Antioxidant Supplements for Your Dog


Antioxidants are powerful natural medicines. They offer support for a wide range of problems in dogs, and reduce inflammation in normal and healthy animals. They are so important that I recommend all my patients be given antioxidant supplements. This article will explore the value of antioxidants, and will also introduce you to several veterinary tests – CRP, TK and vitamin D3 – that help determine your dog’s inflammatory load and the right antioxidants for him.

Antioxidants vs. free radicals

Antioxidants are molecules that reduce oxidation and oxidative cell damage in your dog’s body. Oxidation is a chemical reaction that occurs constantly in the body due to cell damage and death. Basically, as chemicals (oxidants, also called free radicals) are released from damaged cells, they cause damage to healthy cells in the area. (Note that free radicals are formed normally during day-to-day living, and can increase during exercise as well as through exposure to environmental stresses, toxins and chemicals, including vaccines and flea/tick medications.)

Antioxidants produced by cells help damper this damage. Cells produce both free radicals and antioxidants; in normal states, there is a balance between acceptable cell damage and cell protection due to a fine-tuning of the formation of both oxidants and antioxidants. But when oxidative damage overwhelms antioxidant systems, disease can result. Which diseases develop depends on which tissues are most damaged, but holistic doctors believe every disease not caused directly by a toxin or microorganism is caused by oxidation and inflammation. Typical diseases I see in practice that are linked to oxidation and inflammation include cancer, arthritis, allergies, inflammatory bowel and bladder disorders, seizures, and cognitive disorder.

Use antioxidant supplements under veterinary supervision

Well known examples of antioxidants include vitamins E, A and C. Other powerful antioxidants include glutathione, melatonin, coenzyme Q10, peroxidase and catalase. Many herbs also have antioxidant properties (e.g. oregano, rosemary, thyme, sage and peppermint).

  • Having said this, it’s important to know that sometimes an antioxidant supplements like vitamin C can function as a pro-oxidant, which is why it’s important not to simply pick up a supplement off the shelf and use it without veterinary supervision.
  • It’s also important to know that the names of antioxidants, especially vitamins, can be misleading. For example, the “vitamin E” sold as a supplement is often really alpha tocopherol, one of many components of “vitamin E”. Using only alpha tocopherol when vitamin E is more appropriate may not help the pet and could even harm him. Studies showing negative effects from antioxidants such as vitamin A and E often used only one part of the vitamin molecule, rather than the entire intact complex.
  • Finally, dosing is important. In human studies, high doses of antioxidant supplements sometimes showed side effects, interactions with other supplements or medications, or a worsening of the disease. While this hasn’t been researched much in pet medicine, human studies indicate that certain antioxidants work better than others for some diseases. Because we don’t have enough data yet to give us more direction, the best we veterinarians can do is use our knowledge to prescribe what we believe is the most appropriate therapy for the individual animal.

Testing for inflammation/oxidation

One way to help us properly prescribe antioxidant supplements is by testing to determine an animal’s inflammatory load. There is no specific test routinely done to check for excessive levels of oxidation in pets, but we can test for inflammation.

The best, easiest and least expensive test is for CRP, or C-reactive protein. CRP is produced by the liver and increases when there’s inflammation throughout the body. CRP is one of the acute phase reactant proteins that go up in response to inflammation. Basically, when white blood cells called macrophages and T cells are stimulated, they produce cytokine chemicals such as interleukin-6, which stimulates the liver to make more CRP. Various inflammatory conditions such as cancer and heart disease, traumatic injury to tissues, hard and constant exercise, and cell death can increase CRP levels. Infections with bacteria and fungi can also stimulate synthesis. (In people, but not dogs, fat cells stimulate increased levels of CRP; increased body weight is a common cause of low grade inflammation in people, predisposing them to inflammatory disorders.)

CRP rises within two hours of the onset of inflammation, and peaks at 48 hours. Its half-life in people is about 18 hours; in dogs, elevated CRP levels are measured for one or two weeks following the initial insult. Therefore, dogs with increased CRP levels have something internal that’s causing inflammation, and further testing is needed.

Increased levels of CRP indicate the need for further investigation and/or treatment with appropriate antioxidant supplements, or herbal or homeopathic medications. Once the CRP levels are normalized, the animal is maintained on the therapy to keep inflammation in check.

In my practice, about half the normal dogs we test have increased levels of CRP, and virtually all dogs with obvious inflammatory diseases show high levels. When I find an increased CRP level, it indicates excessive inflammation somewhere in the body. If the levels are mildly elevated, I will usually treat these pets with anti-inflammatory doses of herbs or fish oil, or both. Following treatment for increased levels of CRP, pets are maintained on antioxidant supplements and closely monitored for any indication that CRP levels (or TK levels — see sidebar) are increasing, at which time more testing may be needed. Dogs with very high levels of CRP need more immediate evaluation that may include cultures, specialized blood tests for infectious diseases, and radiographs and ultrasound examination to look for tumors and abscesses.

Oxidation and inflammation are common causes of disease in our dogs. Testing for markers of inflammation can help reduce the incidence of these diseases by allowing us to properly prescribe antioxidants. Rather than simply choose whatever “supplement of the week” is recommended at the local health food store, you need to get the right one for your individual dog’s health. Even if he doesn’t suffer from or test positive for inflammation, your veterinarian can recommend a general comprehensive antioxidant to keep him healthy.

Testing for TK and vitamin D3

In addition to testing for CRP levels, I routinely test my patients for two other parameters of health: TK and vitamin D3.

  1. TK (thymidine kinase) is an enzyme that rises with inflammation, most specifically with diseases such as cancers and certain infectious disorders (e.g. rickettsial diseases like Rocky Mountain spotted fever transmitted by ticks).
  2. Low levels of vitamin D are often seen in the general population of dogs, and predispose them to developing both inflammatory diseases (such as cancer) and infectious diseases (kennel cough, dog flu, etc.).

In my own practice, the majority of normal dogs we test have an increased incidence of higher TK, CRP and/or low vitamin D levels (over 90% are low on vitamin D, as dogs do not make this vitamin from sunlight, and diets are too low in it to produce high enough blood levels to be considered “healthy”).

Because there is such a high incidence of positive test results when checking dogs for these inflammatory markers, I recommend all dogs be tested every six months.

Abnormal levels are easy to treat using various herbs; vitamin D supplementation is needed for dogs testing low, and supplementation is administered based on the dog’s weight, health condition, and blood levels.

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