Cooking Legumes: A Way for Their Inclusion in the Renal Patient Diet

It has been observed that the consumption of legumes within a varied and Mediterranean diet has beneficial effects in prevention and control of many diseases, including chronic kidney disease (CKD). Recently, legumes have also been considered a good source of protein for CKD patients. However, despite their benefits, guidelines still recommend a limit to their consumption by these patients because of legumes' high potassium and phosphorus content, which are minerals whose intake must be controlled. The aim of this work is to analyze and compare the effect of different cooking methods in the reduction and final content of minerals in legumes to evaluate a possible increase in the frequency of their consumption by CKD patients.

Dried and canned chickpeas and lentils were cooked using different cooking techniques: (1) soaking, (2) pressure cooking, and (3) normal cooking. Initial and final potassium and phosphorus content and the percentage of humidity in each cooking technique were determined in both legumes. Mineral content was analyzed using flame photometry and nitro-vanado-molybdate colorimetry.

The results showed potassium content reductions of up to 80% after soaking and cooking with final values under 120 mg/100 g edible portion. The initial potassium content in canned legumes was low enough, 100 mg/100 g edible portion, but with the application of a subsequent culinary treatment, it was possible to leach up to 95% of the potassium to almost negligible values. Reductions in phosphorus content were not as marked as those of potassium, but culinary treatments reach a phosphorus/protein ratio,11.

These results show that culinary processing of legumes is a very useful tool to reduce potassium and phosphorus content to acceptable levels for their consumption by renal patients, allowing an increase in intake frequency. But, this also reveals the need to update CKD dietary guidelines.