A few years ago - I remember this from the early 2010s - there was a concern that vegan or otherwise "plant-based" diets for cats would lead to more alkaline (less acidic) urine, which in turn might increase the risk for the formation of certain types of kidney stones.
This possibility was particularly thought to be an issue (theoretically) in male cats, because of their longer urethra compared to females.
However, in the meantime there have been two studies with cats that looked at this issue:
- one by Dodd et al. (2021) from Canada, published in BMC Veterinary Research, including 187 cats fed vegan diets (117 were included in the analysis, see below) ...
- ... one by Knight et al. (2023) from the UK, published in PLoS ONE, including 127 cats fed vegan diets.
These two studies suggest that the problem of urine that is too alkaline and kidney stone formation (which can, in the worst case, be lethal) is relatively uncommon and may be no more common in vegan cats than in their omnivorous counterparts.
From the paper by Dodd et al. (2021):
"[...][...]
[...] it was hypothesized that more cats fed PB diets would be reported to have lower urinary tract disorders as compared to cats fed MB [meat-based] diets.
[...]
[...] the reported prevalence of disorders expected to be higher in cats fed PB diets, such as urinary tract disease [22], did not differ between diet groups in this study. At this time, to the authors’ knowledge, no cases of any adverse health outcome associated with PB diets in cats have been published, though a lack of evidence should not be interpreted as evidence of lack of risk. Nutrient deficiencies and imbalances may take many years to develop clinical signs, particularly in adult animals, and may go undetected.
[...]
[For statistics fans:] Considering the suggested increased risk of urinary tract diseases in cats fed PB diets [22], this health disorder was chosen for sample size estimation. [This means that urinary tract diseases was the main outcome parameter of the study, i.e., the study's statistical results are clearest, statistically speaking, for this outcome.]
[...]
[From their Table 2:]
|
Health disorder |
Total |
MB |
PB |
PB+MB/H |
||||
|
n = 1208 |
% |
n = 667 |
% |
n = 117 |
% |
n = 139 |
% |
|
|
Lower urinary tract disease |
132 |
11 |
74 |
11 |
13 |
11 |
12 |
13 |
Numbers of cats per category may not add up to total due to non-responders and indeterminable diet type. No statistically significant differences were detected
[...]"
From the paper by Knight et al. (2023):
"[...]The ten most common disorders overall (i.e., regardless of diet) within these 988 cats were reportedly: dental/oral (11%), body weight (9%), gastrointestinal (e.g., diarrhoea, vomiting) (6%), skin/coat (5%), hormonal (e.g., diabetes, hyper-/hypothyroidism, Addison’s, Cushing’s) and lower urinary tract (both 4%), kidney, heart, eyes and mobility (all 3%) (Table 9, Fig 12).
[...]
[From their Table 9:]
Table 9. The 10 most common disorders or affected bodily systems among 988 cats fed meat-based or vegan diets, based on reported assessments of veterinarians.
|
Meat [n = 1241] |
Vegan [n = 127] |
Overall [n = 1368] |
|
Lower urinary tract (3%) |
Lower urinary tract (4%) |
Lower urinary tract (4%) |
