What is PRAL?

PRAL stands for “Protein Renal Acid Load” or “Potential Renal Acid Load”, both mean the same thing. Each food we eat has a PRAL score that determines how the food will impact the acid balance in the body; each food is either acidic or basic (aka “alkali”). The higher the PRAL value for a food, the more acid is produced when the body metabolizes that food. A negative PRAL score indicates that base, the opposite of acid, is produced. 

Think back to chemistry for just a second. When thinking of pH, the higher the pH, the more alkaline a substance is. The lower the pH, the more acidic. The body strives to keep a healthy pH level, which is regulated by the kidneys and the lungs. Your kidneys work hard to remove extra acid from the food we eat.

How is PRAL calculated?

PRAL is calculated by comparing the protein and phosphorus of a food versus the potassium, magnesium and calcium. Protein has the largest impact on PRAL score; foods higher in protein will be higher PRAL.

PRAL = [0.49 x protein (g/day) + 0.037 x phosphorus (mg/d)] – 0.021 x potassium (mg/day) – 0.026 magnesium (mg/day) – 0.013 x calcium (mg/day)

Chicken breast: 9.64

Zucchini: -4.6

This means that chicken is more acid producing than zucchini. Here is a list of a few common foods and their PRAL values. If you start looking up PRAL scores, you may notice a trend. Fruits and vegetables tend to be negative PRAL while protein rich foods and grains are often positive PRAL. 

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PRAL and kidney disease

PRAL and kidney disease are linked because the kidneys are responsible for the body’s acid-base balance. When the kidneys don’t work at their best, the balance can lead towards more acidic, which is not what we want. 

Since each food has a PRAL score, eating more negative PRAL foods can help reduce the overall acid load in the body. PRAL scores are not intended to be used in looking at individual foods but rather in looking at the overall diet. Comparing certain foods can certainly be helpful when learning which foods may contribute to higher PRAL scores. 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 foods that produce alkali or base.  What does this mean for our actual meals?

Plant proteins (such as beans, nuts and lentils) are often negative in PRAL value while animal proteins have positive PRAL values. Fruits and vegetables also usually have negative PRAL values. To lower your overall PRAL index, aim for more fruits, vegetables and plant protein choices.

PRAL is a topic covered in the CKD+Diabetes Group Course. If you’d like to learn more about PRAL and other topics, please check out the course.

How else can PRAL impact my health

Research has shown that those who follow a lower PRAL diet, meaning more negative PRAL foods have stronger bones.

PRAL and Acidity

It is worth noting that PRAL value is not at all related to the overall acidity of a given food. Lemon or pineapple, for example, are acidic but have a negative PRAL value meaning it is more base producing in the body. The acid in food is very different from the acid produced in the body. Acidic foods are neutralized during digestion and do not impact the acid in the body.

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