November 13, 2009
Early phosphorus control is recommended for people with chronic kidney disease
I went to a DaVita Dietitian meeting this week and heard a talk by Dr. Shagun Chopra-Sonthalia, a nephrologist from San Diego, CA. I want to share with you some important points from the presentation about new emphasis on earlier phosphorus control.
If you have later stage 4 or stage 5 chronic kidney disease (CKD, your labs may show a high phosphorus; calcium may be low. This is seen frequently in later stages because low active vitamin D levels (due to kidney failure) cause less calcium absorption from the gastrointestinal (gi) tract. Phosphorus rises because the kidneys can’t remove enough dietary phosphate and because bones are breaking down and releasing phosphorus. In some cases calcium may be high if there is a lot of bone breakdown.
Before this occurs, in early stages of CKD, phosphorus and calcium tend to stay normal. If you have your lab work done and it shows a normal phosphorus and calcium, you and your doctor may assume you don’t need to worry about a low phosphorus diet. Today’s researchers are leading us to change this thinking.
If you have stage 3 CKD, you may want to start paying attention to phosphorus. If you limit processed foods with phosphate additives and eat smaller amounts if foods naturally high in phosphorus, you may keep your bones and heart healthier and live longer.
In early kidney disease as the kidneys slow down and phosphorus rises even a little bit, a protein called FGF-23 (fibroblast growth factor) is released from bone cells. This protein directs the kidneys to get rid of more phosphorus in the urine so blood levels stay normal. FGF-23 also reduces active vitamin D so there is less phosphorus and calcium absorbed from the gi tract.
Parathyroid hormone (PTH) production begins to increase in early kidney disease too. It is overproduced to keep phosphorus and calcium in the normal range. As PTH goes up it leaches phosphorus out of your bones. High phosphorus in the blood causes calcifications in the blood vessels and heart.
Studies show that early dietary phosphorus restriction helps keep PTH lower. The benefit of controlling PTH by reducing phosphorus intake is phosphorus and calcium will remain in the normal range and your heart and bones will stay healthy longer.
The next time you visit your doctor ask about your phosphorus, calcium and PTH results.
Kidney diet resources from DaVita.com
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