Vitamins — Core Principles

Core Principles

Vitamins are essential organic micronutrients required in small amounts for normal physiological function, growth, and health. They do not provide energy directly but act as coenzymes or cofactors in metabolic processes.

Vitamins are broadly classified into two groups based on their solubility: fat-soluble (A, D, E, K) and water-soluble (B-complex and C). Fat-soluble vitamins are absorbed with fats, stored in the body, and can accumulate to toxic levels if over-consumed.

Water-soluble vitamins are not stored significantly and are readily excreted, requiring regular dietary intake. Each vitamin has specific functions, and its deficiency leads to characteristic diseases (e.

g., Vitamin C deficiency causes scurvy, Vitamin D deficiency causes rickets). Key aspects for NEET include chemical names, major sources, primary functions (especially coenzyme roles for B vitamins), and associated deficiency diseases.

A balanced diet is crucial to obtain all necessary vitamins, as the body cannot synthesize most of them.

Important Differences

vs Water-Soluble Vitamins

Aspect	This Topic	Water-Soluble Vitamins
Examples	Vitamin A, D, E, K	B-complex vitamins (B1, B2, B3, B5, B6, B7, B9, B12), Vitamin C
Absorption	Absorbed with dietary fats into the lymphatic system, then into blood.	Absorbed directly into the bloodstream.
Storage in Body	Stored in significant amounts in the liver and adipose tissues.	Not stored in significant amounts (except B12 to some extent).
Excretion	Not readily excreted; remain in the body for longer periods.	Readily excreted in urine; daily intake generally required.
Toxicity (Hypervitaminosis)	Higher risk of toxicity with excessive intake due to accumulation.	Lower risk of toxicity; excess is usually excreted.
Daily Requirement	Not necessarily required daily due to storage.	Generally required daily due to limited storage and rapid excretion.
Chemical Nature	Often contain long hydrocarbon chains, making them non-polar.	Typically contain polar groups, making them soluble in water.

The fundamental distinction between fat-soluble and water-soluble vitamins lies in their chemical structure, which dictates their solubility and, consequently, their physiological handling. Fat-soluble vitamins (A, D, E, K) are lipophilic, requiring dietary fat for absorption and bile salts for emulsification. They are stored in the body's fat reserves and liver, leading to a higher potential for toxicity with excessive intake. Conversely, water-soluble vitamins (B-complex and C) are hydrophilic, absorbed directly into the bloodstream, and are not significantly stored, necessitating regular dietary replenishment and posing a lower risk of toxicity due to easy excretion.