Zinc is an important mineral found in every cell in the body and required by more than 300 enzymes in the body. In people, mild zinc deficiency seems to be fairly common. Severe zinc deficiency can cause a major loss of immune function, and mild deficiency might impair immunity slightly.

In people, zinc supplements may have benefits, including directly killing cold viruses in the throat, helping stomach ulcers heal, and relieving symptoms of rheumatoid arthritis. Zinc is sometimes recommended in people for the following conditions as well: macular degeneration, benign prostatic hyperplasia, Alzheimer’s disease, wound healing, inflammatory bowel disease (ulcerative colitis and Crohn’s disease), osteoporosis, diabetes, AIDS, bladder infection, cataracts, and periodontal disease. With the exception of shortterm use for people with colds, these other uses involve longterm use of high dosages of zinc, which can cause toxic effects.

Zinc is necessary for normal growth, formation of the epidermis, metabolism of protein, metabolism of carbohydrates, and normal immune function. Zinc-deficient diets fed to puppies produce fewer T lymphocytes (an important constituent of the immune system) in the lymph nodes, spleen, and thymus gland.

There are two specific, rarely seen zinc-responsive skin disorders in dogs. The first is seen in dogs (usually puppies) fed a zinc-deficient diet (diets high in plant material such as vegetable fiber and soybean meal). Plant materials contain calcium phytate, which binds zinc, interfering with intestinal absorption and leading to a zinc deficiency. The diets most likely to cause zinc deficiency are those generic (least expensive) diets that use the less expensive plant ingredients rather than meat ingredients as protein sources.

The second syndrome is a genetic defect that causes decreased absorption of zinc from the intestines in Siberian Huskies, Malamutes, and Bull Terriers that carry the gene for lethal acrodermatitis.

Clinical signs include a crusting dermatitis, mainly around the eyes, nostrils, and mouth.

Therapeutic Issues
Zinc administration (10 to 15 mg/kg IV weekly for four to six weeks, zinc sulfate at 10 mg/kg daily, or zinc methionine at 4 mg/kg/day) is curative of acrodermatitis. Higher doses may be needed in some pets, and those pets with the genetic form may only respond to the IV administration of zinc (the oral form was found ineffective in some but not all studies). Changing generic diets to better diets (preferably homemade) is also important.

Oral administration of zinc was not found to be effective in treating dogs with atopic dermatitis.

In dogs, oral administration of zinc acetate has been helpful for treating copper hepatotoxicosis. Zinc induces increased concentrations of metallothionein in intestinal cells (preventing copper absorption) and in liver cells (which binds to copper in the damaged liver cells). Zinc acetate is administered at 100 mg per dog twice daily for three to six months; the zinc acetate dosage is reduced to 50 mg twice daily. Treatment may need to continue for the life of the pet. Zinc acetate is best administered without food (give at least one hour before meals) to decrease zinc binding by constituents (such as phytates) in the food.

Zinc is found in high concentrations in the pancreatic islet cells and performs a distinct role in the synthesis, secretion, and storage of insulin. Zinc deficiency has been shown to increase the risk of diabetes while zinc supplementation seems to have positive effects on glucose balance.

Zinc is also a precursor to the antioxidant enzyme superoxide dismutase (SOD), a powerful antioxidant that destroys the highly reactive form of oxygen known as superoxide. In order to maintain adequate levels of SOD, it is critical to consume adequate amounts of selenium and zinc.

Deficiencies of zinc can lead to decreased SOD production, increasing the risk of lipid peroxidation. Diabetics have been found to have elevated levels of peroxidation end-products. Supplementing with 30 mg of zinc daily has been shown to increase plasma concentrations, which may have a positive effect on SOD activity.

Manganese and high intake of copper and iron may impair zinc absorption. Neither calcium nor folic acid appears to significantly affect zinc absorption. Diuretics can cause excessive loss of zinc in the urine.

Sources
Zinc can be taken as a nutritional supplement, in one of many forms. Zinc citrate, zinc acetate, or zinc picolinate may be the best absorbed, although zinc sulfate is less expensive. The most holistic approach is to feed your pet a whole food supplement containing zinc.

Safety Issues
In people, zinc seldom causes any immediate side effects other than occasional stomach upset, usually when it’s taken on an empty stomach. Some forms do have an unpleasant metallic taste. However, long-term use of zinc at dosages of 10 mg or more daily can cause a number of toxic effects, including severe copper deficiency, impaired immunity, heart problems, and anemia.

Use of zinc can interfere with absorption of manganese, soy, Coumadin (warfarin), verapamil, penicillamine, and antibiotics in the tetracycline or quinolone (Cipro, Floxin, enrofloxcin) family.

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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