Phosphorus and chronic kidney disease

What is phosphorus and what does it do in the body?

Phosphorus is a mineral found in the body. About 85% of the phosphorus in the body is in bones. Phosphorus is the body’s next most abundant mineral after calcium. The body uses phosphorus to:

• form strong bones and teeth
• maintain a normal pH balance
• get oxygen to tissues
• make energy
• change protein, fat and carbohydrate into energy
• develop connective tissues and organs
• move muscles
• produce hormones
• use B vitamins

How does the body get phosphorus?

Phosphorus is absorbed in the small intestines and stored in the bones. Healthy kidneys get rid of the extra amounts not needed in the body. It is recommended that healthy adults get between 800 mg and 1,200 mg of phosphorus each day. A balanced, nutritious diet provides plenty of phosphorus, because it is found naturally in so many foods.

In addition, most Americans consume a lot of prepared foods, colas and other canned or bottled drinks, which have high amounts of added phosphorus.  According to the Food and Nutrition Board, over the last 20 years, phosphorus intake by Americans has increased 10% to 15%. Part of this increase is attributed to phosphorus-containing food additives in processed food. It is very rare that people have a phosphorus deficiency; in most cases people get too much.

Phosphorus, calcium, vitamin D and parathyroid hormone

Phosphorus, calcium, vitamin D and parathyroid hormone and their interaction with the kidneys all play a part in controlling the level of phosphorus in the bloodstream.

Together, phosphorus and calcium create healthy bones and teeth. Healthy kidneys work to keep these two minerals in balance in the blood. The kidneys also turn vitamin D into an active hormone (calcitriol), which helps increase calcium absorption from the intestines into the blood.

When the calcium level in the blood is low, the parathyroid glands (four small glands in the neck) make more parathyroid hormone (PTH). This causes calcium to be pulled from the bone into the blood. Too much parathyroid hormone can cause the bones to become weak and break more easily. This is called renal osteodystrophy.

High levels of phosphorus and bone disease

Because unhealthy kidneys are no longer able to remove phosphorus from the blood and get rid of the excess in urine, high levels of phosphorus (hyperphosphatemia) is a problem for people with stage 4 and 5 kidney disease, especially stage 5 (also known as end stage renal disease or ESRD).

High levels of phosphorus in the blood can cause:

• bone and heart problems that lead to hospital stays and in some cases death
• too much PTH to be released, which over time can weaken bones and make them more likely to break and develop renal osteodystrophy
• low blood calcium, which causes calcium to be taken from the bones
• calcification or hardening of tissues when phosphorus and calcium form hard deposits in the heart, arteries, joints, skin or lungs that can be painful and lead to serious health problems
• bone pain
• itching

Treatments for controlling phosphorus

People with kidney disease are urged to eat foods that are low in phosphorus. This will help keep the blood level of phosphorus in a healthy range.

One goal in treating people with end stage renal disease is to prevent phosphorus in the foods they eat from being absorbed into their bloodstream. To help with this, doctors prescribe medicines called phosphorus binders. In most cases doctors prescribe a binder to be taken along with meals and snacks that have phosphorus. Binders are like sponges that soak up phosphorus. Instead of going into the bloodstream, phosphorus stays in the stomach and then passes through the gastrointestinal system. A low phosphorus diet is necessary for phosphorus binders to work well.

Doctors may prescribe an active form of vitamin D, called calcitriol, to help balance the calcium and phosphorus levels. Active vitamin D cannot be taken if calcium or phosphorus levels are too high because it will increase the risk of phosphorus deposits in soft tissues such as arteries, lungs, eyes and skin.

A new medicine seems to help keep bones healthier in kidney disease patients. Called “calcimimetic” medication, it lowers PTH and calcium, and may even lower phosphorus. But it does not take the place of phosphorus binders. It’s still too early to know, but doctors hope this new drug will help kidney patients have healthier bones and lower the risk of calcifications and heart problems.

