Mennella and Beauchamp further determined that if a mother consumed nonalcoholic beer, there was no change in the baby's suckling pattern. This indicates that it is not just the odor of the milk that affects the baby, it is the alcoholic component. It is important for a mother to remember that her baby may choose to discontinue a feeding earlier than usual if she has been drinking. The medical journal Lancet published a letter by G. De Rosa in 1981 describing his efforts to determine whether or not the ingestion of beer or an alcohol solution would alter prolactin secretion in women. Although the study used non-lactating women, he found that the ingestion of beer increased the levels of prolactin in the blood within 30 minutes after it was ingested.
Prolactin is the hormone that helps synthesize milk.
Later, in 1988, a study on suckling rats by M. G. Subramanian further defined the effect of alcohol on lactating females. Although this study was done on rats, it shows an inhibitory effect of alcohol on the release of prolactin. Another hormone in mothers' bodies, oxytocin, is also affected by the ingestion of alcohol. Oxytocin governs the milk-ejection reflex, among other things. When a mother hears her baby cry, oxytocin causes her milk to let down.