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In this article, we will understand the basics of vitamins, their classification, rich sources and diseases caused by the deficiency of the same. Questions related to these regularly appear in various exams conducted by UPSC, SSC and other bodies/institutions.
What are Vitamins?
Vitamins are organic (carbon containing) compounds that are essential for normal growth and nutrition. They are required in small quantities in the diet because they cannot be synthesised by the body. In short, vitamins are organic substances required in small quantities by the human body for smooth functioning of many processes and to prevent diseases caused by the lack of it, such as pellagra, scurvy, rickets, beriberi, among others.
Classification of Vitamins:
Vitamins can be classified into two main categories: Water Soluble and Fat soluble
1. Water Soluble Vitamins – Vitamin B and Vitamin C
Water soluble vitamins refer to those that can be easily absorbed into the blood stream and quickly get eliminated through urine.
2. Fat Soluble Vitamins – Vitamins A, D, E & K
Fat Soluble vitamins, as the name suggests, are absorbed in the fat tissues only. These vitamins can be stored up to several days inside the body and therefore excess of the same may be toxic.
Since there is a need for constant supply of vitamins in varying amounts, a limit is set and regulated by the US Food and Drug Administration (USFDA) for the quantity of vitamins that can be safely consumed. This limit is known as the Recommended Daily Allowance (RDA).
Given below are various vitamins, their rich sources, the diseases/symptoms that are caused in case of their deficiency and the respective Recommended Daily Allowance (RDA)
Vitamin A
- Alternate names: Retinol, Retinal, Retinoic Acid
- RDA: 900 mcg for males, 700mcg for women.
- Significance: Vitamin A ensures good vision. It helps in maintenance of healthy skin, skeletal and soft tissues, teeth and mucus membranes. However, large doses can cause acute Vitamin A poisoning. Children are more sensitive to Vitamin A even at smaller doses.
- Rich sources – Dark green leafy vegetables, carrots, bell peppers, fishes, legumes, lentils, papayas and sweet potatoes.
- Deficiency diseases – Night Blindness, Keratomalacia/ Xerophthalmia.
Vitamin B-complex
Vitamin B-complex is further classified into its 8 subtypes, namely:
- Vitamin B1 (Thiamine): The first vitamin B to be discovered, it plays an important role in energy production from dietary fats and carbohydrates. Legumes, nuts and whole grains are the richest sources of vitamin B1. The RDA for B1 is 1200 mcg for men and 1100 mcg for women. Its deficiency can cause beriberi.
(ii) Vitamin B2 (Riboflavin): It is known to give antioxidant protection. It aids energy metabolism along with iron metabolism. Rich sources of vitamin B2 include green leafy vegetables, milk, cheese, fish and legumes. The RDA for B2 is 1300 mcg for men and 1100 mcg for women. Its deficiency can cause anaemia, inflammation of the tongue and fissures at the corner of the mouth.
(iii) Vitamin B3 (Niacin/ Niacinamide): It acts as an antioxidant and aids energy metabolism. Rich sources of vitamin B3 include yeast, milk, whole grains, lean meat and peanuts. The RDA for B3 is 16000 mcg for men and 14000 mcg for women. Its deficiency can cause skin inflammation, diarrhoea and dementia.
(iv) Vitamin B5 (Pantothenic acid): It is known for metabolism of fats and carbohydrates. It is is abundantly found in organ meat, brewer’s yeast, egg yolks, chicken and sweet potatoes. The RDA for B5 is 5000 mcg for men and 5000 mcg for women. Its deficiency is very rare and has no clinical symptoms.
(v) Vitamin B6 (Pyridoxine/ pyridoxamine): It plays a key role in formation of red blood cells (RBCs), aids liver detoxification and maintains the nervous system by production of neurotransmitters. Rich sources of vitamin B6 include vegetables, tuna, salmon, beef and chicken. The RDA for B6 is 1300 mcg for both men and women. Its deficiency can cause weight loss, anaemia, convulsions in infants and disturbances in the functioning of central nervous system.
