For People With Kidney Disease, A Balance Between Too Much Protein and Too Little

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For many Americans with kidney disease, even just moderate amounts of protein in the diet can worsen the condition. One of the kidneys' jobs is to filter certain breakdown products of protein out of the blood and into the urine; thus, the more protein eaten, the heavier the burden on an already-faltering filtration system.

Some doctors put kidney patients on protein-restricted diets to lighten the kidneys' load. But that only exacerbates the muscle wasting that's part and parcel of kidney disease. People with kidney problems don't absorb nutrients, including protein, as well as others do, so they're already often at a protein deficit and therefore not able to sustain their muscle size and strength. Decrease their protein consumption, and there's even less protein available to maintain muscle mass.

How to balance the needs of the compromised kidneys with the need to maintain the body's muscle tissue? Tufts researcher Carmen Castaneda Sceppa, MD, PhD, may have found the answer: a moderately protein-restricted diet in combination with strength training. Strength training, she reasoned, increases muscle mass. And that creates a greater "reservoir" for the protein that's eaten--it goes straight into the bigger muscles rather than getting broken down and excreted in the urine. That, in turn, leaves the kidneys less taxed.

To test her hypothesis, Dr. Sceppa asked a group of people with kidney disease to follow a diet with less protein than usual and conduct about 45 minutes of strength training three times a week (chest presses, knee extensions, and the like), comparing them to a similar group who restricted their protein to the same degree but who did not strength train. All of the subjects had moderate kidney disease, which meant that they were not on dialysis but were already weak, needing some assistance to perform

For 12 weeks, the volunteers ate an average of 24 percent less protein than they typically did and, in order to maintain their calorie levels, more in the way of carbohydrate-containing foods such as fruits and vegetables. It was not always easy. "One man of Greek descent," relates Dr. Sceppa, "was used to eating 4 to 5 ounces of lamb a day and had to cut back to 1 1/2 ounces" in order to accommodate other foods. "Even pasta has some protein," she points out.

But when the 12 weeks had passed, those who had been participating in the strength-training routine retained more of the protein they had been eating than the non-exercisers, as evidenced by various blood and urine tests. They increased their muscle fiber as well, a crucial component of lean muscle tissue. At the same time, their kidneys were functioning better, with less stress. The best part: The exercisers felt better, were stronger, and were better able than the non-exercising protein restricters to perform day-to-day activities such as walking. "Their quality of life improved significantly,"

Dr. Sceppa says. They experienced more hunger for their food, too--a good thing, since people with kidney disease often eat too little because of a decrease in appetite. Presumably, the hunger was the result of the energy used during exercise coupled with the enlarged muscles needing more calories to sustain themselves. Dr. Sceppa notes that you cannot reverse kidney disease with a protein restriction/strength training regimen, but you can potentially slow its progression and also live more independently. She hopes future studies that last longer and include people in more advanced stages of kidney disease will confirm her findings as well as offer help to those who are even sicker than the ones she studied.

PHOTO (BLACK & WHITE): Tufts researcher Carmen Castaneda Sceppa, MD, PhD, found that strength training in combination with moderate protein restriction improves quality of life "significantly" for people with kidney disease.

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