From the Director's Chair: Phosphorus – The 'Silent Killer'

By Paul Kellerman, MD

Although we are not in your shoes, we know how difficult it is to lie under the dietary restrictions of dialysis. You are unable tot excrete the phosphorus that you take in with your food, which is food in protein-containing items, such as dairy products and meats. We want you to eat good amount of protein, but limit phosphorus intake.

Why can't I eat high phosphorus-containing foods?
Since your kidneys don't excrete phosphorus, the phosphorus you take into your body when eating is not excreted. Dialysis removes some phosphorus, but not as much as your kidneys would remove. Thus, the phosphorus level rises in your blood, with multiple bad effects on your body.

What is a normal phosphorus level in the body?
If your kidneys were working, your kidneys would excrete the phosphorus and keep your blood levels at 2.5-4.5 mg/dl.

What is the goal for my phosphorus level?
In patients on dialysis, we want to keep your phosphorus level below 5.5 mg/dl.

What happens to my body if my phosphorus level is higher than 5.5 mg/dl?
When the phosphorus level goes up, it combines with the calcium in your blood. Two bad things happen from that combination. First, as the calcium combines with the phosphorus, the calcium phosphate, which is essentially chalk, goes outside your blood system and hardens all the tissues it comes into contact with, such as your heart and your skin and muscles. Second, as the calcium leaves the blood system with the phosphorus, the lower calcium amount in your blood causes a hormone called PTH to be released, which take the calcium out of your bones to keep the calcium normal in the bloodstream. Plus, if your phosphorus is really high, we can't give you vitamin D you receive on dialysis (Zemplar) which you need to keep the PTH down and preserve your bones.

So what does high phosphorus mean for my body?
You get hardening of the arteries all over your body, you may get very serious skin ulcers, and your bones get soft.

So why call phosphorus a killer?
Because hardening of the arteries, either to your heart or the rest of your body, is the number one killer of people on dialysis, or even with people who aren't yet on dialysis but have kidney disease. If you control the phosphorus, the hardening of the arteries slows down or stops.

How do I keep my phosphorus below 5.5 mg/dl in my blood?
First, the dietitians counsel you on a low phosphorus diet. Second, you take "binders," which are pills which bind up the phosphorus in your food before your stomach can absorb it into your system. That is why you should take your binders when you start to eat, not after you eat.

If you have questions about controlling your phosphorus, please ask your dietitian, nurse or physician.