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This month we begin a two-part discussion on orthomolecular medicine (often called “megavitamin therapy”). Orthomolecular medicine seeks to use increased levels of vitamins and minerals (mainly antioxidants) to help treat a variety of medical disorders. While daily amounts of vitamins and minerals have been recommended as an attempt to prevent nutritional deficiencies, orthomolecular medicine uses higher doses as part of the therapy for disease.

The pet food industry relies on recommendations by the National Research Council (NRC) to prevent diseases caused by nutrient deficiencies in the “average” pet; yet, the NRC has not attempted to determine the optimum amount of nutrients or their effects in treating medical disorders. While a minimum amount of nutrients may be satisfactory in preventing diseases caused by nutrient deficiencies, it is important to realize that there is no “average” pet, and every pet has unique nutritional needs.

It is unlikely that our current recommendations are adequate to maintain health in every pet. Each pet has unique requirements for nutrients. Additionally, these needs will vary depending upon the pet’s health. For example in times of stress or disease additional nutrients above and beyond those needed for health will be required. Orthomolecular medicine evaluates the needs of the pet and uses increased nutrients to fight disease.


The principles of orthomolecular medicine, summarized below, are adapted from “Orthomolecular Medicine: A Practitioner’s Perspective,” in Complementary and Alternative Veterinary Medicine: Principles and Practice, Mosby, 1998.

  • Nutrition forms the basis of medical diagnosis and treatment.
  • Universal recommended daily amounts of vitamins and inerals are inadequate due to individual needs among pets.
  • Drug therapy is used when needed and always with consideration or potential side effects.
  • Most foods (even those organically raised, although usually less so) are polluted due to environmental contamination that is unavoidable in our society. We use nutrition to replace those nutrients lacking in the pet’s diet due to pollutions and leeching of nutrients from the soil.

Therapeutic Uses

Orthomolecular medicine has shown promise in treating a variety of medical disorders. These disorders and the recommended therapies are described below.

  • Feline Leukemia is caused by a retrovirus transmitted by the saliva. There is no cure; conventional therapy seeks to reduce secondary infections and offer support with fluid therapy or force-feeding as needed.
Orthomolecular therapy of feline leukemia utilizes 750mg of sodium ascorbate, 750 IU of vitamin A, and 75 IU of vitamin E. A number of cats on this protocol tested negative for leukemia virus within two years of initial diagnosis on both ELISA and IFA tests. Also, many cats displaying signs of chronic illness became devoid of symptoms. Since false negative test results are possible, all cats that tested negative on blood ELISA testing treated with orthomolecular therapy should have follow-up IFA testing done.
  • Allergic (Atopic) Dermatitis is a common cause of itching in dogs and cats. This genetic disease is most commonly treated conventionally with corticosteroids and antihistamines.

The orthomolecular approach uses a hypoallergenic, healthful diet as the starting point. This diet should be free of chemicals, impurities, and by-products. A blood profile is done to rule out endocrine diseases such as Cushing’s disease and hypothyroidism, as antioxidants may create changes in blood values that are normally used to screen for these common disorders. Treatment uses vitamin A (10,000 IU for small dogs and cats, and up to 30,000 IU for large dogs), crystalline ascorbic acid (750 mg for small dogs and cats, and up to 3,000 mg for large dogs), and vitamin E (800 IU for small dogs and cats, and up to 2,400 IU for large dogs). The antioxidant mineral selenium (20 mcg for small dogs and cats, and up to 60 mcg for large dogs) is also added to the regimen. Once the animal is asymptomatic, a maintenance protocol using lower dosages of vitamins A and E and the mineral selenium are prescribe to reduce the chance of toxicity.

Next month we will discuss more therapeutic uses of orthomolecular medicine for diseases.

Owners should not diagnose and treat their pets without veterinary supervision. Many medical disorders present similar symptoms. Also, megavitamin therapy can be toxic if not used properly.

Shawn Messonnier, DVM

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Shawn Messonnier DVM Past Supporting Member, Oncology Association of Naturopathic Physicians Author, the award-winning The Natural Health Bible for Dogs & Cats, The Natural Vet’s Guide to Preventing and Treating Cancer in Dogs, and Breast Choices for the Best Chances: Your Breasts, Your Life, and How YOU Can Win The Battle!

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