I have a 36-year-old woman, a recreational athlete. She goes to the gym three to five times a week. She’s 5’3”, around 160 pounds, muscular build, great Paleo eater. She wants to lose some weight. She has slightly diminished renal function with elevated BUN/creatinine ratio and microhematuria. She has congenital atrophic right renal pelvis and a history of IBS, blasto, gas, and bloating that we’re working hard on. We just sent another round of stool and SIBO testing. I’m nervous to increase her protein intake because of her diminished kidney function and would love your advice. Do you think this is safe? How many grams per day would you recommend and what source? I want to support her training and weight loss goals, but I don’t want to hurt her renal function.

Chris Kresser:  There are a couple of ways to approach this. You are obviously monitoring her quite closely, so one thing that you could do—and what I would probably do in this situation—is to increase her protein intake. I’m not sure where she is now. If she’s Paleo, it’s probably not low, but you could go up to maybe 25 percent of calories of protein if she’s not there already and let her do that for two or three weeks and then monitor her BUN/creatinine ratio and the microhematuria to see if there’s any change there. It may be that there’s not, given how well she’s doing already with Paleo. It sounded like those conditions were pre-existing to her Paleo approach. Of course, if they weren’t and she developed those while she was eating Paleo and a higher-protein diet, there was almost certainly some pre-existing predisposition there because we know that moderate or even moderately high protein intakes aren’t associated with impaired kidney function unless the person already has impaired kidney function. So I would think of it more in terms of a percentage of calories. Maybe go up to 25 percent—animal protein, as usual—but test her frequently and see where it’s going. You could potentially even consider 30 percent. That would be at a range where I would start to feel a little bit uncomfortable. I would definitely feel uncomfortable without any testing at all, but even with testing, I would be a little more aggressive in the testing to make sure that you’re not making that situation worse.