Whole grains in the renal diet--is it time to reevaluate their role?

Abstract

Organizations such as the National Kidney Foundation, the American Kidney Fund, the National Institute of Diabetes and Digestive and Kidney Diseases, and the US Department of Health and Human Services recommend not including whole grains as part of the renal diet. The rationale for this recommendation is the high phosphorus content in these foods. While the phosphorus content in whole grains may be indeed high, it is covalently bound to organic molecules (primarily phytate) and requires the enzyme phytase to be released and become available for absorption. While some phytase is contained in some whole grains (corn, oats, and millet have little to no phytase activity), the enzyme is decreased in milling, food preparation and over time. Since the human intestine does not express phytase, the enzyme required for the release of phosphorus from phytate is not present in the intestinal lumen when ingesting cooked food. Consequently, the bioavailability of phosphorus from whole grains is low. For the reasons presented here we believe that the 'grain ban' in the diet for kidney patients should be reconsidered. By doing this, the kidney diet would be enriched and it would provide needed fiber along with its health benefits, diversify the diet with low sodium choices, and possibly provide adequate protein without increasing phosphorous levels.