Vitamins

Latin - Vita (Life) + English - Amine (compound derived from ammonia)

Vitamins are a class of organic (carbon-containing) compounds that are required in small amounts for normal physiological and metabolic functions. As essential micronutrients, they cannot be synthesized in adequate quantities by the human body and must therefore be obtained through dietary intake. Most vitamins exist not as single chemical entities, but as a group of structurally related compounds known as vitamers, which share a common biological activity.

Fat Soluble Vitamins

Fat-soluble vitamins - A, D, E, and K are absorbed with dietary fats, facilitated by bile acids, and transported via chylomicrons through the lymphatic system. They are stored primarily in adipose tissue and the liver, allowing for sustained availability.

These vitamins are predominantly found in animal-based foods.

Animals consuming a natural diet typically maintain higher reserves due to consistent intake and efficient storage.

  • Vitamin A supports vision, immune function, and epithelial integrity.

  • Vitamin D regulates calcium and phosphate metabolism, essential for bone health.

  • Vitamin E functions as a major lipid-soluble antioxidant, protecting cell membranes.

  • Vitamin K is essential for the synthesis of clotting factors and bone metabolism.

Vitamin A (Retinol)

Chemical Formula: C₂₀H₃₀O

Functions: Essential for visual phototransduction in the retina, epithelial cell differentiation and maintenance, bone growth and remodeling, reproductive system function, and the regulation of innate and adaptive immune responses.

Deficiency Symptoms: Night blindness, keratomalacia, hyperkeratosis, follicular hyperkeratosis, impaired immunity, growth retardation

Sources: Cod Liver Oil, liver, fish oil, dairy fat (Raw Milk, Raw Butter), egg yolks

Vitamin D3 (Cholecalciferol)

Chemical Formula: C₂₇H₄₄O

Functions: Regulates calcium and phosphate homeostasis by promoting intestinal absorption and renal reabsorption, essential for bone mineralization, remodeling, and maintenance of skeletal integrity

Deficiency Symptoms: Rickets in children characterized by impaired bone mineralization and skeletal deformities; osteomalacia in adults, presenting as bone pain and increased fracture risk

Sources: Endogenously synthesised in the skin via UVB-mediated conversion of 7-dehydrocholesterol; dietary sources include oily fish, fish liver oils, dairy fat, egg yolks

Vitamin E (Tocopherol)

Chemical Formula: C₂₉H₅₀O₂

Functions: Lipid-soluble antioxidant protecting polyunsaturated fatty acids in cell membranes by terminating lipid peroxidation chain reactions and neutralising carbon-centred free radicals, thereby preserving cellular integrity and function

Deficiency Symptoms: Hemolytic anemia due to increased red blood cell fragility, peripheral neuropathy, and myopathy resulting from oxidative damage to nerve and muscle tissues

Sources: Fish oil, animal fats, avocado, nuts, wheat germ oil

Vitamin K2 (Menaquinone)

Chemical Formula: C₄₆H₆₄O₂

Functions: Serves as a cofactor for γ-glutamyl carboxylase, activating blood clotting factors and carboxylating bone and vascular proteins essential for coagulation and bone metabolism

Deficiency Symptoms: Impaired blood coagulation leading to bleeding diathesis

Sources: Liver, Fermented foods

Water Soluble Vitamins

Water-soluble vitamins are essential micronutrients that dissolve in water and are absorbed directly into the bloodstream. They are poorly stored and rapidly excreted by the kidneys, necessitating regular dietary intake to maintain plasma levels and support vital functions such as energy metabolism, DNA synthesis, and enzymatic cofactor activity.

  • Vitamin B1 (Thiamine): Cofactor in carbohydrate metabolism and neural function

  • Vitamin B2 (Riboflavin): Component of redox cofactors FAD and FMN for energy production

  • Vitamin B3 (Niacin): Precursor of NAD⁺/NADP⁺ for redox reactions and DNA repair

  • Vitamin B5 (Pantothenic Acid): Part of coenzyme A, essential for fatty acid metabolism

  • Vitamin B6 (Pyridoxine): Cofactor in amino acid metabolism and neurotransmitter synthesis

  • Vitamin B7 (Biotin): Cofactor for carboxylase enzymes in gluconeogenesis and fatty acid synthesis

  • Vitamin B9 (Folate): Required for nucleotide synthesis and cell division

  • Vitamin B12 (Cobalamin): Essential for DNA synthesis, red blood cell formation, and nervous system maintenance

  • Vitamin C (Ascorbic Acid): Antioxidant, collagen synthesis, immune support, and iron absorption

Vitamin C (Ascorbic Acid)

Chemical Formula: C₆H₈O₆

Functions: Acts as a potent antioxidant and coenzyme in enzymatic reactions, essential for collagen synthesis, carnitine and norepinephrine biosynthesis, and maintenance of connective tissue and bone integrity.

