Holy basil (Ocimum sanctum, also known as tulsi) is traditionally used in Ayurvedic medicine as an adaptogen—a substance believed to help the body adapt to stress. Modern scientific research has started to investigate these claims, particularly in relation to the hypothalamic-pituitary-adrenal (HPA) axis and cortisol regulation. Several animal studies and a few small human clinical trials suggest that holy basil extracts may reduce markers of stress and anxiety, potentially by modulating cortisol levels and supporting the body's stress response.

For example, a 2012 randomized, double-blind, placebo-controlled study found that holy basil extract was associated with reductions in stress and anxiety scores in healthy volunteers. Animal studies have further shown that holy basil may normalize elevated cortisol levels in response to stress, although the exact mechanisms remain unclear. The leaves contain bioactive compounds such as eugenol and ursolic acid, which may contribute to these effects through antioxidant activity and possible modulation of neurotransmitters.

While these findings are promising, the overall body of evidence is still limited, especially in terms of large-scale, long-term human trials specifically measuring cortisol levels. Thus, while there is scientific support emerging for holy basil's use in stress management and potential cortisol modulation, more robust research is needed for definitive conclusions.