Caffeine is a member of the
methylxanthine family of drugs, and is the most widely consumed behaviourally active substance in the western world. This article is focused on the impact of
caffeine on immune function. In this regard, a number of in vitro and in vivo studies have demonstrated that
caffeine modulates both innate and adaptive immune responses. For instance studies indicate that
caffeine and its major metabolite
paraxanthine suppress neutrophil and monocyte chemotaxis, and also suppress production of the pro-inflammatory
cytokine tumour
necrosis factor (
TNF)-alpha from human blood.
Caffeine has also been reported to suppress human lymphocyte function as indicated by reduced T-cell proliferation and impaired production of Th1 (
interleukin [IL]-2 and
interferon [IFN]-gamma), Th2 (IL-4, IL-5) and Th3 (IL-10)
cytokines. Studies also indicate that
caffeine suppresses antibody production. The evidence suggests that at least some of the immunomodulatory actions of
caffeine are mediated via inhibition of cyclic
adenosine monophosphate (
cAMP)-phosphodiesterase (PDE), and consequential increase in intracellular cAMP concentrations. Overall, these studies indicate that
caffeine, like other members of the
methylxanthine family, is largely anti-inflammatory in nature, and based on the pharmacokinetics of
caffeine, we suggest that many of its immunomodulatory effects occur at concentrations that are relevant to normal human consumption. Finally, the potential of
caffeine-induced
immunomodulation to significantly impact upon health and well-being are discussed.