Staying heart healthy: The importance of phosphorus for Veterans with chronic kidney disease


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Dr. Anna Jovanovich is a kidney specialist and a clinical researcher at the VA Eastern Colorado Health Care System in Denver. She splits her time between seeing patients and conducting research. She is also an assistant professor at the University of Colorado, Denver.

The thrust of her clinical research is investigating the effects of kidney disease on the body—specifically cardiovascular or heart disease. Veterans and others with chronic kidney disease are at a much higher risk of developing heart disease, compared with the general population. In fact, they are more likely to suffer a cardiovascular event, such as a heart attack, than progress to needing dialysis or transplant.

They also may need help managing the level of certain chemicals within their bodies. In a healthy person, the kidney monitors and controls the level of many hormones, minerals, and other chemicals within the body. One of those is phosphorus—a mineral found in certain types of food, like milk. In the body, phosphorus is a necessary component for many cellular functions. One form of phosphorus—phosphate—is essential for building healthy bones and driving cellular metabolism.

People with advanced kidney disease may not be able to adequately control the level of phosphorus within their body. If diet modification does not work, they may need to take phosphate binders—drugs that bind to excess phosphate in the gut and help the body excrete it.

VA Research Quarterly spoke with Jovanovich about her work studying the potential effectiveness of phosphate binders in preventing cardiovascular disease.

Can you explain what chronic kidney disease is?

Chronic kidney disease is the gradual loss of kidney function over time. The main job of the kidneys is to balance what we take in and what we put out, basically. Substances like water, salt, and other electrolytes are regulated by the kidneys. And the kidneys also excrete toxins in the urine. So when the kidneys fail, they can’t do that job anymore.

The kidneys are also important for regulating blood pressure, and they produce hormones that control red blood cell production and vitamin D, as well as regulate phosphorus and calcium homeostasis. Again, if the kidneys fail, some of these processes are disrupted. Usually, people with chronic kidney disease don’t feel sick or ill until their disease is very advanced. So it is largely a very silent disease, in terms of how a person actually feels.

How prevalent is chronic kidney disease in the general population?

Chronic kidney disease in the general population in the U.S. has a prevalence of about 13 to 15 percent, depending on what year you look at. But in the Veteran population that is treated at VA, the prevalence is much, much higher. Some studies have reported it to be 20 percent, and one recent study—in a single region—has reported the prevalence of chronic kidney disease to be 47 percent in Veterans. This is significantly higher than in the general adult U.S. population.

How is chronic kidney disease usually diagnosed?

Because it is such a silent disease, the only way we can tell if people have chronic kidney disease is through blood and urine tests. If a Veteran receives usual care through a primary care doctor at the VA, it’s pretty standard to do at least annual blood tests. And part of these blood tests measure kidney function. There is a substance called creatinine, which is made by the muscles and excreted through the kidneys. When kidney function declines, the level of creatinine rises in the blood—so that is what we test for. We look for higher levels of creatinine in the blood to indicate chronic kidney disease. Protein and/or red blood cells in the urine can also indicate kidney disease.

Why is it important to regulate the level of phosphorus in a person’s blood?

Phosphorus is needed by the body—it is one of the main minerals for structure and strength. Eighty-five percent of our body’s total phosphorus is found in the bone and teeth. And it’s also important for energy—the main energy compound within the cells uses phosphorus. We get phosphorus from the foods we eat and excrete the excess into our urine via the kidneys.

As the kidneys fail, they are not as able to excrete extra phosphorus, so blood levels of phosphorus rise. Even phosphorus that is on the high-end of the normal laboratory range has been associated with a higher risk of cardiovascular disease, in large epidemiologic studies.

Most people with moderate and even severe kidney disease can control their phosphorus levels with diet alone. That means avoiding foods that are high in phosphorus. But some people with very severe advanced chronic kidney disease, certainly people on dialysis, have to take phosphate binders—which are medications that you take with food. When the food and phosphate binders mix in your intestines, the phosphate binders attach to the phosphorus in your food so that the phosphorus is not absorbed into your intestine. With these medications, along with a low phosphate diet, we can control the blood levels of phosphorus.

To read more of the conversation with Dr. Anna Jovanovich and VA Research Quarterly, click here for the full article.


About the author: Erica J. Sprey is a writer in VA’s Office of Research and Development. She is also the editor of the VA Research Quarterly Update, a digital publication that is produced four times a year.

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