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I strongly assume that, if the looks from people all over the world vary, then also there metabolic system should vary and wonder, if there are noticeable differences how caffeine affects people from different cultures.
I tried to look it up on the Internet, however I didn't find much, so I would assume there is not much of a difference. But surely there are people, who know a lot more than me in this field. Therefore I were very happy for any constructive comment.
I do not consider myself an expert, but I do remember one study done on this. In "The world of caffeine: The science culture and world's most popular drug," do indeed hypothesize that Japanese (and Asians in general) metabilise coffee slower than other races. So the effects of caffeine are felt longer.
