This post was written by Atziri Villafana, dietetic intern, and reviewed/edited by Edith Yang, RD, CSR, CLT, FAND.
Patients with kidney disease are often told to follow a low-phosphorus diet. Unfortunately, most people do not know what phosphorus is or why too much can be harmful. A low phosphorus diet can be overwhelming to learn about all at once. This post will help you understand why it is essential to reduce phosphorus intake and learn what foods are high in phosphorus.
What is Phosphorus?
Phosphorus is an essential mineral naturally present in various foods and is available as a dietary supplement. Along with calcium, phosphorus is vital in building strong, healthy bones and teeth and maintaining proper nerve and heart function. In addition, phosphorus helps to activate enzymes, maintain blood pH at a normal range, and maintain our energy levels. Phosphorus is also a building block of our genes.
Why is phosphorus important for your health?
The kidneys play an important role in removing excess minerals, such as phosphorus, sodium, magnesium, calcium, and potassium from the body. With chronic kidney disease (CKD), the kidneys cannot remove these minerals very well. It is important that those with kidney disease actively monitor the amount of phosphorus in their diet because the buildup of phosphorus in the blood can weaken bones and damage the eyes, blood vessels, lungs, and heart. Several studies have also found an increased risk of mortality or disease progression in patients with CKD and high phosphate levels.
In a study conducted in 2017, researchers found that abnormal phosphorus levels among CKD patients on dialysis had a higher risk of mortality, while patients with low phosphate levels had a significantly lower mortality risk. To prevent complications of high phosphate levels in patients with CKD, doctors or renal dietitians often encourage patients to limit their phosphorus intake.
Phosphorus and Cardiovascular Disease
Higher phosphorus levels have been linked to an increased risk of heart disease, even in patients without kidney disease. Excess phosphorus can build up in the blood vessels, leading to blockage and cardiovascular problems, such as heart attack, stroke, or death. In another study involving 120,269 participants, researchers found that individuals with the highest phosphorus levels had a higher risk of cardiovascular disease (CVD) and mortality compared to the individuals with the lowest levels. Although several studies suggest that elevated phosphorus levels are linked to an increased risk of CVD, it is unclear if restricting dietary phosphorus can prevent CVD in healthy adults. Regardless, it is good practice for people with or without chronic diseases to be cautious of consuming excess phosphorus.
Phosphorus and Bone Health
Phosphorus is an important mineral for bone health, but dietary intakes often exceed the daily recommendations. This is problematic because excessive dietary phosphate has been linked to harmful effects on bone health. When there is more phosphorus than calcium in the body, the body will use calcium stored in bones, which can cause fragile bones (osteoporosis).
What is a normal phosphorus level?
Elevated phosphorus levels are often a sign of kidney damage or disease. People with high phosphorus levels may not notice any symptoms or feel unwell. The only way to determine if your levels are high is through specific blood tests. A normal phosphorus level is 2.5 to 4.5 mg/dL. If your level is above 4.5 mg/dL, your doctor may conduct additional tests to check for kidney disease.
How Much Phosphorus Should I Eat?
Learning about the health risks of consuming foods high in phosphorus for those with CKD can seem overwhelming or feel like everything is off the table. The good news is that you do not need to completely cut phosphorus out of your diet! Your body still needs phosphorus to function properly. If you begin restricting phosphorus while your kidneys are still functioning at a certain rate, then you could be endangering yourself with low phosphorus levels, otherwise known as hypophosphatemia. Studies suggest that low phosphate levels could lead to bone pain, muscle weakness, or bone disease.
How much phosphorus you should consume depends on your age, gender, and how much protein you need. According to the National Institutes of Health, the recommended dietary allowance (RDA) for adults (19+ years) is 700 mg/day. The RDA is defined as the average daily dietary nutrient intake level sufficient to meet the nutrient requirements of healthy individuals. Ask your kidney doctor or renal dietitian how much phosphorus you should be consuming.
Organic vs Inorganic Phosphorus
Phosphorus in food products exists in two forms: organic and inorganic. Organic phosphorus is naturally found in animal and plant foods, such as poultry, fish, nuts, and legumes. Your body only absorbs about 40-60% of the organic phosphorus from plant foods and about 60-80% from animal foods that you eat. Phosphorus found in animal foods is absorbed more easily compared to plant foods.