Deficiency Symptoms: Scurvy characterized by fatigue, anorexia, impaired wound healing, bleeding gums, and petechiae.

Sources: Citrus fruits, berries, raw meat, liver

Vitamin B1 (Thiamine)

Chemical Formula: C₁₂H₁₇N₄OS

Functions: Serves as a coenzyme (thiamine pyrophosphate) in carbohydrate metabolism, facilitating energy production. Essential for normal growth, and supports proper function of the cardiovascular, nervous, and digestive systems.

Deficiency Symptoms: Beri-beri characterized by muscle weakness, anorexia, tachycardia, cardiomegaly, and peripheral edema.

Sources: Muscle meats, organ meats

Vitamin B2 (Riboflavin)

Chemical Formula: C₁₇H₂₀N₄O₆

Functions: Precursor of coenzymes FAD and FMN, essential for flavoprotein-mediated redox reactions and activation of other vitamins.

Deficiency Symptoms: Cheilosis, glossitis, oral mucosal edema and hyperemia, angular stomatitis, photophobia

Sources: Liver, red meat, milk, oysters

Vitamin B3 (Niacin)

Chemical Formula: C₆H₅NO₂

Functions: Integral to NAD and NADP coenzymes, facilitating hydrogen and electron transfer in carbohydrate, fat, and alcohol metabolism

Deficiency Symptoms: Pellagra characterized by diarrhea, dermatitis, and mental confusion

Sources: Fish, Liver, Poultry, Meat

Vitamin B4 (Adenine)

Chemical Formula: C₅H₅N₅

Functions:
A purine base critical for nucleic acid structure (DNA and RNA); involved in energy metabolism as a component of ATP, NADH, and FADH₂; essential for cellular replication and metabolism.

Deficiency Symptoms:
Not established as an essential vitamin since adenine is synthesized endogenously; thus, no classical deficiency syndrome.

Sources:
Endogenously synthesized in cells; present in all nucleic acid-containing foods.

Vitamin B5 (Pantothenic Acid)

Chemical Formula: C₉H₁₇NO₅

Functions: Precursor to coenzyme A, vital for oxidation of fatty acids and carbohydrates, and synthesis of amino acids, fatty acids, ketone bodies, cholesterol, phospholipids, steroid hormones, neurotransmitters, and antibodies

Deficiency Symptoms: Numbness and tingling of extremities, vomiting, fatigue

Sources: Egg yolk, liver, kidneys

Vitamin B6 (Pyridoxine)

Chemical Formula: C₈H₁₁NO₃

Functions: Active form pyridoxal 5’-phosphate (PLP) acts as a coenzyme in amino acid metabolism and neurotransmitter biosynthesis.

Deficiency Symptoms: Dermatitis, Glossitis, convulsions

Sources: Meat, fish, fruit

Vitamin B7 (Biotin)

Chemical Formula: C₁₀H₁₆N₂O₃S

Functions: Cofactor for carboxylase enzymes involved in fatty acid synthesis and gluconeogenesis

Deficiency Symptoms: Anorexia, nausea, glossitis, depression, dry, scaly dermatitis

Sources: Liver, kidney, egg yolks

Vitamin B8 (Inositol)

Chemical Formula: C₆H₁₂O₆

Functions: Plays a key role in cell membrane phospholipid synthesis, intracellular signaling (as part of phosphatidylinositol), and lipid metabolism; supports nerve function and lipid regulation.

Deficiency Symptoms: Deficiency is rare; experimental deficiency may cause neuromuscular symptoms and lipid metabolism disturbances.

Sources: Meat, organs, eggs

Vitamin B9 (Folic Acid)

Chemical Formula: C₁₉H₁₉N₇O

Functions: Essential for DNA synthesis, repair, and methylation; critical for rapid cell division and growth, particularly during infancy and pregnancy

Deficiency Symptoms: Megaloblastic anemia, diarrhea, fatigue, depression, confusion

Sources: Liver

Vitamin B12 (Cobalamin)

Chemical Formula: C₆₃H₈₈CoN₁₄O₁₄P

Functions: Coenzyme in DNA synthesis and regulation, fatty acid and amino acid metabolism, crucial for hematopoiesis and nervous system integrity

Deficiency Symptoms: Megaloblastic anemia, peripheral neuropathy, glossitis, skin hypersensitivity

Sources: Meat, organs, fish, shellfish, poultry, eggs

References

Sareen Gropper (2021). Advanced Nutrition And Human Metabolism. 8th ed. S.L.: Cengage Learning Custom P.

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