A grain-based vegetarian diet helps chronic kidney disease patients avoid accumulating toxic levels of phosphorous in their bodies, according to new research from the US.

Dr Sharon Moe, of the Indiana University School of Medicine and Roudebush Veterans’ Affairs Medical Center in Indianapolis, and colleagues, write about their findings in a study due to be published this week in the Clinical Journal of the American Society of Nephrology.

If your body can’t get rid of phosphorous, it builds up and causes heart disease and eventually death. Healthy kidneys filter toxic minerals like phosphorous so they don’t build up toxic levels in the bloodstream. This blood cleaning process doesn’t work so well in people with chronic kidney disease (CKD) who have to find other ways to compensate.

One way is to follow medical guidelines that recommend low phosphorous diets for people with CKD, but since food labels don’t list phosphorous content, that is easier said than done, so Moe and colleagues decided to compare a vegetarian diet against a meat diet to see how they affected phosphorous levels in patients with CKD.

They recruited nine volunteers with CKD and got them to follow a vegetarian or meat-based diet for a week, and then two to four weeks later, got them to follow the opposite diet. The volunteers gave blood and urine samples at the end of each week on both diets.

Moe and colleagues found that despite the two diets offering equivalent protein and phosphorous concentrations, when they were on the vegetarian diet, the patients had significantly lower levels of phosphorous in their blood and urine samples, than when they were on the meat-based diet.

Although the study was not designed to examine the reason for this difference, we already know that a grain-based diet has a lower ratio of phosphate to proteins and much of it comes from phytate, which is not absorbed in the human body.

Moe and colleagues concluded that these findings show that where protein comes from in a diet has a significant effect on phosphorous levels in CKD patients.

If these findings are confirmed by larger studies, then it provides a good reason for recommending that patients with CKD follow a diet where most of the protein comes from grain-based vegetarian sources of protein, they added.

Such a diet “would allow increased protein intake without adversely affecting phosphorus levels,” they wrote.

They also recommended that when patients with CKD receive counselling about food and diets, they should be told about phosphorous and its effects and the sources of protein from which it derives.

“Vegetarian Compared with Meat Dietary Protein Source and Phosphorus Homeostasis in Chronic Kidney Disease.”
Sharon Moe, Miriam Zidehsarai, Mary Chambers, Laurie Trevino, Lisa Jackman, J. Scott Radcliffe, Susan Donahue, and John Asplin.
Clinical Journal of the American Society of Nephrology anticipated publication date: 23 December 2010.
DOI:10.2215/CJN.05040610

Additional source: American Society of Nephrology.

Written by: Catharine Paddock, PhD