Whereas there is a considerable interest of high-protein, low-carbohydrate diets to manage weight control, their safety is still the subject of considerable debate. They are suspected to be detrimental to the renal and hepatic functions, calcium balance and insulin sensitivity.
However, the long-term effects of a high protein diet on a broad range of parameters have not been investigated. We studied the effects of a high-protein diet in rats over a period of 6 months. 48 Wistar male rats received either a normal-protein (NP: 14 % protein) or high-protein (HP: 50 % protein) diet. Detailed body composition, plasma hormones and nutrients, liver and kidney histopathology, hepatic markers of oxidative stress and detoxification and the calcium balance were investigated. No major alterations of the liver and kidney were found in HP rats, whereas NP rats exhibited massive hepatic steatosis. The calcium balance was unchanged and detoxification markers (GSH and GST) were moderately enhanced in the HP group. In contrast, HP rats showed a sharp reduction in white adipose tissue and lower basal concentrations of triglycerides, glucose, leptine and insulin. Our study suggests that the long-term consumption of a HP diet in male rats has no deleterious effects and could prevent metabolic syndrome.
We performed this study in order to explore whether or not HP diets might be detrimental to healthy animals over a long period representing a quarter of their life span. It would be almost impossible to perform a study on an equivalent period in humans. We can conclude that in male rats, a protein intake of three times the requirements did not produce any adverse effects on the renal and hepatic functions, on oxidative stress or on the calcium balance.
