Prevent Kidney Stones (and UTIs?) by Optimizing Urine pH

Many organisms that infect the urinary tract alter the urine pH, for example by secreting the enzyme urease, which generates the alkaline ammonia from the neutral urea.

While a urine pH above 7.5 has often been seen by clinicians as indicative of a urinary tract infection (UTI), there is no evidence I know of that you can reduce your risk of a UTI by modifying your urine pH.

For example, this study in children found that urine pH was 6.24 in controls and 6.27 in those with urinary tract infections, which is a level of precision beyond what a home pH meter could provide.

Furthermore, urine pH was strongly correlated with the specific infecting organism, consistent with experimental data that different organisms will cause different urine pH readings based on their metabolism.

Even if we assume the metabolic effect the infecting agent has on the urine causes it to survive and multiply better, all we could directly modify is the relative risk of E coli, which prefers acidity, and P mirabilis, which prefers alkalinity.

Similarly in a study of 510 pregnant women, urine pH was of no value in screening for asymptomatic presence of bacteria in the urine.

On the other hand, each antibiotic used to treat UTIs has an optimal urine pH for its activity, but that does not mean you can prevent UTIs by optimizing your urine pH.

However, it is likely very different for kidney stones!

The role of urine pH in the risk of kidney stones is controversial and not completely ironed out, but this figure shows the influence of urine pH on in vitro calcium oxalate (top) and calcium phosphate (bottom) crystal formation:

Calcium oxalate crystals are minimized at a pH of 7 or higher, while calcium phosphate crystals are minimized at a pH of 6.5 or lower. It would appear that total kidney stone risk would be minimized with a urine pH somewhere in the region of 6.5-7.

The studies on urine pH and UTIs are probably inadequate to determine whether the risk of a UTI bottoms out in this range, because they often make large groupings such as “normal” is 5.5-8 and “average” is 5.5-6.5 and “alkaline” is 6.5-9. (Obviously to a chemist 6.5 is acidic…)

So, it certainly isn’t going to hurt your risk of a UTI to optimize your urine pH against the risk of kidney stones, and perhaps it would help.

Sulfur amino acids (methionine and cysteine) will decrease your urine pH, and they are found in protein, twice as abundant in animal protein than plant protein, and richest in dairy and eggs.

Getting one gram of collagen or 0.33 grams of glycine for every 10 grams of non-collagen animal protein will probably reduce the acidifying effect of the sulfur amino acids.

The potassium content of a food (if you measure raw, you must preserve the cooking juices!) is a very reliable index of the organic acid content. Organic acids that feed into the citric acid cycle (for example, citrate, alpha-ketoglutarate, succinate, fumarate, malate) are alkalinizing.

Glutamine is especially alkalinizing and glutamate is also alkalinizing. The glutamine content of animal proteins is low in eggs (4.65%), organ meats (5.51% in a blend of “chicken byproducts”), beef loin (6.61%) and chicken breast (6.11%); it is intermediate in dairy proteins (9.4% in cow milk, 9.1% in whey protein, 11.3% in casein); and it is high in the leg meat of chicken and pork (22.5% in chicken gastrocnemius and 21.12% in pig gastrocnemius). The gastrocnemius is part of the drumstick in chicken and the hindshank in pigs.

As a starting default, it is best to limit sulfur amino acids to 3 grams per day, get 5 grams or more of food potassium per day, get 1 gram of collagen for every 10 grams of non-collagen animal protein, and to get 20-30 grams of the sum of glutamate and glutamine from food per day with a bias toward glutamine.

However, if you wish to optimize your urine pH beyond this you could play with the levers described above. pH should go down with sulfur amino acids, up with collagen, glycine, glutamate, and glutamine, and up with potassium.

You can also use supplements that contain citrate, alpha-ketoglutarate, succinate, fumarate, or malate for their alkalinizing properties.

You can use baking soda too, but it will be less efficient because it will release CO2 gas in the stomach, and it could cause some GI discomfort.

To measure urine pH, use either a pH meter or pH strips that cover the range between 3 and 8, using two types of strips if needed to cover all of that range. I recommend the meter because I find it very useful as a long-term investment, and the strips only make sense if you’re going to use them a few times and never use them again.

Here are some resources I have for further help:

• Missing From the Databases: Glutamine

• Balancing Methionine and Glycine in Foods: The Database

• How to Track Your Vitamin and Mineral Intake

• Nutrient Targets