Vitamins are classified into two categories: fat-soluble and water-soluble. Vitamins A,D,E and K, are fat-soluble and are stored in the body. Excessive supplementation of fat-soluble vitamins can be toxic to a cat. Water-soluble vitamins include the B-complex vitamins and vitamin C. They are not stored in any appreciable amount in the body and those not metabolized must be excreted in the urine. Consequently, they must be replaced daily.
Fat-Soluble Vitamins
Vitamin A (retinol) helps maintain vision and also helps to protect against infection. In proper amounts, it is essential for healthy skin and haircoat and normal bone development.
Cats lack the enzyme to convert carotene (the compound found in plants that is the precursor to vitamin A) to retinol. They are completely dependent on dietary sources of vitamin A. Feeding a high quality, nutritionally complete and balanced cat food such as Purina Cat Chow brand cat food ensures a sufficient level of this vitamin.
Vitamin A deficiency is sometimes seen in growing animals. Adults seldom develop signs of a deficiency because they use stored vitamin A slowly. Nutrition studies show that vitamin A deficiency results in night blindness and other vision problems, rough haircoat, muscle weakness and retarded growth.
Vitamin A toxicity occurs either when too much is taken over a long period of time or when there is a sudden abundance in the diet. Toxicity signs include protrusion of the eyeballs, lameness, pain and skeletal immobility.
Vitamin D regulates calcium absorption and is necessary for calcium and phosphorus metabolism. It promotes normal bone calcification and is necessary for bone and joint formation.
Vitamin D requirements of a cat are influenced by the dietary levels and ratio of calcium and phosphorus. Feeding a high quality, nutritionally complete and balanced cat food assures both the proper levels and ratio.
Excessive vitamin D can result in rickets, depressed growth and calcification of soft tissue including the heart muscle, stomach wall, lung and blood vessels.
Vitamin E, also known as a tocopherol, is a biological antioxidant which helps prevent rancidity in fats and is important for normal reproduction.
In a cat, a deficiency of vitamin E can result in steatitis, the deposit of a yellow-pigmented substances in the body fat which produces a painful inflammatory response. Affected cats develop sensitivity to being touched, reluctance to move, fever and loss of appetite. Steatis is seldom seen in cats being fed a nutritionally complete and balanced cat food.
Prolonged consumption of excessively high levels of vitamin E can have depressing effect of other fat-soluble vitamins and may cause prolonged blood-clotting time.
Vitamin K promotes blood-clotting. A dietary deficiency of vitamin K has not been described in a cat.
Water-soluble Vitamins
Vitamin B-12 and folic acid are involved in numerous metabolic functions and are essential for the formation of red blood cells and the function of the nervous system. Anemia is the most common sign of a deficiency of either of these vitamins.
Riboflavin (B-2) is required for the functioning of the nervous system, energy utilization, healthy skin and haircoat, and tissue repair. A deficiency can result in weight loss, dermatitis and neurological disorders.
Niacin and pantothenic acid are needed to maintain the integrity of the hair, skin and nervous system and for efficient energy utilization. A niacin deficiency may result in the loss of appetite, dermatitis and alternating diarrhea and constipation. Signs of pantothenic acid deficiency include intestinal disorders, poor growth and haircoat discoloration.
Choline aids nervous system functions, bone development and building cell structure maintenance. Deficiency signs include poor growth and fat deposits in and around the liver.
Thiamine (B-1) is required for nervous system function and efficient energy utilization. Loss of appetite, weight loss, weakness and convulsive seizures are deficiency signs.
Pyridoxine (B-6) is needed for nervous system function. A deficiency can result in anemia, poor growth, degeneration of the nervous system and convulsions.
Biotin is required for healthy skin and hair. Dermatitis and poor haircoat are indications of a deficiency.
Based on current knowledge, no evidence indicates that vitamin C is necessary in the diet of cats. Both cats and dogs are able to make adequate quantities of this vitamin.