Alkaline urine and crystals on a plant-based dog food diet

There is a concern amongst plant-based feeders that their dogs may develop bladder stones or crystals (typically struvite) when on a plant-based diet as plants in the diet are alkalinising. The normal range for a dog’s urine is pH 5–7.

A pH > 7 indicates alkalinity and < 5 indicates an acidic diet. A diet that is too acidic (high meat diets) predispose dogs to calcium oxalate urinary bladder stone formation.

During my many years as a vet, I have had a few cases of bladder stones in dogs and none of those were fed a plant-based diet, so dogs do get bladder stones – it does not depend on the diet in most cases. Certain breeds are also particularly predisposed such as Dalmatians, Miniature Poodles, Cocker Spaniels, Schnauzers, Bichon Frise, Shih-tzu’s, and the little dog I remember surgically removing a handful of stones from her tiny bladder was a Norfolk Terrier.

Bladder stones are more common in female dogs, perhaps because they’re more likely to have urinary tract infections with a wider genital tract so bacteria can enter more easily. Struvite crystals can build up with a urinary tract infection as the bacteria make the pH alkaline and this can result in stones with recurrent infections over time.

To prevent bladder stone formation, especially in animals predisposed by breed or if they have had prior urinary infections or stones, try these –

1) Increase water intake – even consider adding water to food or homecooking to result in wetter food.

2) If you are homecooking, add our JUST BE KIND supplement to the nutrient-rich ‘icing’ that we recommend in our recipes. When choosing vegetables, these are acidifying – asparagus, peas, brown rice, oats, lentils, corn, brussel sprouts and yeast. Our supplement contains the amino acid methionine that helps to acidify the urinary tract. All the dry premium foods we recommend such as Solo-Vegetal, Hownd, Greta and Green Crunch, contain the addition of methionine so you do not need to be concerned about the urine alkalinity if feeding these diets. There is no indication of the addition of methionine in Benevo dog food so it would be better to check your dog’s urine if feeding Benevo as the main food.

3) If feeding Benevo, buy urine pH strips and test your dog’s urine. Collect the urine in a foil tray Check the urinary pH weekly for the first 3 months, then at least monthly thereafter. You can purchase urine test strips online. Normal dogs typically have a urine pH between 6 – 7 but this can vary. Note that the urine pH also varies throughout the day so do not be alarmed if it keeps changing in a day (if you are collecting over the course of a day:)

3) If the urine pH is consistently alkaline (2 or 3 consecutive readings over 7), see your vet for a full urinalysis and recommendations to add a supplement to acidify the urine.

For further information, this section is taken from the article – Vegetarian versus Meat-Based Diets for Companion Animals by Andrew Knight

Urinary Alkalinisation

For animals on vegetarian diets, one additional factor warrants consideration. The excretion of the nitrogenous waste products of protein catabolism results in the acidic urine of carnivores. Plants are relatively deficient in acidifying amino acids, and due to the higher pH of plant-based protein, vegan and vegetarian diets can result in more alkaline urine. The pH (acidity) alterations predispose to the crystallisation of certain urinary salts, resulting in the formation of stones in the urinary system (urolithiasis), which may result in feline urological syndrome or canine equivalents: partial or complete urinary obstruction (which may be life threatening), dysuria (difficulty in urinating) and haematuria (blood in the urine) [78].

Struvite crystals (magnesium ammonium phosphate) are more likely to form in alkaline urine, and are of particular concern [50,84]. Although due to their narrow urethral diameters, male cats are most at risk, similar problems may occur in dogs, and in females of either species. Alterations in bacterial flora, with increases the possibility of urinary infections, may also result.

Accordingly, special attention to urinary pH is warranted for animals (and particularly, male cats) maintained on vegetarian diets. Regular monitoring of the urine acidity of both sexes of cats and dogs is essential, at least weekly during any dietary transition, illness or instability, and monthly after stabilization. Urine can be collected from dogs using containers such as foil baking trays, and from cats using non-absorbent plastic cat litter available from veterinarians. pH test strips are also available from veterinarians, although electric pH metres provide the most accurate results.

The normal pH of a cat’s urine is 5.5–7, and the normal range for a dog’s urine is pH 5–7 [85]. A pH > 7 indicates alkalinity. A variety of dietary products (e.g., “Vegeyeast” from Harbingers of a New Age—see [26]) and additives can correct alkalinization, should it occur. Asparagus, peas, brown rice, oats, lentils, corn, brussel sprouts and yeast may be included in feline and canine diets, and are all urinary acidifiers [27]. Vitamin C (ascorbic acid) is also a urinary acidifier.

The British Small Animal Veterinary Association (BSAVA) Small Animal Formulary [86] recommends a dosage of 50–80 mg/kg every 24 h for cats and dogs. And for more serious cases, the amino acids methionine and cysteine may be used [13]. The BSAVA Small Animal Formulary [86] recommends a dosage of 200 mg/cat every 8 h. More detailed advice about urinary alkalinisation and corrective strategies is available via www.vegepets.info, or within veterinary medical texts.

Increased urinary acidity, decreased urinary magnesium and increased water consumption all help to keep the urinary pH within a healthy acidic range, and help to prevent the formation of struvite crystals. However, acidifying nutrients, agents, or products should be used carefully, as excessive levels can lead to metabolic acidosis. Increased urinary acidity may also promote higher urinary excretion of calcium and lower excretion of magnesium, and magnesium is a natural inhibitor to the formation of urinary stones associated with calcium [87].