Phosphorus Foods 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 percent 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
• create 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’s 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 from 10 percent to 15 percent. Part of this increase is attributed to phosphorus-containing food additives in processed food. It’s rare that people have a phosphorus deficiency; in most cases people get too much.

What is the connection between phosphorus, calcium, vitamin D and parathyroid hormone?

Phosphorus, calcium, vitamin D and parathyroid hormone (PTH) 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 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.

What is the connection between 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

Manage your phosphorus levels when you have kidney disease

Phosphorus can be in many foods you consume. When you have kidney disease, it’s good to keep levels under control. Work with a renal dietitian to help you manage your phosphorus intake.