Vitamins : Functions, food sources, requirements and effects of deficiency

Vitamins : Functions, food sources, requirements and effects of deficiency

Fat soluble vitamins:

Vitamin A

Vitamin A was the first fat soluble vitamin to be recognized. Three forms of Vitamin A are active in the body,  retinol, retinal and retinoic acid. They are collectively called as retinoids .

Beta carotene is the provitamin of Vitamin A. Provitamins are substances that are chemically related to a vitamin but must be changed by the body into the active form of the vitamin. Vitamin A in the diet comes in two forms.

Retenoids (preformed Vitamin A) and carotenoids. Vitamin A is present in vegetable foods which contain yellow pigment called carotenes. It was isolated from carrots hence called carotenoids which are provitamins of Vitamin A.

Functions.

1.     A well understood function of retinol is in the visual process. The retina of the human eye contains two distinct photo receptors of which one is sensitive to light intensities . Vitamin A is essential for the formation of rhodopsin and normal functioning of the retina for clear vision in dim light. Lack of Vitamin A leads to impaired adaptation to darkness.

2.     Participates in protein synthesis and cell differentiation and thereby maintaining the health of the epithelial tissues and skin.

3.     Supports reproduction and growth

4.     Vitamin A regulates the antibodies and cellular immune response. It is essential for maintaining the epithelial tissue which is the first line of defence against invading microorganism.

5.     Beta carotene acts as an antioxidant capable of protecting the body against disease like cancer, cardiovascular diseases and cataract.

Sources

Vitamin A in the human diet exist as retinol or as retinal or beta carotene which has to be converted to Vitamin A. Foods of animal origin contain retinol.

Plant sources are rich in Beta carotene. Only one third of the dietary beta Carotene is absorbed.

Beta Carotene from green leafy vegetables is well utilized than from carrots and papayas.

Good sources of Vitamin A are sheep liver, butter, ghee, egg, milk, curds, liver oils of shark and halibut.

Good sources of beta carotene are agathi, amaranth, drumstick leaves, green leafy vegetables, mango, papaya, carrot and jack fruit.

Requirements:

The ICMR recommended dietary allowance for retinol is given in table-21C.

ICMR recommended dietary allowance for Retinol

Group        Retinol µg/day

Man  600

Woman       600

Pregnant     600

women       

Lactation    950

Infants        350

Children      400-600

Effects of Deficiency

Deficiency of Vitamin A is manifested as nutritional blindness and increased susceptibility to infection. Nutritional blindness is an important public health problem among young children in India .

Night blindness is an early symptom of Vitamin A deficiency. The individual cannot see in dim light. This can be corrected with adequate supply of Vitamin A. In the absence of adequate Vitamin A intake the outer lining of the eye ball loses its usual moist, white appearance and becomes dry and wrinkled called xerosis.

This condition is followed by raised muddy dry triangular patches on the conjunctiva called the bitots spots. Redness and inflammation of the eye and gradual loss of vision may follow. The central portion of the eye loses its transparency and becomes opaque and soft if not treated and leads to total blindness termed Xeropthalmia. Xeropthalmia encompasses all ocular manifestations of Vitamin A deficiency.

Increased susceptibility to infection occurs because the mucous membrane lining becomes dry and rough which is easily invaded by the micro - organism.

Hypervitaminosis

Intake of large amount of Vitamin A for prolonged periods can lead to toxic symptoms which include irritability, headache, nausea and vomitting.

Vitamin D

Vitamin D can be synthesized in the body in adequate amounts by simple exposure to sunlight, even for 5 minutes per day is sufficient.

It is essential for bone growth and calcium metabolism. It acts as a hormone in the body by facilitating calcium absorption and deposition in the bone.

Functions

1.     Vitamin D helps in the absorption of calcium and phosphorous by increasing the synthesis of calcium binding protein.

2.     Vitamin D helps to maintain the calcium and phosphorous levels in the body by stimulating,

Absorption in the gastro intestinal tract.

Retention by the kidney

3.     Vitamin D helps in deposition of calcium in the bones.

The bones grow denser and stronger.

Food Sources

The Vitamin D content of food sources from animals varies with the diet, breed and exposure to sunlight of the animal.

The good sources of Vitamin D are cod liver oil, shrimp, liver, butter, yolk, cheese, milk, spinach and cabbage.

