What is Potential Renal Acid Load?

Introduction

I recently realized I had never written a blog about Potential Renal Acid Load (PRAL). It’s the foundation of what I teach all my clients, and it’s one of the most important concepts to understand if you have chronic kidney disease (CKD).

What is PRAL?

PRAL estimates how much acid or base a food is likely to produce in the body after digestion and metabolism — and therefore how much work the kidneys have to do to maintain acid–base balance.

It is not the actual acidity, or pH, of the food. In fact, many foods that have an acidic pH become alkaline in the body, and many foods that have an alkaline pH become acidic in the body.

For reference: a pH of 7 is neutral, less than 7 is acidic, and more than 7 is alkaline.

Example: Lemons have a pH of about 2 (very acidic). But they contain potassium salts of organic acids, like citrate. When metabolized, citrate is converted to bicarbonate, which is alkaline.

Why You’ve Probably Never Heard of PRAL

PRAL may also appear under other names, including:

• Net acid load
• Net endogenous acid production (NEAP)
• Dietary acid load
• Acidogenic potential of food
• Renal net acid excretion estimate

Most people haven’t heard of PRAL because it’s a specialized concept rooted in kidney physiology and biochemistry, not everyday nutrition. It can also feel counterintuitive — foods that taste acidic, like lemons, actually reduce acid load in the body, while some neutral-tasting foods can increase it.

Calculating PRAL precisely requires nutrient data that isn’t practical for most people. Public nutrition guidance typically focuses on overall dietary patterns — plenty of fruits and vegetables and balanced protein — which indirectly manages acid load. Finally, PRAL is most relevant for people with CKD or metabolic acidosis, since healthy kidneys can usually handle dietary acid efficiently.

Why PRAL Matters for Kidney Health

The kidneys do much more than filter blood and produce urine. One of their key jobs is to maintain acid–base balance by excreting excess acid in the urine. When kidney function declines, this process becomes less efficient, allowing acid to build up in the blood — a condition called metabolic acidosis.

Chronic acid retention puts additional stress on the kidneys and can contribute to further kidney function decline.

Beyond kidney function, metabolic acidosis can also cause:

• Elevated potassium levels
• Muscle breakdown
• Protein-energy wasting
• Bone disease
• Insulin resistance
• Inflammation and cardiovascular risk
• Impaired healing
• Kidney stones

For these reasons, preventing metabolic acidosis through a low-PRAL diet is important for kidney health.

Top Low-PRAL Foods for Your Plate

Here’s a list of foods with a low PRAL, based on realistic serving sizes that fit a kidney-friendly plate (vegetables covering half the plate, a whole grain ¼ of the plate, protein the remaining ¼).

What about potassium?

Many of these foods are high in potassium, because potassium contributes to a negative PRAL.

But CKD patients don’t automatically need to restrict potassium. Research shows that dietary potassium has limited effect on serum potassium levels; medications, constipation, metabolic acidosis, and blood sugar control play a larger role.

Reducing potassium unnecessarily can increase PRAL and may actually worsen kidney function over time.

How PRAL is Calculated

PRAL involves the protein and phosphorus content of the food compared with its potassium, magnesium, and calcium content.

• Foods with more protein and phosphorus relative to minerals have a higher PRAL (more acid-producing).
• Foods with more potassium, magnesium, and calcium relative to protein and phosphorus have a lower PRAL (more alkaline-forming).

Exact formula:

PRAL (mEq/day) = 0.49 × protein (g) + 0.037 × phosphorus (mg) − 0.021 × potassium (mg) − 0.026 × magnesium (mg) − 0.013 × calcium (mg)

Example calculation:

Daily intake:

• Protein: 70 g
• Phosphorus: 1,200 mg
• Potassium: 3,500 mg
• Magnesium: 350 mg
• Calcium: 900 mg

Step by step:

PRAL = (0.49 × 70) + (0.037 × 1200) − (0.021 × 3500) − (0.026 × 350) − (0.013 × 900)
PRAL = 34.3 + 44.4 − 73.5 − 9.1 − 11.7
PRAL = −15.6 mEq/day

A lower PRAL is desirable, so −15.6 mEq/day is a pretty good number.

Depending on your math skills, calculating PRAL for every food may seem daunting. Don’t worry — I’ll show you an easier way later in this post.

Putting it into practice

You don’t have to calculate PRAL for every meal. In my Kidney Health Clarity VIP Program, you can use an app to track your intake, and it calculates PRAL automatically — even from a photo of your meal!

If you’re interested in maintaining or improving kidney function, you can book a call below to learn more about the program. I can’t wait to meet you!

References

1. Remer, T., & Manz, F. (1995). Potential renal acid load of foods and its influence on urine pH. Journal of the American Dietetic Association, 95(7), 791–797. https://doi.org/10.1016/S0002-8223(95)00282-5
2. Remer, T., & Manz, F. (1997). Estimation of the renal net acid excretion by adults consuming diets containing variable amounts of protein. American Journal of Clinical Nutrition, 65(3), 535–543. https://doi.org/10.1093/ajcn/65.3.535
3. Goraya, N., & Wesson, D. E. (2012). Dietary acid reduction with fruits and vegetables or bicarbonate in patients with CKD. Nature Reviews Nephrology, 8(11), 635–642. https://doi.org/10.1038/nrneph.2012.194
4. Lynch, S., & Briscoe, C. (2014). Dietary potassium in CKD: More than just serum potassium. Advances in Chronic Kidney Disease, 21(6), 474–480. https://doi.org/10.1053/j.ackd.2014.06.005
5. Goraya, N., Simoni, J., Jo, C. H., & Wesson, D. E. (2013). Treatment of metabolic acidosis in CKD stage 3: Effects on kidney function and progression. Clinical Journal of the American Society of Nephrology, 8(3), 371–378. https://doi.org/10.2215/CJN.07200712