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Vitamins are organic compounds used in many metabolic processes. Vitamins can be subdivided into fat-soluble vitamins (A, E, D and K) and water-soluble (C and B complex). Fat-soluble vitamins are stored in fat cells (lipocytes), whereas water-soluble vitamins are not normally stored but used at once and the excess is cleared from the body. This is why an overdose of fat-soluble vitamins presents more risk to the cat than overdosing with water-soluble vitamins. Vitamins are an essential part of a cats diet but are required only in minute
Vitamin A is required for many processes including sight, growth, immune function, fetal development, cellular differentiation and transmembrane protein transfer. Deficiency in this vitamin can cause conjunctivitis, cataracts, retinal degeneration and other eye problems, muscle weakness, reproductive abnormalities and weight loss. So an appropriate supply of vitamin A is very important. However, vitamin A is also one of the the two vitamins (the second one being vitamin D) which is toxic in excess. Cats require 100 IU (IU stands for international units) per kg of body weight per day if the level exceeds 5000 IU/kg. it becomes harmful to the cat's health. The toxic effects are not immediate and the animal has to be fed at this dose for at least a month before toxicity develops. Vitamin A is usually obtained from Beta Carotene - a plant pigment which is then converted by intestinal cells into soluble vitamin A (For example in carrots, which is why carrots really are good for human eyes.). But while this is true for most mammals, it does not apply to cats. Cats lack the enzyme required to convert carotene into vitamin A and therefore need to be fed with the fats of an animal which has already processed the vitamin. Good sources of processed vitamin A are liver and fish liver oil. (Though it may be added as a supplement by your cat food supplier - check the label).
There are two sources from which the cat can obtain vitamin D. One is through food and the other is through the conversion into active form of Vitamin D precursors present in the outer skin layer. Vitamin D precursor require ultraviolet from the sun to convert into active form. It is for this reason that vitamin D is often referred to as "the sunshine vitamin". One of the major functions of vitamin D is to regulate the calcium and phosphorus level in the bloodstream. Because of this vitamin D is integral to bone development and muscle and nerve cell function. Deficiency in vitamin D leads to rickets (a condition in which bones are weakened and become brittle), abnormalities in skeletal development, ataxia (imbalance) lack of appetite and consequently weight loss. Although an excess of vitamin D can cause excess deposits of calcium in the heart muscle and other muscles as well as in the soft tissue, the condition is almost unheard of in cats. Cats require much lower doses of vitamin D than humans and the toxic level is about 0.1mg per kg body weight. Good sources of vitamin D are dairy products (for example cheese) and fish liver oil and of course, sunshine. Obtaining the vitamin D from sunshine is a bit tricky bacause of their thick fur so any vitamin D produced is not absorbed through skin as it is in humans but end up on the cat's fur. But cats are excellent groomers so some of the vitamin D produced will end up in their tummies.
Vitamin E is another of the fat-soluble vitamins and it is found in good quantities in meat such as liver and also in animal fat. Not all functions of vitamin E are well understood but it is clear that it is an antioxidant which protects various hormones from oxidation. It is also involved in the metabolism of fats and cell membrane formation. Vitamin E deficiencies are well known in cats. An inadequate level of vitamin E leads to a syndrome known as the 'Brown Bowel Syndrome' in which the main symptoms are ulceration, hemorrhage and degeneration of bowels. Another syndrome called 'Yellow Fat Disease' predominantly affects cats which are fed a diet of nothing but fish, because there is very little vitamin E in fish. 'Yellow Fat Disease' is manifested by inflamed fatty tissue through inadequate processing of fat. As a result there an excessive accumulation of subcutaneous fat which may be hard, lumpy and painful. Cats require 2-20 IU of vitamin E per day.
Vitamin K is a blood-clotting agent so a Vitamin K deficiency will lead to excessive bleeding. Vitamin K comes in three forms: vitamin K1 is present in green plants, vitamin K2 is found in high levels in fish and is synthesized by bacteria in the gut and vitamin K3 is a synthetic precursor. Because vitamin K is synthesized in sufficient quantities in the gut there is no daily recommended requirement. This also means that a deficiency in vitamin K is unlikely unless your cat has ingested rat poison. Rat poisons remove clotting agents from the rat's blood causing the rats to die from internal hemorrhage. Unfortunately the same happens to cats, so if you suspect that your cat has eaten rat poison, induce vomiting at once and call your vet immediately. The vet will administer Vitamin K1, which when done early enough will generally save the cat's life.
Unlike humans cats can synthesize vitamin C in sufficient quantities within their own bodies, and therefore it is not needed in the diet. The only time you could consider giving your cat an additional vitamin C is if it is feeding kittens. Vitamin C is not toxic in excess.
Vitamin B complex comprises an number of vitamins among which the most relevant in a cat's diet are: B1 (thiamin), niacin, B2 (riboflavin), B5 (pantothenic acid), B6 (pyridoxine), folic acid, B12, and biotin. Most of these vitamins can be found in meat and meat byproducts. There are however some dietary risks associated with deficiencies of one or more of these vitamins.
Vitamin B1 converts glucose to energy. It is therefore important for muscle and nerve cell function. A deficiency can arise in cats which are fed large amount of raw fish which contains an enzyme called thiaminase which destroys thiamin. Cooked fish does not present any problems, because the cooking process destroys the thiaminase.
Vitamin B1 deficiency in is manifested by loss of appetite, weakness, poor reflexes and loss of nerve control. Deficiency in niacin may cause a syndrome called 'Black tongue'. This is an ulceration of the inside of the mouth which prevents the cat from eating properly. The deficiency normally arises when the diet has insufficient meat.
Vitamin B5 is found in raw food (both meat and vegetables) but large amounts of vitamin B5 are destroyed during cooking. B5 is important in converting carbohydrates and proteins into energy and a deficiency may lead to loss of hair, diarrhea, and gastric upsets. Another essential vitamin from the B complex is vitamin B6. Although present in most food it, like vitamin B5, is destroyed by cooking. Deficiencies in vitamin B6 lead to anemia, poor growth, kidney stones, tooth cavities, skin lesions, and in advanced cases, death.
Both folic acid and B12 are necessary for bone marrow production of red blood cells and deficiency of one or both of them leads to anemia. Biotin is important for maintaining healthy skin and hair. The biotin blocker avidin is present in egg whites but it is disactivated during cooking. It is therefore not advisable to feed cats with raw eggs.
The information supplied here is intended as a guideline only.
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