In vivo enhancement of natural killer cell activity through tea fortified with Ayurvedic herbs.

The effect of a tea fortified with five herbs selected from Indian traditional medicine (Ayurveda) for their putative immunoenhancing effect (Withania somnifera, Glycyrrhzia glabra, Zingiber officinale, Ocimum sanctum and Elettaria cardamomum) on innate immunity was investigated. Ex vivo natural killer (NK) cell activity was assessed after consumption of fortified tea compared with regular tea in two independent double-blind intervention studies. Both studies were conducted in India with healthy volunteers (age >or= 55 years) selected for a relatively low baseline NK cell activity and a history of recurrent coughs and colds. In a pilot study conducted with 32 volunteers, the consumption of Natural Care tea significantly improved the NK cell activity of the volunteers in comparison with a population consuming regular tea. These results were validated in an independent crossover study with 110 volunteers. Data from these two studies indicate that regular consumption of the tea fortified with Ayurvedic herbs enhanced NK cell activity, which is an important aspect of the (early) innate immune response to infections.