By Jocelynn Jacobs DVM, CVC

Many activities we do with our dogs can be stressful. Training and showing in conformation, obedience or agility, or participating in field trial events, sled races or herding trials are just a few activities that can add stress to their lives. Of course, we all know our dogs love to participate in these events as much as we do. However, the stress of training, traveling to the events, and actually performing can be intense.

It has been well known for many years that stress can be detrimental to the immune system of both humans and animals. Without a healthy immune system, competitive dogs have a higher risk of contracting various illnesses and potentially becoming noncompetitive. Thus, many breeders and exhibitors are continually looking for ways they can help stimulate or boost their dog’s immune system to combat the effects that stress may have on it. Providing beta-carotene in their diet may be the key to accomplishing that goal.

Nutrition and the Immune System

Since the late 1950’s, there has been on-going research in the area of how nutrition can potentially alter or enhance the immune system of both humans and animals. As expected, there is a direct correlation between poor nutrition or deficiencies of certain nutritional components and an increase risk of infection. There also have been studies conducted demonstrating that the supplementation of certain nutrients beyond accepted requirements may actually enhance certain types of immune responses.(1) One of those nutrients is beta-carotene.

The immune system of the dog is composed of two major defense systems: the first and secondary defense systems. If, for example, there is a virus attempting to infect your dog’s body, the first line of defense involves the first defense system. This system is comprised of physical or protective barriers to stop a virus, germ, or foreign substance from infecting or penetrating the body’s cells. The skin, the lining of the intestinal tract, or various protective mechanisms of the nasal passages and lungs are just a few examples of these protective barriers.(2) In this example, if it was an air-borne virus, then the lining of the nasal cavities and lungs have ways to protect the body by not allowing the virus to attach to and infect the cells of the respiratory system.

Many viruses never get past this first line of defense, and consequently, your dog does not get sick. However, if the virus is successful and does infect cells in the lungs or penetrates the blood stream, the secondary line of defense comes to the rescue. Cells such as phagocytes, for example, are part of this secondary defense team. Phagocytes are normal cells found in the body that eat infected or dying cells. Also, there are B and T cells that produce antibodies (IgG and IgM, for example) or secrete materials (such as interferon) that are harmful to viruses or bacteria.(2)

A dog’s ability to stay healthy and live normal lives each day is very dependent on a strong, well-functioning immune system. Beta-carotene is an important part of keeping that immune system strong. It has been shown over the years of research that beta-carotene is extremely beneficial for both first and second lines of defenses of the immune system.

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Beta-Carotene: What is it?

Beta-carotene falls within the vitamin category, and more specifically is part of the family of carotenoids. Carotenoids are the dark red pigments that provide the orange or deep yellow color to many plants and vegetables such as carrots or corn. Even green vegetables contain carotenoids, but their color is masked by the deep green color of chlorophyll.(3) It is one of the most important and plentiful carotenoids. However, beta-carotene is not produced by the dog’s body, so therefore, it must be ingested either through eating plant material, or by ingesting a supplement or diet than has beta-carotene in it.

Until recently, there was little understood on how important beta-carotene was on the immune system in dogs. In fact, it wasn’t even known if beta-carotene was absorbed well by the intestinal tract of dogs. However, it has been shown that dogs that have supplemented beta-carotene in their diets have significant levels of beta-carotene absorbed and utilized by the body. And, dogs that were provided with beta-carotene in their food or as a supplement over many days had better absorption than those dogs supplemented only once.(1)

Beta-Carotene: Building Block for a Strong Immune System

Beta-carotene can be an extremely important building block for the immune system. Both the first and secondary lines of defenses can be improved by providing beta-carotene to our dog’s diet.

The first line of defense is positively affected by beta-carotene through the production of Vitamin A. Dogs that ingest beta-carotene have an enzyme in their intestine that metabolizes beta-carotene into an active form of vitamin A. Thus, beta-carotene can be called a “precursor” to vitamin A. Vitamin A is extremely important for the formation and maintenance of healthy skin and membranes that line the respiratory or intestinal tracts of the dog.(3) Remember, the skin and lining of the respiratory or intestinal tract are important for the first line of defense of the immune system. Thus, without the benefits of beta-carotene, the immune system may be compromised.

As a boost for the secondary lines of defense of the immune system, beta-carotene also has been proven to significantly increase B and T cell functions and abilities. As one example, dogs that were fed certain levels of beta-carotene had significantly higher levels of antibodies produced compared with the control dogs with no beta-carotene in their food.(1) There are many other secondary immune responses that were very beneficial to the dogs with beta-carotene added to their diet as well.

We all know there are many situations in which our dogs may encounter stressful situations. If we, as owners, can improve the immune system of our dogs while under stress, our dogs will benefit greatly. Beta carotene recently has been shown to be very important for well-functioning first and secondary lines of defense of the immune system. It may be one of the “keys” to helping our dogs stay healthy and competitive longer.


  1. Recent Advances in Canine and Feline Nutrition – 1998 Iams Nutrition Symposium
    Proceedings. Gregory Reinhard and Daniel Carey, 1998.
  2. Immunology . Ivan Roitt, Johnathon Brostoff, David Male. Gower Medical
    Publishing, Ltd., 1985.
  3. Canine and Feline Nutrition . Linda Case, Daniel Carey, and Diane Hirakawa.
    Mosby-Year Book, Inc, 1995.