Do antioxidants improve immune responses in dogs?

Question

The claim "Antioxidants can also be important in improving immune responses in dogs." is being made on this web page. They go on to say

Because antioxidants play a key role in minimizing damage to cells, such as those that make up the immune system, recent research examined the benefits of certain antioxidants on the immune system activity of dogs. The results of these studies confirmed that antioxidants are important in helping dogs maintain a healthy immune system.

Though they don't say exactly what the "recent research" is. Is this just a case of noting that if you have too few nutrients then you will be ill, so eating these nutrients "improves" your health?

Answer 1

The US National Center for Complementary and Alternative Medicine (NCCAM) says that:

Large, long-term studies (randomized, controlled trials) funded primarily by NIH have generally found that antioxidant supplements have no beneficial effects.

It is worth noting that NCCAM is a division of the US National Institutes of Health (NIH) which is generally pretty keen on backing their statements with evidence (or noting the absence of it). As one of the institutes of NIH, NCCAM is charged to

… define, through rigorous scientific investigation, the usefulness and safety of complementary and alternative medicine interventions and their roles in improving health and health care.

which I read as biasing them toward favorable CAM results if supportable.

Since the statements of the NIH are generally about humans, one would expect that there is even less evidence on anti-oxidant benefits in dogs.