“It’s possible they would be overwhelmed, because an adult has larger established colony of billions and billions of bacteria,” Quinn said.
Still, most experts agree it can’t hurt adults to drink it.
“There are many things in breast milk which are potentially useful even for adults,” said Dr. Jack Newman, co-creator of Breastfeeding Inc. In addition to vitamins and immune properties, "the milk has other very useful properties like the delivery of long chained polyunsaturated fatty acids, which many people are buying in pharmacies and health food stores.
"Basically, if the milk is properly screened or comes from a reliable source, it can’t hurt to drink it. Why would it be considered ‘normal’ to drink cow’s milk but not human milk?”
While studies haven’t focused on athletic performance, some research shows that a component of breast milk called HAMLET can kill cancer cells.
Even if breast milk were discovered to be the next Muscle Milk, there’s the issue of cost and demand.
“For jocks, my instinct would be to say it seems unlikely to have much benefit unless you could drink very large quantities of it, as the normal 3-ounce dose wouldn’t mean much to an adult,” said Florence Williams, author of "Breasts: A Natural and Unnatural History." “Any more of that would be very expensive and probably overkill, since the major benefits of breast milk are nutrition and immune-boosting, neither of which a very fit, post-workout guy likely needs.”
Some, however, argue that since supply is so limited -- there’s never enough for babies who need it, Quinn said -- it should be reserved for infants only.
“I would be concerned if it became a widespread fad,” Quinn said. “The benefits are enormous for babies, particularly those at high risk, so we should be prioritizing it for infants.”