what is PRAL

What Is PRAL & How Does It Affect Kidneys?

What is PRAL?

“PRAL” stands for Potential Renal Acid Load.  PRAL is a measurement of the amount of acid your diet produces in your body.  Higher PRAL values indicate more acid is produced from that food.  Negative PRAL values indicate that base (the opposite of acid) is produced.  PRAL is measured in milliequivalents of acid per day1.

The pH of your body is the amount of acid relative to the amount of base.  Whole body pH is tightly regulated by your lungs and kidneys.  Acid is produced in our bodies from normal processes such as digestion and metabolism.  Some diet patterns create more acid compared to others1. Your body relies primarily on the kidneys to get rid of extra acid your diet generates. Your lungs help a little too!

PRAL is becoming more and more common in kidney disease research and more dietitians and nephrologists are beginning to recommend eating based on PRAL.  Keep reading to learn more!

Calculation of PRAL

PRAL is calculated from 5 nutrients that create either acid or base in our bodies.  Protein and phosphorus create acid during metabolism; whereas potassium, magnesium and calcium produce base.  By far, protein is the biggest determinant of PRAL; the higher the protein of a food, the higher the PRAL value1.

Nutrients impact on PRAL

Acid and Kidney Disease

Why do we care so much about acid from our diets? Dietary protein is the biggest factor that determines how much acid your kidneys have to deal with2.  In Chronic Kidney Disease (CKD), kidneys cannot get rid of extra acid as well as they should.  This causes acid to build up in blood (a condition called “acidosis”), which has many negative health effects.

Acidosis is very common in people with CKD.  An estimated 13% of people with CKD stage 3 have acidosis, and this increases to almost 40% by CKD stage 43.  Even people with earlier stages of kidney disease (CKD stages 1 and stage 2) keep more acid in their bodies compared to people without kidney disease4.  Almost every time your kidney doctor draws labs, they check how much carbon dioxide (CO2) is in your blood.  C02 is a measurement of how acidic your body is.  Most doctors want your C02 level to be at least 22 mEq/L5.

Consequences of Acidosis

  • Weak bones and osteoporosis
  • Faster progression of kidney disease
  • Muscle loss
  • Possible worsening of heart disease and inflammation
  • Taste changes
  • Poor appetite
  • Fatigue
  • Headache3,6

Treatment for Acidosis

Acidosis is usually treated with a medication called sodium bicarbonate6.  This medication gives you a large dose of base, which helps neutralize extra acid in your body.  Another common medication to treat acidosis is potassium citrate.  However, potassium citrate is not used as much for people with kidney disease because of the large amount of potassium in it.

I know all this acid talk can sound sort of scary.  But, I have good news! What you eat directly impacts how much acid you have in your body.  In fact, some foods can actually help get rid of extra acid.  You can use diet to help treat acidosis!

PRAL and Food

PRAL is best used for evaluating an entire diet, not just a single food.  However, for the sake of education, I think it is useful to compare the PRAL for single foods to understand the benefit of eating more (or less!) of those foods.

To reduce the acid load on our kidneys, our goal is to reduce the amount of protein in our diet (acid producing), and increase the amount of potassium, magnesium and calcium (base, or alkali producing).  What does this mean for our actual meals?

Take a look at this chart. Notice that most animal proteins such as beef and chicken have a very high PRAL.  This is because most animal proteins have a lot of protein and phosphorus, and are relatively low in potassium, magnesium and calcium.  Some of the plant proteins (lentils, beans and nuts) have a negative PRAL, representing that these foods produce base in our body.  In addition, most fruits and vegetables have a negative PRAL.

