A method for stimulating or enhancing the immune system with a composition that includes a Eurycoma longifolia aqueous extract. Also provided is a method for reducing the risk of infectious disease by administering the composition. Further disclosed is a method for treating an individual with a Eurycoma longifolia aqueous extract to increase the number of T-cells, improve Scoring of Immunological Vigor, lower immunological age, reduce fatigue, or alleviate or reduce stress.
