JĪRṆA ĀHĀRA LAKṢAṆA AS A PUTATIVE PHYSIOLOGICAL TIMER OF KṢUT: AN AYURVEDIC–ENDOCRINE–CHRONOBIOLOGICAL FRAMEWORK FOR FUTURE FUNCTIONAL FOOD RESEARCH

Ayurveda considers digestion not as a process that only begins and ends with the food being consumed, but one that is complete when specific bodily signals are observed, collectively referred to as Jīrṇa Āhāra Lakṣaṇa. Of special interest is Kṣut which can be translated as ‘natural emergence of hunger’, as it is this sign that signals the organism’s readiness to receive nourishment. Other signs include Udgāraśuddhi, Lāghava, Utsāha, Viṣṭabdha/normal bowel movement and Pipāsā, with variations reported in different Ayurvedic traditions. Modern physiologists recognize that appetite is controlled by neuroendocrine circuits connecting the gut, hypothalamus and reward centres, with ghrelin, leptin, GLP-1, PYY, CCK, insulin, nutrient sensing and circadian clocks contributing to the control of feeding. Ghrelin decreases after eating and increases before meals. Leptin plays a role in long-term energy regulation and displays diurnal variation. Thus, it is tempting to hypothesize that the Ayurvedic sequence of physiological signs announcing the end of digestion and the natural emergence of hunger might encode an ancestral physiological clock. This review suggests that Jīrṇa Āhāra Lakṣaṇa might provide an Ayurvedic functional phenotype for the development of chrono-functional foods, to maintain or enhance the body’s natural temporal organisation of hunger and satiety.