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Vitamins: Classification, Daily Recommendation, Deficiency, And Dietary Sources

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The term vitamin was coined in 1911 by Casimir Funk, a biochemist. Vitamins are organic molecules which are essential dietary nutrients. They are non-energy yielding and non-body building agents but are required for proper functioning of bodily functions and regulation of metabolism. Vitamins have various biochemical and regulatory functions. They regulate cells and tissue growth and differentiation. They also act as co-factors for enzymes. Our body cannot synthesize vitamins and hence they should be supplemented in diet. The deficiencies of vitamins have been linked to various diseases.

Traditionally vitamins are classified as:

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  1. Water soluble – Vitamin B, C.
  2. Fat soluble-Vitamin A, D, E, K.

Vitamin B.

Overall vitamin B plays a vital role in maintenance of healthy life, proper brain function, adrenal gland function and cell metabolism. Vitamin B promotes RBC maturation, good eyesight and digestion, proper nerve and hormonal function. It also regulates cholesterol metabolism.

Vitamin B Complex is composed of 8 vitamins:

  1. Vitamin B1 known as Thiaminei
  2. Vitamin B2 known as Riboflavin
  3. Vitamin B3 known as Niacin
  4. Vitamin B5 known as pantothenic acid
  5. Vitamin B6 known as pyridoxine
  6. Vitamin B7 known as Biotin
  7. Vitamin B9 known as Folic acidv
  8. Vitamin B12 known as Cobalamine.

These are discussed in details below:

  • Vitamin B1 (Thiamine)
  • It is also known as aneurine. Vitamin B1 is associated with carbohydrate metabolism. It plays a key role in maintaining function of nerves, muscles and heart. It is converted in body to thiamine pyrophosphate, and acts as a coenzyme in carbohydrate metabolism.

    Daily recommendation: For women the RDA of vitamin B1 is 1. 1mg/day whereas for males it is 1. 2mg/day.

Deficiency: Vitamin B1 deficiency leads to a condition known as beriberi. It is of 2 types:

  1. Dry beriberi: It involves neurological symptoms like polyneuritis with numbness, muscular weakness, tingling resulting in wrist drop, foot drop, paralysis, mental disturbances, sluggishness, memory impairment, loss of appetite and constipation.
  2. Wet beriberi: It involves CVS disturbances which include ECG changes, shortness of breath, palpitations and increased cardiac output.

Dietary sources: Food reach in vitamin B1 includes outer layer and germ of cereals, yeast, pork, whole grams, pulses and almonds. In addition to this, cauliflower, liver, oranges, eggs, potatoes and kale also have vitamin B1.

  • Vitamin B2 (Riboflavin)
  • It is involved in reductive-oxidative (redox) reactions as co-enzymes for flavoproteins. It is required for digestion of food and absorption of nutrients. It helps in generating energy from protein, carbohydrates and fats. Riboflavin converts carbohydrates into ATP. It maintains healthy liver, digestive tract, eyes, nerves, muscles and skin. It prevents development of cataract.

Daily requirement: RDA in adult males is 1. 3mg/day whereas in adult females it is 1. 1mg/day while breast feeding mothers RDA is 1. 6mg/day.

Deficiency: Vitamin B2 deficiency is associated with poor diet as it is not stored in body and continuously excreted. These are two types of vitamin B2 deficiency.

  1. Primary: This due to poor diet
  2. Secondary: This is due to improper absorption of vitamin B or its rapid excretion.
  3. Riboflavin deficiency is known as ariboflavinosis. The sign and symptoms of vitamin B2 deficiency includes Angular chelitis i. e cracking of corner of mouth and lips, dry skin, inflammation of tongue and lips leading to mouth, ulcers, store throats, scrotal dermatitis, anemia, itchy and watery eyes.

    Dietary Sources: Sources of vitamin B2 includes fish. Meat, eggs, milk and dairy products, nuts, avocado, parsley, pumpkins, sweet potatoes and vegetables likes broccoli, brussels, spinach and dandelion green.

  4. Vitamin B3 (Niacin)
  5. It is referred to as nicotinic as well as nicotinamide-pyridine compounds, initially termed pellagra preventing factor. It plays role in maintenance of healthy skin, digestive system and mental health. It acts as cofactor for more than 200 enzymes in the body. Nicotinic acid is converted to nicotinamide, which is a component of coenzyme nicotinamide-adenine-dinucleotide (NAD) and its phosphate (NADP) involved in redox reactions. These function as hydrogen acceptors in mitochondrial electron transport chain in respiration, glycolysis and lipogenesis.

