Water Soluble Vitamins

Water Soluble Vitamins-

WATER-SOLUBLE vitamins consist of a large number of substances. These include ascorbic acid and the B-complex vitamins. The water-soluble vitamins are absorbed quickly in the body and the amounts not utilised are excreted in the urine.

Vitamin B-Complex-

Six members of this group, namely-

  • Thiamine
  • Niacin
  • Pyridoxine
  • Folic acid
  • Vitamin B12

 are included in the RDA, because definite requirements of these vitamins have been established through research. A diet, which provides adequate amount of these six vitamins, also, carries enough of the other members of this group.


Thiamine (also known as vitamin B1 and Aneurin) was first isolated in 1926 from rice polishings by Jansen and Donath.

Functions: -

The basic function of thiamine as a coenzyme is related to release of energy from glucose and its storage as fat, thus it makes energy available for normal growth and function of the body. Thiamine pyrophosphate, the coenzyme form of thiamine, is necessary for catalysing the oxidation of carbohydrates in the body.

Thiamine is needed to maintain normal function of three systems in the body, gastrointestinal, nervous and cardiovascular system.

  • Gastrointestinal System: -

Thiamine helps to produce energy needed for the cells of smooth muscles and secretory glands. In its lack, there is lack of muscle tone and deficient gastric secretions as a result there is poor appetite, indigestion, constipation and poor stomach function.

  • Nervous System: -

The central nervous system needs glucose as energy source for its function. When there is a lack of thiamine, the energy is not released and nerves are unable to work, with loss of response and alertness. The result is apathy, fatigue and irritability. If the deficit continues, nerve tissues may be damaged causing pain and finally paralysis.

  • Cardiovascular System: -

If energy supply is not continuous, due to lack of thiamine, the heart muscle weakens and may lead to heart failure. The blood vessel walls become weak, the vessels may dilate and fluid may accumulate in the lower part of legs.

Food Sources: -

  • Nearly all foods, except sugars, fats and oils, contain some thiamine.
  • Plant sources include pulses, nuts, oilseeds and whole grain cereals.
  • Parboiled rice and fresh peas are good sources of thiamine.
  • Leafy green vegetables and animal foods such as milk, eggs, fish and meat are fair sources

Recommended Daily Allowance-

 The recommended thiamine allowance is 0.5 mg per 1000 calories for all age groups.

Effect of Deficiency:

  • The digestive system is disturbed resulting in loss of appetite (anorexia), poorly toned muscles and constipation.
  • Loss of appetite may be accompanied by nausea and vomiting.
  • Thiamine deficiency can also affect the nervous system Mental depression, moodinesss, irritability, forgetfulness, confusion and fear.
  • Severe deficiency leads to beri-beri a disease of the nervous system, which has been known since antiquity. The name ‘beri beri’ is a Singhalese word meaning ‘I can’t I can’t’, which describes the disease, as the person is always too ill to do anything.
  • Thiamine deficiency is found in association with chronic alcoholism, due to very low food intake and increased demand. Intake of thiamine restores normalcy.


It was isolated from yeast by Warburg and Christian. Kuhn and coworkers synthesised it in 1935. It was formerly known as vitamin B2 or vitamin G.

The name riboflavin is derived from its chemical structure. It is a yellow-green (Latin word ‘flavus’ means yellow) fluorescent pigment containing the sugar ‘ribose’, hence the name riboflavin.


  • Riboflavin functions as a vital part of coenzymes in both energy production and tissue protein building.
  • It is thus essential for tissue health and growth of all animal and plant life (including microorganisms).
  • It plays an important role in maintaining the integrity of mucocutaneous structures.

Food Sources:

Milk is a rich source of riboflavin. So also are products derived from milk such as yoghurt (curds), butter milk, milk powder and concentrated milk.

Recommended Daily Allowance-

Riboflavin requirement is related to total energy requirements. For practical purposes the general RDA standard is based on 0.60 mg of riboflavin per 1000 kcal for all ages. Thus the recommended allowance varies from 0.7mg for an infant to 1.7 mg for an adolescent.

Effect of Deficiency: -

  • Lack of riboflavin affects the eyes, skin and nerves.
  • The eyelids become rough and the eye becomes sensitive to bright sunlight. This condition is called photophobia (fear of light).
  • The skin changes are found around the area of the mouth, on the lips, tongue and nose. The lips become inflamed, cracks are observed at the corners of the mouth and the tongue is swollen, red and sore.
  • Dermititis- The deficiency symptoms can be corrected by administering riboflavin.

👉🏻Niacin (VitaminB3)-

Goldberger in 1915 observed the existence of a pellagra-preventing factor, which he related to B vitamins. He found that the same factor cured black tongue in dogs.

Functions: -

  • Niacin functions in the body as a component of two important co-enzymes NAD and NADP. These coenzymes are involved in tissue respiration and synthesis and the breakdown of glucose to produce energy.
  • Niacin works in close association with riboflavin and thiamine in the cell metabolism system that produces energy. It is necessary for growth.

Souces: -

In plant foods, groundnuts are the best source of niacin. Liver, an organ meat, is a rich source of niacin. But both groundnuts and liver are included in the diet occasionally.

Recommended Dietary Allowance

Total niacin equivalent required daily on the basis of calorie requirement could range from 8 mg to 26 mg depending on the age and occupation of the individual.