Dialysis treatments remove some phosphorus from the blood. It is important that the patient stay on dialysis for their full treatment time for best results. Between dialysis treatments, patients should be careful to limit how much phosphorus they eat.

Exercise can help increase physical strength and, in some case, even strengthen bones. Patients should ask their doctors to recommend an exercise program to help maintain their healthy bones and body.

To keep bone health, doctors will monitor their patients’ lab test results and adjust binders, medicines, supplements and dialysis treatments as necessary. In some cases, surgery to remove part of the parathyroid glands may be recommended to prevent long-term release of PTH. Patients should be sure to let their doctor and dietitian know all of the medicines and supplements they are taking because some of these may contain phosphorus. All of these efforts will help keep phosphorus in a healthy range, so that calcium will not be lost from the bones.

Treatment for high levels of phosphorus may include one or more of the following:

• reducing the amount of phosphorus you eat
• taking a medicine called a phosphorus binder
• taking the active form of vitamin D
• taking a calcimimetic medicine
• making changes in dialysis treatment
• starting an exercise program approved by a doctor
• getting an operation to remove some of the parathyroid glands

Know your phosphorus and calcium levels

Patients can work with a renal dietitian and their doctors to keep their phosphorus and calcium levels in balance. Regular blood test will show the phosphorus and calcium levels in the blood. According to the “Clinical Practice Guidelines for Bone Metabolism and Disease in Chronic Kidney Disease” put out by the National Kidney Foundation, kidney disease patients in stages 3 and 4 should keep their phosphorus between 2.7 and 4.6 mg/dL. Dialysis patients should keep their phosphorus levels in the 3.5 to 5.5 mg/dL range. The goal for calcium is between 8.4 to 10.2 mg/dL with a best range of 8.4 to 9.5 mg/dL.

What to eat?

Anyone who has ever tried to limit the amount of phosphorus they eat will tell you that almost every food has phosphorus. Knowing what to eat and how much is the key to keeping phosphorus levels in a good range. Nutrition Facts on food labels often do not give information on phosphorus. Because it is not listed does not mean the food is phosphorus free. Since food labels don’t list phosphorus, talking to a renal dietitian or using a nutritional reference guide will be help you learn the phosphorus content of most foods.

In many cases there are low phosphorus options for foods high in phosphorus. When limiting phosphorus in the diet, portion size is important. Resources such as food lists, grocery lists and recipes provided by the dietitian help you learn about phosphorus control. Visit the DaVita.com recipe section for renal-friendly meals and snacks that are low in phosphorus.

Lower phosphorus food tips

The renal dietitian is specially trained to help kidney patients make the best food choices. Each patient will be given individual guidance, taking into consideration their lab results, medical condition and food preferences. Make sure you consult with your dietitian and doctor about your situation. Below are some general tips to decrease your phosphorus intake.

• Instead of milk, use substitutes like non-dairy creamers, rice milk (unenriched) or soy milk. Because some non-dairy creamers and soy milks are high in phosphorus, check with a renal dietitian for a list of acceptable brand name products.
• Instead of cheese, use cream cheese or sour cream.
• Instead of cola or Dr. Pepper® have cream soda, lemon-lime soda, grape soda, homemade lemonade, homemade iced tea or root beer.
• Instead of ice cream have gelatin, Popsicles®, sherbet or sorbet (remember to count as fluid).
• Instead of chocolate or nuts have jellybeans, fondant, gumdrops, hard candy, unsalted popcorn or unsalted pretzels.
• Instead of chocolate cookies or cake have sugar cookies, shortbread cookies, vanilla wafers or vanilla, lemon or angel food cake.
• Instead of hot chocolate or cocoa have hot apple cider or hot spiced cranberry juice.
• Instead of bran, oat or whole wheat cereals use cereals made from corn, refined wheat or rice.
• Instead of whole grain breads use French, Italian or white bread.
• Instead of peanut butter use jam, jelly, honey, cream cheese margarine or butter.
• Instead of dried beans or peas have green beans or wax beans.
• Instead of brown rice or wild rice use white rice, pasta, macaroni, grits or couscous seasoned with margarine and herbs.
• Instead of processed meats, fish and poultry use fresh or fresh frozen items.

