Vitamins speak-                                                  

"We are for growth, health and welfare of Human body; Discharge our duties directly or through coenzymes; Deficiency symptoms are our alert signals; Satisfied we shall be, with additional supplements."

essentials of vitamins

Welcome to the vitamins world and problems you will face following their deficiencies. In this article we will discus about how vitamins are invented, what do vitamins do for you and how will you get remedy from their deficiency by natural foods. We examine vitamins and in what amount they are needed on daily basis, how they are categorized and explore foods where we can easily find these nutrients. We will also go over the limitations of using supplements as a source of these nutrients.

deficiency of vitamins

Vitamins are considered as micronutrients, which mean that they are needed in small amount but do some essential functions of body. They helps to promote and regulate chemical reactions and processes within cells. Most vitamins are raw material for the production of blood cells (RBC, WBC & Platelets) in the bone marrow and thus they keep your body strong and healthy.

They may also act as antioxidants (especially Vitamin-A, C & E) which prevent your aging process and keeps your youth evergreen. Vitamins are abundant in fruits, vegetables, and grains; they are also added in as a supplement form to some processed foods such as cereals and commercial orange juice. Daily intake of vitamins within normal requirements keeps you healthy. But excess intake may produce toxicity (especially by Vitamin-A & D, E in lesser extent) which commonly results from supplements. One things should be cleared that, more intake of vitamin is more good for health believed by many people - but it's wrong.


It is difficult to define vitamins precisely. Vitamins may be regarded as organic compounds required in the diet in small amounts to perform specific essential biological functions for normal maintenance of optimal growth and health of the Human body and also for other organisms. One and only bacterium E.coli does not require any vitamin, as it can synthesize all of them. Interesting fact is that Human develop vitamin deficiencies not much due to presence of this bacteria in the alimentary tract (usually in Colonic part) as a normal flora/commensals. It is believed that during the course of evolution, the ability to synthesize vitamins was lost. Hence, the higher organisms have to obtain them from diet. The vitamins are required in small amounts, since their degradation is relatively slow.

History of vitamins

In the beginning of 20th century, it was clearly understood that the diets containing purified carbohydrate, protein, fat and minerals were not adequate to maintain the growth and health of experimental rats, which the natural foods (such as milk) could do. Hopkins coined the term accessory factors to the unknown and essential nutrients present in the natural foods. Funk( 1913) isolated an active principle (an amine) from rice polishings and later in yeast, which could cure beri-beri in pigeons. He coined the term vitamine (Greek : vita-life means Essential for Life) to the accessory factors with a belief that all of them were amines. It was later realized that only few of them are amines. The term vitamin, however, is continued without the final letter 'e'.

Fat Soluble Vitamins

The usage of A, B and C to vitamins was introduced in 1915 by McCollum and Davis. They first felt there were only two vitamins fat soluble A and water soluble B (anti-beriberi factor). Soon another water soluble anti-scurvy factor named vitamin C was described. Vitamin A was later found to possess two components - one that prevents night blindness( vitamin-A ) and another anti-ricket factor named as vitamin D. A fat soluble factor called vitamin-E, in the absence of which rats failed to reproduce properly, was discovered. Yet another fat soluble vitamin concerned with coagulation was discovered in mid 1930s. It was named as vitamin-K. In the sequence of alphabets it should have been F, but K was preferred to reflect its function (koagulation).

Water Soluble Vitamins

As regards the water soluble factors, vitamin-C was identified as a pure substance and named as ascorbic acid. Vitamin-B was found to be a complex mixture and nomenclature also became complex. B-1 was clearly identified as anti-beriberi factor. Many investigators carried out intensive research between 192O and 1930 and went on naming them as the water soluble vitamins B-2, B-3, B-4, B-5, B-6, B-7, B-8, B-9, B-10, B-11 and B-12. Some of them were found to be mixtures of already known vitamins. And for this reason, a few members (numbers!) of the B-complex series disappeared from the scene. Except for B-1, B-2, B-6 and B-12 names are more commonly used for other B-complex vitamins.


The term vitamers represents the chemically similar substances that possess qualitatively similar vitamin activity. Some good examples of vitamers are given below -

  • Retinol, retinal and retinoic acid are vitamers of vitamin A.
  • Pyridoxine, pyridoxal and pyridoxamine are vitamers of vitamin B-6.


