Introduction
Vitamins are organic compounds that are required in small amounts to perform specific biological functions for the normal maintenance of optimum growth and health of the organism. Fun fact! The bacteria Escherichia coli does not require vitamins as they are synthesized. It is believed that the ability to synthesize vitamins is lost as an evolutionary process. So, higher organisms like humans require vitamins in their diet for normal functions.
Classification of vitamins
Vitamins are classified into fat-soluble vitamins and water-soluble vitamins.
· Fat-soluble vitamins are vitamins A, D, E, K
· Water soluble vitamins are vitamins B, C
Fat-soluble vitamins are absorbed and transported through fats. They are stored in the liver and adipose tissue. Excess of fat-soluble vitamins can lead to hypervitaminosis.
Water-soluble vitamins are not stored in the body except for vitamin B12.
Intestinal bacteria synthesize vitamins!
Although the human body cannot produce vitamins, the bacteria in the intestine especially the colony synthesize various vitamins required for growth.
It is said that the vitamin K and biotin synthesized by the intestinal bacteria itself are sufficient for human survival.
The use of antibiotics kills these bacteria and hence there will be a requirement of vitamins from the diet.
Fat-soluble vitamins
Fat-soluble vitamins | Dietary sources | Recommended dietary allowance - day | Deficiency | Overdose |
Vitamin A | Animal sources include liver, kidney, egg yolk, fish, oil, milk, butter, and cheese. Plant sources include yellow and green vegetables like carrots, papaya, pumpkin, spinach, etc.
| 3,500 IU for man and 2,500 IU for woman | Eye: night blindness, xerophthalmia, keratomalacia
Growth: impaired skeletal formation
Reproduction: sterility in males
Skin: dry and rough skin. Keratinisation of GI, urinary and respiratory tract leading to bacterial infection | Dermatitis, raised intracranial tension, weight loss, skeletal decalcification, bone pain, and joint pain. |
Vitamin D | Fatty fish, fish liver oils, egg yolks.
Vitamin D is also called a hormone since it can be partially synthesized in the body by exposure of the skin to sunlight. | In India, 200 IU (or 5 mg cholecalciferol) | Rickets in children; osteomalacia in adults.
Bone deformities like pliable bones, and bow legs, increase susceptibility to fractures. | Hypercalcemia, bone resorption, risk of kidney stones, loss of appetite, nausea, weight loss, etc. |
Vitamin E | Cotton seed oil, wheat germ oil, peanut oil, sunflower oil, milk, butter, eggs, meat | 10mg for male, 8mg for females | Sterility, degenerative changes in muscles, megaloblastic anemia | Least toxic |
Vitamin K | Cabbage, cauliflower, tomatoes, alfa alfa, spinach, egg yolk, meat, liver, cheese | Nil – produced by intestinal bacteria | lack of active prothrombin in the circulation leading to increased blood clotting time | Hemolytic anaemia, jaundice |
Water soluble vitamins
Vitamin | Dietary source | RDA | Deficiency |
Vitamin C | Citrus fruits, gooseberries, guava, green vegetables, tomatoes, potatoes. | 60-70mg | Scurvy - sore gums, loose teeth, anemia, swollen joints, fragile blood vessels, decreased immunocompetence, delayed wound healing, osteoporosis, hemorrhage etc. |
Vitamin B1/ thiamine | Cereals, pulses, oil seed, nuts, pork, liver, kidney milk etc. | 1-1.5mg | Beri-beri seen in the population eating polished rice as a staple food Wet beri beri: affects cardiovascular system - Edema of legs, face, breathlessness, palpitations, death due to heart failure Dry beri beri: neurological manifestation. Peripheral neuritis Wernicke-Korsakoff syndrome: cerebral beri beri. Seen in chronic alcoholics. memory loss, apathy and a rhythmical to-and-fro motion of the eyeballs |
Vitamin B2/ Riboflavin | Milk, meat, egg, cereals, vegetables, fish | 1.2-1.7mg | Cheilosis, glossitis, dermatitis |
Vitamin B3/ Niacin | Yeast, whole grains, cereals, pulses, milk, fish, eggs and vegetables | 15-20mg | Pellagra - dermatitis, diarrhea, dementia Seen in people whose staple diet is corn or maize. |
Vitamin B6/ Pyridoxine | Egg, fish, wheat, corn, cabbage, tubers | 2-2.2mg | Depression, irritability, nervousness and mental confusion, Convulsions and peripheral neuropathy |
Vitamin B7/H/ Biotin | Tomato, grains, milk, egg, liver | 100-300mg | Anemia, loss of appetite, nausea, dermatitis, glossitis, depression, hallucinations,
muscle pain and dermatitis. |
Pantothenic acid | egg, liver, meat, yeast, milk | 5-10mg | Burning feet syndrome - pain and numbness in the toes, sleeplessness, fatigue etc. Anemia, fatty liver, decreased steroid synthesis etc |
Vitamin B9/ Folic acid | green leafy vegetables, whole grains, cereals, liver, kidney, yeast and eggs | 200 micrograms | pregnant women, lactating women, women on oral contraceptives, and alcoholics are susceptible to folate deficiency. Megaloblastic anemia Neural tube defects in fetus |
Vitamin B12/ Cyanocobalamin | liver, kidney, milk, curd, eggs, fish, pork and chicken | 3 micrograms | Pernicious anemia Neuronal degeneration and demyelination - paresthesia of fingers and toes, confusion, memory loss and even psychosis |
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