High-Protein, Low-Carb Diet Safe for Kidneys

For decades, medical experts have been concerned that high-protein, low-carb diets like Atkins could be damaging to the kidneys, but a new study found that this isn't the case in otherwise healthy patients.

Researchers from the Indiana University School of Medicine compared the effects of such a diet to that of a standard low-fat diet in 307 obese people who did not suffer from kidney disease or other chronic illnesses.

After a two-year period, they found that the high-protein, low-carb diet didn't cause noticeable harmful effects on healthy obese patients' kidney function compared to obese people who followed a low-fat diet.

"Despite decades of concerns about low-carb, high-protein diets that may cause kidney damage in healthy people, there were no signs that this would be the case after a 2-year period," said Dr. Allon Friedman, lead author of the study, published in the Clinical Journal of the American Society of Nephrology.

Protein in the blood contributes to important protective benefits to the body, including fighting infections, blood clots and improving circulation in the body. Normally proteins are too big to pass through the kidneys' filter into the urine, but proteins from the blood can leak into the urine when kidney filters are damaged, according to the NIH.

Abnormal amounts of protein in the urine, known as proteinuria, usually point to some sort of kidney disease, regardless of diet. But, researchers found that the most important way to reduce protein in urine did not have to do with the type of diet was the actual amount of weight lost, "not really how you get there," Friedman said.

The results are relevant to the millions of healthy obese adults who use dieting as a weight-loss strategy, researchers noted. More than one-third of American adults are obese, according to the CDC.

Despite the promising results, Dr. Joseph Vassalotti, chief medical officer of the National Kidney Foundation, cautioned people to take the findings with a grain of salt.

"The population studied does not apply to most patients with or at risk for chronic kidney disease, since the study participants had no evidence of chronic kidney disease or other illnesses," said Vassalotti.

"The best diet is obviously one that is balanced, that reduces calories and encourages daily exercise," said Friedman. "For this study, we really showed that it's not important how someone loses weight, but whether they can do it and keep it off."

But Vassalotti added that the most "successful nutrition therapy will include a treating clinician, registered dietitian or certified diabetes educator and the patient to consider an individualized nutrition plan."