VITAMINS: A TEACHER’S COMPREHENSIVE GUIDE
Welcome, future pharmacists and healthcare professionals!
Vitamins are organic substances that maintain the normal structure and function of cells. They are mostly obtained from plants or animals, so they are ingested as constituents of plant or animal foods. They are required in amounts much lesser than that of essential amino acids and fatty acids. They do not aid in energy production.
Dpharmguru’s exam insights:
In my years of teaching biochemistry, I have observed that students often get confused between fat-soluble and water-soluble vitamins. Remember: Fat-soluble vitamins (A, D, E, K) are stored in the liver and can cause toxicity if taken in excess. Water-soluble vitamins (B-complex and C) are not stored and must be taken daily. This is a very common exam question!
CLASSIFICATION OF VITAMINS
- Fat-Soluble Vitamins: Vitamin A, D, E, and K. Hydrophobic in nature, stored in the liver, not excreted out of the body. Excessive intake can produce toxic effects (hypervitaminosis).
- Water-Soluble Vitamins: Vitamin B-complex and Vitamin C. Not stored in the body, required daily in small quantities.
FAT-SOLUBLE VITAMINS
Vitamin A (Retinol)
Vitamin A is also known as axerophthol or anti-xerophthalmic or anti-nyctalopic vitamin. It is an unsaturated alcohol.
Sources: Pro-vitamin A (β-carotene) is obtained from green vegetables, fruits, and cereals. Liver, milk, butter, and egg yolk are good sources.
Functions:
- Necessary for normal vision and overall body growth.
- Accelerates the growth of the neurological system and bones.
- Keeps cell membranes, lysosomes, and mitochondria in good shape.
- Improves carbohydrate metabolism, particularly gluconeogenesis.
- Boosts protein synthesis by triggering aminoacyl-tRNA synthetisation.
- Speeds up the cell’s transcription and translation processes.
- Necessary for DNA metabolism.
Coenzyme Form: Retinol, Retinal, Retinoic acid
Recommended Dietary Allowance: 600 μg/day
Deficiency Diseases:
- Night blindness (nyctalopia)
- Xerophthalmia (drying of conjunctiva) and keratomalacia (ulceration of cornea) in children
- Toad’s skin (dry and rough skin)
Dpharmguru’s exam insights:
A common exam question is: “Which vitamin deficiency causes night blindness?” The answer is Vitamin A. Also, remember that β-carotene is a precursor of vitamin A found in carrots and green vegetables.
Vitamin D (Calciferol)
Vitamin D is also known as anti-rachitic vitamin due to its property of curing or preventing rickets.
Sources: Cod liver oil, fish liver oil, egg yolk, milk, and animal liver. Vitamin D3 is made photochemically from 7-dehydrocholesterol by the action of sunlight.
Functions:
- Produces calcitriol hormone which regulates calcium and phosphate metabolism.
- Triggers mRNA transcription for calcium-binding protein.
- Aids in the growth and development of bones and teeth.
- Increases phosphate excretion.
Deficiency Diseases:
- In children: Rickets (bow legs, knock knees, pigeon’s breast)
- In adults: Osteomalacia (weak and fragile bones)
Dpharmguru’s exam insights:
Vitamin D is called the “sunshine vitamin” because it is synthesized in the skin upon exposure to sunlight. Rickets in children and osteomalacia in adults are deficiency diseases of vitamin D. This is frequently tested!
Vitamin E (Tocopherol)
Vitamin E is also known as anti-sterility vitamin or fertility vitamin.
Sources: Meat, liver, fish, chicken, vegetable oils, green leafy vegetables, and egg yolk.
Functions:
- Prevents polyunsaturated fatty acid peroxidation in tissues and membranes.
- Protects liver cells from toxicity.
- Protects nerve fibres from demyelination.
- Plays a role in reproductive physiology.
- Acts as an antioxidant, preventing rancidity.
Deficiency Diseases:
- Permanent sterility in males
- Foetal death in females
- Anaemia, oedema, and necrosis of hepatic cells
Vitamin K (Phylloquinone)
Vitamin K is also known as anti-haemorrhagic vitamin or coagulation vitamin for blood clotting.
Sources: Green leafy vegetables (cabbage, spinach), soya beans, wheat germ. Also synthesized by intestinal bacteria.
Functions:
- Increases the activity of blood clotting factors.
- Starts the manufacture of proconvertin, which catalyses the formation of prothrombin.
- Aids in the carboxylation of glutamate to γ-carboxyglutamate as a coenzyme.
Deficiency Diseases:
- Delayed blood clotting process
- Haemorrhagic disease of newborn
- Impaired liver functioning
Dpharmguru’s exam insights:
Remember: Vitamin K is essential for blood clotting. The “K” comes from the German word “Koagulation.” Newborns are given vitamin K injections to prevent haemorrhagic disease. This is a very common exam question!
WATER-SOLUBLE VITAMINS
Vitamin B₁ (Thiamine)
Vitamin B₁ is also known as anti-beri beri vitamin and anti-neuritic vitamin.
Sources: Rice bran, wheat bran, whole grains, nuts, pulses, yeast, liver, eggs, fish, meat, and milk.
Functions: Needed for utilising carbohydrates, maintaining good appetite, and normal brain metabolism.
