Dialysis patients have to control their phosphorus intake and phosphorus levels. The kidneys normally excrete excess phosphorus into the urine; however, kidney disease can prevent the body from getting rid of any buildup of phosphorus and that can cause problems for the bones and heart. And unfortunately hemodialysis removes only a small amount of phosphorus from the blood, hence the need for phosphorus binders while on dialysis. Recent research published in the Journal of Renal Nutrition suggests that boiling in water or stewing in oil can reduce the phosphorus content of some foods.
The results vary for different foods stuffs, this is not a universal panacea but it does help a lot with some foods. However the calcium levels increased when boiling in water when using hard water
Most of the thermal processing methods did not significantly reduce protein content. Boiling increased calcium content in all foodstuffs because of calcium absorption from the hard water. In contrast, stewing in oil containing a small amount of water decreased the calcium content of vegetables by 8% to 35% and of chicken meat by 12% to 40% on a dry weight basis. Some types of thermal processing significantly reduced the phosphorus content of the various foodstuffs, with levels decreasing by 27% to 43% for fresh and frozen vegetables, 10% to 49% for meat, 7% for pasta, and 22.8% for rice on a dry weight basis. On the basis of these results, we modified the thermal processing methods used to prepare a standard hospital menu for dialysis patients. Foodstuffs prepared according to the optimized menu were similar in protein content, higher in calcium, and significantly lower in phosphorus than foodstuffs prepared according to the standard menu.
If you examine the references section in the link to the journal article (above) you will find links to several other studies on how different cooking methods for your food can be of benefit to dialysis patients.
