“Three cups of coffee a day can make your breasts shrink” – but not quite

Decoding a new study which links coffee, breast size, and breast cancer

There I was, on my daily tour of Internet news, with my second cup-a-joe in hand, when I was stopped in my tracks by a headline: “Three cups of coffee a day can make breasts shrink.” Well, shit.

Now don’t get me wrong, this news wouldn’t have made me put down the cup. But as I read on, the article revealed that coffee can simultaneously help to protect against breast cancer. I breathed a small sigh of relief at the fact that this provided me with a more concrete, though frankly unnecessary, reason to continue the habit.

But wanting to know more about the seemingly magical breast-cancer-risk-reducing powers of coffee, I looked up the two Swedish-based studies – published in the British Journal of Cancer earlier this fall – which the article was based upon.

After deciphering these heavily scientific papers on the relationship between coffee, breast size, and cancer – and talking to Helena Jernström, one of the researchers behind them – a different version of the story came out.

According to Jernström, it’s not so much that “three cups of coffee a day can make breasts shrink.” Rather, an increased intake of caffeinated coffee in young women who are not on birth control, but are carriers of the alternative gene variation of CYP1A2 for an enzyme that metabolizes both caffeine and estrogen, have exhibited smaller breast size. But this makes for a less snappy headline.

Jernström said that the only real conclusion to be drawn from the studies is that caffeinated coffee may protect women with the specific enzyme variant against breast cancer, but she stressed that the link still needs more research to be substantiated.

And as for your B-cup dwindling to an A during exam season?

“Women with the [specific gene] variant who drank three or more cups of coffee per day had smaller breasts than other women…. [But] we don’t yet know whether coffee actually shrinks the breasts or if these women had smaller breasts anyway,” Jernström said. “It is too early to draw any conclusions.”

So thank you, Internet news, for providing me with that brief moment of doubt over whether I should get up for a refill. But going by Jernström’s reasoning, we may not have to choose between our breasts and our espresso; in fact, if your gene variants align just so, that third cup may help your breasts stay healthy and cancer-free.