[SciShow intro plays]

Hank: We all know that it’s a bad idea to drink alcohol when you’re pregnant – it can cause problems with the pregnancy and with the baby’s health. But have you heard from people that it might be okay, or even helpful, for a mother to drink beer while breastfeeding?

Some people say drinking beer supposedly helps a mother produce milk, also known as lactation. So is there any truth to it? Well, maybe. But different scientific studies seem to disagree.

Lactation relies on two main hormones: prolactin and oxytocin. Prolactin helps trigger cells in the mammary glands to synthesize milk and fill up little sacs called alveoli. On the other hand, oxytocin causes the let-down, or milk-ejection, reflex – where the cells surrounding the alveoli contract, basically pushing out the milk.

So most of the research on beer, or any alcohol, and breastfeeding focuses on these two hormones. Some experiments have found that prolactin levels might increase thanks to one of the components of some beer: barley. A carbohydrate in barley has been shown to make lab animals, like rats and ewe -- ewe being female sheep, not, not YOU, you are not a lab animal -- it makes them synthesize more prolactin. So that could possibly mean that barley, in alcoholic or non-alcoholic beer, could have a similar effect in new mothers, and the extra prolactin might stimulate some more milk production.

But that was a lot of “maybe”s in that sentence. Another study with 13 lactating women found if they drank alcohol – in this case, alcohol mixed with orange juice – the levels of prolactin in their breast milk changed. If the woman’s blood alcohol concentration, or BAC, was rising when the milk was pumped, prolactin levels were higher. If her BAC was falling, prolactin levels were lower. And despite those changing prolactin levels, the women consistently expressed less milk after drinking alcohol.

So, all these prolactin studies don’t really tell us much about beer and breastfeeding. But what about the other hormone: oxytocin? Well, some research has shown that drinking alcohol may decrease oxytocin levels and inhibit the milk-ejection reflex. Like one study which focused on 12 lactating women, who breastfed their babies within four hours after drinking alcoholic or non-alcoholic beer.

The researchers found the babies drank less milk if their moms had an alcoholic beer – possibly because of an inhibited milk-ejection reflex. And on top of all this hormone stuff, as long as a lactating woman has alcohol in her bloodstream, a tiny fraction of it will enter her milk – and that could affect how infants breastfeed. Basically, lactation is just complicated, and there’s still a lot that scientists don’t know about how beer – or any alcohol – affects breastfeeding.

More research, with more participants, is definitely needed to understand how all these hormonal changes work together. And because of that, if you’re a new or expectant mother, and you want to have some beers, you might wanna talk to a lactation consultant or a doctor for breastfeeding advice.

Thank you for asking, and thanks especially to all of our patrons on Patreon who keep these answers coming. If you’d like to submit questions to get answered, or get some videos a few days early, you can go to Patreon.com/SciShow. And don’t forget to go to YouTube.com/SciShow and subscribe!