From The July 2000 Issue of Nutrition Science News

Pet Supplements with Promise

by Anthony L. Almada

Maybe you've noticed the daunting array of dietary supplements available for pets. If so, you've probably read the brochures and labels that claim the products are "research proven" or "veterinarian tested." How can you tell what's effective and, hence, what you should carry in your store? For starters, here are two popular pet dietary supplements with promising research to back them up.

Antioxidants
Enthusiasm for free radical fighters has spilled over into pet products. Research in old and young dogs indicates that, as found in rats and humans, age influences the biological responsiveness to high and low doses of vitamin E. In one study, 10 old (7.5­11.1 years) and 10 young (0.9­4.4 years) beagles were supplemented with vitamin E amounting to four times more than what is found in commercial dog food. Supplementation produced a 50 percent increase in blood vitamin E in young dogs and 20 percent in the old. A secondary study showed that a diet low in vitamin E (amounting to half what is found in standard food) decreased the immune cell responsiveness of only young dogs. These data suggest younger dogs (at least beagles) have a higher vitamin E requirement.¹

Studies presented at the 1999 Experimental Biology meetings in Washington addressed the issue of biochemical differences among breeds. In one, researchers from the Waltham Centre for Pet Nutrition in Leicester, England, found that total blood plasma antioxidants (TPAO) and superoxide dismutase (SOD) enzyme activity varies among breeds. Beagles, for example, have lower antioxidant activity than Labrador retrievers or Yorkshire terriers.²

Antioxidants are one side of a tenuous biochemical balancing act, the other side being free radicals. Certain metabolic events and environmental exposures can overwhelm the capacity of antioxidant systems and produce oxidative stress. One oxidative stressor first revealed in animal studies is intense physical exercise. A study of 14 mixed-breed dogs also conducted by the Waltham Centre for Pet Nutrition showed a 22 percent increase in lipid peroxidation products after 20 minutes of vigorous exercise.³ Owners of active pets may be able to fight exercise-induced oxidative stress by daily squeezing a capsule of natural vitamin E (400 IU) onto the animal's food.

The dark side of oxidative stress often manifests itself through viral infections.⁴ Cats can contract feline immunodeficiency virus (FIV), a viral infection similar to human immunodeficiency virus (HIV). FIV is characterized by a depletion of lymphocytes through a process called apoptosis, or programmed cell death.

Antioxidants can help. Similar to results found in human lymphocytes infected with HIV, ascorbic acid (vitamin C) and N-acetylcysteine (NAC) separately produced significant declines in FIV replication and cell death within two types of infected feline cells.⁵ The researchers noted an increase in glutathione, another key antioxidant, following incubation with either antioxidant.

This reinforces the findings of in vitro work showing that NAC and vitamin C can favorably influence cellular glutathione content. These data, besides offering promise for FIV-infected cats, suggest vitamin C or NAC may be promising immunomodulators.

Glucosamine
Almost every pet supplement line offers at least one glucosamine-containing product. One proprietary product, a blend of sodium chondroitin sulfate, glucosamine hydrochloride and manganese ascorbate, has been the subject of several canine and equine studies. In a recent unblinded study, 13 healthy beagles were given 1,000 mg glucosamine sulfate and 800 mg chondroitin sulfate as two capsules twice daily for 30 days. Researchers then evaluated cartilage metabolism with blood samples and a bovine cartilage culture system.

Relative to presupplement values, the supplementation produced notable increases in blood amino sugars, which are markers of cartilage and cell metabolism.⁶ The cartilage culture studies, performed by adding blood serum from the dogs before and after supplementation, showed an increase in cartilage component (amino sugars as glycosaminoglycans) and biosynthesis as well as a decrease in the breakdown of cartilage protein. These data suggest the product may benefit dogs with hip dysplasia and other arthritic diseases. Controlled studies on these specific conditions remain to be performed.

Good products require good scientific research. The burgeoning pet supplements market should have the same level of product scrutiny and integrity as we strive for with supplements for humans. This will lead to healthier pets as well as happier owners.

Anthony L. Almada, a nutritional/exercise biochemist, co-founded Experimental and Applied Sciences Inc. (EAS) in Golden, Colo. He now leads Imaginutrition and MetaResponse Sciences in Aptos, Calif.

Photo ©Robert Morrissey/Dot for Dot

References

1. Meydani M, et al. Effect of vitamin E supplementation on plasma E and immune response of young and old beagle dogs. FASEB J 1999;12:A840.

2. Harper EJ, et al. Total plasma antioxidant and superoxide dismutase status in dogs: are normal ranges influenced by breed? FASEB J 1999;13:A565.

3. Obra R, et al. Exercise in healthy adult dogs increases plasma TBARS—an indicator of oxidative stress. FASEB J 1999;13:A565.

4. Israel N, Gougerot-Pocidalo MA. Oxidative stress in human immunodeficiency virus infection. Cell Mol Life Sci 1997;53(11-12):864-70.

5. Morzola E, et al. Inhibition of apoptosis and virus replication in feline immunodeficiency virus-infected cells by N-acetylcysteine and ascorbic acid. J Vet Med Sci 1998;60:1187-93.

6. Lippiello L, et al. Cartilage stimulatory and antiproteolytic activity is present in sera of dogs treated with a chondroprotective agent. Canine Pract 1999;24:18-9.