Safe amount of vitamin A?

OK, so this is purely to win an argument :tongue2:. Some guy on my dog forum said he gives his dog 100,000 IU of vitamin A daily, I said that isn't safe, as the tolerable upper limit for humans is 10,000 IU daily and dogs are smaller than humans. He said that dogs, as carnivores, have a much higher tolerance for vitamin A and there has never been a reported case of vitamin A toxicity in dogs. So I figured, if that's true of dogs, it should be true of cats, too, since they're even more carnivorous than dogs.

So, what's the research? Is there any proven upper tolerance limit of vitamin A for cats? Any reported cases of toxicity? I know that in one thread it was determined that you would need to feed "a lot!" of freeze-dried liver before it became an unsafe amount, but other than that I don't remember any discussion on vitamin A toxicity.

Hmmm. I'm going to let the master researcher (Laurie) tackle this one

Here you go: http://www.vetinfo.com/vitamin-a-toxicity-in-dogs.html

The American Association of Feed Control Officials (AAFCO) regulates the vitamin levels in all pet food. The group has determined that the recommended minimum daily dose of vitamin A for dogs is 2,272 International Units (IU) per pound of food or 50 IU per pound of body weight.

The toxic dose of vitamin A for dogs has been set at between 2,500 and 113,600 IU per pound of food, but only if this elevated level of vitamin A is fed to a dog daily for months or even years.

Click to expand...

Now, this doesn't exactly jive with what I'm looking at in the NRC. In Table 15-5 (p. 360), "Nutrient requirement of adult dogs for maintenance," shows in the table a "safe upper limit" of 64,000iu per kg of food (on a DM basis).

That works out to 29,088 iu per pound of food, or 1,818 iu per ounce of food.

FYI, in the cat, according to the table for adult cats (Table 15-12, P. 366) , the safe upper limit is 100,000 iu per kg of food (DM basis). That works out to 2,841 iu per ounce of food.

Now - the "safe upper limit" is not the same as the "maximum." For cats ( http://maxshouse.com/nutrition/aafco_cat_food_nutrient_profiles.htm ) the maximum amount (DM basis) is 750,000 iu per kg. That works out to 340,875 iu per pound of food or 21,305 iu per ounce of food.

For dogs, the maximum is 200,000 iu per kg of food (DM basis). http://www.merckvetmanual.com/mvm/htm/bc/tmgn46.htm That works out to 90,900 iu per pound of food, or 5,681 iu per oz of food.

So you need to know the weight of his dog (based on the 50 iu per pound of body weight, which is only the minimum) - though to compare to the info we have for maximum (or safe upper limit), you'd need to know how much food he's feeding a day, convert to DM, etc. The maximum for his dog would be 100,000 iu if his dog eats a little over a pound of food a day: the "safe upper limit" is well exceeded unless his dog eats a couple of pounds of food.

...and to give a feel for safe upper limits vs maximums, raw chicken liver has 3,168 iu per oz.

The NRC says (P. 197), "Dietary carotenoids are assumed to have a low toxicity for dogs."

P. 200 (in relation to cats) states "Naturally occurring cases of hypervitaminosis A have occurred almost exclusively as a consequence of feeding a diet largely or totally of liver to growing kittens."

I have had 2 dogs with Vitamin A toxicity. One I am treating right now. She is 60 lbs and was getting 10000-14000 IU every 12 hours for 2 months. All her symptoms indicate Vitamin A toxicity. Yes they can get it and should only get the amount for a child of the same body weight.  

Children (under 18 years old)

Recommended dietary allowances (RDAs) have been established by the U.S. Institute of Medicine of the National Academy of Sciences. The recommendations are as follows: for children 1-3 years old, 300 micrograms (1,000 IU) daily; for children 4-8 years old, 400 micrograms (1,300 IU) daily; and for children 9-13 years old, 600 micrograms (2,000 IU) daily. For pregnant women 14-18 years old, 750 micrograms (2,500 IU) daily is recommended. For lactating women 14-18 years old, 1,200 micrograms (4,000 IU) daily is recommended.

I'm so sorry your dogs have vitamin A toxicity.

But the AAFCO minimum recommended amount of vitamin A for a 60 pound dog, based on animal body weight, exceeds the recommended dose for children. :dk: It would work out to 3,000iu daily for a 60 pound dog - as a minimum. I don't know how much food your dogs eat daily, but the amount you were feeding them is close to the "safe upper limit" as listed by the NRC (if they eat a pound of food a day).

Were you supplementing that much on top of feeding a usual diet containing vitamin A? :dk:

From what I've found since I made this post is that you'd pretty much have to feed a cat or dog only liver for quite a long time to overdose him on vitamin A in his diet. Supplementing on top of feeding a normal diet, it would be easier to overdose.