what is a renal diet?

What is a Renal Diet?

The phrase “renal diet” may be one of the most confusing in the nutrition world. If you Google it, you will find endless lists of foods to avoid. These lists and advice are often conflicting, which can be confusing and frustrating. 

You may even find websites that claim foods or regimens will “cure” kidney disease. This is completely bogus 99% of the time, and these recommendations can be dangerous to people with kidney disease. I’d steer clear of sites making claims like these.

Read on to learn what a “renal diet” might mean for you.

What Does a “Renal Diet” Even Mean?

“Renal” is simply a fancy word for “kidney”. In the medical world, kidney has many different names including “renal” and “neph”. For example, the formal title for your kidney doctor is a “nephrologist”.

So, “renal diet” is really just an umbrella term that includes MANY different diets. The right renal diet for you is very dependent on what kind of kidney disease you have, what your kidney function is, and what your other labs look like.

Know that there is no single food that will cure or prevent progression of kidney disease. A healthy renal diet must focus on whole diet patterns instead of eating (or limiting!) single foods.

The Renal Diet is Different For Everyone!

Some of the “renal diet” confusion comes from the fact that a kidney friendly diet is not the same for everyone. For example, a renal diet for someone with early stages of kidney disease is very different than a renal diet for the later stages of disease.  And, both of those diets are different than one for someone who is on dialysis or has a history of kidney stones. No wonder everyone is confused!

Here is an overview of how the recommendations for a renal diet are different for everyone. This will help you learn what a renal diet means for you.

Renal Diet for Chronic Kidney Disease

A healthy diet for Chronic Kidney Disease (CKD) changes drastically depending on the stage of CKD you have. I’ll walk you through each aspect of a renal diet for CKD and help you understand needs change.

Sodium

No matter what stage of kidney disease, sodium should be limited to 1,500-2,300mg per day on a renal diet. (1) This helps control blood pressure (which is key to preventing more kidney damage!) and control swelling.

Choosing foods low in sodium is the first step to follow a low sodium diet.

Protein

In CKD stage 1-3a (or, a GFR of 45ml/min or more), a healthy renal diet is moderately low in protein. Aim for 0.8 grams of protein per kilogram body weight in these early stages. This is plenty of protein to maintain or build muscle!

If CKD progresses to stages 3b-5 (or, a GFR less than 45ml/min), protein recommendations go down. For this stage, the National Kidney Foundation recommends a protein intake between 0.55-0.6 g/kg body weight. (1)

Of note, people who have both diabetes and CKD should not limit protein this much. Aim for 0.8 g/kg body weight if you have diabetes. (1)

On dialysis, protein needs increase. A diet high in protein is important to maintain muscles and prevent poor nutrition in people on dialysis. Protein recommendations go up to 1.2 g/kg body weight per day for people on dialysis. (1)

Protein needs are tricky and may be different based on your body size, nutrition status, medical history, and age. Ask your dietitian how much protein is right for you!

Potassium

Potassium only needs to be limited in people with high blood potassium. In the early stages of kidney disease, blood potassium levels are usually normal! In fact, a diet high in potassium can help control blood pressure and protect your kidneys. (2)

If kidney disease progresses to stage 4 or 5, high blood potassium levels are more common. The kidney is not able to get rid of potassium as well and it can build up in your blood. If blood potassium starts to go up, then cutting back how much potassium you eat is a good idea. (1)

Phosphorus

Artificial phosphorus should be limited for everyone with kidney disease, no matter the stage.

Natural sources of phosphorus, such as in whole grains, beans, nuts, seeds, and lentils, usually do not need to be restricted until very advanced CKD (if ever). This is especially true if phosphorus from animal products is avoided and plant proteins with natural phosphorus are eaten in place of meat, chicken and fish at meals.

Natural phosphorus is poorly absorbed, so does not have as big an impact on phosphorus levels as artificial phosphorus does. (3)

Dietary Acid Load

Reducing dietary acid load is the most important thing you can do nutritionally to slow the progression of kidney disease. (4)

Dietary acid load primarily comes from animal protein. Fruits and vegetables help neutralize acid. This is why it is so important that any renal diet includes LOTS of fruits and veggies, no matter the stage! Aim for at least 5 servings of fruits and vegetables every day.

