(Excerpts from Medscape): Even a high-protein diet, often recommended to
lose weight or build muscles can be harmful to normally functioning kidneys as
per two separate new studies from the Netherlands and Korea, published online
in Nephrology Dialysis Transplantation. Many earlier studies have
shown that a high-protein diet may harm kidney function, and this is why
doctors recommend kidney patients a low-protein diet.
The high-protein culture (Atkins, Zone, South
Beach, and Ketogenic diets) involve daily protein intake of 20% to 25% or more
of the total daily energy intake. As per the 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 if
kidney health cannot be adequately protected.
1. In the
Dutch study, Kevin Esmeijer, MD, of Leiden University Medical Center, the Netherlands
collected dietary data using a food frequency questionnaire from 4837 patients
60-80 years of age with a history of heart attack involved in the
Alpha Omega Trial. At baseline and 41 months follow-up, serum cystatin C (cysC)
and serum creatinine were measured from stored blood samples. The mean age
of the cohort was 69 years and mean estimated glomerular filtration rate was 82
mL/min/1.73m2. Compared with the general population, patients with a
history of heart attack have double the rate of annual decline in kidney
function and thus are at higher risk for chronic kidney disease. For the entire
cohort, mean total protein intake was 71 g/day, of which approximately two
thirds was from animal protein and the remaining third from plants.
Analyses indicated
that the total amount of protein intake per day was inversely associated with
the annual rate of kidney function decline. The annual change in eGFR was
doubled in patients with a total daily protein intake in excess of 1.20 g/kg
ideal body weight, compared with an intake less than 0.80 g/kg.
Specifically, the
annual change in eGFR in those with the highest total daily protein intake was
–1.60 mL/min/1.73m2 compared with –0.84 mL/min/1.73m2 for
those with the lowest total daily protein intake.
And for each extra
daily intake of animal protein of 0.1 g/kg ideal body weight, there was an
additional decline in eGFRcysC of –0.12 mL/min/1.73m2 per
year.
Subgroup analyses also
indicated that the association between protein intake and decline in eGFR was
threefold stronger in patients with diabetes compared to those without
diabetes.
2. In the
Korean study, Jong Hyun Jhee, MD, of the Institute of Kidney Disease Research,
Yonsei University, Seoul, and colleagues analyzed the effect that a
high-protein diet had on renal hyperfiltration and declining kidney function in
9226 participants from the Korean Genome and Epidemiology Study.
Patients were
classified into quartiles of daily protein intake as assessed by a food
frequency questionnaire. The mean age of study participants was 52 years and
the mean follow-up was 11.5 years.
Among the four
quartiles of daily protein intake, the prevalence of renal hyperfiltration was
significantly higher among those in the highest quartile of protein intake, at
6%, compared with 5.2% among those in the lowest protein intake quartile.
And the annual mean
decline in eGFR was again highest, at –2.34 mL/min/1.73m2, among
those in the highest quartile of daily protein intake, compared with –2.01
mL/min/1.73m2 among those in the lowest quartile of protein
intake.
Rapid decline in
kidney function is defined as a decrease in eGFR of > 3 mL/min/1.73m2 per
year. They found that those in the highest quartile of protein intake had a 32%
greater risk of experiencing a rapid decline of eGFR per year compared with
those in the lowest quartile.
They also found that
the faster drop in renal function happened only among those with pre-existing
hyperfiltration. These findings indicate that a higher intake of protein may be
an independent risk factor for renal hyperfiltration that can accelerate
deterioration of kidney function.
Comments
The recommended
dietary allowance for protein intake is only 0.8 g/kg/day and the requirement
for protein is likely even lower, at only about 0.6 g/kg/day, provided adequate
essential amino acids are consumed. However, most adults in Western societies
eat 1.0 to 1.4 g/kg/day of protein. Protein intake may be as high as 20% to 25%
or more of the total energy source they add — considerably higher than the 10%
to 15% recommended by most guidelines.
Emerging data across
individuals and populations suggest that glomerular hyperfiltration associated
with a high-protein diet may lead to a higher risk of de novo CKD or may
accelerate progression of pre-existing CKD.
Dr KK Aggarwal
Padma Shri Awardee
President Confederation of Medical
Associations in Asia and Oceania (CMAAO)
Group Editor-in-Chief IJCP Publications
President Heart Care Foundation of
India
Past National President
IMA
