Vitamins are organic substances found in food and play an essential role in bone development, normal eye function, blood clotting and metabolism of proteins and amino acids. Vitamins A, D, E and K are fat soluble while B complex and C vitamins are water soluble. Fat and water soluble vitamins are absorbed and stored in the body differently. Water soluble vitamins are absorbed in the small intestine and any excesses are excreted in urine. Fat-soluble vitamins are primarily stored in the liver and excesses also excreted.
A dog’s and cat’s body can also manufacture some vitamins itself e.g. vitamin C, however sometimes the body isn’t able to make enough so vitamins must be consumed in its natural diet to prevent a vitamin deficiency. Also, there are some vitamins a cat can’t synthesise itself so they must be provided as part of its diet. A deficiency can also be result of disease conditions which may deplete an animals vitamin reserves, while medication may prevent the body from synthesising some vitamins, e.g. vitamin K.
Although a vitamin deficiency can occur so can vitamin toxicity, which may happen when more vitamins are consumed than are required or can be excreted by the body. As water soluble vitamins are not stored in the body, it is more likely that a deficiency of these vitamins can occur, while fat soluble vitamins are stored in the body it is these vitamins that may lead to toxicity when over consumed. It is therefore wise for a pet to consume the appropriate balance of vitamins it requires for each stage of its life, e.g. puppy, adult or senior pet.
A vitamin deficiency causes skin lesions, disorders and hair loss, blindness, scurvy, disorders of the nervous system, impaired immune system, susceptibility to infectious disease, stroke, rickets, bone problems, degenerative diseases (cancer, arthritis, heart and kidney disease).
Vitamins are essential to ensure ongoing functioning of the body and help to prevent disease. Pet food contains low vitamin levels as it is made mostly from grains, poor quality ingredients and cooked animal by-products. Billinghurst (1993, p. 84), claims that “many vitamins are destroyed by heat” during the cooking process and “many vitamins are destroyed by the presence of mineral supplements” in pet food. As exposure to heat, light, air and moisture comprises or destroys vitamins, pet food not consumed shortly after manufacture may have comprised levels of vitamins.
Minerals are essential for the growth and maintenance of a healthy body in people and animals and are fundamental as structural components of organs and tissues. They must be maintained within certain limits for optimal growth, health and fertility. Minerals are found in plant and animal food sources.
The right balance of minerals is important to ensure that pets are not adversely affected by an overabundance or low level of minerals which can lead to disease and/or growth and bone formation problems. Minerals are necessary in the correct ratio to ensure they are effectively used by the body.
A mineral deficiency may be caused by not only a lack of them in the diet, but an animals inability to absorb them. Some minerals are chemically altered, destroyed or bond to other minerals during the cooking process rendering them unavailable for absorption or toxic. As pet food is manufactured from a cooking process this leads to a loss of both mineral and vitamin content. Minerals, when heated, “inactivates a number of vitamins, particularly members of the B complex” (Billinghurst, 1993, p. 53).
However, some commercial pet foods may not lack vitamins and minerals, but they may be supplemented in an unnatural form (synthesised) which the body is either unable to or has difficulty utilising. Unnatural minerals are cheaper than natural minerals and may also impair the function of vitamins reducing their health benefits. According to Lazarus (1999, p. 30), “the unnatural forms of minerals are a lot cheaper” hence their use by pet food companies.
Some minerals are provided in excess in pet food, calcium for example being one. Unfortunately zinc, iron, copper and phosphorous chemically combine with excess calcium in the gut and are excreted in the faeces. This leads to a deficiency in these minerals causing a host of health issues and diseases from skin, growth and reproductive problems to anaemia and an impaired immune system.
1. Billinghurst, Dr. Ian, 1993, Give Your Dog a Bone, 22nd Print, Warrigal Publishing, Bathurst, NSW, Australia
2. Hand, M, Thatcher, C, Remillard, R, Roudebush, P, Novotny, B, 2010, Small Animal Clinical Nutrition, 5th Edition, Mark Morris Institute, USA
3. Lazarus, Pat, 1999, Keep Your Dog Health the Natural Way, The Ballantine Publishing Group, New York, USA
4. Mindell, Earl, RPh, PhD, Elizabeth Renaghan, 2007, Dr. Earl Mindell’s Nutrition and Health For Dogs, Basic Health Publications, Inc, California, USA