There are about 15 vitamins, essential for humans. They are classified as fat soluble (A, D, E and K) and water soluble (C and B-group) vitamins. The B-complex vitamins may be sub-divided into energy-releasing (B-1, B-2, B-6, B-7 etc.) and hematopoietic (folic acid and B-12). Most of the water soluble vitamins exert the functions through their respective coenzymes while only one fat soluble vitamin (K) has been identified to function as a coenzyme.

classification of vitamins


The four vitamins, namely vitamin A, D, E, and K are known as fat or lipid soluble. Their availability in the diet absorption and transport are associated with fat. They are soluble in fats and oils and also the fat solvents (alcohol, acetone etc.). Fat soluble vitamins can be stored in liver and adipose tissue. They are not readily excreted in urine. Excess consumption of these vitamins (particularly A and D) leads to their accumulation and toxic effects.


The fat soluble vitamin-A, as such is present only in foods of animal origin. However, its provitamins carotenes are found in plants. It is recorded in the history that Hippocrates (about 500 B.C.) cured night blindness. He prescribed to the patient’s ox liver (in honey), which is now known to contain high quantity of vitamin A.

chemistry of vitamin A

Chemistry :

In the recent years, the term vitamin A is collectively used to represent many structurally related and biologically active molecules. The term retinoids is often used to include the natural and synthetic forms of vitamin-A. Retinol, retinal and retinoic acid are regarded as vitamers of vitamin-A.

Functions of Vitamin-A :

Vitamin-A is necessary for a variety of functions such as vision, proper growth and differentiation, reproduction and maintenance of epithelial cells. The biochemical function of vitamin-A in the process of vision was first elucidated by George Wald (Nobel Prize 1968). The events occur in a cyclic process known as Rhodopsin cycle or Wald's visual cycle.

  1. Vitamin-A synthesize the cells of vision (Rods & Cones cells) of our eyes. Night blindness is the major manifestation following deficiency of Vitamin-A.
  2. Retinol and retinoic acid regulate the protein synthesis of cells and thus are involved in the cell growth and differentiation.
  3. Vitamin-A is essential to maintain healthy epithelial tissue. This is due to the fact that retinol and retinoic acid are required to prevent keratin synthesis (responsible for horny surface).
  4. Retinyl phosphate synthesized from retinol is necessary for the synthesis of certain glycoproteins, which are required for growth and mucus secretion.
  5. Retinol and retinoic acid are involved in the synthesis of transferrin, a protein that transport iron through blood circulation.
  6. Vitamin A is considered to be essential for the maintenance of proper immune system to fight against various infections.
  7. Cholesterol synthesis requires vitamin A.
  8. Carotenoids (most important β–carotene) function as antioxidants and reduce the risk of cancers initiated by free radicals and strong oxidants.

Special functions of β–carotene (a precursor of Vitamin A): Increased consumption of β-carotene is associated with decreased incidence of heart attacks, skin and lung cancers. This is attributed to the antioxidant role of β-carotene which is independent of its role as a precursor of vitamin A. Ingestion of high doses of β-carotene for long periods are not toxic like vitamin A.

Dietary source :

Animal sources contain (preformed) vitamin-A.

The best sources are liver, kidney, egg yolk, milk, cheese, butter. Fish (cod or shark) liver oils are very rich in vitamin A.


Vegetable sources contain the provitamins β–carotenes.

Yellow and dark green vegetables and fruits are good sources of β–carotenes e.g. carrots, spinach, amaranthus, pumpkins, mango, papaya etc.

recommended dietary allowance (rda) :

The daily requirement of vitamin-A is expressed as retinol equivalents (RE) rather than International units (IU).

Retinol Equivalent (RE)

1 Retinol equivalent = 1 microgram retinol

                                     = 12 microgram other carotenoids

                                     = 3.33 IU of vitamin-A activity from retinol

                                     = 10 IU of vitamin-A activity from β–carotene.

The RDA of vitamin A for adults is around 1000 retinol equivalents (3,500 IU) for man and 800 retinol equivalents (2,500 IU) for woman. One International unit (IU) equals to 0.3 mg of retinol. The requirement increases (may be doubled) in growing children, pregnant women and lactating mothers.

consequences of deficiency :

The deficiency symptoms of vitamin-A are not immediate, since the Liver store it to meet the body requirements for quite sometime (2-4 months). It is recorded in the history that Hippocrates (about 500 B.C.) cured night blindness. He prescribed to the patients ox liver (in honey), which is now known to contain high quantity of vitamin A.

The deficiency manifestations are related to the Eyes, Growth, Reproduction, Skin & epithelial cells.

vitamin a deficient eye

1. Deficiency manifestations on the Eyes:

Night blindness (nyctalopia) is one of the earliest symptoms of vitamin-A deficiency. The individuals have difficulty to see in dim light since the dark adaptation time is increased.