Requirements

The expert group of ICMR has not recommended dietary intake of Vitamin D for Indians.

Only in those cases where the Vitamin D requirement is not met due to inadequate exposure to sunlight the ICMR recommends 400 µg/day of Vitamin D .

Deficiency

Deficiency of Vitamin D leads to decreased absorption of calcium which is manifested as muscular tetany, rickets in children and osteomalacia in adults.

Due to faulty calcification of bones the following derfomities is manifested in children which is called rickets. It is a disease in which there is weakness and abnormalities in bone formation. Rickets primarily affects children.

Manifestations:

1. faulty deposition of calcium on the bones.

2. Bowing of legs

3. Enlargement of ends of long bones

4.  Deformities of ribs - beading of ribs

5. Delayed closing of frontanel

6.Slow erruption of teeth.

7.  Malformed, decay - prone teeth

Osteomalacia in Adults

Osteomalacia is a condition where the quality of the bone is reduced. It occurs in women who are not exposed to sunshine and who have depleted mineral reserves resulting from successive pregnancies and prolonged lactation.

Osteomalacia is associated with low phosphorous level

but low blood calcium level is the most frequent cause. The following symptoms occur

1.    softening of the bones

2.    deformities of the limbs, spine, thorax and pelvis

3.    demineralization of the bones

4.    pain in pelvis, lower back and legs

5.    frequent bone fractures.

Hypervitaminosis

As in the case of Vitamin A intake of excessive amounts of Vitamin D leads to toxic symptoms which include irritability, nausea , vomiting and constipation.

Vitamin E

Vitamin E is known as antisterility vitamin because it is required for normal reproduction in animals and men.

Functions

Vitamin E is the primary antioxidant in the body and serves to protect polyunsaturated fatty acids (PUFA) from oxidation in cells and maintain integrity of the cell membrane. It also prevents the oxidation of beta carotene and Vitamin A. Vitamin E helps to maintain cell membrane integrity and protect RBC against hemolysis.

1.     Vitamin E reduces platelet aggregation

2.     Vitamin E is essential for the iron metabolism and the maintenance of nervous tissues and immune function.

3.     Vitamin E is been promoted as an anti-aging vitamin, because as cells age they accumulate lipid breakdown products. Vitamin E prevents this accumulation in maintaining cell health.

Food Sources

Vitamin E is widely distributed in foods. It is present in high concentration in vegetable oils and in cereal grains. Wheat gum, sunflower seeds, almonds, safflower oil, eggs, butter are good sources.

Meat, fruits and vegetables contain small amounts. Sesame oil and mustard oil are good sources of Vitamin E.

Requirement :

The requirement of Vitamin E is linked to that of essential fatty acids (linoleic and linolenic acids). The requirement of Vitamin E is 0.8 mg/g of essential fatty acid.

Deficiency

1.     Prolonged intake of Vitamin E deficient diets produces uncoordinated movement, weakness and sensory disturbances.

2.     It causes haemolytic anaemia in low birth weight infants

3.     Defective functioning of the retina leading to permanent blindness in premature infants occurs.

4.     It leads to reproductive failure in humans

5.     Vitamin E deficiency is associated with decreased ability of the lymphocytes.

Vitamin K :

Vitamin K is recognized as the anti haemorrhagic factor owing to its vital role in blood clotting mechanism.

Functions

Synthesis of blood clotting proteins. Vitamin K is essential for the activation of prothrombin. This gets converted to thrombin, which in turn activates fibrinogen to form fibrin. The process of blood clotting occurs as follows:

Injured tissue releases thromboplastin, which catalyses prothrombin formation. Vitamin K catalyses, conversion of prothrombin to thrombin. This in turn causes conversion of fibrinogen to fibrin which forms the clot.

Food Sources:

Dark green leafy vegetables are good sources of vitamin K. Fruits, tubers, seeds, dairy and meat products contain

Vitamin K.

Requirements :

The ICMR committee considered that no recommendation is needed for this Vitamin, as the synthesis of Vitamin K occurs in the lower intestine by the colonic bacteria and present widely in foods.

Effects of Deficiency:

Primary deficiency arises in infants resulting in delayed blood clotting and hemorrhage. This is because the new born babies have a sterile intestinal tract thus lack in the colonic bacterial colonies which produces Vitamin K. Vitamin K deficiency does not occur in adults.

