How often have you been told to eat more protein and less carbohydrates to stay healthy? Many go for high-protein diets that typically promise rapid weight loss and other health benefits. However, even a high-protein diet that is recommended to lose weight or build muscles can be harmful to normally functioning kidneys, particularly in some categories of people, according to an editorial titled ‘High-protein diet is bad for kidney health: unleashing the taboo’ in the journal Nephrology Dialysis Transplantation.
Review of studies
Authored by a team of doctors, led by Kamyar Kalantar-Zadeh, chief, Division of Nephrology, Hypertension and Kidney Transplanation at the University of California, Irvine, this editorial is based on a review of two new studies from the Netherlands and Korea.
A high-protein diet generally involves daily protein intake of 20 to 25% or more of the total daily energy intake. “As per these studies, one should avoid recommending high-protein intake for weight loss in obese or diabetic patients, or those with prior cardiovascular events, or a solitary kidney. What is important is that studies also suggest that a high-protein diet is harmful even on normal kidneys,” Dr. Zadeh told The Hindu.
The recommended dietary allowance for protein intake is only 0.8 to 1 gm/kg/day. “High-protein intake causes stress even on normal kidneys and leads to glomerular hyperfiltration. It is like having five to seven heavy passengers and other heavy load in your car. A car with a good engine can take the load, but it is extra burden,” Dr. Zadeh explained.
However, in patients who are obese, diabetic and at risk for chronic kidney disease (CKD), the harm is even more impactful. It is like having an impaired car that you can drive carefully but cannot overburden it, Dr. Zadeh explained.
The two studies suggest the potential harm of a high-protein diet on kidney health across large populations.
According to the review of the studies, there is evidence to show that the ingestion of a high-protein meal leads to increased glomerular filtration rate (GFR), resulting in ‘glomerular hyperfiltration’ due to a surge in amino acids. This leads to dilatation of the ‘afferent’ arteriole and increased intraglomerular pressure. Inversely, a lower intake of dietary protein leads to more constriction of the afferent arteriole, resulting in decreased intraglomerular pressure and lowered GFR. Hence, a low-protein diet is recommended for those with chronic kidney disease (CKD) or at risk of CKD such as diabetic or obese patients with micro-albuminuria and even those with a solitary kidney.
Corroborating the studies, Sankaran Sundar, consultant nephrologist from Manipal Hospitals, said if the GFR goes up, kidneys start failing in the long run. “Emerging data across individuals and populations suggests that glomerular hyperfiltration associated with a high-protein diet may lead to higher risk of CKD or may accelerate progression of pre-existing CKD. While those with healthy kidneys may not be affected immediately, those who are at risk of CKD may be more vulnerable,” he said.
“We have been seeing several cases of bodybuilders and those following a high-protein diet developing renal issues. Youngsters, especially in the age-group of 20 to 30, who are on fad diets, have been reporting with swelling in the feet and elevated creatinine levels. I get at least one case a month,” he said.
Venu Madhav Reddy G., associate consultant nephrologist at Sakra World Hospital, said he was also seeing several cases of youngsters, following a high-protein diet, reporting with mild renal dysfunction. “If not treated on time, it may lead to chronic problems,” he added.
The doctors asserted that those going on a high-protein diet should first get their kidney functioning analysed. It is advisable to start such diets under medical supervision, they said.