(vi) Vitamin B7 (Biotin) or Vitamin H: It helps the body to metabolise carbohydrates, proteins and fats. It helps in maintenance of healthy hair and skin and hence is found in many skin products. Rich sources of vitamin B7 include liver, yeast, pork, salmon and cheese. The RDA for B7 is 15 – 100 mcg for both men and women. No deficiency disease is associated with this vitamin.
(vii) Vitamin B9 (Folic acid/ Folinic acid): Vitamin B9 is extremely important at cellular levels. It plays an important role in cell division, synthesis and repair of DNA and RNA. Rich sources of vitamin B9 include cabbage, broccoli, cauliflower, lettuce, egg yolk, spinach, sunflower seeds and nuts. The RDA for B9 is 200 mcg for both men and women. Its deficiency can cause anaemia, fatigue, loss of appetite and weight, irritability and forgetfulness.
(viii) Vitamin B12 (Cyanocobalamin): It helps in the formation of RBCs and is an important co-factor in the production of DNA. Since no plant can synthesise it, rich sources of vitamin B12 include only animal sources like beef, pork, sardines, salmon, tuna and organs of ruminants like cattle and buffalo. The RDA for B12 is 2400 mcg for both men and women.
Vitamin C
- Alternate name: Ascorbic Acid
- RDA: 90,000 mcg for men, 75,000 mcg for women.
- Significance: It helps in maintaining healthy connective tissues and accelerates wound healing. Overdose of vitamin C is a rare phenomenon since it cannot be stored in the body. However, at very high doses, it can cause stomach pain and flatulence.
- Rich sources: Citrus fruits, tomatoes, berries, broccoli, peas and papayas.
- Deficiency diseases: Scurvy, bleeding gums, impaired healing of wounds, rashes.
Vitamin D
Vitamin D is further classified into 2 subtypes, namely D2 (Ergocalciferol) and D3 (Cholecalciferol)
- RDA: 5 – 10 mcg for both men and women.
- Significance: It helps in maintenance of normal levels of calcium and phosphorus, enhances absorption of minerals like calcium, magnesium and zinc and also strengthens bones. Vitamin D is found in rare foods. Primarily, it is synthesised in human skin on exposure to sunlight. Hence, vitamin D is also known as the “sunshine vitamin”.
- However, its overdose can lead to Hypervitaminosis D (vitamin D toxicity), which in turn can cause Hypercalcemia (abnormally higher levels of calcium in blood) with symptoms like nausea, weakness and frequent urination. Kidney damage/ failure is a potential threat with prolonged duration of Hypervitaminosis D.
- Rich sources: Dairy products, egg yolk, beef liver, fatty fishes like tuna, mackerel.
- Deficiency diseases: Rickets in children, Osteomalacia in adults.
Vitamin E
- Alternate names: Tocopherols, Tocotrienols
- RDA: 15,000 mcg for both men and women.
- Significance: It plays an important role in metabolic processes and in immune system. It is also used in managing diabetes and its complications. It also helps to prevent cancer, Premenstrual syndrome (PMS) and menopausal syndrome. At higher doses, it can cause impaired blood clotting, allergic skin reactions, increased risk of stroke and kidney dysfunction.
- Rich sources: Soybean, nuts and oils from sunflower, safflower, olive, groundnut and cod liver.
- Deficiency diseases: Hemolytic anemia, muscle weakness, hair loss, cramps.
Vitamin K
- Vitamin K is further classified into 2 subtypes, namely K1 (Phylloquinones) and K2 (Menaquinones).
- RDA: 120 mcg for men, 90 mcg for women.
- Significance: Vitamin K plays a crucial role in blood clotting (controls the formation of coagulation factors II (prothrombin), VII, IX, and X in the liver), thereby preventing excessive blood loss from wounds. It helps in managing osteoporosis and bone loss caused by steroids. However, patients using blood-thinning medication should avoid consuming vitamin K since it can reverse the effect of the medication. Vitamin K1 does not cause toxicity even when consumed in high amounts.
- Rich sources: Beans, eggs, strawberries, meat.
- Deficiency diseases: Delayed blood clot formation.
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