WebMD Medical News Laura J. Martin, MD April 7, 2011 -- DNA may
play a large role in determining how much caffeine people
consume in beverages such as coffee, tea, and soda and food such
as chocolate, new research indicates. Scientists from the
Harvard School of Public Health, the National Cancer Institute,
and other institutions say they have discovered two genetic
variations that influence the metabolism of caffeine and are
associated with how much caffeine people consume. People with
particular variations of two specific genes are more likely to
consume caffeine, and to drink more of it when they do, study
leader Marilyn C. Cornelis, PhD, of the Harvard School of Public
Health, tells WebMD. The genes are identified as CYP1A2, long
known to play some role in caffeine metabolism, and another
called AHR, which affects regulation of CYP1A2. All people have
both genes, but the study, involving more than 47,000 middle-
aged Americans of European descent, finds that people with the
highest-consumption variant for