PRAL for Individual Foods

 Portion SizePotential Renal Acid Load (PRAL, mEq/day)
Proteins
Beef Steak4oz, cooked12.9
Chicken4oz, cooked16.3
Cod4oz, cooked13.5
Shrimp4oz, cooked14.5
Black Beans½ cup, cooked-2.6
Lentils½ cup, cooked-1.5
Walnuts¼ cup1.7
Egg1 whole3.7
Grains
Whole Grain Bread1 slice1.8
White Bread1 slice0.8
Brown Rice½ cup, cooked2.2
Quinoa½ cup, cooked2.1
Dairy
2% milk1 cup-1.5
Low Fat Plain Yogurt1 cup0.4
Cheddar Cheese1 slice3.5
Fresh Mozzarella Cheese1 slice3.8
Fats
Olive Oil1 tablespoon0.0
Unsalted Butter1 tablespoon0.1
Vegetables
Broccoli1 cup, cooked-5.5
Green Beans1 cup, cooked-3.5
Tomatoes½ cup, chopped-3.7
Carrots1 cup, cooked-6.4
Fruits
Banana1 medium, raw-8.2
Peaches1 medium, raw-4.7
Blueberries1 cup, raw-1.5
Pineapple1 cup, cubes-3.6

PRAL Food Chart

To make this a little easier, I classified foods into what group they generally fall into.  Our goal is to eat enough of the negative PRAL foods to offset the high PRAL foods we eat.

PRAL Food Table

High PRAL Foods (Acid Producing)Overall Neutral PRAL FoodsNegative PRAL Foods (Base Producing)
BeefFats & OilsAll fruits
PorkAll vegetables
LambBeans
Chicken & TurkeyLegumes
Fish & SeafoodMilk & Yogurt
**Moderately acid producing foods**
Grains
Eggs
Cheese

Diet Patterns and PRAL

Of course, none of us live off only one food.  What a terribly boring life that would be! Because we eat a variety of foods, it is most important to consider PRAL for your entire diet. This whole idea of PRAL boils down to three important points to reduce the acid load on your kidneys.

  1. Eat more foods that produce base. This will help neutralize acid from the protein that you do eat (and you do need some protein!). This means eating large amounts of vegetables and fruits.  Yet another reason all that produce is good for us!
  2. Eat the right kind of protein. We know that plant proteins like beans, lentils and nuts create much less acid in our bodies compared to meat, poultry and fish. Some plant proteins even produce base!  Swapping out the meat for plant-based proteins, even for just 1 meal per day, will help reduce the acid load on your kidneys.
  3. Eat the right amount of protein. Meat, poultry and fish create the most acid in your body by far. Figuring out how much of these foods is right for you is a very personal question. Some people choose to completely cut them out.  Others choose to limit them to only once per day.  This is an important discussion to have with your dietitian to figure out what you feel comfortable with and what makes the most sense for your health.

Good advice for almost everyone is to pay attention to portion size when you eat meat, poultry or seafood.  Shoot for portion sizes of 3-6oz, or, about ½ the size of your palm.

Popular Diet Patterns

A few popular diet patterns fall into these three points nicely.  The Dietary Approaches to Stop Hypertension (DASH) diet focuses on eating 10 servings of fruits and vegetables per day.  In addition, the DASH diet recommends 3 servings of dairy with a focus on incorporating plant-based proteins. This dietary pattern would have a low PRAL.  In addition, this diet as been shown to be incredibly effective at lowering blood pressure7! Check out more info about the DASH diet, or download this handout.

The Mediterranean diet is another popular, well-researched, diet that would overall have a low PRAL.  The Mediterranean diet is most known for its benefit on heart health8.  It has also shown benefit in reducing risk for Alzheimer’s, dementia and cognitive decline in old age9,10. Read more about the Mediterranean diet.

High PRAL Foods vs. Acidic Foods

High PRAL foods are not necessarily acidic foods.  This can be confusing and is an important difference.   High PRAL foods are not necessarily acidic before we eat them.  For example, tomatoes and pineapple are acidic, but they have a negative PRAL.  This is because the acid in food is very different than the acid PRAL measures.  The acid in food is neutralized by hydrochloric acid in our stomach and does not increase the amount of acid in our bodies.  PRAL measures the acidity of food’s metabolites, not the food itself.

People with heartburn or gastroesophageal reflux (GERD) may find relief from avoiding high acid foods such as tomatoes, orange juice, pineapple or vinegar.  Of course, if you suffer from this condition and avoiding these foods helps your symptoms, by all means, avoid these foods!  However, if you do not have heartburn, there is absolutely no reason to avoid acidic foods.

Who Should Follow a Low PRAL Diet?

A low PRAL diet is going to be high in fruits & veggies, focus on plant proteins and keeping meat portions reasonable.  Honestly, this diet has been shown to be good for almost everyone!