Water soluble Vitamins:

Vitamin C (Ascorbic Acid)

The chemical name for Vitamin C is ascorbic acid. It was discovered in 1747 by the British physician Lind and demonstrated that citrus fruit juices prevented and cured scurvy.

Functions :

1.     Ascorbic Acid is essential for formation of cement substances and collagen which is found in blood vessels teeth and bones.

2.     It helps in the biosynthesis of non-essential amino acids (eg) hydroxy proline, tyrosin.

3.     It is required for absorption of iron as it reduces ferric to ferrous form which is easily absorbed.

4.     Vitamin C is essential for the formation of collagen a major structural protein of connective tissues.

5.     It is required for normal wound healing because it helps in the formation of connective tissue.

6.     Vitamin C is required for carnitine synthesis which aids in the transport of fatty acids in the cell.

7.     Vitamin C is essential for the synthesis of norepinephrine a neurotransmitter.

8.     It activates hormones (eg) growth hormone, gastrin releasing peptide, calcitonin, gastrin oxytocin.

9.     Drug detoxifying metabolic systems in the body require Vitamin C for its optimal activity.

10.            Vitamin C is an excellent anti-oxidant. It combines with free radicals oxidizing them to harmless substances that can be excreted.

Food Sources:

Amla, drumstick leaves, guava, cashew fruit, agathi, cabbage, bitter gourd, oranges, tomatoes are good sources of ascorbic acid. Cereals and pulses are poor sources. Vitamin C content of pulses increases on germination.

Requirements:

The recommended dietary allowances of ICMR for ascorbic acid is as given in table-21D.

Effects of Deficiency:

Prolonged deficiency of ascorbic acid produces a disease condition called as ' scurvy' in both infants and adults.

Infantile scurvy:

There is loss of appetite, failure to gain weight, irritability, palor, defective growth of bones. Haemorrhage occurs under the skin. There is defective formation of teeth and gums are swollen. The ends of the ribs become prominent resulting in beaded appearance called scorbutic rosary.

Adult Scurvy:

1.     General manifestation are fever, susceptibility to infection, and delayed wound healing.

2.     Anaemia: Microcytic hypochromic anaemia develops due to failure of absorption of iron.

3.     Gums become spongy and bleed easily. Gums become swollen and ulcerated.

4.     The blood vessels become fragile and porous due to defective formation of collagen. Joints become swollen and tender.

5.     Clinical symptoms appear when total body pool of ascorbic acid decreases. Skin becomes rough and dry. There are small petechial hemorrhages around hair follicles.

Thiamine

Thiamine is known as Vitamin B₁. Deficiency of thiamine leads to beri - beri. This condition is widely prevalent among population whose diet contains more of polished cereals.

Functions

1.    Thiamine is converted to thiamine pyrophosphate (TPP), which is an important co enzyme in the carbohydrate metabolism.

2.    It is involved in transmission of nerve impulses across the cells

Thiamine as TPP is an essential cofactor for the conversion of amino acid tryptophan to niacin.

Sources:

Yeast, whole wheat, millets, hand pounded rice, parboiled rice are good sources of thiamine. The bran contains most of the thiamine in the cereals. Gingelly seeds, groundnut, soyabean, cashewnuts, organ meats, pork, liver and eggs supply thiamine.

Requirements

Thiamine is involved in the carbohydrate metabolism. Its requirement is related to energy derived from carbohydrate. The ICMR expert group recommends an allowance of 0.5 mg per 1000 Kcal for adults and for infants 0.3 mg/1000 Kcal is suggested. The recommended dietary allowance per day is given in table-21E.

Effects of Deficiency

Deficiency of thiamine is associated with low calorie intake. Severe deficiency of thiamine produces a disease known as beri - beri.

It is manifested as

1.     Dry beri - beri

2.     Wet beri - beri

3.     Infantile beri - beri

a. Dry beri - beri

There is loss of appetite, tingling numbness and burning sensation in hands and feet. Calf muscles are tender. Knee and ankle jerks are sluggish.

