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. Oxytocin is released by many sensory pathways including vision, touch, smell, hearing or thinking about her infant. Edgard Cobo, an early researcher of oxytocin, established the normal conditions of the milk-ejecting response. In 1992, V. Coiro studied the effect of ethanol on non-lactating women. Breast stimulation increased the level of oxytocin in the blood stream, but when ethanol was given, the release of oxytocin was inhibited.