Findings differed slightly when the source of caffeine was considered singly. Consuming 200 milligrams or more of caffeine from coffee mirrored the findings for overall caffeine consumption, with Asians having elevated estrogen levels, whites having lower estrogen levels, and the results for blacks not statistically significant. However, consumption of more than one cup each day of caffeinated soda or green tea was associated with a higher estrogen level in Asians, whites, and blacks.
Gotta control those variables in the study!