Restricting phosphate intake is often necessary, especially in the late stages of chronic kidney disease, to prevent secondary diseases. Ever wondered what phosphate is all about in kidney disease? You can learn more about it here.
The role of phosphate in the body
Phosphate is responsible for various tasks in our body. On the one hand, together with calcium, it is responsible for a functioning bone metabolism. Simply put, it regulates the balance between bone formation and bone resorption. This ensures that your bones remain strong. But phosphate is also an important building block for your energy metabolism and for your genetic material (=DNA) in the body.
If a person has too little phosphate in the body, phosphate is absorbed from the food in the intestine. The excess is filtered out and excreted by the kidneys. However, if the kidneys no longer work properly, this regulation no longer happens sufficiently. The cycle gets out of balance because your body can no longer excrete phosphate well. In the following, you will learn how you can keep your phosphate balance as balanced as possible and which reference values help you to do so.
Why is it so important that phosphate is in the green zone?
An elevated phosphate level in the body binds calcium in the blood. Together, calcium and phosphate are then deposited as a calcium-like substance on the walls of the blood vessels. You want to avoid this at all costs. An elevated phosphate level in the blood is called hyperphosphatemia. Over time, this gradually causes specific forms of osteoporosis and arteriosclerosis. In other words, too much phosphate in the body "softens" the bones. The bones "decalcify," become brittle, and the blood vessels "calcify" and become harder. Deposits of hydroxyapatite are seen in the blood vessels. This is a mineral composed of phosphate and calcium, among other things.
You can think of it as making the blood vessels narrower, which is why the blood can no longer flow well through your body. This can lead to various problems, even life-threatening ones. This is exactly why it is very important to keep your phosphate levels within a target range. Vessels with very pronounced deposits of the calcium phosphate mineral can also make it difficult for the surgeon to connect a transplant kidney to your blood vessels if worst comes to the worst.
What is the approximate target value for phosphate?
As a rough guide in kidney disease, blood phosphate levels should be adjusted toward the reference range of 1.45 mmol/l (or 4.5 mg/dl). Also important to know: Your phosphate level changes rather slowly in your body. In order for phosphate to fluctuate quickly, you would have to consume a lot of phosphate at once.
How do I manage my phosphate?
Phosphate management in kidney disease consists of three pillars:
- A phosphate-reduced diet - this is recommended at the latest from a glomerular filtration rate (=GFR) of below 60 mL/min (G3) and depending on your blood phosphate level.
- The correct use of phosphate binders, if prescribed by your medical team.
- Dialysis therapy in case of kidney failure - If you eventually need dialysis, dialysis helps to keep your phosphate under control, even if only to a very small extent, as it can remove some of it.
1. A phosphate-reduced diet
In case of persistently high blood phosphate levels, a phosphate-reduced diet is recommended already from a GFR of less than 60 mL/min, corresponding to stage 3 kidney disease according to the current medical guidelines of KDIGO (an international organization for the development and implementation of evidence-based guidelines for clinical practice in kidney disease). This means that you should make sure that you eat foods with lower phosphate content. At the same time, you should keep in mind that you still need to eat enough calories and protein. After all, your body needs enough energy every day to function properly. In the Mizu app you will find many tools, tips & tricks to make such a phosphate-reduced diet easier for you in everyday life.
2. The correct intake of phosphate binders
The second pillar of phosphate management is medication - so-called phosphate binders. There are different phosphate binders, all of which work in slightly different ways. Phosphate binders cause the phosphate you eat to be bound directly in your intestines and excreted right away. You have to take phosphate binders in combination with a meal and ideally you have to dose them correctly. This is not so easy at first, because you need to know how much phosphate is in the food you eat. Your doctor will choose the most suitable phosphate binder for you together with you over a longer period of time.
3. Good dialysis in case of kidney failure
If your kidney disease progresses to kidney failure, you may eventually need dialysis. Dialysis cleans your blood and helps your body get rid of phosphate from your blood and keep phosphate levels in balance. However, even the currently available procedural methods do not currently manage to adequately remove the phosphate in your body. In fact, dialysis therapy can only remove about 2,500 to 3,500 mg of serum phosphate from your body per week, depending on the duration and procedure. Unfortunately, this is much less than a usual weekly amount of phosphate you take in through food. The reason phosphate cannot be adequately removed by available dialysis procedures is that your body also stores phosphate outside of the blood. Hemodialysis and peritoneal dialysis can remove only the phosphate in the blood. This is relatively quick, as it is out after only 2.5 hours. In response, however, phosphate from other parts of the body shifts into the blood, and the phosphate level in the blood rises again shortly afterward. As such, longer dialysis can remove phosphate a little bit better. The bottom line is that dialysis alone is not enough to control phosphate in your body. This makes it all the more important for you to emphasize a low-phosphate diet if your phosphate levels seem to be climbing upward.
Which foods contain phosphate?
Phosphate is present in many foods. For example, many meat and cheese products are high in phosphate - some more and some less. You should pay particular attention to processed foods and convenience foods, as many of these products are packed with additives. Some of these additives are real phosphate bombs. By the way, beverages (e.g. Coca Cola or beer) can also contain relatively high amounts of phosphate! Since protein-rich foods often have a lot of phosphate, it's handy to know which foods have a lot of protein in relation to phosphate. Also, the phosphate in plants is absorbed less by your intestines than the phosphate in meat. You can find out exactly where and how much phosphate is in each food in the Mizu app. It contains thousands of texts, foods and recipes and interprets them directly for kidney disease.
How much phosphate can I eat?
For people with kidney disease, a daily intake of 600 to 1000 mg per day may be recommended, especially in later stages of the disease. Current guidelines for renal failure therapy recommend this target range starting at stage 3, or a decline in kidney function with a laboratory glomerular filtration rate (eGFR) of less than 60 ml/min.
This range could be seen as a starting point for your phosphate-conscious diet. How much phosphate per day balances your body is best discussed with your nephrology team and your nephrology diet counselor (and also with your stomach). You can then also store your daily guideline value in the Mizu app and update it at any time. This way, you can personalize the app for yourself.
Will I sense if something is wrong with my phosphate?
Too much phosphate in the body rarely leads to symptoms immediately. Over time, the noticeable consequences are then the occlusion or narrowing of your arteries, leading to insufficient blood flow in the affected areas of the body. The death of skin - so-called necrosis - can also occur. On the whole, however, you notice too high phosphate levels only to a limited extent until they then cause problems. Therefore, it is all the more important to try to get a possibly too high value under control through medication and nutrition!
