The Pet Longevity Marker Almost Everyone Ignores

working dogs

Story at-a-glance -

  • During exercise, your dog’s body produces free radicals, which are DNA-damaging molecules that cause oxidative stress
  • It’s important to ensure all dogs, and especially canine athletes, are consuming adequate amounts of antioxidants to protect against free radical damage
  • A recent study of hunting dogs concludes that supplementing antioxidants can help them maintain healthy levels of important nutrients throughout hunting season
  • Fresh foods are the best way to provide antioxidants to your dog; it’s also important to ensure your canine companion is getting adequate dietary taurine to protect his heart — especially if he’s an athlete
  • Athletic dogs need a nutrient-dense diet that provides optimum energy in a small quantity of food; the protein source should be excellent-quality and animal-based, and the diet should be relatively high in dietary fat

By Dr. Karen Shaw Becker

You may or may not know that during exercise, your dog's body (and yours) produces free radicals like crazy. It seems counterintuitive, because it doesn't make sense that exercise, which is good for the body, triggers the production of boatloads of DNA-damaging molecules as an end-byproduct.

But since that is indeed what occurs when bodies exercise, it's important to consider what type of diet is best for canine athletes, since they may need to consume more antioxidants than less active dogs to protect against free radical damage. Fortunately, a new study sheds some light on the subject.

Researchers Measured Antioxidant Levels in American Foxhounds During Hunting Season

A team of university scientists and two pet food industry representatives conducted the study, which was published recently in the Journal of Animal Science.1 The dogs involved in the study were American Foxhound hunting dogs.

The researchers visited the dogs' kennel in Alabama during a single hunting season, and provided one group of with a "high-performance commercial diet," and another group with a similar diet supplemented with antioxidants, including vitamins C and E, lutein, zinc and taurine. During the course of the study, dogs from both groups were taken to hunt for two to five hours at a time, two to three times a week.

"We think of it as unstructured endurance exercise," says study author Kelly Swanson, Ph.D., a professor in the department of animal sciences and the division of nutritional sciences at the University of Illinois. "They're not running the entire time. They might stop to sniff or go more slowly to pick up a scent."2

The researchers took blood samples from the dogs to evaluate oxidative stress markers and other blood metabolites before they were put on the diets, and four additional times during the seven-month study.

Antioxidant-Supplemented Dogs Had Less Oxidative Stress and Maintained Adequate Taurine and Vitamin E Levels

The researchers anticipated that the dogs eating the antioxidant-enriched diet would have lower levels of oxidative stress and improved performance compared to the other group. The study results showed the dogs did have improved measures of oxidative stress, but there didn't appear to be a difference in their level of performance compared to the other group.

"It turns out performance wasn't affected by diet," said Swanson, "but the test diet did improve indirect measures of oxidative stress. Therefore, improved performance may be expected with more strenuous exercise when metabolic demands are higher."

The researchers also discovered that over the course of the hunting season, the dogs fed the diet without antioxidant supplementation showed a decline in both taurine, an important nutrient for heart health, and vitamin E. One of the dogs even came close to a "critically low" level of taurine during the study.

Taurine and vitamin E levels for the dogs eating the supplemented diet remained at or above the baseline, which suggests these nutrients are compromised in athletic dogs over months of unstructured exercise. The researchers also believe more active dogs (e.g., sled dogs) may experience even greater nutrient depletion.

"We can conclude that athletic dogs may benefit from supplementation of vitamin E and taurine to minimize oxidation and maintain taurine status," Swanson says.

A Word About Taurine Levels in Dog Food

If you haven't read this important article about taurine and heart disease in dogs, I encourage you to do so. A link has been established between grain-free dog food formulas and taurine deficiency in certain dogs that can lead to dilated cardiomyopathy, a heart muscle disease.

Until we have much more information on the subject, my current recommendation is to supplement all dogs with high-taurine foods, no matter what type of diet they're eating. An easy way to do this is to simply mix a can of sardines into your pet's meal once a week. You can also find the taurine content of many other foods on page two of this study and also in this Raw Feeding Community article.

Fresh Foods Are the Best Source of Antioxidants for Dogs

As I touched on earlier, antioxidants are beneficial molecules that neutralize the toxic free radicals floating around in your pet's body before they can harm healthy cells and tissue, thereby reducing oxidative stress and DNA damage. As such, they play a key role in longevity, and high levels of circulating antioxidants are commonly seen in the "oldest old" among us.

Several studies of older dogs have proved the benefits of an antioxidant-rich diet for the aging canine brain.3,4,5,6 The results of a seven-year study of 90 cats aged 7 to 17 who were fed an antioxidant-rich diet showed fewer decreases in lean muscle mass; improved body weight, lean body mass, skin thickness and red cell quality; decreased incidence of disease; general improvement in quality of life; and significantly longer life span.7

The same is true for dogs. The more free radicals the body makes, the more antioxidants the body requires, and research shows puppies may have antioxidant deficiencies.

Most commercially available pet foods, even high-quality formulas, contain synthetic vitamins and minerals that have not undergone absorption or assimilation studies. Your dog's body is designed to absorb nutrients from fresh, living foods very efficiently. Antioxidants are contained in the vitamins in fresh foods, including:

  • Vitamin A and carotenoids, which are found in liver and bright-colored fruits and veggies like apricots, broccoli, cantaloupe, carrots, peaches, squash, sweet potatoes and tomatoes
  • Vitamin C, found in citrus fruits and strawberries, as well as green peppers, broccoli and green leafy vegetables
  • Vitamin E, found in nuts and seeds
  • Selenium, found in protein sources like nuts, fish, chicken, beef and eggs

Phytochemicals also contain antioxidant properties:

  • Flavonoids/polyphenols are in berries and tea (decaffeinated, for pets)
  • Lycopene is in tomatoes and watermelon
  • Lutein sources are dark green vegetables like spinach, broccoli and kale
  • Lignan is found in seeds

Canine Athletes Also Thrive on Animal Protein-Packed Diets

Dr. Joseph J. Wakshlag of Cornell University College of Veterinary Medicine studies nutrition as it relates to active dogs, in particular, their protein requirements. Most of what is known on the subject focuses exclusively on sprinting dogs like the Greyhound, or endurance sled dogs like the Husky.

According to Wakshlag, there was one study in particular that focused on dietary protein, and its unparalleled ability to preserve musculoskeletal integrity, as well as appropriate total protein, albumin and red blood cell status.8

Hematocrit and serum albumin levels tend to drop while a dog is training and racing, and adequate dietary protein intake can improve the situation. Studies in endurance and sprinting dogs suggest that from 24 to 30 percent of the metabolizable energy (ME) in the dogs' diets should be highly digestible animal protein, for example, lamb, beef and chicken.

According to, "Active, sporting, working — whatever term you use to describe dogs that do a specific job like running, hunting, sniffing or jumping, really means that they are a canine that requires a very specific diet to maintain their rigorous lifestyle."9

A very active, athletic dog needs a nutrient-dense diet that provides optimum energy in a small quantity of food. The protein source should be excellent-quality and animal-based, and the diet should be relatively high in dietary fat, including supplementation with raw organic coconut oil.

The main components of a balanced fresh food diet for a canine athlete with no health problems include raw meaty bones, muscle and organ meats, a few dark green vegetables, appropriate supplementation as needed and a constant supply of fresh, clean water.