In later stages complete loss of sensation in hands and legs occur. It is characterized by foot and waist drop. Mental depression and confusion occurs.

b. Wet beri - beri

In this case there is enlargement of heart and the cardiac output is high. Oedema or accumulation of fluid in legs, face and trunk is observed. palpitations are marked.

c.  Infantile beri - beri

It occurs in first few months of life if the diet of the mother is deficient in thiamine. Symptoms are restlessness, sleeplessness, constipation, enlargement of the heart and breathlessness.

Riboflavin

Riboflavin or Vitamin B2 is the yellow enzyme which is heat stable unlike other B Vitamins. Riboflavin in the combined form with proteins form flavo proteins or yellow enzymes.

This enzyme is of two types FAD - Flavin-di-nucleotide. FMN- Flavin mono-nucleotide.

1.     These substances act as coenzymes in many biological reactions primarily in oxidation -reduction, and dehydrogenation reaction

2.     Release of energy from glucose, fatty acids and amino acids. Conversion of vitamin B₆ and folate to active coenzymes.

3.     It is essential for the formation of red blood cells

4.     It is required for the synthesis of glycogen

Food Sources:

Rich sources are liver, dried yeast, egg, milk , meat, fish, whole cereals, legumes, and green leafy vegetables.

Requirements

Riboflavin requirement is related to energy intake - 0.6 mg/1000Kcal. The ICMR recommends the following requirement per day as given in table-21F.

Effects of Deficiency

Riboflavin deficiency is prevalent mainly among the low income groups particularly the vulnerable group and the elderly adults. Riboflavin deficiency is characterized by

1.     Soreness and burning of the mouth and tongue.

2.     Lesions at the angles of the mouth called Angular  Stomatitis.

3.     The inflammation of the tongue called glossitis

4.     Dry chapped appearance of the lip with ulcers termed cheilosis.

5.     The skin becomes dry and results in seborehoeic dermatitis.

6.     Photophobia, lacrimation, burning sensation of the eyes and visual fatigue.

7.     Decreased motor co-ordination

8.     Normocytic anaemia

Niacin

Niacin or Nicotinamide (amide form) is required by all the cells of our body.

Like thiamine and riboflavin it plays a vital role in the release of energy from carbohydrates , protein, fat and alcohol.

Functions

1.     Nicotinamide is essential for tissue metabolism. The active forms of nicotinanide are NAD - Nicotinamide adenine dinucleotide and NADP - Nicotinamide adenine dinucleotide phosphate.

2.     NAD and NADP are involved as coenzymes in large number of reversible oxidation reduction reactions.

3.     Nicotinic acid enhances stomach secretion

4.     NAD  is  involved  in  catabolic  reactions and  NADP  is involved in anabolic reaction in our body.

Food Sources

Dried yeast, liver, rice polishing, peanut, whole cereals, legumes, meat, fish, are good sources.

Tryptophan present in dietary protein is converted to niacin in humans. 60 mg of tryptophan yields 1 mg of niacin.

Requirements :

ICMR recommended dietary allowance of Niacin per day is given in table 21G.

Effects of Deficiency

Deficiency of nicotinic acid causes a disease known as pellagra. It is characterized by three D's à Dermatitis, Diarrhoea and Dementia.

1.     Dermatitis - Name pellagra comes from pelle-skin and agra-rough. Marked changes occur in the skin especially in the skin exposed to sun and friction areas like elbows, surfaces of arms, knees.

Lesions are symmetrically distributed, in the affected parts. At first there is reddening, thickening and pigmentation of the skin.

Later on there is exfoliation leading to ultimately parchment of skin - butterfly like appearance.

2.     Diarrhoea - Diarrhoea enhances the deficiency state. There are structural and absorptive defects in the small intestine. Tongue appears raw, and mucous membrane of the tongue is inflammed.

3.     Dementia - There is irritability, depression, poor concentration and loss of memory. Delirium is a common mental disturbance.

Folic Acid

Folic acid was first extracted from dark green leafy vegetables. It forms yellow crystals and is a conjugated substance made up of three acids namely pteroic, para amino benzoic acid and glutamic acid.

Functions

1.    Folic acid coenzyme is essential in bringing about transferring single carbon units for many interconversions. A number of key compounds are formed by these reactions like (i) Purines which are essential constituents of living cells.

(ii) Thymine - this essential compound forms a key part of DNA.

(iii)          the formation of haem group of haemoglobin.

The conversion of phenylalanine into tyrosin.

Food Sources:

Green leafy vegetables, liver, kidney, gingelly seeds, cluster beans, are rich sources of folic acid.

