Low Urinary pH, Acid Producing Foods, and Alkaline Water

The human body is skilled at maintaining a blood pH of between 7.35 to 7.45 for optimal functioning.  The pH of our urine, however, is under no such strict parameters.  While a urinary pH will ideally be between 5.8 to 6.2 for kidney stone prevention, it can be much lower (acidic) or higher (alkaline).

A low urinary pH can provide the perfect condition for most types of kidney stones to form.  Correcting a low pH (acidic) urine is key to prevent stone recurrence. ¹ ² ³

How to Increase Urinary pH:

Urine pH can be lowered due to hereditary conditions, certain medications and some diseases, such as metabolic syndrome or diabetes.  For these individuals, maintaining a healthy body weight, eating right, exercising, practicing stress management and following any regimen prescribed by a physician is key to improving urinary pH. ⁴ ⁵ ⁶

Urine pH can also be lowered due to dietary habits. Part of improving urinary pH involves limiting the use of foods that have a high potential renal acid load (PRAL) or that result in high net endogenous acid production (NEAP).  The other part of improving urinary pH entails increasing the use of alkaline-generating foods.  These dietary changes are enough to improve the urinary pH of most people.

Acid-Producing or Alkaline-Producing Foods:

So, what foods result in a high acid load?  Meats, eggs, fish and hard cheeses are the biggest sources.  Limiting the portion sizes of these foods is recommended by the American Urological Association (AUA) to improve urinary pH. ⁷  If a person desires to try eliminating these foods, it is important to consult with a dietitian to ensure you have the information needed to avoid dietary deficiency of protein, essential amino acids, and vitamins/minerals. 

What about alkaline-generating foods?  While many of the foods we associate with being acidic involve fruits and vegetables (think lemon juice or tomato sauce), actually become alkaline when digested and absorbed into the body.  Increasing the use of fruits and vegetables in the diet is also recommended by the AUA. ⁷  At minimum, aim for 2 servings of fruit and 3 servings of vegetables daily.  A serving of fruit may be ½ cup chopped fruit, a small piece of whole fruit, or 4 oz fruit juice.  A serving of vegetables may be 1 cup of most raw vegetables, 2 cups of raw leafy vegetables, or ½ cup cooked vegetables. 

What to Know about Acid Load Food Lists:

Acid load food lists found on the internet should only be viewed with the understanding that the information represented may not be accurate. The methods for calculating acid load of foods differ, and there are many factors involved.  Food components like sodium, potassium, magnesium bicarb, and organic acids (citric, lactic, malic, etc.) generally result in an alkaline food.  Food components like protein, phosphorus, sulfur, purines, and fructose generally result in high acid load foods. ⁸

To complicate matters, in real-world situations, gastrointestinal issues and even gut microflora also play a role in how much acid or alkaline are actually absorbed from food.  Those with a history of GI surgeries or conditions like irritable bowel syndrome or inflammatory bowel disease may be absorbing less alkaline-producing substances. ⁹

It is also crucial to recognize the potential for misinterpretation due to discrepancies between studied portion sizes and typical dietary servings. For instance, a study may utilize 100g portions for analysis, which may not align with standard serving sizes. Using grapes and raisins as an example, 100g of grapes corresponds to one serving, whereas 100g of raisins equates to four servings. Without appropriate conversion to dietary serving sizes, a misleading impression of relative alkalinity may arise.

Also, keep in mind if viewing a food list, the portion sizes studied are not necessarily

reflective of typical dietary servings.  For instance, a study may use 100 gram portions of all foods for their analysis. Using grapes and raisins as an example, 100 grams of grapes is about 1 typical serving of fruit, whereas 100 grams of raisins is about 4 servings of fruit. Without doing some math to convert grams into typical servings, a person may be under the impression that raisins are many folds more alkaline than grapes.

The Best Approach:

While it may be tempting to ‘count’ up your potential daily acid load, it is best to stick with the general recommendations about decreasing animal proteins and increasing fruits and vegetables.  This simple strategy is challenging enough; there is no need to stress over numbers.

A Note on Fruits:

A search of the internet may result in very ambiguous information about the acid load of certain fruits like cherries, bananas, plums, and cranberries.  While intake of fruits is important for health, it may be wise to avoid over-consumption of fruit. Too much of a good thing can also be harmful.  Limiting fruit intake to 5 servings per day and specifically limiting use of fruit juice to 4 oz daily are reasonable recommendations.  However, discussing intake with a dietitian can help tailor this recommendation a person’s specific situation.

Alkaline Water and pH

Alkaline water has been gaining popularity recently.  While it may help relieve some symptoms related to indigestion and heart burn, it does not have any significant effect on urinary pH.  One recent study by Paul Piedras and cohorts at the University of California determined the physiologic alkali content of all five different alkaline water brands they tested was below 1 mEq/L. 

For perspective, many physicians will prescribe supplements to increase the pH of urine such as sodium bicarbonate or citrate salts (like potassium citrate).  For Potassium citrate, the AUA and European Association of Urology recommend between 30 to 60 mEq per day for beneficial effect on urine pH.  Considering alkaline water has less than 1 mEq in an entire liter, it is a poor substitute.¹⁰

Again, it is important to consult with a physician or dietitian before considering the use of supplements.

What About Your Urine pH?

Your urinary pH and other kidney-stone risk markers can be determined with a simple 24 hr urine test.  If you live in the state of Florida and are seeking a Nephrologist and Dietitian team to help you prevent kidney stone recurrence, book your free discovery call today! Click the link below for the Kidney Stone Prevention Clinic of Florida.

KidneyStoneClinic

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References

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8. McMullen MK. Many foods are more acid-forming than acid-alkaline formulas indicate. Nutrition and Health. 2024;30(3):419-427.

9. Cury DB, Moss AC, Schor N. Nephrolithiasis in patients with inflammatory bowel disease in the community. Int J Nephrol Renovasc Dis. 2013;6:139-42.

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