Last week, we talked about how much water cats need and where that water come from. Today let’s take a look at whether or not cats have a “low thirst drive,” a statement that is bandied about with some frequency particularly when the “bandier” is speaking in opposition to dry cat foods.
I haven’t been able to find any scientific evidence behind the claim that cats have a low thirst drive. I assume what is meant by the phrase is that cats will wait to drink until they are in greater need of water than will some other species and that this is harmful to them. In the absence of supportive research, I’m not sure I buy into that hypothesis.
If cats “wait” to drink, they do so because they are biologically built to behave in that manner. Domestic cats evolved from desert-dwelling ancestors. A low thirst drive doesn’t make a lot of sense given this natural history. If an animal suited to living in the desert needs water and water is available, I suspect they are hard wired to drink to take advantage of the situation. In the wild, cats do get a large amount of their water from eating prey, but not all of it.
I wonder whether this controversy (such as it is) is in some ways similar to the now debunked myth that we should all be drinking eight, eight-ounce glasses of water a day. As a review of available research showed:
No scientific studies were found in support of 8 x 8. Rather, surveys of food and fluid intake on thousands of adults of both genders, analyses of which have been published in peer-reviewed journals, strongly suggest that such large amounts are not needed because the surveyed persons were presumably healthy and certainly not overtly ill. This conclusion is supported by published studies showing that caffeinated drinks (and, to a lesser extent, mild alcoholic beverages like beer in moderation) may indeed be counted toward the daily total, as well as by the large body of published experiments that attest to the precision and effectiveness of the osmoregulatory system for maintaining water balance. It is to be emphasized that the conclusion is limited to healthy adults in a temperate climate leading a largely sedentary existence, precisely the population and conditions that the "at least" in 8 x 8 refers to.
A talk given by Nick Cave, BVSc, MVSc, PhD, DACVN of Massey University at the 2013 World Small Animal Veterinary Association World Congress suggests that just like us, healthy cats are perfectly capable of determining when they need to drink. In his work, he has found that when cats eat a diet containing “between 65% and 5% moisture, cats adequately adjust voluntary intake [of water] such that the total water intake remains constant.”
Evidence does show that cats with diseases like renal failure and obesity benefit from supplemental water in their diet. But as long as a cat is healthy, you can feed an appropriate amount of food (canned, dry, or ideally a bit of both), keep the water bowl clean and full, and trust the cat to figure out the rest.
Dr. Jennifer Coates
Valtin H."Drink at least eight glasses of water a day." Really? Is there scientific evidence for "8 x 8"? Am J Physiol Regul Integr Comp Physiol. 2002 Nov;283(5):R993-1004. Review.
Cave N. Water — The Forgotten Nutrient. World Small Animal Veterinary Association World Congress Proceedings, 2013.