How a Lower Phosphorus Diet Can Benefit People with Chronic Kidney Disease

Chronic kidney disease (CKD) is a condition that affects millions of people worldwide, and it can have serious consequences for one's health and quality of life. CKD occurs when the kidneys lose their ability to filter waste and excess fluids from the blood, leading to a buildup of toxins and electrolytes in the body. This can cause various complications, such as high blood pressure, anaemia, bone disease, cardiovascular disease, and kidney failure.

One of the electrolytes that can accumulate in the blood due to CKD is phosphorus, a mineral that is essential for many bodily functions, such as bone health, energy metabolism, and cell signaling. However, too much phosphorus can be harmful, as it can interfere with the balance of calcium and other minerals in the body, leading to bone loss, joint pain, itching, and calcification of soft tissues and blood vessels. High phosphorus levels can also increase the risk of death in people with CKD.

Therefore, managing phosphorus intake is an important aspect of CKD care, and it can have significant benefits for kidney function and overall health. In this article, we will explore the different sources of phosphorus in the diet, and how a lower phosphorus diet can help people with CKD, even in the early stages of the disease.

Different Sources of Phosphorus in the Diet

Phosphorus is found naturally in many foods, and it is also added to many processed and packaged foods as a preservative, stabiliser, flavour enhancer, or colour agent. Depending on the source, phosphorus can have different effects on the body, and some sources are more easily absorbed than others.

Phosphate Additives

Phosphate additives are synthetic forms of phosphorus that are added to foods to improve their texture, taste, appearance, or shelf life. Some examples of foods that may contain phosphate additives are:

• Processed meats, such as ham, bacon, sausage, hot dogs, and deli meats

• Canned or bottled beverages, such as cola, flavored water, tea, and sports drinks

• Dairy products, such as cheese, yogurt, ice cream, and milk

• Baked goods, such as bread, muffins, cakes, and biscuits

• Cereals, muesli bars, and snack foods

• Condiments, sauces, and dressings

Phosphate additives are more readily absorbed by the body than natural phosphorus, and they can contribute to a high phosphorus intake, especially if consumed in large amounts or frequently. Therefore, people with CKD should avoid or limit foods that contain phosphate additives, and check food labels for ingredients that contain the word "phos", such as:

• Disodium phosphate

• Phosphoric acid

• Monopotassium phosphate

• Sodium acid pyrophosphate

• Sodium tripolyphosphate

Animal-Derived Foods

Animal-derived foods, such as meats, poultry, fish, eggs, and dairy products, are rich sources of natural phosphorus.. However, animal-derived foods also have a high bioavailability of phosphorus, meaning that they are easily absorbed by the body, and they can increase the phosphorus load on the kidneys.

For people with CKD, it is recommended to moderate the consumption of animal-derived foods, and preference plant-based sources of protein, such as legumes, tofu, and quinoa. If consuming animal-derived foods, portion size should be controlled, and a general guideline is to limit the intake of animal protein to 0.8 grams per kilogram of body weight per day, which on average is approximately 200 - 250g of meat, poultry, or fish per day.

Plant-Based Sources

Plant-based sources of phosphorus include fruits, vegetables, grains, legumes, nuts, and seeds. These foods also provide fibre, antioxidants, vitamins, and minerals that can support kidney health and overall wellness. However, plant-based sources of phosphorus have a lower bioavailability than animal-derived sources, meaning that they are less absorbed by the body, and they have a lower impact on the phosphorus level in the blood.

This is because plant-based sources of phosphorus are bound to a compound called phytate, which reduces the absorption of phosphorus in the intestine. The amount of phytate in plant-based foods can vary depending on the type, variety, and processing method of the food. For example, whole grains, bran, and wheat germ have higher phytate content than refined grains, such as white rice, white bread, and white pasta. Similarly, raw nuts and seeds have higher phytate content than roasted or sprouted nuts and seeds.

For people with CKD, plant-based sources of phosphorus are a favourable alternative to animal-based ones, as they can help lower the phosphorus intake due to decreased phosphorous absorption, whilst providing other health benefits. However, plant-based sources of phosphorus should still be consumed in moderation, and the portion size should be appropriate for the individual's nutritional needs and kidney function.

Research Findings on Early-Stage CKD

While a lower phosphorus diet is well-established as a beneficial intervention for people with advanced CKD or kidney failure, recent studies have shown that it can also have positive effects on people with early-stage CKD, who may not have elevated phosphorus levels in the blood yet.

A review published in the Journal of Renal Care, highlights how high-normal blood phosphate levels may be a risk factor for the advancement of CKD and suggests phosphate lowering interventions, such as a lower phosphate diet, may benefit outcomes in early stage CKD ¹. Another study, published in the Journal of Renal Nutrition in 2020, found that a lower phosphorus diet, compared to a control diet, reduced the risk of CKD progression and cardiovascular events in people with stage 1 or 2 CKD².

These findings suggest that a lower phosphorus diet can have beneficial effects on kidney function and overall health outcomes, even in the early stages of CKD, by reducing the burden on the kidneys to eliminate excess phosphorus, and by preventing or delaying the complications associated with high phosphorus levels.

Conclusion

Phosphorus is an important mineral for the body, but too much of it can be harmful, especially for people with CKD, who have impaired kidney function and cannot regulate the phosphorus level in the blood. A lower phosphorus diet can help people with CKD manage their phosphorus intake and improve their kidney function and overall health outcomes, even in the early stages of the disease.

A lower phosphorus diet involves avoiding or limiting foods that contain phosphate additives, moderating the consumption of animal-derived foods, and choosing plant-based sources of phosphorus. It also requires checking food labels, controlling portion sizes, and consulting with a practitioner experienced in renal nutrition for individualized guidance and support.

By following a lower phosphorus diet, people with CKD can take charge of their health and slow the progression of the disease.

Source:

(1) Sigrist MK, Chiarelli G, Lim L, Levin A. Early initiation of phosphate lowering dietary therapy in non-dialysis chronic kidney disease: a critical review. J Ren Care. 2009 Mar;35 Suppl 1:71-8.

(2) Amir S, Kim H, Hu EA, Ricardo AC, Mills KT, He J, Fischer MJ, Pradhan N, Tan TC, Navaneethan SD, Dobre M, Anderson CAM, Appel LJ, Rebholz CM; CRIC Study Investigators. Adherence to Plant-Based Diets and Risk of CKD Progression and All-Cause Mortality: Findings From the Chronic Renal Insufficiency Cohort (CRIC) Study. Am J Kidney Dis. 2023 Dec 14.