Dietary Acid Load: What PRAL and NAE Mean
Your lungs and kidneys help keep arterial blood pH within a usual range of 7.35 to 7.45. A dietary acid-load score is not a measurement of that pH. [1]
Dietary acid-load models estimate the acid your kidneys may need to excrete from your eating pattern. They do not directly measure kidney strain or tissue damage. [2]
Updated
What this factor estimates
PRAL means Potential Renal Acid Load. It estimates a food's acid-forming or base-forming contribution from protein, phosphorus, potassium, magnesium and calcium. [3]
NAE means Net Acid Excretion: acid excreted in urine. Estimated NAE is different: the Remer and Manz model adds an organic-acid estimate based on body surface area to dietary PRAL. [2]
Daily dietary PRAL is expressed in milliequivalents per day, or mEq/day. Negative values indicate a base-forming contribution; positive values indicate an acid-forming contribution. [3]
PRAL is dietary context, not a pass-or-fail health target. The original estimation studies did not establish a universal ideal score. [2] [3]
What the evidence says about bone, muscle and kidneys
Bone findings are not consistent. A two-year trial in 276 postmenopausal women found no clear bone-density benefit from potassium citrate or additional fruit and vegetables. [4]
A three-month potassium bicarbonate trial found improvements in some bone-turnover markers, but no significant improvement in strength or physical function. Marker changes do not prove stronger bones. [5]
In chronic kidney disease, acid excretion can become impaired. Plant-rich dietary changes may help manage acidosis, but preventing kidney failure through acid lowering remains uncertain. [6]
With kidney disease, ask your GP or renal dietitian about protein and potassium needs. A family history warrants discussing kidney assessment, not self-treating a PRAL score. [6]
Food choices and practical steps
Hard cheeses, meat, eggs and many grains generally have positive PRAL values. Portion size matters. This classification alone is not a reason to exclude a food. [3]
Most fruit and vegetables have negative PRAL values, even when they taste acidic. Taste and dietary acid load are different. [3]
For variety, try leafy greens, broccoli, cauliflower, kūmara, courgette, tomato, citrus, berries, kiwifruit, banana, avocado and herbs.
Try two handfuls of vegetables with a main meal and fruit elsewhere in the day. Broccoli and kūmara with dinner or kiwifruit at breakfast are practical options, not a guaranteed PRAL balance.
Bicarbonate-rich mineral water reduced urinary acid excretion in a 28-day trial. This does not establish long-term health benefits or the same effect from every alkaline-water product. [7]
How to read this factor in your report
A weekly PRAL estimate can be calculated from food-log nutrient data using the Remer and Manz approach. Its usefulness depends on the completeness of the log and nutrient information. [2]
Treat scores and bands as educational models, not measurements or diagnoses. Read PRAL alongside protein and calcium intake, not as proof of muscle or bone change. [2]
An arterial blood gas test measures blood pH. Urine testing can measure acid excretion. Neither is interchangeable with a food-log estimate, which cannot diagnose kidney disease. [1] [2]
In CKD, protein advice may differ from sports-nutrition advice. Adding vegetables does not remove the need for an individual protein plan or mean everyone needs potassium restriction. [6]
Make any food-log recommendation concrete: choose a food, a portion and a meal. Review whether it fits your preferences and overall nutrition needs rather than chasing a neutral score.
Evidence and interpretation
- A lower calculated PRAL reflects changed model inputs. It is not independent evidence of improved kidney function, bone density or strength. [2]
- Trials of alkali-providing interventions show mixed bone findings. Changes in turnover markers are not proof of better bone density or fewer fractures. [4] [5]
- CKD can impair acid excretion. Dietary management needs individual protein and potassium advice, not a universal PRAL target. [6]
Frequently asked
- Does drinking alkaline water help my acid load?
- Some bicarbonate-rich mineral waters lower urinary acid excretion. This does not prove a long-term health benefit or apply to every alkaline-water product.
- Should I eat less protein to lower my acid load?
- Not solely to improve a PRAL score. Review your overall diet and goals. If you have kidney disease, agree an individual protein target with your care team.
- Are NZ-grown fruits and vegetables enough to balance a high-protein diet?
- Local produce can be part of the approach. No fixed serving count guarantees a neutral PRAL score; the amounts and composition of the whole diet matter.
References
- 1.MedlinePlus. Arterial Blood Gas (ABG) Test.
Explains arterial blood pH and blood gas testing. Official patient guidance, not evidence of dietary PRAL outcomes.
- 2.Remer and Manz. Estimation of the renal net acid excretion by adults consuming diets containing variable amounts of protein.
Compared estimated NAE with urine measurements in six healthy adults across four five-day diet periods. Does not establish individual health-risk bands.
- 3.Remer and Manz. Potential renal acid load of foods and its influence on urine pH.
Supports food PRAL and broad food patterns. The indexed abstract was available to the reviewer; direct record access was blocked. Does not establish NZ norms or clinical targets.
- 4.Effect of potassium citrate supplementation or increased fruit and vegetable intake on bone metabolism in healthy postmenopausal women: a randomized controlled trial.
Two-year trial in 276 postmenopausal women aged 55 to 65. Did not establish a bone-density benefit from the tested interventions.
- 5.Potassium Bicarbonate Supplementation Lowers Bone Turnover and Calcium Excretion in Older Men and Women: A Randomized Dose-Finding Trial.
Three-month supplement trial in adults aged 50 and over. Strength and function were exploratory outcomes; this was not a vegetable intervention.
- 6.KDIGO. 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease.
Supports CKD-specific acidosis management and individualised protein and potassium advice. Relevant sections include 3.3, 3.10 and 3.11; not a universal PRAL target.
- 7.Acid-Base Balance in Healthy Adults: Beneficial Effects of Bicarbonate and Sodium-Rich Mineral Water in a Randomized Controlled Trial: The BicarboWater Study.
Trial in 94 healthy participants over 28 days using specific mineral compositions. Short-term urinary findings cannot be generalised to all alkaline-water products.
Turn the evidence into practical food choices.
The free metabolic audit suggests coaching priorities from your answers. It does not measure blood markers or diagnose a condition.