The issue of alcohol consumption while breastfeeding is one of the most debatable ones and it is hard to find reliable information on it. However, I was able to dig out the following:
There is a rough calculator of the length of time that alcohol will be present in breast milk, depending on the number of drinks and the mother’s body weight. As a general guideline, it takes as long for alcohol to clear the milk as it does for the blood alcohol level to subside. Alcohol taken with food takes longer to clear out of the system. Motherisk provides a reference table that can be used for the calculation as well.
Motherisk also has a good article on drinking alcohol while breastfeeding, including references to several studies on the subject. They state that “Because alcohol elimination follows zero-order kinetics, drinking water, resting, or ‘pumping and dumping’ breast milk will not accelerate elimination. Unlike urine, which stores substances in the bladder, alcohol is not trapped in breast milk, but is constantly removed as it diffuses back into the bloodstream.” It takes longer to process high-alcohol drinks as opposed to beer or wine. The amount of alcohol passed to the baby through breast milk is around 2% of the entire alcohol content consumed by the mother, much less than the amount passed through the placenta in a pregnant woman.
The statement that alcohol increases milk production and stimulates let-down due to relaxing the mother appears to be a myth. Beer might increase prolactin levels and milk production, however this appears to not be due to ethanol, but possibly to barley. Thus non-alcoholic beer should do the trick as well. One study suggested that there was a 23% reduction in breast milk production due to alcohol consumption.
American Academy of Pediatrics provides a listing of drugs and their effect on breast milk.
La Leche League states that consumption of one drink or less per day has not been shown to have a negative effect on the baby. Excessive alcohol consumption is harmful to the baby and should be avoided.
Dr. Jack Newman says: “Reasonable alcohol intake should not be discouraged at all. As is the case with most drugs, very little alcohol comes out in the milk. The mother can take some alcohol and continue breastfeeding as she normally does. Prohibiting alcohol is another way we make life unnecessarily restrictive for breastfeeding mothers.”
So, it appears that drinking one drink or less per day shortly after a feeding and waiting the appropriate amount of time (depending on the mother’s body weight) before the next feeding is the best approach if the mother does not want to avoid alcohol altogether.
If you are dealing with substance addiction, the Desert Hope resource page provides many studies and resources designed to help understand the basics of addiction and to offer guidance to help women safely stop drug and alcohol use.