    Daily requirement: For children the RDA is between 2-16mg/day, depending on age. For men it is about 16mg/day while for women it is 14mg/day, but increases up to 18mg/day in pregnancy.

    Deficiency: Vitamin B3 deficiency causes a condition termed as pellagra, which effects skin, nervous system and digestive system. Symptoms include lesions on both side of body which are prominent at pressure points and those parts of body which are exposed to sun. Swelling, pain, inflammation of mouth, vagina and urethra along with redness and swelling of tongue, pain and burning sensation in throat, chest and stomach, vomiting, diarrheoa and constipation also includes other symptoms of pellagra. Dietary Sources: It is found in fish, milk, meat, egg, yeast green leafy vegetables.

  6. Vitamin B5 (Pantothenic acid)
  7. Vitamin B5 helps in synthesizing coenzyme A which is involved in fatty acid synthesis. Coenzyme A which is involved in fatty acid synthesis also plays a role in synthesis of sphingolipids and acetylcholine needed for signal transduction. Vitamin B5 has a role in glucose and cholesterol metabolism also. It is also involved in synthesis of sex and stress hormones and blood cells. It acts as a moisturizer to the skin and also enhances wound healing.

    Daily requirement: For infants up to 6 months the recommended dose is 1. 7mg/day. For children up to 8 years dose ranges between 1. 8 mg/day to 4 mg/day depending on age. For adults the RDA is 5mg/day and for pregnant women it is 6mg/day.

    Deficiency: Vitamin B5 deficiency is extremely rare, but it may result in tiredness, depression, irritation, sleep disorders, hypoglycemia, burning feet and respiratory infections.

    Dietary sources: the name ‘pantothenic’ has been derived from greek word ‘Pantos’ which means everywhere. As the name suggest it is nearly found in all foods and therefore its deficiency is rare. It occurs in high amount in meat, fishes, grains, milk and milk products. It is also present in fruits and vegetables.

  8. Vitamin B6 (Pyridoxine)
  9. Pyridoxine acts as coenzymes in metabolism of carbohydrates, fats and proteins. Pyridoxine and pyridoxamine are oxidized to pyridoxal, which is further phosphorylated to pyridoxal phosphate. It is coenzyme for enzymes like transaminases and decarboxylases. It also plays role in production of neurotransmitters. It is also immunomodulatory.

    Daily requirement: The RDA for vitamin B6 for infants up to 6 months is 0. 1mg/day whereas for children up to 13 years it ranges between 0. 3mg/day to 1mg/day. In adults it is around 1. 3mg/day. In pregnant and lactating females it is 1. 9mg/day and 2mg/day respectively.

    Deficiency: Vitamin B6 deficiency results in neuronal damage particularly in the area of hands and feet. It also leads to cervical dysplasia. Its other symptoms include dermatitis, lip sores, constipation, depression and insomnia.

    Dietary Sources: It is selectively present in foods like chick pea, meat, fishes, eggs, potatoes, banana, cheese, onions, spinach and water melon.

  10. Vitamin B7 (Botin)
  11. It is also known as Vitamin H or coenzyme R. it is sulfur containing vitamin function as co-factors for various metabolic enzymes. It has been shown to be beneficial in type 2 diabetes mellitus. It is required for maintenance of healthy hair and nails. It acts as a coenzyme carboxylase enzymes. It is also associated with fatty acid synthesis, amino acid metabolism and gluconeogenesis.

    Daily requirement: For infants up to 6 months the RDA is 6µg/day and children up to 13 yrs it is between 8µg/day to 25µg/day depending upon age. For adults the RDA of vitamin B7 is around 30µg/day. It increases to 35µg/day for pregnant and lactating mothers.

    Deficiency: Deficiency of Biotin is common in breast feeding mothers. Raw egg consumption also leads to its deficiency as biotin binds to avidin. The main symptoms of vitamin B7 deficiency are hair fall, dermatitis, depression, lethargy, hallucinations, numbness and tingling of hands and feet and conjunctivitis. Biochemical manifestation of biotin deficiency includes ketolactic acidosis, hyperammonemia and aciduria. D

    ietary Sources: Foot sources rich in biotin content includes meat, fishes, eggs, milk and milk products, cereal, broccoli, cauliflower, cheese, legumes, mushroom and spinach.

  12. Vitamin B9 (Folic acid)
  13. It is crucial for blood cell formation. Vitamin B9 is necessary for proper neuronal development and brain functioning. It is beneficial in preventing strokes and heart diseases as it reduces the elevated levels of homocysteine (an amino acid). Vitamin B9 also leads to better growth of fetus and strengthens placenta. It is essentials for development of fetal brain and spinal cord. Folic acid has been listed in WHO’s list of essential medicine.

