Did you know the concept of vitamins is relatively new? They weren't a part of nutritional studies until the early 1900s, after Polish scientist Kazimierz Funk coined the term "vital amines."
Quickly, scientists across the world started discovering their effects. Several studies showed that diets composed of purified ingredients couldn't support life alone, and scientists sought to find out why. As we now know, these diets were missing vitamins. Once that was discovered, vitamins became the subject of global study, revolutionizing our approach to both human and pet nutrition.
Compared to the other groups of nutrients, vitamins are required in the smallest amounts. And unlike minerals, vitamins are complex substances. Vitamins are classified as either fat-soluble (Vitamins A, D, E, K) or water-soluble (B-Vitamins and Vitamin C). Fat-soluble vitamins depend on the presence of dietary fat and normal fat absorption for their uptake and utilization in the body.
Like so many of the other nutrients discussed thus far, vitamins work in concert with other vitamins and nutrients to nourish the animal. This makes it important to provide balanced amounts of vitamins and other nutrients in complete diets. Adding supplements to diets, which are already complete and balanced, may create imbalances with detrimental effects.
Vitamin A has been the subject of much research in the fields of animal nutrition and veterinary medicine. Vitamin A has a number of functions necessary for the health and well-being of pets including a role in normal vision, growth, immune system function and reproduction. In addition, Vitamin A and its precursor, beta-carotene, have antioxidant functions. The plant source of Vitamin A is beta-carotene, which animals must convert to the actual vitamin before it becomes active and functions as Vitamin A.
Although Vitamin D (cholecalciferol) is considered a vitamin, it is also considered a hormone and is one of three major hormones involved in the regulation of calcium in the body. Its primary functions are to help in the mineralization of bone and to increase the absorption of calcium and phosphorus from the intestine. Vitamin D can be acquired in the diet, or, in most species, it can be produced in the skin following exposure to ultraviolet radiation from sunlight.
Vitamin E is used to describe a family of chemical compounds called tocopherols, derived from the Greek words meaning child-bearing, which refers to its role in reproduction. It is also known for its action as a biological antioxidant. Tocopherols are found in plant oils, particularly in association with the polyunsaturated oils from seeds such as safflower and wheat germ, or soybean oil. Lack of Vitamin E in the diet could result in damage to the wall or membrane of cells throughout the body. As a nutrient, Vitamin E works in conjunction with other nutrients and compounds (selenium, a micro mineral, and glutathione, an amino acid-derived compound) as an antioxidant to minimize damage to cells from oxidation.
Some tocopherols are more active in the body than others. The alpha form of the vitamin is the most active as a nutrient, and it is the compound added to dog food to meet the animal's dietary requirement. When Vitamin E is used as a preservative, a mixture of several forms of tocopherol are added to help prevent oxidation of the fat in the diet. The form of tocopherol most effective at preventing oxidation of fat in foods has low biological activity in the body and is not considered part of the nutrient content of the diet.
There is no known toxicity due to oral ingestion of even moderately high amounts of Vitamin E in animals. Good quality commercial dog foods contain adequate amounts of this vitamin to meet a dog's dietary needs.
Vitamin K was the last of the four fat-soluble vitamins to be discovered. The most common forms of Vitamin K in the diet are called menadione and phylloquinone, which come from green, leafy plants and vegetables. The major function of this vitamin is as a clotting agent within the blood.
B Complex Vitamins - What do they do?
B-complex vitamins are those vitamins originally identified as B1, B2, B6, B12 and others which are listed below. These vitamins are required in small amounts in the daily diet and are essential to many functions in the body. Although these nutrients don't provide energy in and of themselves, they are critical in the metabolism of protein, carbohydrate and fat, which results in energy for body processes. Unlike the fat-soluble vitamins, the B Vitamins are not stored to any extent in the body and must be consumed daily.
Water-Soluble B Vitamins include:
- Thiamine (B1)
- Riboflavin (B2)
- Pantothenic acid
- Pyridoxine (B6)
- Vitamin B12
- Folic acid
Vitamin C (Ascorbic Acid) is also a water-soluble vitamin and has a primary metabolic role in the body of all mammals involving the synthesis or production of collagen. While ascorbic acid is essential in the diet of humans, other primates and guinea pigs, dogs have no dietary requirement for this vitamin since they make their own Vitamin C.