23/08/2026
🧬 Complete Overview of Vitamins
Vitamins are essential organic nutrients required by the body for normal growth, metabolism, immunity, blood formation, vision, and maintenance of healthy tissues. They are mainly divided into fat-soluble vitamins (A, D, E, K) and water-soluble vitamins (B-complex and C).
🟠 Vitamin A
Main functions: Vision, immune function, skin and epithelial tissue maintenance, growth and development.
Sources: Liver, eggs, dairy products, carrots, sweet potatoes, and leafy green vegetables.
Deficiency: Night blindness, dry eyes, impaired immunity, and skin changes.
Excess: Can cause toxicity, especially with high-dose supplements.
☀️ Vitamin D
Main functions: Calcium and phosphorus absorption, bone and teeth health, and muscle and immune function.
Sources: Sunlight, fatty fish, egg yolks, fortified foods.
Deficiency: Rickets in children, osteomalacia in adults, and increased risk of weak bones.
Excess: May cause high blood calcium and kidney problems.
🟢 Vitamin E
Main functions: Antioxidant protection of cells and support of immune and neurological functions.
Sources: Nuts, seeds, vegetable oils, and green leafy vegetables.
Deficiency: Rare, but may cause neurological and muscle problems.
Excess: High-dose supplementation may increase bleeding risk.
🩸 Vitamin K
Main functions: Essential for blood clotting and bone metabolism.
Sources: Leafy green vegetables, broccoli, cabbage, and some fermented foods.
Deficiency: Increased bleeding tendency.
Clinical note: Vitamin K interacts with some anticoagulant medications.
⚡ Vitamin B1 — Thiamine
Main functions: Carbohydrate metabolism, energy production, and normal nerve function.
Sources: Whole grains, legumes, nuts, seeds, and pork.
Deficiency: Beriberi and neurological problems; severe deficiency can cause Wernicke-Korsakoff syndrome.
🔥 Vitamin B2 — Riboflavin
Main functions: Energy metabolism and maintenance of skin, eyes, and red blood cells.
Sources: Milk and dairy products, eggs, meat, and leafy vegetables.
Deficiency: Cracked corners of the mouth, sore throat, inflammation of the tongue, and skin changes.
🧪 Vitamin B5 — Pantothenic Acid
Main functions: Important for energy metabolism and synthesis of fatty acids and hormones.
Sources: Meat, eggs, dairy products, legumes, mushrooms, and whole grains.
Deficiency: Very rare but may cause fatigue, irritability, and neurological symptoms.
💪 Vitamin B6 — Pyridoxine
Main functions: Amino-acid metabolism, neurotransmitter production, hemoglobin synthesis, and immune function.
Sources: Poultry, fish, potatoes, bananas, legumes, and fortified cereals.
Deficiency: Anemia, skin changes, neurological symptoms, and weakened immunity.
Excess: Long-term high doses can cause peripheral neuropathy.
🧠 Vitamin B12 — Cobalamin
Main functions: DNA synthesis, red blood cell formation, and normal nervous-system function.
Sources: Meat, fish, eggs, milk, and fortified foods.
Deficiency: Megaloblastic anemia, fatigue, numbness/tingling, and neurological problems.
Clinical note: Deficiency is more common in people with poor absorption or very low intake of animal-derived foods.
🍊 Vitamin C — Ascorbic Acid
Main functions: Collagen synthesis, wound healing, antioxidant protection, iron absorption, and immune function.
Sources: Citrus fruits, guava, peppers, tomatoes, and other fruits and vegetables.
Deficiency: Scurvy, bleeding gums, poor wound healing, and fatigue.
Excess: High supplemental doses may cause gastrointestinal symptoms and increase kidney-stone risk in susceptible people.
🔬 Key Laboratory Point
Vitamin deficiencies can sometimes be suspected from CBC, biochemical tests, clinical symptoms, and medical history, but specific vitamin tests may be required to confirm certain deficiencies, such as 25-hydroxyvitamin D for vitamin D status and serum vitamin B12 for suspected B12 deficiency.