Inorganic phosphorus, or phosphate additives, is used by the food industry to extend the shelf life of food, improve food coloring, or make foods taste better. Common foods with phosphate additives include fast food, canned or bottled drinks, frozen meals, and processed deli meats. More than 90% of inorganic phosphorus is absorbed by the body.
Unlike other components in our food, such as salt, sugar, or fat found in packaged foods, the U.S. Food and Drug Administration (FDA) does not require food manufacturers to clearly list the amount of phosphorus on the nutrition label. Being an informed consumer is important because knowing the amount of phosphorus you are consuming and the source it comes from may help to monitor your intake. On your next grocery trip, read the ingredients label to identify any phosphate additives.
Identifying Added Phosphorus
Check the list of ingredients, which is usually located on the back of a product and below the nutritional facts label for hidden phosphorus or words that contain the letters “pho” such as:
- Disodium Phosphate
- Trisodium Phosphate
- Disodium Tripolyphosphate
- Potassium Tripolyphosphate
- Tetrasodium Pyrophosphate
- Monosodium Phosphate
Be cautious of phosphorus added to packaged goods, instant products, certain snacks, and frozen meals. Milk and milk products add protein to your diet, but they tend to be high in phosphorus and calcium. Look for dairy substitutes that are lower in phosphorus and without phosphate additives. Fast foods are also packed with high amounts of phosphate additives. Whenever possible, choose non-fast-food restaurants or make home-cooked meals using fresh ingredients. Making healthy swaps is a great way to avoid foods high in phosphorus. For example, instead of buying frozen chicken nuggets, try fresh chicken breast.
Phosphorus Alternatives
You may be wondering, what foods can I eat? Don’t worry! There are plenty of low-phosphorus alternatives that you can still enjoy. The table below will give you a better idea of what foods you can enjoy while staying healthy. Note: All information listed is intended for educational purposes only and should not be used to replace medical advice.
As you can see, limiting phosphate additives still allows plenty of room in your diet to enjoy a variety of foods. Research shows that monitoring dietary phosphorus can alter kidney disease progression, even in early kidney disease, and make a difference in bone and cardiovascular health.
Bottom Line
You may be wondering; do I need to avoid foods high in phosphorus? While it is almost impossible to completely cut out phosphorus from your diet because many foods contain either organic or inorganic phosphorus, your body still needs this mineral for important body functions. Whether you have properly functioning kidneys or kidney damage, it is important to limit foods high in phosphorus. Nutrition information varies across brands and changes over time – be sure to read food labels to check for phosphate additives! Everyone’s needs vary, so speak with your doctor or dietitian about your specific nutrition needs.
Seeing a dietitian is the best way to get evidence-based nutrition information if you are looking for more guidance on what to eat while living with a chronic disease. A renal dietitian can help you learn to navigate healthy foods for you and show how you can still include your favorite foods in your diet. Healthy Mission Dietitian is your primary resource for learning all you need to know about managing your chronic disease to regain control of your life and learn to enjoy food again!
Need more guidance? List your questions below and they may be chosen as a future blog post topic! If you are seeking individual nutrition counseling, visit Healthy Mission Dietitian to work 1:1 with me!
References
Bai, W., Li, J., & Liu, J. (2016). Serum phosphorus, cardiovascular and all-cause mortality in the general population: A meta-analysis. Clinica Chimica Acta, 461, 76–82. https://doi.org/10.1016/j.cca.2016.07.020
Hou, Y., Li, X., Sun, L., Qu, Z., Jiang, L., & Du, Y. (2017). Phosphorus and mortality risk in end-stage renal disease: A meta-analysis. Clinica Chimica Acta, 474, 108–113. https://doi.org/10.1016/j.cca.2017.09.005
Phosphorus and your kidneys. National Kidney Foundation. (2020, June 5). Retrieved September 25, 2022, from https://www.kidney.org/news/monthly/phosphorus_kidneys
Phosphorus and your diet. National Kidney Foundation. (2022, August 11). Retrieved September 15, 2022, from https://www.kidney.org/atoz/content/phosphorus
Top low-phosphorus foods for a healthy kidney diet. DaVita. (n.d.). Retrieved September 24, 2022, from https://www.davita.com/diet-nutrition/articles/advice/top-low-phosphorus-foods-for-a-healthy-kidney-diet
U.S. Department of Health and Human Services. (n.d.). Office of dietary supplements – phosphorus. NIH Office of Dietary Supplements. Retrieved September 24, 2022, from https://ods.od.nih.gov/factsheets/Phosphorus-HealthProfessional/
