The idea that a diet containing relatively high amounts of protein leads to kidney damage is persistent. And even this Australian study, in which the subjects ate a high-protein, low-carb diet for a whole year without experiencing any pain, is unlikely to change that.
Nutritionists at the Australian research organisation CSIRO [csiro.au] got 115 fat adults with type-2 diabetes to lose weight by eating a diet containing 500-1500 kilocalories less than they burned. In addition they got the subjects to do fitness three times a week.
Half of the subjects were put on a traditional weight-loss diet. Their diet consisted of 53 percent energy derived from carbohydrates, 17 percent from proteins and the remaining 30 percent from fat. [HC] The researchers ensured that at least two-thirds of the fat was unsaturated.
The other half of the subjects were put on a high-protein, low-carb diet. The energy in their diet was derived for 58 percent from fat, 28 percent from proteins and the remaining 14 percent from carbohydrates. [LC]
The researchers measured the subjects’ kidney function before and after the diet period. They looked, among other things, at the amount of albumin in the subjects’ urine. The lower this is, the better the kidneys are working.
The researchers also measured the amount of creatinine in the subjects’ blood. If you are not taking creatine supplements and your kidneys are healthy, there won’t be much creatinine in your blood.
For all the values that the researchers checked, they found no statistically significant effects in either group, as the table below shows.
“Compared with a traditional high carbohydrate weight loss diet, consumption of a very low carbohydrate, high-protein, low saturated fat diet does not adversely affect clinical markers of renal function in obese adults with type 2 diabetes and no pre-existing kidney disease”, the researchers summarized.
The research was financed by the Australian government.
Long-Term Effects of a Very Low Carbohydrate Compared With a High Carbohydrate Diet on Renal Function in Individuals With Type 2 Diabetes: A Randomized Trial
Abstract: To compare the long-term effects of a very low carbohydrate, high-protein, low saturated fat (LC) diet with a traditional high unrefined carbohydrate, low-fat (HC) diet on markers of renal function in obese adults with type 2 diabetes (T2DM), but without overt kidney disease.
One hundred fifteen adults (BMI 34.6?±?4.3?kg/m2, age 58?±?7 years, HbA1c 7.3?±?1.1%, 56?±?12?mmol/mol, serum creatinine (SCr) 69?±?15??mol/L, glomerular filtration rate estimated by the Chronic Kidney Disease Epidemiology Collaboration formula (eGFR 94?±?12?mL/min/1.73?m2)) were randomized to consume either an LC (14% energy as carbohydrate [CHO?< ?50?g/day], 28% protein [PRO], 58% fat [<10% saturated fat]) or an HC (53% CHO, 17% PRO, 30% fat [<10% saturated fat]) energy-matched, weight-loss diet combined with supervised exercise training (60?min, 3 day/wk) for 12 months. Body weight, blood pressure, and renal function assessed by eGFR, estimated creatinine clearance (Cockcroft–Gault, Salazar–Corcoran) and albumin excretion rate (AER), were measured pre- and post-intervention.
Both groups achieved similar completion rates (LC 71%, HC 65%) and reductions in weight (mean [95% CI]; ?9.3 [?10.6, ?8.0]?kg) and blood pressure (?6 [?9, ?4]/?6[?8, ?5]?mmHg), P???0.18. Protein intake calculated from 24?hours urinary urea was higher in the LC than HC group (LC 120.1?±?38.2?g/day, 1.3?g/kg/day; HC 95.8?±?27.8?g/day, 1?g/kg/day), P?0.001 diet effect. Changes in SCr (LC 3 [1, 5], HC 1 [?1, 3]??mol/L) and eGFR (LC ?4 [?6, ?2], HC ?2 [?3, 0]?mL/min/1.73?m2) did not differ between diets (P?=?0.25). AER decreased independent of diet composition (LC ??2.4 [?6, 1.2], HC ?1.8 [?5.4, 1.8]?mg/24?h, P?=?0.24); 6 participants (LC 3, HC 3) had moderately elevated AER at baseline (30–300?mg/24?h), which normalized in 4 participants (LC 2, HC 2) after 52 weeks.
Compared with a traditional HC weight loss diet, consumption of an LC high protein diet does not adversely affect clinical markers of renal function in obese adults with T2DM and no preexisting kidney disease.