Prolonged deficiency irreversibly damages a number of visual cells.Severe deficiency of vitamin-A leads to xerophthalmia. This is characterized by dryness in conjunctiva and cornea, and keratinization of epithelial cells. In certain areas of conjunctiva, white triangular plaques known as Bitot's spots are seen.If xerophthalmia persists for a long time, corneal ulceration and degeneration occur. This results in the destruction of cornea, a condition referred to as keratomalacia, causing total blindness. Vitamin-A deficiency blindness is mostly common in children of the developing countries.

2. Deficiency manifestations on the Growth:

Vitamin A deficiency results in growth retardation due to impairment in bone formation.

poor-growth-in-children due to vit- a deficiency
sterility due to vit A deficiency

3. Deficiency manifestations on Reproduction:

The reproduction system is adversely affected in vitamin A deficiency. Degeneration of germinal epithelium leads to sterility in males.

4. Deficiency manifestations on Skin & Epithelial cells:

The skin becomes rough and dry. Keratinization of epithelial cells of gastrointestinal tract, urinary tract and respiratory tract is noticed. This leads to increased bacterial infections. Vitamin-A deficiency also associated with formation of urinary stones.

Dry-skin-due to vit A deficiency

Medications for deficiency :

For severe deficiency (severe corneal damage) - Cap. Ratinal FORTE (Retinol), 5 lac unit/day for 3 days, followed by 50,000 unit/day for 2 months as follow up therapy.

For mild to moderate deficiency (minimal corneal damage) - Cap. Ratinal FORTE (Retinol), 10,000 to 25,000 unit/day until clinical improvement occurs (usually for 1-2 weeks).

Eating Vitamin-A enriched foods are essential along with medications.


Vitamin D resembles sterol in structure and functions like a hormone. It synthesized by our Liver & Kidney following sunlight exposure over skin. The symptoms of rickets and the beneficial effects of sunlight to prevent rickets have been known for centuries. Hess (1924) reported that irradiation with ultraviolet light induced anti-rachitic activity in some foods. Vitamin-D was isolated by Angus ( 1931) who named it calciferol.

vit D synthesis

Chemistry :

Ergocalciferol (vitamin D2) is formed from ergosterol and is present in plants. Cholecalciferol (Vtamin-D 3) is found in animals. Both the sterols are similar in structure except that ergocalciferol has an additional methyl group and a double bond. Ergocalciferol and cholecalciferol are sources for vitamin D activity and are referred to as provitamins.

Functions of Vitamin-D :

Calcitriol/Cholecalciferol/Vtamin-D 3 ( 1-25-DHCC) is the biologically active form of vitamin-D . It regulates the plasma levels of calcium and phosphate. Calcitriol acts at 3 different levels (Intestine, kidney and bone) to maintain plasma calcium level within normal range (9-11 mg/dl).

1. Action on Gut:

Calcitriol increases the intestinal absorption of calcium and phosphate from dietary sources.

action of vit d on gut

2. Action of calcitriol on the Bone:

In the osteoblasts (bone forming cells) of bone, calcitriol stimulates calcium uptake for deposition as calcium-phosphate, thus calcitriol is essential for bone formation. The bone is an important reservoir of calcium and phosphate.

Calcitriol along with parathyroid hormone increases the mobilization of calcium and phosphate from the bone. This causes elevation in the plasma calcium and phosphate level.

vitamin D and bone

3. Action of calcitriol on the Kidney :

Calcitriol is also involved in minimizing the excretion of calcium and phosphate through the kidney, by decreasing their excretion and enhancing reabsorption from the kidney tubules into blood.

function of vitamin d

sources :

Vitamin D can be provided to the body in three ways -

  1. Exposure of skin to sunlight for synthesis of vitamin D.
  2. Consumption of natural foods containing Vitamin-D.
  3. By irradiating foods (like yeast) that contain precursors of vitamin D and fortification of foods (milk, butter etc.).
vit d and bone

Good sources of vitamin D include fatty fish, fish liver oils, egg yolk etc. Milk is not a good source of vitamin D.

recommended dietary allowance (rda) :

The daily requirement of vitamin D is 400 IU or 10 mg of cholecalciferol. In countries with good sunlight (like Bangladesh, India) the RDA for vitamin D is 200 IU or 5 mg of cholecalciferol.

consequences of deficiency :

Vitamin D deficiency is relatively less common, since this vitamin can be synthesized in the body. However, insufficient exposure to sunlight and consumption of diet lacking vitamin-D results in its deficiency.Vitamin D deficiency occurs in strict vegetarians, chronic alcoholics, individual with Liver and Kidney diseases or fat malabsorption syndromes. In some people, who cover the entire body (purdah) for religious customs, vitamin D deficiency is also observed, if the requirement is not met through diet.