Requirements

The recommended dietary allowances of Folic acid by ICMR are given in table-21H .

Deficiency

1.     Simple folate deficiency results in the bone marrow producing immature cells (megaloblasts cells) and few matured red blood cells. This results in reduced oxygen - carrying capacity causing anaemia termed - Megaloblastic anaemia.

2.     Folate deficiency during pregnancy causes neural tube disorders of the foetus.

3.     Folate deficiency impairs the ability of the immune system to fight infection.

Pyridoxine (B₆)

Pyridoxine is unique among B - complex Vitamins in that it functions primarily in protein metabolism.

Pyridoxine denotes related substances such as Pyridoxine, Pyridoxal and Pyridoxamine are three forms in which it is present in our body.

Functions

Vitamin B₆ in the form of pyridoxal phosphate functions as a co-enzyme in many biological reactions

1. Pyridoxine is essential for the process of

a.     Transamination : transfer of amino group from one aminoacid to another.

b.     Deamination :  Removal of the amino group

c.      Decarboxylation:  Removal of the carboxyl group

2.     Vitamin B₆ is involved in several biochemical steps for the conversion of the amino acid tryptophan to niacin

3.     It aids in the formation of elastin, synthesis of messenager RNA and haem part of haemoglobin.

4.     It aids in the conversion of linoleic acid to arachidonic acid.

5.     In the carbohydrate metabolism it aids in the release of glycogen from liver and muscle.

Food sources:

Meat, pulses and wheat are rich sources. Other Cereals are fair sources of this vitamin. Fruits and vegetables are poor sources. Cooking and processing of food causes loss of this vitamin.

Requirement: The ICMR recommended dietary allowance for pyridoxine is given in below.

The ICMR Recommended Dietary Allowance for Pyridoxine

Group        Pyridoxine mg/day

Adults         2.0

Pregnant woman  2.5

Lactation    2.5

Infants        0.1 - 0.4

Children (1 - 9 years)    0.9 - 1.6

Boys and girls (10 - 18 years) 1.6 - 2.0

Deficiency

Vitamin B₆ deficiency leads to abnormalities in protein metabolism which is manifested as poor growth, convulsions,  anaemia, decreased antibody formation and skin lesions. Severe deficiency leads to microcytic hypochromic anaemia.

Symptoms such as weakness, nervousness, irritability, insomnia and difficulty in walking is predominant.

Vitamin B₁₂ (Cyanocobalamin)

Until 1926, pernicious anaemia was a fatal disease of unknown origin with an unknown cure. In 1926 Minot and Murphy found that pernicious anaemia could be cured by feeding a patient atleast 0.3 kg of raw liver per day.

Also in 1926 Castle noted that patients with pernicious anaemia had a low level of gastric secretion. He suggested that the anti-pernicious anaemia factor had two components.; an ' extrinsic factor' found in food and an ' intrinsic factor' within normal gastric secretions. The extrinsic factor is now known as vitamin B₁₂ - cobalamine.

Functions :

Vitamin B₁₂ is necessary for normal growth and maintenance of healthy nervous tissue and normal blood formation.

Vitamin B₁₂ is involved in DNA synthesis and thus in cell replication.

In the bone marrow the Vitamin B₁₂ co-enzymes are essential for the formation of red blood cells.

It facilitates the formation of folate co-enzymes needed for nucleic acid synthesis.

Vitamin B₁₂ is also required for the synthesis of myelin sheath that surrounds the nerve fiber.

Food sources

Vitamin B₁₂ is present only in foods of animal origin. Liver sheep, shrimp, mutton , egg, milk are good sources of Vitamin B₁₂.Vitamin B₁₂ is synthesized by the colonic bacteria.

Requirements :

The recommended dietary allowance prescribed by ICMR for B₁₂ are given in below.

The ICMR Recommended Dietary Allowance for VitaminB12

Group        Vs Vitamin B12 mg/per day

Man  1.0

Woman       1.0

Pregnancy   1.0

Lactation    1.5

Infants        0.2

Children boys and girls  0.2 - 1.0

Deficiency

Pernicious amaemia is the major problem arising from an inadequate amount of vitamin B12.

Pernicious amaemia is a condition characterized by very large, immature red blood cells with normal amounts of haemoglobin.