Phosphorus Binders

If your doctor has prescribed phosphorus binders:

• Ask your dietitian how to adjust your phosphorus binder dose to the phosphorus content of your meal. For example, if you're planning to enjoy a large steak dinner on a special occasion, you may need to take an extra phosphorus binder.
• Taking your phosphorus binder as prescribed along with following your prescribed diet is one of the most important things you can do to take care of yourself.
• Phosphorus binders work in the stomach and gastrointestinal tract where food is broken down and digested. It is important to take the pills along with your meals or snacks.  Waiting 30 minutes or longer after eating greatly reduces phosphorus binding.
• Let your doctor or dietitian know if you are having difficulty tolerating your phosphorus binder. Sometimes a different binder can be prescribed.
• The number of pills needed to control phosphorus may change based on your appetite and lab results. Make a habit or reviewing your correct dose frequently with your dietitian, nurse or doctor.

Find out more about phosphorus

• Ask your healthcare team questions about phosphorus and your blood levels.
• Contact kidney organizations such as the National Kidney Foundation to request educational materials.
• Checkout food product websites. Some provide nutritional information including phosphorus.
• Keep checking for updates, new articles and recipes at www.davita.com.

Some High Phosphorus Foods

• Milk
• Cheese
• Yogurt
• Ice Cream
• Beer, Cola, Milk-based Coffee and Chocolate Drinks
• Chocolate
• Bran
• Brown Rice, Wild Rice
• Whole Grain Breads, Cereals & Crackers
• Corn Tortillas
• Pancakes, Waffles, Biscuits
• Pizza
• Avocado
• Nuts, Seeds, Nut butters
• Dried Beans & Peas
• Corn & Peas
• Processed Meats such as: Hot Dogs, Sausage, Turkey Sausage, Bologna
• Organ Meats
• Sardines

Note: The above list does not include all foods high in phosphorus. Portion size also plays a role in the amount of phosphorus you get from foods. Consult your dietitian and doctor to provide specific recommendations based on your individual needs.

Some Low Phosphorus Foods

• Certain brands of Nondairy Creamers, Rice Milk (Unenriched), Soy Milks
• Cream Cheese, Sour Cream
• Soda-Lemon-lime, Grape, Strawberry, Cream Soda, Root Beer, Homemade Iced Tea, Homemade Lemonade, Hot Apple Cider, Cranberry Juice
• Gelatin, Popsicles®, Sherbet, Sorbet
• Jellybeans, Fondant, Gumdrops, Hard Candy
• Unsalted Popcorn or Pretzels
• Sugar Cookies, Shortbread Cookies, Vanilla Wafers, Lemon Cake, White or Yellow Cake, Angel Food Cake
• Jam, Jelly, Honey, Cream Cheese
• Margarine, Butter
• Corn or Rice Cereals, Refined Wheat Cereals
• Cream of Wheat, Cream of Rice, Grits
• French, Italian or White Bread
• White Rice, Pasta, Couscous
• Fresh or Fresh Frozen Meat, Fish and Poultry (compared to processed)
• Fruits such as: Apples, Berries, Grapes, Plums, Pineapple, Canned Pears, Peaches, Fruit Cocktail
• Vegetables such as: Green Beans, Cabbage, Carrots, Cauliflower, Eggplant, Summer Squash, Bell Pepper, Cucumber, Lettuce, Onion, Radish

Note: Even if food is considered low in phosphorus, portion size also plays a role in the amount of phosphorus you get from foods. Consult your dietitian and doctor to provide specific recommendations based on your individual needs.