Coenzyme Form: Thiamine Pyrophosphate (TPP)
Deficiency Diseases:
- Beri-Beri (polyneuritis, oedema, cardiovascular changes, muscular atrophy)
- Anorexia (loss of appetite)
- Wernicke’s encephalopathy (in alcoholics)
Vitamin B₂ (Riboflavin)
Sources: Milk, liver, kidney, heart, egg yolk, and sprouts.
Functions: Essential for growth, development, cellular function, and conversion of tryptophan to niacin.
Coenzyme Forms: Flavin Mononucleotide (FMN); Flavin Adenine Dinucleotide (FAD)
Deficiency Diseases: Cheilosis (cracks at the mouth’s angle), eczema on face, hair loss, coloured tongue, itchy red eyes, cataracts.
Vitamin B₃ (Niacin)
Sources: Liver, fish, beans, and peanuts. Tryptophan amino acid also helps in the formation of niacin.
Functions: Essential for cellular processes and energy production. Acts as coenzyme in the form of NAD⁺ and NADP⁺.
Coenzyme Forms: NAD⁺, NADP⁺
Deficiency Disease: Pellagra (characterised by dermatitis, diarrhoea, and dementia — the 3 Ds).
Dpharmguru’s exam insights:
Pellagra is the deficiency disease of niacin, characterised by the “3 Ds”: Dermatitis, Diarrhoea, and Dementia. This is a classic exam question!
Vitamin B₅ (Pantothenic Acid)
Sources: Honey (most abundant), cereals, nuts, oil seeds, eggs, liver, wheat grain, legumes, milk, meat, and fish.
Functions: Involved in energy production, hormone formation, and metabolism of fats, proteins, and carbohydrates. Coenzyme A is required for activation of acetate.
Coenzyme Form: Coenzyme A
Deficiency Symptoms: Nausea, vomiting, GIT issues, irritability, anaemia, fatty liver, hair loss, burning feet syndrome.
Vitamin B₆ (Pyridoxine)
Sources: Yeast, rice polishing, milk, meat, eggs, leafy vegetables, and liver.
Functions: Antioxidant that helps in protein metabolism, production of RBCs, neurotransmitters, and haemoglobin.
Coenzyme Form: Pyridoxal phosphate
Deficiency Diseases: Irritability, depression, confusion, hypochromic microcytic anaemia, dermatitis, peripheral neuropathy.
Vitamin B₇ (Biotin)
Sources: Eggs, liver, fish, meat, beans, germinating seeds, intestinal flora, and peanuts.
Functions: Involved in metabolism of lipids, proteins, and carbohydrates. Acts as a coenzyme for carboxylase enzymes.
Deficiency Diseases: Hair loss (alopecia), periorificial dermatitis (scaly red rash around eyes, nose, and mouth), conjunctivitis, skin infections.
Vitamin B₉ (Folic Acid)
Sources: Synthesised by intestinal flora. Exogenous sources: liver, eggs, and leafy vegetables.
Functions: Transfer of one carbon unit, production of DNA and RNA, and red blood cell production.
Coenzyme Form: Tetrahydrofolic acid (THF)
Deficiency Diseases: Megaloblastic anaemia, weakness, fatigue, irregular heartbeat, shortness of breath, hair loss, pale skin.
Dpharmguru’s exam insights:
Folic acid deficiency causes megaloblastic anaemia. It is especially important during pregnancy to prevent neural tube defects. This is a frequently tested concept!
Vitamin B₁₂ (Cobalamin)
Sources: Liver, egg, meat, and fish. Synthesised only by specific microbes.
Functions: Involved in formation of genetic material, RBC production, and nervous system maintenance.
Coenzyme Form: Methylcobalamin, Deoxyadenosylcobalamin
Deficiency Diseases: Demyelination, neurological abnormalities, infertility, and megaloblastic anaemia.
Vitamin C (Ascorbic Acid)
Vitamin C is also called antiscorbutic acid because it prevents scurvy.
Sources: Citrus fruits (lemons, oranges), grapes, apple, papaya, guava, vegetables.
Functions:
- Necessary for iron absorption.
- Keeps gums and capillary walls healthy.
- Provides immunity against cold and viruses.
- Required for wound healing.
- Acts as a coenzyme in hydroxylation and oxidation-reduction processes.
Deficiency Disease: Scurvy (swollen, bleeding gums, fragile capillaries, delayed wound healing, anaemia, weakness, bone fractures).
Dpharmguru’s exam insights:
Vitamins are essential micronutrients that play crucial roles in metabolism. In exams, pay special attention to: (1) The difference between fat-soluble and water-soluble vitamins, (2) The deficiency diseases of each vitamin, (3) The coenzyme forms of B-complex vitamins, and (4) The sources and functions of each vitamin. Remember: “Vitamins are vital amines!”
REFERENCES AND FURTHER READING
- Lehninger, A. L., Nelson, D. L., & Cox, M. M. (2017). Lehninger Principles of Biochemistry (7th ed.). W. H. Freeman.
- Berg, J. M., Tymoczko, J. L., & Stryer, L. (2019). Biochemistry (9th ed.). W. H. Freeman.
- Satyanarayana, U., & Chakrapani, U. (2021). Biochemistry (5th ed.). Elsevier.
- Vasudevan, D. M., Sreekumari, S., & Vaidyanathan, K. (2022). Textbook of Biochemistry for Medical Students (9th ed.). Jaypee Brothers.
- National Institutes of Health (NIH). (2022). Vitamin and Mineral Resources. Retrieved from https://www.nih.gov.
Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult qualified healthcare professionals for medical concerns.
written by:
Dr. N. Sujith Kumar
