Are low-carb diets safe for the kidneys?

A new study eases long-term concerns regarding the potential adverse effects low-carbohydrate diets may have on the kidneys.

Low-carb, high-protein diets—such as the Atkins diet—have been popular for years, but experts have long worried that these weight loss strategies may have harmful effects on a person’s kidney function or fluid and electrolyte balance.

As far back as the 1970s, the American Medical Association even released an editorial labeling the Atkins diet "potentially harmful."

“The belief among many experts was eating lots of protein could ‘rev up’ the kidneys, like an engine, and cause damage or failure over time,” lead researcher Dr. Allon Friedman, from the Indiana University School of Medicine, told

“High levels of protein have also been known to change electrolytes in the blood in ways that could be harmful,” he added.

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However, in a study of 200 obese patients who participated in a low-carb, high-protein diet over a two-year period, Friedman and his colleagues did not find any noticeably harmful effects on kidney health or function compared to people who ate a low-fat diet instead.

“We did not find that a high-protein diet led to any kidney-related problems like lower filtration rates, kidney stones or problems with blood electrolytes,” Friedman said.

Based on the results, Friedman said high-protein diets appeared to be healthy from both a kidney and weight loss standpoint.

“As long as the diet is sensible, the most important thing is weight loss, regardless,” Friedman said.  “Other studies have suggested high-protein diets allow patients to lose at least as much weight as heart-healthy diets.”

However, he warned that despite the encouraging results, these diets may not be safe for everybody.

“We did not perform the study in patients with other illnesses,” he said.  “I would be hesitant to extrapolate these results to patients with diabetes or advanced kidney disease.”

Further follow-up is needed to look at even longer-term effects of these diets on the kidneys, as well as study the effects in individuals who do have existing kidney problems or other illnesses.

The study was published in the Clinical Journal of the American Society of Nephrology.  People should consult with their doctors before embarking on any new diet or fitness regimen.