Plant proteins produce significantly less acid than animal proteins. Eating more plant proteins like nuts, seeds, lentils, whole grains, and beans in place of animal proteins can slow CKD progression.

Learn more about dietary acid load and PRAL.

Fluid

Dehydration and not drinking enough fluid can hurt kidneys. Most people on a renal diet for CKD should drink at least 2 liters of water each day.

However, people with some health conditions may need to limit fluid. Here are some examples:

  • Dialysis
  • Advanced stages of CKD
  • Heart failure
  • Liver failure

Ask your doctor how much fluid is right for you.

Renal Diet for Polycystic Kidney Disease

A healthy renal diet for polycystic kidney disease (PKD) is based on GFR level and what stage of CKD you have. If you have PKD with normal kidney function (GFR >90ml/min), you have stage 1 CKD. See “Renal Diet for Chronic Kidney Disease” above for more specific recommendations.

Sodium and fluid are especially important for people with PKD. Eating too much salt can cause faster cyst growth, in addition to raising blood pressure. (5)

A very high fluid intake is often recommended for people with PKD to slow cyst growth too! Drinking 3-4 liters of fluid each day reduces a hormone called “vasopressin”. Vasopressin can accelerate cyst growth in PKD. So, drinking a lot of water can help slow cyst growth. (5)

More about a healthy diet for polycystic kidney disease. And, if a keto diet is good for PKD.

Renal Diet for People with a Kidney Transplant

Nutrition is an important piece of protecting a new kidney! A renal diet after kidney transplant will be individualized to your lab values. For most people, this means a renal diet similar to the early stages of CKD. Limiting sodium, avoiding high amounts of protein and eating lots of fruits and vegetables will help keep your kidney working as long as possible!

Food safety is also important for people with a transplant. The transplant medications you must take to protect your kidney also increase risk of foodborne illness. Learn how to keep your food safe!

Renal Diet for Proteinuria

Proteinuria (or, too much protein in your urine) often goes hand-in-hand with kidney disease. Proteinuria is especially common for people who have kidney disease as a result of diabetes.

Kidney disease with proteinuria is usually more severe and progresses faster. So, we want to do everything we can to keep urine protein levels down!

Limiting protein (based on your stage of CKD) and sodium to 2,300mg/day will help lower protein in your urine. (1)

Renal Diet for Glomerulonephritis

There are not separate nutrition recommendations for glomerulonephritis. A renal diet will be based on your GFR and stage of kidney disease.

Renal Diet for Kidney Stones

There is no one renal diet that is good for kidney stones. Healthy eating for kidney stones is based on the type of stone you make and your urine risk factors.

Calcium oxalate kidney stones are most common, and make up about 80% of kidney stones. The most common urine risk factor for kidney stones is hypercalciuria (or, high urine calcium). A dietary pattern that limits sodium to 2,300mg, protein to 0.8-1.0g/kg body weight and added sugar can help lower urine calcium. Contrary to popular belief, people who have calcium kidney stones actually need to make sure they eat enough calcium. (6)

Dairy and other sources of calcium are an important part of a renal diet for calcium kidney stones

No matter the type of kidney stone, drinking at least 3 liters of fluid each day is very important.

A low oxalate diet may also be important for kidney stone prevention. But, this is not the case for everyone.

Learn more about nutrition for calcium oxalate kidney stones. And, check out my online course, Kidney Stone Nutrition School.

Figuring Out What To Eat On a Renal Diet

As you can see, there really is NO one “renal diet”. Kidney friendly eating must be individualized to your labs and medical history.

Putting all of this information together to figure out what to eat can be overwhelming. I highly recommend asking your nephrologist for a referral to meet with a Registered Dietitian to help you.

In the United States, most insurance covers dietitian visits for kidney disease! It is never too early (or, too late!) to work with a dietitian for kidney health.

Check out the list of dietitians who specialize in kidney disease on my resources page. The Academy of Nutrition & Dietetics and the National Kidney Foundation also have tools to help you find a renal dietitian near you!

Happy Eating!

Melanie

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