Charaka Samhita, Sutrasthana 21.36
Sukham duhkham pushtihi karshyam jnanam ajnanam jivitam mrityu ca — Happiness and suffering, nourishment and wasting, knowledge and ignorance, life and death — all depend on proper or improper sleep. There is no health without proper sleep. This verse establishes Nidra as fundamental — not optional.

Nidra as one of the three pillars

Charaka Samhita, Sutrasthana 11 documents three Upastambha (supporting pillars) of health: Ahara (food), Nidra (sleep), and Brahmacharya (regulated conduct). These three, properly maintained, support the body's Dhatus, Agni, and Ojas throughout life. Of the three, Nidra is documented as the one most commonly neglected in the classical patient population — and modern epidemiology confirms that sleep deprivation is now one of the most prevalent health risk factors globally.

The classical documentation of Nidra's functions: Charaka Samhita lists the processes that occur during proper sleep — Preenana (nourishment of tissues), Deha Pushti (bodily nourishment), Bala Vriddhi (strength increase), Varna Samrakshanam (complexion maintenance), Dhatu Poshan (tissue feeding), and Prana Rakshanam (preservation of the life force). These correspond closely to what modern sleep science documents as occurring during deep sleep: tissue repair, growth hormone secretion, immune consolidation, and memory consolidation.

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Classical sleep science — Tamas theory, Ojas, and the five stages
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Sleep and Doshas — how each Dosha affects sleep quality and quantity
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Improving sleep — classical dietary, herbal, and lifestyle interventions