The present invention discloses the use of a composition comprising an effective amount of an extract of Eurycoma longifolia for the production of a preparation to stimulate and/or enhance the immune system. In a preferred embodiment, the extract comprises active ingredients, which include eurycomanone, protein, polysaccharide and glycosaponin in appropriate amounts. In another preferred embodiment, the extract has an activity selected from the group consisting of: increasing the number of T-cells improving Scoring of Immunological Vigor (SIV), a comprehensive index of overall immune function lowering the immunological age, a comprehensible form of immune function based on T-cell number and proliferative activity reducing fatigue and alleviating or reducing stress. Also disclosed is a method of for treating an individual to achieve an outcome selected from the group consisting of increasing the number of T-cells, improving SIV (i.e. a comprehensive index of overall immune function), lowering the immunological age (i.e. a comprehensible form of immune function), reducing fatigue and alleviating or reducing stress comprising administering to the individual an effective amount of an extract of Eurycoma longifolia.
