Caffeine is the only drug that is present naturally or added to widely consumed foods (quinine is the other drug used in foods). It is mildly addictive, one possible reason that makers of soft drinks add it to their products. Many coffee drinkers experience withdrawal symptoms, such as headaches, irritability, sleepiness, and lethargy, when they stop drinking coffee. More background on caffeine » November 2014. Most information was obtained from company Web sites or direct inquiries. Serving sizes are based on commonly eaten portions, pharmaceutical instructions, or the amount of the leading-selling contaner size. Additional information: Juliano, L.M. & Griffiths, R.R. (2005).
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