Deficiency of vitamin D causes rickets in children and osteomalacia in adults. Rickets is derived from an old English word “wrickken”, meaning to twist. Osteomalacia is derived from Greek (osteon-bone; malakia-softness). Vitamin D is often called as anti-rachitic vitamin.

  • Rickets in children is characterized by bone deformities due to incomplete mineralization, resulting in soft and pliable bones and delay in teeth formation. The weight bearing bones are bent to form bow-legs. In rickets, the plasma level of calcitriol is decreased and alkaline phosphatase activity is elevated. Alkaline phosphatase is concerned with the process of bone formation. There is an overproduction of alkaline phosphatase related to more cellular activity of the bone. It is believed to be due to a vain attempt to result in bone formation.
rickets 1
  • In case of osteomalacia (adult rickets) demineralization of the bones occurs (bones become softer), increasing their susceptibility to fractures.

Vitamin E (tocopherol) is a naturally occurring Antioxidant. It is essential for normal reproduction in many animals, hence known as anti-sterility vitamin. Vitamin E is described as a ‘vitamin in search of a disease.' This is due to the lack of any specific vitamin E deficiency disease in humans.

Evans and his associates (1936) isolated the compounds of vitamin E activity and named them as tocopherols (Greek: tokos - child birth; pheros - to bear; ol - alcohol).

vitamin -e

Chemistry :

Vitamin E is the name given to a group of tocopherols and tocotrienols. About eight tocopherols (vitamin E vitamers) have been identified - α, β, γ, 𝛿 etc. Among these, α - tocopherol is the most active. The tocopherols are derivatives of 6-hydroxy chromane ring (tocol) with isoprenoid (3 units) side chain. The antioxidant property is due to the chromane ring.

Functions of Vitamin-E :

Most of the functions of vitamin E are related to its antioxidant property. It prevents the nonenzymatic oxidations of various cell components (e.g. unsaturated fatty acids) by molecular oxygen and free radicals such as superoxide (O2-) and hydrogen peroxide (H2O2). The element selenium (a mineral) helps in these functions. Vitamin E acts as a scavenger and gets itself oxidized (to quinone form) by free radicals and spares PUFA. The biochemical functions of vitamin E, related either directly or indirectly to its antioxidant property.

  • Vitamin E is essential for the cell membrane structure and integrity, hence it is regarded as a cell membrane antioxidant.
  • It protects RBC from haemolysis by oxidizing agents (e.g. H2O2).
  • It is closely associated with reproductive functions and prevents sterility. Vitamin E preserves and maintains germinal epithelium of gonads for proper reproductive function.
  • It increases the synthesis of heme by enhancing the activity of enzymes 6-aminolevulinic acid (ALA) synthase and ALA dehydratase enzymes.
  • It is required for cellular respiration through electron transport chain (ETC).
  • Vitamin E prevents the oxidation of vitamin A and carotenes.
  • Vitamin E is needed for optimal absorption of amino acids from the intestine.
  • It is involved in proper synthesis of nucleic acids of cellular nucleus.
  • Vitamin E protects liver from being damaged by toxic compounds such as carbon tetrachloride.
  • It works in association with vitamins A , C and β-carotene, to delay the onset of cataract (opacification of lens of eye).
  • Vitamin E has been recommended for the prevention of chronic diseases such as cancer and heart diseases. It is believed that vitamin E prevents the oxidation of LDL. (Note: The oxidized LDL have been implicated to promote heart diseases by the formation of atherosclerosis).

dietary source:

Many vegetable oils are rich sources of Vitamin E. Wheat germ oil, cotton seed oil, peanut oil, corn oil and sunflower oil are the good sources of this vitamin. It is also present in meat, milk, butter and eggs.

Vitamin-E rich foods

recommended dietary allowance (rda) :

Intake of Vitamin E is directly related to the consumption of poly unsaturated fatty acids (PUFA). i.e., requirement increases with increased intake of PUFA.

A daily consumption of about 10 mg (15 IU) of α-tocopherol for man and 8 mg (12 IU) for woman is recommended. One mg of α-tocopherol is equal to 1.5 IU.

