effects of a high-protein diet in subjects with type 2 diabetes. Abstract #701. Presented at the 49th Annual Meeting of the European Association for the Study of Diabetes. 2015.