Scientists at Monell Chemical Senses Center in the US report that even moderate doses of alcohol will impact the hormones responsible for lactation in a counterproductive manner.
Their findings run up against recent surveys that indicate 25 per cent of women report being encouraged by their health professionals to drink alcohol while breastfeeding.
"There was no valid scientific evidence to support this claim," says lead author Julie Mennella.
The role of alcohol in society, and its impact on a nation's health, continues to be the focus of ongoing research.
A string of recent studies, for example, suggest that the powerful antioxidant resveratrol found in red wine, could protect against blood clots and possibly high cholesterol levels - both associated with heart conditions.
Targeting this burgeoning market, the food industry continues to roll out food and beverage products designed to tackle heart health. Set to grow 7.6 per cent in the UK market alone, according to Datamonitor, these products are slated to achieve sales of £145 million in the UK by 2007.
But this latest small study on breastfeeding mothers finds that alcohol disrupts the hormonal milieu of lactation "in a way that could impede successful breastfeeding."
For the research 17 women, nursing infants between 2 and 4 months of age, each drank a beverage containing alcohol in orange juice on one day and plain orange juice on a different day.
The dose of alcohol was equivalent to that found in one to two glasses of wine.
Blood samples taken throughout the procedure were analyzed for oxytocin and prolactin, the two key hormones that control lactation.
Alcohol disrupted release of both hormones during lactation: oxytocin levels decreased on average by a considerable 78 per cent, and prolactin levels increased by a massive 336 per cent, compared to when women consumed plain orange juice.
"Under normal breastfeeding conditions, oxytocin and prolactin usually behave in tandem… but following alcohol consumption we saw divergent responses in these two key hormones that control lactation," comments co-author Yanina Pepino.
Seeking to calm mothers, the researchers add that a lactating woman who drinks occasionally can wait a few hours after she stops drinking to breastfeed so that her infant is not exposed to the alcohol in her milk.
Full findings are published in the April issue of The Journal of Clinical Endocrinology & Metabolism.