Role of Rasayana in Preserving Health, Function and Longevity - A Literary Review and Comparative Textual Analysis of the Brihat-Trayi

Background: Aging involves progressive loss of physiological reserve, function and resilience. Healthy-aging science therefore emphasizes healthspan and preservation of function. In Ayurveda, Rasayana is a major preventive and rejuvenative discipline concerned with longevity, strength, cognition, sensory function, nourishment and resistance to disease. Objective: To identify and synthesize classical descriptions of Rasayana, aging and preservation of function across Charaka Samhita, Sushruta Samhita and Ashtanga Hridaya, and to interpret these findings cautiously within contemporary healthy-aging science. Methods: A structured literary review and comparative textual analysis was undertaken using the Brihat-Trayi as primary sources. Sanskrit terms and transliteration variants related to Rasayana, Jara, Vaya, Ayu/Ayushya, Bala, Ojas, Medha, Smriti, Indriya, Dhatu, Agni, Srotas, Vyadhikshamatva, Achara Rasayana and named formulations were used to identify relevant passages. Modern peer-reviewed literature was used for contextual interpretation only. Results: The three texts consistently describe Rasayana as a multidimensional health-promoting strategy rather than a single anti-aging medicine. Recurrent domains include longevity, strength, tissue preservation, cognition, sensory function and resistance to disease. Charaka provides the most systematic early exposition; Sushruta emphasizes health preservation within its therapeutic framework; Ashtanga Hridaya integrates Rasayana with Jara-cikitsa and practical regimens. Modern studies of selected interventions, especially Amalaki Rasayana, provide preliminary biological and functional signals but do not establish a generalized anti-aging effect. Conclusion: The Brihat-Trayi supports interpreting Rasayana as a framework for healthy aging, preservation of physiological function and potential delay of premature decline. Modern evidence should be considered intervention-specific and hypothesis-generating. Rigorous translational and clinical research is required.