Effect of Deficiency: -

  • Lack of niacin affects the skin, gastrointestinal tract and nervous system.
  • The skin, especially the part exposed to the sun, itches and burns.
  • Lack of appetite in early stages is followed by diarrhoea in later states.
  • Nervous changes include dizziness, insomnia, irritability, fear, depression and forgetfulness; later on there may be dementia.
  • The deficiency disease is known as pellagra which is seen in endemic form in some parts of India.


Three naturally occurring pyridine derivatives (pyridoxine, pyridoxal and pyridoxamine) are known as vitamin B6.

Functions: - Vitamin B6 is a co-factor for several enzymes connected with the metabolism of amino acids. It is also believed to have a role in the formation of antibodies.

 Sources: -

However, pulses, wheat and meat are known to be rich sources, while other cereals are fair sources. Vegetables and fruits are relatively poor sources.

Requirements: -

The average requirement for adults would appear to be about 1.5 mg per day. Cooking losses in normal Indian diets are negligible; hence no allowances for losses need be made. The suggested daily intake varies from 0.4 mg for infants to 2.0 mg for adults and 2.5 mg for expectant and nursing mothers

Deficiency: -

The symptoms of vitamin B6 deficiency—such as peripheral neuritis, anaemia, glossitis, cheilosis and seborrhic dermatitis are similar to those of other B vitamins.

👉🏻Folic Acid: -

Folic acid and related compounds, which is one of the B vitamins, was discovered in 1941, It was found to be essential for all vertebrates including man. Its name was derived from the Latin word folium, which means leaf, because it was first isolated from spinach leaves and is widely distributed in green, leafy plants.

Functions: -

 The primary function of folic acid is related to the transfer of single carbon in the synthesis of a number of metabolites in the body. It is also involved in the synthesis of nucleic acid along with vitamin B12. Folic acid undergoes a series of metabolic conversions to its various coenzyme forms after it is absorbed.

 Sources: -

It is widely distributed in foods. Green leafy vegetables, liver, legumes and yeast are rich sources of folic acid. It is a relatively stable vitamin but storage and cooking losses can be as high as 50 per cent, especially if cooking water is discarded.

 Suggested Daily Intake: -

 The safe level of folate intake would be 100 mcg per day for adults and adolescents with 25 mcg in infancy increasing to 40 mcg at pre-school stage, gradually increasing with age to 100 mcg of folates at adolescence.

It was observed in one study that the birth weights of infants, born to mothers who had taken 300 mcg folate per day during pregnancy, were higher than those born to mothers who had received 100 or 200 mcg daily.

Deficiency: -

 Prolonged and severe folic acid deficiency leads to abnormal formation of red blood cells resulting in megaloblastic anaemia. It responds to administration of folic acid.

👉🏻Vitamin B12-

Vitamin B12 or cyanocobalamin was the last member of the B vitamins discovered in 1948. It contains cobalt and phosphorus and is red in colour. It is found only in animal foods and higher plants are unable to synthesise it.


  • It promotes normal growth and development.
  • It helps with certain types of nerve damage, and treats pernicious anaemia.
  • It is an essential component of several coenzymes, which are needed in the synthesis of nucleic acids. Its metabolism and use in the body is closely related to folic acid.
  • It is essential for the normal functioning of all cells, especially those of bone marrow, the nervous system and the gastrointestinal tract.

 Sources: -

The richest sources are liver, and organ meats. Milk, eggs, muscle meat and fish are good sources. Plant foods do not contain vitamin B12.

Deficiency: -

  • As sore tongue, weakness, loss of weight, tingling of extremities, apathy, mental and other nervous abnormalities.
  • When there is a lack of intrinsic factor, essential for the absorption for the vitamin, pernicious anaemia results, in which there is degeneration of the spinal cord.
  • There is a low level of vitamin B12 in the blood and an inability of new RBCs to develop normally resulting in megaloblastic anaemia.

👉🏻Ascorbic Acid (Vitamin C)-

Ascorbic acid (vitamin C) was isolated and its chemical structure elucidated in 1932 by C.G. King. Its lack in human diet has long been known to cause a disease called scurvy.

Functions: -

  • It is a part of the cementing material which hold the body cells firmly in place. Thus it plays an important role to build and maintain strong tissues in general, especially connective tissues (bone, cartilage, dentin, collagen, etc).
  • Blood vessel tissue depends on vitamin C to form strong capillary walls.
  • Vitamin C is an important partner of protein for tissue synthesis.
  • It helps the body to build resistance to infection. It helps in the absorption of calcium and ensures the health of bones.

Recommended Dietary Allowance: -

The recommended daily allowance increases with age from 20 to 40 mg for children and is 40 mg per day for adult. An intake of 80 mg per day is recommended for a nursing mother.

Deficiency: -

  1. If ascorbic acid is not present in sufficient quantity, the cementing material is not formed in adequate amounts. Tiny breaks occur in the walls of very small blood vessels and haemorrhages result.
  2. There is general weakness, lack of appetite and thickened and scaly skin. Spongy gums and haemorrhages in body tissues are other symptoms of scurvy.
  3. The tissues of the gums become tender and often bleed. In severe cases, soft tissues around the joints become swollen and are painful.