A low PRAL diet may be especially helpful for people with health conditions that impact kidney function such as: Chronic Kidney Disease, Focal Segmental Glomerulosclerosis (FSGS), Polycystic Kidney Disease (PKD), renal cancer, lupus nephritis, minimal change disease or IgA nephropathy.

To my knowledge, PRAL has NOT been researched for any other health condition besides kidney disease.  However, given the fact that a low PRAL diet will be high in fruits, vegetables and plants, this diet could be beneficial for people with heart disease, high blood pressure, diabetes, gastrointestinal issues, osteoporosis or those struggling with maintaining a healthy weight. This dietary pattern is really just good for general health!

A Note on Potassium

Some people with advanced kidney disease need to limit how much potassium they eat.  If you fall into this category, some fruits and vegetables are not the best choice for you, even though they have a low PRAL.  Talk to your doctor or dietitian to know if you need to limit how much potassium you eat. More about potassium and kidney disease. 

Alkali from Supplements

A Google search will reveal endless supplements and food products claiming to change the pH of your body and cure all ailments from anxiety to diabetes.  Most of this is completely unsupported by research and I do not recommend most of them.

Some of these products, such as alkaline water, do have a large dose of base, and could change the pH of your blood.  However, getting alkali (or base) from specialized foods or supplements robs you of the benefit of getting alkali from fruits and vegetables.  Fruits and vegetables have countless benefits other than just alkali.  In addition, as with any dietary supplement, you could get too much alkali, which can be dangerous.  It would be almost impossible to get too much alkali from food.  Also, these products have not been well researched.

Of course, if your doctor has prescribed you a medication to treat acidosis, such as sodium bicarbonate, you should absolutely take it.  Taking medications as your doctor prescribes them is one of the best ways to slow progression of kidney disease.

Happy Eating!

Melanie

References

  1. Scialla JJ, Anderson CAM. Dietary Acid Load: A Novel Nutritional Target in Chronic Kidney Disease? Adv Chronic Kidney Dis. 2013;20(2):141-149. doi:10.1053/j.ackd.2012.11.001
  2. Gennari FJ, Hood VL, Greene T, Wang X, Levey AS. Effect of Dietary Protein Intake on Serum Total CO2 Concentration in Chronic Kidney Disease: Modification of Diet in Renal Disease Study Findings. Clin J Am Soc Nephrol. 2006;1(1):52-57. doi:10.2215/CJN.00060505
  3. Metabolic Acidosis of CKD: An Update | Elsevier Enhanced Reader. doi:10.1053/j.ajkd.2015.08.028
  4. Wesson DE, Simoni J, Broglio K, Sheather S. Acid retention accompanies reduced GFR in humans and increases plasma levels of endothelin and aldosterone. Am J Physiol-Ren Physiol. 2011;300(4):F830-F837. doi:10.1152/ajprenal.00587.2010
  5. CKD Evaluation and Management – KDIGO. https://kdigo.org/guidelines/ckd-evaluation-and-management/. Accessed April 4, 2020.
  6. Kraut JA, Madias NE. Consequences and therapy of the metabolic acidosis of chronic kidney disease. Pediatr Nephrol. 2011;26(1):19-28. doi:10.1007/s00467-010-1564-4
  7. Sacks FM, Svetkey LP, Vollmer WM, et al. Effects on Blood Pressure of Reduced Dietary Sodium and the Dietary Approaches to Stop Hypertension (DASH) Diet. N Engl J Med. 2001;344(1):3-10. doi:10.1056/NEJM200101043440101
  8. Estruch R, Ros E, Salas-Salvadó J, et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet. N Engl J Med. 2013;368(14):1279-1290. doi:10.1056/NEJMoa1200303
  9. Scarmeas N, Stern Y, Tang M-X, Mayeux R, Luchsinger JA. Mediterranean diet and risk for Alzheimer’s disease. Ann Neurol. 2006;59(6):912-921. doi:10.1002/ana.20854
  10. Petersson SD, Philippou E. Mediterranean Diet, Cognitive Function, and Dementia: A Systematic Review of the Evidence. Adv Nutr. 2016;7(5):889-904. doi:10.3945/an.116.012138

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