Friday, January 30, 2009

Irradiation and pet food

Champion Petfoods has pulled out of the Australian market following the recall of all Orijen raw foods sold there. The foods were associated with an outbreak of serious neurologic disease in Australian cats. Some cats have had to be euthanized and a few seem to be improving slightly on antioxidant therapy.

As it turns out, Australia requires that raw pet food be subjected to large doses of radiation to kill parasites, and that level of radiation destroys the Vitamin A. The company researched the industry extensively and found supporting science:

From the Champion Petfoods website:

"1. Research findings of a 2007 study published by the AMERICAN COLLEGE OF VETERINARY PATHOLOGISTS.... determined that the feeding of a gamma-irradiated diet of 35-45 kGy was associated with the development of the same conditions as are reported in cats in Australia.

2. JOURNAL OF THE AMERICAN ASSOCIATION FOR LABORATORY ANIMAL SCIENCES, vol 47, no. 6, 61-66. November 2008 entitled “EFFECTS OF GAMMA IRRADIATION AND PASTEURIZATION ON THE NUTRITIVE COMPOSITION OF COMMERCIALLY AVAILABLE ANIMAL DIETS” finds that “results raise questions regarding the suitability of gamma-irradiated diets for
the long-term exclusive feeding of cats in particular, given that such feeding regimes have been associated with the development of leukoencephalomyelopathy in this species”

So apparently much higher levels of radiation are used on raw pet foods than would be considered for raw meat for human consumption. Still. I'll continue to try and buy organic and local.

Tuesday, January 27, 2009

Antioxidants for well pets?

Supplementation with antioxidants has been a well-loved and popular strategy for people and pets for decades, on the assumption that aging is associated with oxidative stress, and that antioxidants can slow some of these aging changes. As a practitioner who has seen clear turn-arounds in the quality of life of geriatric pets when I first began using antioxidants 18 or 19 years ago, I believe there is a shortage in some patients. I believe that antioxidants are clinically useful in old dogs and cats with inflammatory and degenerative conditions.

However, some naturopaths and veterinarians have recommended more antioxidants in healthy middle aged people and pets, presumably to slow aging changes before they become clinically obvious. I was one of them for a few years. But recent large clinical trials in people have suggested that taking extra antioxidants (mostly vitamins A,E,C and selenium) actually *increase* all cause mortality in people taking them for wellness and disease prevention (Bjelakovic 2007). It would appear that Vitamin C and selenium appear safest but that vitamins A and E are associated with problems. Of course, this paper does not prove a temporal relationship, explore whether different doses pose different risks, discuss the various forms of vitamins that might be involved, or really explore cause-specific mortality .... but still. It's a worry.

Now a study (Moyer 2009) shows that canine red blood cell concentrations of a major intracellular antioxidant (glutathione) are not different between young and old dogs. Similarly, plasma cysteine, an extracellular antioxidant, did not differ between young and old dogs. In well dogs. Granted, these were dogsowned by students and employees at the University of Wisconsin's veterinary school, and the dogs were fed a variety of diets. It might be possible to find a subgroup of dogs, eating particular types of diets, who did show evidence of antioxidant depletion. But the point is that this is a real world situation - most healthy old dogs are not antioxidant depleted. Oh, and many food companies are increasing antioxidant levels in their senior diets, which might not be a good thing.

As it turns out, 19 of the 35 older dogs were being fed diets that are supplemented in vitamin E, and 10 were being fed diets supplemented with Vitamin C. Calculations showed that although there was no real difference in vitamin C concentrations being fed to young and old dogs, the young dogs were recieving significantly more Vitamin E. These levels really don't approach those that we would use therapeutically in a nutraceutical supplement, however.

Now on the other hand, the same group from University of Wisconsin measured red blood cell glutathione, and plasma cysteine and Vitamin C in ill dogs (Viviano, 2008). Clinically ill, client-owned dogs and cats were compared to well dogs and cats. In this study, significantly lower erythrocyte glutathione concentrations were found in ill dogs compared with controls, and glutathione depletion correlated with illness severity as well as mortality. Interestingly, cats had higher ascorbate concentrations when ill compared with controls. So this looks like ill dogs are antioxidant depleted and that low glutathione levels lend a poor prognosis. In cats, the elevation in vitamin C is a strange finding and yet another example of why cats really cannot be treated like dogs or people.

So here's the take home. Don't supplement vitamins A,C,E, or selenium to healthy pets who are eating balanced diets. If you are feeding homemade diets, on the other hand, make sure that the diet has been computer balanced to provide at least the daily requirements of Vitamins A,E and selenium. And if a pet has a chronic inflammatory problem (like arthritis, immune-mediated diseases, cancer, kidney disease...) or undergoes a number of days of hospitalization, supplementation makes sense.


Bjelakovic G, Nikolova D, Gluud LL, Simonetti RG, Gluud C. Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: systematic review and meta-analysis.JAMA. 2007 Feb 28;297(8):842-57.

Moyer KL, Trepanier LA. Erythrocyte glutathione and plasma cysteine concentrations in young vs old dogs. J AM Vet Med Assoc 2009;234:95-99

Viviano KR, Lavergne SN, Goodman L, Vanderwielen B, Grundahl L, Padilla M, Trepanier LA. Glutathione, Cysteine, and Ascorbate Concentrations in Clinically Ill Dogs and Cats. J Vet Intern Med. 2008 Dec 16.

Why do people supplement enzymes to perfectly healthy dogs?

This is a very common recommendation, especially among raw feeders, that I have failed in understanding. Let's back up a minute.

Enzymes are vital to growth and life. Digestive enzymes break down fats, proteins and carbohydrates so that food is transformed into building blocks that can be absorbed by the intestine. Metabolic enzymes are present in every cell to allow the cell to do its work, which is usually producing a functional product of some sort, or maintaining its structure for support of body activities.

Supplementation of metabolic enzymes is not common, and even if it were, not much make it to the cells that the supplementer is theoretically targeting because they would be, to a large degree, digested in the GI tract and not absorbed in whole, functional form. On the other hand, digestive enzymes are active right in the gut where we put them. We use them for animals who have diminished digestive capacity, such as those with exocrine pancreatic deficiency, or in geriatric animals who may have atrophy in some of the cells that produce these enzymes.

Sounds good on the surface of it - help animals digest their food better. But that implies that there is some problem with digestion in healthy animals. Here's the rub - supplementation of pancreatic enzymes actually *inhibits* normal pancreatic enzyme excretion. In fact, we use digestive enzyme supplements in dogs and people with pancreatitis for just this purpose - to suppress the release of pancreatic enzymes which contribute to the pain of pancreatitis after meals.

So not only are paying for expensive enzyme supplements that probably are not necessary, but we are chronically telling a normal pancreas not to do its job.

Here is just a recent clinical study that proves this feedback inhibition in people, and it has been shown in dogs as well.

Walkowiak J, Witmanowski H, Strzykala K, Bychowiec B, Songin T, Borski K, Herzig KH. Inhibition of endogenous pancreatic enzyme secretion by oral pancreatic enzyme treatment. Eur J Clin Invest 2003; 33 (1): 65–69

Nustede R, Schmidt WE, Jager M, Stockmann F, Kohler H, Folsch UR et al. Gastrin-releasing peptide and CCK after intraduodenal inhibition of proteases in dogs. Int J Pancreatol 1994;15:209–14.

So I'd like to hear convincing arguments from those who recommend supplementing healthy animals with digestive enzymes. Why do it and what proof do you have that it's good for them?