A reader asked me about this, as they heard some are recommending supplementation of vitamin C for cats, so I dug up some info.
It turns out, according to some studies, given the biology of the cat, this is not only questionable, it may be harmful.
On the other hand, some veterinarians are suggesting vitamin C therapy as a treatment for certain diseases, including FIV and FeLV.
People have a hard time being objective sometimes, and have a tendency to apply their own views to everything. This is often true when it comes to animals.
Vitamin C is said to be good for people, so why not cats as well?
The truth is, though, that while cats are mammals and similar to humans in many ways, cats and humans do have their differences.
One of those differences is in the way certain vitamins and nutrients are metabolized. For humans, supplementation may work, but vitamin C in felines is a different story.
House cats synthesize their own vitamin C from glucose, so they don't normally need supplementation of this vitamin.
This makes sense, since the natural diet of a cat would not include vitamin C intake, or at least not in large quantities. You don't see too many cats craving oranges, for example.
According to the Cornell Book of Cats, unless there is a "high metabolic need or inadequate synthesis," then supplements of vitamin C are not necessary. In fact, a number of studies show that it may actually be harmful.
First, it can contribute to the formation of stones in the urinary tract. Second, it may enhance the absorption of iron, effectively resulting in an overdose of iron.
In addition, there has been more than one study that has failed to show that vitamin C supplementation has any effect on healing viruses or bacterial infections in cats.
As a nutritional supplement for cats, then, vitamin C is probably a bad idea.
There are, however, other nutritional supplements that your cat might benefit from.
And, there are some veterinarians who are using these supplements, including vitamin C to treat pets for certain conditions.
You may have heard, as I have, that intravenous vitamin C treatment has worked for FeLV cats with cancer, at least to reduce symptoms in some cases.
Some integrative veterinarians have claimed that other vitamin supplements have worked well to either improve overall health and well-being, or reduce symptoms of illness in felines.
Most organizations that focus on cat health issues, however, state that little if any scientific evidence exists to support this.
If your cat has a serious illness, you should check with your veterinarian before adding any supplementation. You can likely find veterinarians in your area who use a holistic or integrative approach to veterinary medicine. These vets are more likely to embrace supplementation and alternative treatments.
The best way to prevent major cat illnesses of course, is to limit exposure (keep uninfected cats indoors and keep infected animals quarantined), and to administer vaccines on the proper schedule.
Here's more information with respect to feline leukemia and diet/supplements.