Researchers assumed that the content of caffeine was 137 mg per cup of coffee, 47 mg per cup of tea, 46 mg per can or bottle of cola, and 7 mg per serving of chocolate candy.
The big caffeine Kahuna here, then, is coffee.
Twenty-four percent of the women never drank coffee; 13 percent drank less than a cup a day; 14.2 percent had two to three cups a day, and 15.4 percent had four cups a day. Yikes!
No matter the quantity, though, caffeine had no significant effect on hormone positive breast cancer. But the risk of hormone negative does go up with each cup of coffee. Likewise, the chance of having a tumor larger than 2 cm went up with increased coffee consumption.
Still, as is the case with many breast cancer studies, the number of cases of hormone negative breast cancers was so small that researchers didn’t have enough data to state conclusively that high caffeine leads to hormone negative breast cancer. These findings, they say, may be “due to chance and warrant further study.”
Until the data are in, though, it might be best to cut the coffee.
And, on a side note, most media notices I have read on this focus on the fact that caffeine does not lead to breast cancer, once again making generalizations about breast cancer while ignoring hormone negative.