Herbal supplements and athlete immune function--what's proven, disproven, and unproven?

The purpose of this paper is to critically evaluate current immunological and clinical literature regarding the effects of herbal preparations on athlete immune function. First, we review rates of herbal supplement use by athletes. Second, we use ginseng (Panax ginseng) and coneflower (Echinacea spp.) as models for examining how herbal supplements may influence immune function within the contexts of exercise and sport, while briefly considering several other popular herbal products. Third, we proffer several evidence-based hypotheses to explain apparent discrepancies among the cumulative data, concomitantly advancing a novel conceptual framework which may be useful to understanding herbal supplements and athlete immune function using Echinacea supplements as a model. Fourth, we apply the proposed framework to some prospective data regarding the effects of Echinacea pallida and Echinacea simulata on in vitro cytokine production and cell proliferation in peripheral blood mononuclear cells collected from male collegiate wrestlers and soccer players during training. Fifth and finally, we evaluate the current knowledge on herbal supplements and athlete immune function, identify gaps and limitations in knowledge, and advance several possible options for future research.