Vitamin A Promotes vision and healthy skin Sources: Liver, eggs, milk, butter, cheese, yogurt, carrots and other yellow vegetables and green leafy vegetables. Read more »

Vitamins are substances needed in small quantities but they are indispensable. They perform specific vital functions and are essential components in any diet. Read more »

Most of the vitamins were discovered from theyears 1900 to 1950. It was found that a fat-soluble factor prevented xerophthalmia (dry eye disease) in rats, and the discoverers called it fat-soluble A factor. This factor is now known as vitamin A or retinol. Soon other fat-soluble factors (the fat-soluble vitamins A, D, E and K) were discovered.

Although the four fat-soluble vitamins (A, D, E and K) differ in function, utilisation, and sources, they also have several similar characteristics. They are soluble in fat and fat solvents; are fairly stable to heat, as in cooking; do not contain nitrogen; are absorbed in the intestine along with fat and lipids in foods; and require bile (greenish brown liquid to help the body to deal with fats) for absorption.

The fat-soluble vitamins A, D, E and K differ from the water-soluble vitamins in several ways. The fat-soluble vitamins are found in the fats and oils of food. They are insoluble in water, so they require bile for absorption.

The fat-soluble vitamins are stored in the liver and adipose tissue (fatty tissue) until they are needed. They are not readily excreted from the body as most of the water-soluble vitamins are. Vitamins A and D are stored in large amounts for long periods of time and need not be consumed everyday. A
person only needs to ensure that their average daily intake should be close to the recommended amount. Because the fat-soluble vitamins can
be stored in the body, the risk of toxicity in case of fat-soluble vitamins is greater than it is for the water-soluble vitamins.

The best way to obtain vitamins is to eat a balanced diet that includes a variety of foods such as cereals, pulses, non-vegetarian foods, vegetables, fruits, sugars and fat, that provide an adequate supply of all the vitamins. A Recommended Dietary Allowance (RDA) has been established for most vitamins. The complete summary of dietary allowances for various nutrients as recommended by Indian Council Medical Research, ICMR.

Almost all foods consumed by man are cooked, with the exception of fruits and some vegetables which are used for salads and chutneys. Cooking has both adverse and beneficial effects. The loss of nutrients during cooking depends on the temperature of cooking, duration of cooking and the nutrients present. Precooking practices such as cutting and washing also influence loss ofnutrients.

For example, cutting vegetables into small pieces and exposing them to air before cooking may result in loss of vitamins, particularly vitamin C. Washing and boiling of rice in excess water which is later discarded, also results in loss of vitamins and minerals. Vitamins of the water-soluble group are particularly susceptible to losses during cooking. With some precautions, however, the losses can be minimised. On the other hand, cooking is beneficial as it destroys harmful food-borne microorganisms. Some culinary practices such as fermentation in fact improve the nutritive value of foods.

Some health conscious people take vitamin supplements daily, in the form of tablets. These supplements contain one or more vitamins in the range of their RDAs. But a person who eats a balanced diet has no need for daily supplements.

A person with a vitamin deficiency disease may take large doses of a certain vitamin or of a combination of vitamins under the guidance of a physician. Self-diagnosis and treatment with mega-doses (doses 10 or more times larger than the RDA) can be dangerous.

The following chapters will cover all the major vitamins, their functions in the body, their RDA, important food sources, and consequences of deficiency and excess. Appendix II gives the vitamin content of commonly consumed foods.

Water-soluble vitamins include vitamin C and the B complex vitamins comprising B1 (thiamin), B2 (riboflavin), B3 (niacin), B6 (pyridoxine), pantothenic acid, biotin, folic acid and B12 (cyanocobalamin).

Water-soluble vitamins are directly absorbed into the blood stream and travel freely in the blood. However, they cannot be stored and rapidly leave the body in the form of urine, if taken in greater quantities than the body can use.

Water-soluble vitamins are retained in the body for varying periods of time. A single day’s omission from the diet doesn’t produce deficiency symptoms, but still, water-soluble vitamins must be eaten more regularly than fat-soluble vitamins.

Of the vitamins listed above, biotin, niacin, pantothenic acid, vitamin D and vitamin K are produced by our body in variable amounts. Only biotin, pantothenic acid and vitamin K, which are produced by bacteria in the human intestine, are possibly produced in sufficient quantities to meet the body’s needs.

In addition to some of the roles of vitamins mentioned above, vitamins A, C and E function as antioxidants, which are vital in countering the potential harm of chemicals known as free radicals. If these free radicals remain unchecked, they can make cells more vulnerable to cancer-causing substances. Free radicals can also transform chemicals in the body to cancer-causing agents. Environmental pollutants, such as cigarette smoke, are sources of free radicals. An antioxidant is a substance that prevents the oxidation of another substance. In doing so, the antioxidant gets oxidized itself.

Each vitamin has such specific uses that one cannot replace, or act for, another. But the lack of one vitamin can interfere with the function of another. The continued lack of one vitamin in an otherwise complete diet results in vitamin deficiency diseases like beriberi, pellagra, rickets or scurvy. Most of the vitamins got discovered when scientists were searching for the causes of such diseases.

Welcome to the world of vitamins. The story of vitamins, their discovery, functions in maintaining health, and usefulness in healing deficiency diseases is fascinating. The term ‘vitamins’ was first coined in the year 1912 by Casimir Funk, a Polish chemist. The first vitamin discovered was an amine. Since the substance discovered had life-giving properties, it was described as a ‘vital amine’ or ‘vitamine’. The ‘e’ was later dropped because the substance was found to be a group of essential compounds, not all of which were amines.

Vitamins are not food but they are chemicals contained in food. They furnish no energy or building materials for the body. They participate in processes that are vital for health and normal body functions.

Vitamins is the name given to a group of potent organic compounds, other than protein, carbohydrate and fat, that are essential in minute quantities for specific body functions of growth, maintenance and reproduction. Vitamins regulate the chemical reactions by which the body utilises carbohydrates, proteins and fats to provide energy to the living tissues. They help in formation of blood cells, hormones, nervous system chemicals known as neurotransmitters, and the genetic material Deoxyribonucleic Acid (DNA).

There are about thirteen well-identifi vitamins. Some vitamins are soluble in fat bunot in water and vice-versa. Accordingly, they are classified as fat-soluble and water-soluble vitamins. Fat-soluble vitamins include vitamins A, D, E and K. These vitamins are generally present in foods containing fat. When fat is digested in the body, the fat-soluble vitamins are absorbed along with the breakdown products of fat digestion. Excess amounts of fat-soluble vitamins are stored in the body’s fat deposits, liver and kidneys. Because the body stores fatsoluble vitamins, they can be eaten in large amounts once in a while and still meet the body’s needs over a period of time. However, if fat-soluble vitamins are regularly consumed in very large amounts, they can reach dangerous levels producing toxic effects.

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&copy;Copyright by Sterling Publishers Private Limited, New Delhi. Author: Deepa Mehta
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