Vitamin E supplemented diet is advised for pregnant and lactating women.

consequences of deficiency :

The symptoms of vitamin E deficiency vary from one animal species to another. In many animals, the deficiency is associated with sterility, degenerative changes in muscle, megaloblastic anemia and changes in central nervous system. Severe symptoms of vitamin E deficiency are not seen in humans except increased fragility of erythrocytes (RBC) and minor neurological symptoms.


Only fat soluble vitamin with a specific coenzyme function is Vitamin K. It is required for the production of blood clotting factors (Factor – II, VII, IX & X), essential for blood coagulation to stop bleeding after any injury.


Chemistry :

Chemically Vitamin K exists usually in 3 different forms (Vitamin K1, K2, K3). Vitamin K1 (phylloquinone) is present in plants. Vitamin K2 (menaquinone) is produced by the intestinal bacteria (E. coli) and also found in animals. Vitamin K3 (menadione) is a synthetic form. All the three vitamins (K1, K2, K3) are naphthoquinone derivatives. Isoprenoid side chain is present in vitamins K1 and K2. The three vitamins are stable to heat. Their activity is, however, lost by oxidizing agents, irradiation, strong acids and alkalis.

Functions of Vitamin-k :

  1. The major functions of vitamin K are concerned with blood clotting process. The clotting factors II, VII, IX and X are synthesized as inactive precursors in the liver. Vitamin K acts as a coenzyme to convert it in active form by carboxylation of glutamic acid and this reaction is catalyzed by carboxylase microsomal enzyme of Liver.
  2. Vitamin K is also required for the carboxylation of glutamic acid residues of osteocalcin, a calcium binding protein present in the bone. That helps to increase calcium density of bone and accelerate strength of bone.

In some arterial or venous thrombotic diseases (occlusion by thrombus), Vitamin K antagonist (e.g. Warfarin) are used to prevent clot formation within blood vessels.

dietary source:

Cabbage, cauliflower, tomatoes, alfa-alfa, spinach and other green vegetables are good sources. It is also present in egg yolk, meat, Liver, cheese and dairy products.


recommended dietary allowance (rda) :

Strictly speaking, there is no RDA for vitamin K, since it can be adequately synthesized in the gut. It is however, recommended that half of the body requirement is provided in the diet, while the other half is met from the bacterial synthesis. Accordingly, the suggested RDA for an adult is 7o-140 μgm/day.

consequences of deficiency :

The deficiency of vitamin K is uncommon, since it is present in the diet in sufficient quantity and/or is adequately synthesized by the intestinal bacteria. However, vitamin K deficiency may occur due to its faulty absorption (lack of bile salts in the intestine), loss of vitamin into feces (diarrhoeal diseases) and administration of excessive broad spectrum antibiotics (killing of intestinal floras – E. coli mainly).


Deficiency of vitamin K leads to the lack of active prothrombin (clotting factor II) in the circulation. The result is that blood coagulation is adversely affected. The individual bleeds profusely even for minor injuries. The blood clotting time is increased.


They are 9 in number. There is Vitamin-C and the B complex vitamins.The water soluble vitamins are a heterogeneous group of compounds since they differ chemically from each other. The only common character shared by them is their solubility in water.


Most of these vitamins are readily excreted in urine and they are not toxic to the body.Water soluble vitamins are not stored in the body in large quantities (except B-12). For this reason, they must be continuously supplied in the diet.

Generally, vitamin deficiencies are multiple rather than individual with overlapping symptoms. It is often difficult to pinpoint the exact biochemical basis for the symptoms.

The water soluble vitamins form coenzymes that participate in a variety of biochemical reactions, related to either energy generation or hematopoiesis. It may be due to this reason that the deficiency of vitamins results in a number of overlapping symptoms.

Common Vitamin Deficiencies

Vitamins commonly lacking in the American diet include :

  • Vitamin A, which you can find easily by taking milk, cream, eggs, butter, dark green leafy vegetables and broccoli.
  • Another vitamin lacking in the American diet is Vitamin C. You can find Vitamin C in citrus fruits, cabbage type vegetables, tomatoes potatoes, dark green leafy vegetables, peppers, cantaloupe and strawberries.
  • Another vitamin we tend to be deficient in is Vitamin D. Vitamin D, you can found it from mushrooms, especially portabella mushrooms, fortified milk, eggs, fish and by being in the sun.
  • We also tend to be deficient in Vitamin E, which you can find in vegetable oils, dark green leafy vegetables, whole grains, butter, milk, nuts, seeds and fortified cereals.