Kaféin dikandung dina kacang/siki, daun, jeung buah kalawan kadar anu béda-béda. Gunana taya lian pikeun péstisida alami nu maralisis jeung bisa maéhan serangga nu ngahakan éta tutuwuhan. Sumber kaféin pikeun manusa biasana diala tina ékstrak siki kopi jeung daun Camellia sinensis, sarta kadaharan/inuman nu ngandung produk turunan siki kola.
Pikeun awak manusa, kaféin téh stimulan sistem saraf puseur, nu balukarna sacara samentara bisa ngaleungitkeun rasa tunduh sarta ngaronjatkeun kawaspadaan. Kiwari, kaféin jadi zat psikoaktif nu panglobana dikonsumsi, utamana ku sabab ieu zat mah teu dicaram konsumsina. Di Amérika Kalér, unggal poé 90% sawawa ngonsumsi kaféin[3]. Badan POM AS (FDA) ngadaptar kaféin salaku "multiple purpose generally recognized as safe food substance" (zat kadaharan multiguna nu sacara umum aman)[4].
Kaféin mibanda pasipatan diurétik, sahanteuna mun dibikeun ka nu teu toléran obat kalawan dosis anu cukup[5]. Sabalikna, pikeun nu geus biasa ngonsumsi mah toléransina beuki luat[5], sarta teu ngabalukarkeun déhidrasi[6][7][8]
↑Balentine D. A., Harbowy M. E. and Graham H. N. (1998). G Spiller, ed. Tea: the Plant and its Manufacture; Chemistry and Consumption of the Beverage. Caffeine.
↑ abGriffin, R. J. (2003). "Caffeine ingestion and fluid balance: a review". Journal of human nutrition and dietetics16 (6): 411. doi:10.1046/j.1365-277X.2003.00477.x.
↑Armstrong LE, Casa DJ, Maresh CM, Ganio MS (2007). "Caffeine, fluid-electrolyte balance, temperature regulation, and exercise-heat tolerance". Exerc. Sport Sci. Rev.35 (3): 135–140. doi:10.1097/jes.0b013e3180a02cc1. PMID17620932. (Review article)
↑Armstrong LE, Pumerantz AC, Roti MW, Judelson DA, Watson G, Dias JC, Sokmen B, Casa DJ, Maresh CM, Lieberman H, Kellogg M. (2005). "Fluid, electrolyte, and renal indices of hydration during 11 days of controlled caffeine consumption". Int. J. Sport Nutr. Exerc. Metab.15 (3): 252–265. PMID16131696. (Placebo controlled randomized clinical trial)