What is the PRAL? Usage and application
What is the PRAL?
Potential renal acid load, in short PRAL, is a value that indicates how much a particular food will affect the urine pH levels and the acidity of urine.
In other words, the PRAL value shows how much acid is produced after the digestion of a particular food.
Understanding that blood acidity doesn't behave similarly to urine acidity is essential. Since blood has an excellent buffer system, it always tries to keep blood acidity levels between 7.35-.7.45 pH (1).
Back to urine, acidity is typically between 4.5-8 pH, which can have a very high significance. As the pH levels change, there will be an increased risk of renal stone formation. This is where individuals tend to track the PRAL value (2).
Why would urine pH change with food?
The metabolites of foods tend to have different chemical structures, which can affect pH levels. For example, consuming protein-rich foods increases uric acid levels making urine more acidic. Consuming vegetables makes urine alkaline.
What does the PRAL value depend on?
There are some parameters - nutrients, processes, or metabolites that will affect the acid-base balance of the organism and the PRAL value. Those parameters are protein, phosphorus, potassium, calcium, chloride contents, and the time when a particular nutrient can be absorbed in your intestine.
How to calculate the PRAL value?
The PRAL value has the following equation:
PRAL= (0.49 x total protein intake g/day) + (0.037x phosphorus intake mg/day) - (0.021x potassium intake mg/day) - (0.0.26 x magnesium intake) - (0.013 x calcium intake mg/day)
In summary, as we consume protein and phosphorus, we tend to increase the PRAL value, which makes the urine acidic. On the other hand, as we consume potassium, magnesium, and calcium, we decrease the PRAL value, which alkalinizes the urine (3).
Foodstruct articles contain the PRAL values for all the foods that help you understand which food has a positive or negative PRAL value.
Here are some links that showcase the PRAL values, such as red meat's positive PRAL value, which means it turns urine acidic. In comparison, vegetables like cabbage, tomatoes, and even lemon have a negative PRAL which alkalinizes urine.
Who should care about PRAL values?
Everyone can use the PRAL value in their diets. However, people who suffer from urine crystals and kidney stones should use the PRAL value frequently.
Types of kidney stones with different pH levels. High pH levels (alkaline urine) increase the risk of calcium phosphate and struvite stones. On the other hand, with low pH (acidic urine), there is an increased risk of uric acid and cystine stones.
Calcium oxalate is usually associated with other diseases, but there is also an increased chance of acidic urine.
Thus it is essential to consider the PRAL value of foods based on the type of stone you have in accordance with urine pH (2).
In addition, it is also essential to check the PRAL value to see if there is an increased chance of developing urine crystals. If you have stones that precipitate in acidic urine, you must alkalinize your urine, and vice versa.
More importantly, you have to follow your doctor's guidance.
In addition, several antibiotics are excreted unchanged or metabolized through the renal system. One of the main variables is urinary pH levels (4).
Summary
PRAL value determines how much a food will affect urine acidity.
Protein-rich foods usually make the urine more acidic, and fruits and vegetables tend to alkalinize the urine.
People who suffer from kidney stones should consider the PRAL value and change the acidity of their urine depending on the type of stone.
Blood acidity does not behave similarly as a buffering system keeps blood pH between 7.35-7.45.
References
- https://www.ncbi.nlm.nih.gov/books/NBK507807/
- https://pubmed.ncbi.nlm.nih.gov/21170875/
- https://pubmed.ncbi.nlm.nih.gov/22676161/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2881463/
