Kidney failure, also called kidney disease, reduces kidney function and causes imbalances in blood levels of electrolytes and minerals. Maintaining adequate mineral balance is important for delaying some of the problems associated with kidney failure, such as bone demineralization and its complications. According to the journal “Kidney International,” fractures in patients with end-stage renal disease increase mortality rate.
Calcium Levels in Blood
Calcium and phosphorus are two minerals affected by kidney disease. Normal kidneys control phosphorus levels in blood by excreting excess phosphates in urine. Diseased kidneys cannot regulate this imbalance, which causes calcium levels to decrease as phosphorous levels increase. When they detect a decrease in blood calcium, all four parathyroid glands release parathyroid hormone, PTH, which regulates calcium levels in blood. PTH removes calcium from bones and transfers it to the bloodstream to restore calcium equilibrium. As this process continues, loss of calcium causes bones to become fragile and susceptible to fracture. Patients in kidney failure require a special diet to supplement calcium and control consumption of foods containing high levels of phosphorus.
Calcium Absorption
Kidney failure interferes with production of the active form of vitamin D, which is essential for absorption of dietary calcium and bone health. According to Dr. Morwenna Wood of the Edinburgh Renal Unit at the Royal Infirmary of Edinburgh in Scotland, active vitamin D supplements, such as Alfacalcidol or Calcitriol, combat bone thinning by controlling the calcium imbalance associated with insufficient vitamin D production. According to “Current Opinion in Nephrology and Hypertension,” supplementation with vitamin D increases calcium and phosphorous reabsorption, benefits bone health and the survival rate of patients on dialysis.
Laboratory Tests
Various laboratory tests help monitor kidney function. Parathyroid hormone tests provide a good indication of whether the blood levels of calcium and vitamin D are sufficient to prevent bone thinning and protect bone health. Lab tests, such as creatinine and blood urea nitrogen, or BUN, measure blood wastes, which increase in the presence of kidney disease.
Importance of Diet
Loss of calcium occurs in all stages of kidney failure. Dietary adjustments mitigate calcium and vitamin D deficiencies, control excess phosphorus intake and ensure the adequacy of daily caloric intake. According to Medline Plus, the National Institutes of Health online medical encyclopedia, health-care providers may recommend calcium supplements to prevent bone disease in addition to a diet that limits dairy foods containing high levels of phosphorous, such as milk, yogurt and cheese. Dairy foods with low levels of phosphorous include butter, cream cheese, heavy cream, ricotta cheese, sherbet and nondairy whipped toppings. Fruits and vegetables also contain minimal amounts of phosphorous. Foods high in phosphorous, such as meat, poultry, fish, eggs, dried beans and peas can be eaten in small amounts with doctor approval. Your doctor or dietitian may recommend vitamin D supplements to help control calcium and phosphorus balance. Phosphorous binders, such as Calcichew, Calcium 500 and Renagel provide another means of controlling phosphorus levels.
References
- “Kidney International”; Chronic Kidney Disease and Bone Fracture; Nickolas T.L., et al.; Sept. 2, 2008
- Edinburgh Renal Unit, Royal Infirmary of Edinburgh, Scotland; Chronic Renal Failure and Its Progression; Dr. Morwenna Wood; April 15, 2010
- “Current Opinion in Nephrology & Hypertension”; Vitamin D and Outcomes in Chronic Kidney Disease; Steven Cheng, et al.; March 2007
- Lab Tests Online; Kidney and Urinary Tract Function, Disorders and Diseases; March 31, 2011
- Medline Plus; Diet – Chronic Kidney Disease; Aug. 29, 2011