    Daily Requirement: The RDA for infants up to 6 months is 65µg/day whereas for 6-12 month old it is 150µg/day. For 1-3 yrs old the RDA is 150µg/day. For adults RDA ranges from 300µg/day to 400µg/day. For pregnant females RDA increases to 600µg/day.

    Deficiency: The major effect of folic acid deficiency is production oversized immature red bllod cells known as megaloblastic anemia. In pregnant women it may lead to neuronal tube birth defect and can also result in miscarriage.

    Dietary Sources: Actually the name ‘folium’ has been derived from Latin word meaning leaves because it was first isolated from spinach leaves. Hence folic acid is abundantly present in green vegetables, sprouted beans, beet roots, spearmint, strawberry, nuts, soybean and eggs.

  14. Vitamin B12 (Cobalamine)
  15. Vitamin B12 is associated with metabolism. It serves as cofactor in DNA synthesis, fatty acid and amino acid metabolism. It also plays role in synthesis of myelin in mylinated neurons and maturation of erythrocytes.

    Daily requirement: RDA for children 1-13 yrs is 0. 9µg/day to 1. 8µg/day and for adults is 2. 6µg/day. For lactating mothers RDA increases to 2. 8µg/day.

    Deficiency: The most common result of vitamin B12 deficiency is pernious anemia which results from inability of erythrocytes to carry adequate amount of oxygen. Pernious anemia leads weakness and fatigue. Cobalamine deficiency can also lead to jaundiced skin. It also affects posture and mobility because of nerous system damage. It also results in mouth ulcers and inflammation of tongue, a condition called Glossitis making talking and swallowing painful. It also leads to disturbances in vision and mood swings.

    Dietary Sources: Vitamin B12 is produced only by bacteria and archaeabacteria. In humans it is synthesized in the gut by gut flora. Animals store vitamin B12 in liver and muscles and pass it on to their eggs and milk. Therefore, egg, milk and meat are rich in vitamin B12. Algae like Porphyra yezoensis also contain vitamin B12.

Vitamin C

It is also known as L-Ascorbic acid it is a reducing agent and its levo form is biologically active. Humans cannot synthesize vitamin C. Vitamin C plays a role in many redox reaction and metabolism. It is essential for collagen synthesis and prevents aging. It is essential for conversion of folic acid to usable folinic acid. It is involved in steroid and catecholamine synthesis.

Daily requirement: Infants up to 6 months need 40mg/day while those 6-12 months need 50mg/day. For 1-18 year old children and adolescent RDA of vitamin C is 15-75mg/day. Adult males require 90mg/day and females require 75mg/day. Pregnant and lactating mothers require 85mg/day and 120mg/day of vitamin C respectively.

Deficiency: Vitamin C deficiency is known as Scurvy. In scurvy there is improper collagen synthesis leading to bleeding gums and brittle bones. It also leads to poor wound healing, painful joints, purpurea, hyperkerotosis and corkscrew nails.

Dietary sources: Citrus fruits and vegetables are best sources of vitamin C. Tomatoes, potatoes, red and green pepper, kiwi fruit, broccoli, oranges, strawberry, grapes. It is not present in cereal and milk.

Essential Fatty Acids

Those fatty acids which cannot be synthesized by the body but are needed for physiological processes are Essential fatty acids. The key players are omega -3 and omega -6 fatty acids (ω-3 and ω-6). The main function of fatty acids includes:

  1. Regulation of inflammation by synthesis of eicosanoids and resolvins.
  2. Affect mood and behavior by regulating endocannabinoids.
  3. They affect cell signaling via forming lipid rafts in plasma membrane.
  4. They are involved in cytokine production.
  5. They regulate DNA synthesis.

Examples of ω-3 fatty acids include α-linolenic acid, eicosapentaenoic acid, docossahexaenoic acid. Examples of ω-6 fatty acid include linoleic acid, γ-linolenic acid, dihomo-γ-linolenic acid and arachidonic acid. Mammals cannot introduce double bonds in fatty acids beyond carbon 9 and 10. Therefore ω-3 and ω-6 fatty acids has to be supplemented in diet. Daily requirement: RDA for ω-3 fatty acid is 2g/day whereas for ω-6 fatty acid it is 10g/day.

Deficiency: The symptoms of fatty acid deficiency include pain in joints, allergy, menstrual cramps, dry eyes, dull hairs, excessive ear wax secretion, pre-menstrual breast tenderness and excessive thirst.

Dietary sources: the major source of ω-fatty acids includes fishes and shell fishes. It is also present in flax seed oil, olive oil, hemp oil, walnuts, sunflower oil and pumpkin seeds.


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