Traditionally drunk by farming communities, raw milk is gaining in popularity.
The Centers for Disease Control and Prevention (CDC) warn against consuming raw milk because it can contain bacteria that have the potential to cause serious illness and death.
Pasteurization, which is the process of heating milk to kill bacteria, is the only way to ensure that milk is safe to drink. Yet scientific studies link raw milk consumption - especially in early life - to lower levels of allergy and asthma.
Is this evidence convincing enough to risk drinking potentially unsafe raw milk?
Raw milk during childhood
Georg Loss, from the University of Basel in Switzerland, and his colleagues from across Europe conducted a study in European children aged between 6 and 12. They showed that allergy and asthma rates are lower in those who drank only raw milk.
Children who drank some raw and some regular milk had lower allergy rates, but only if they were exposed to raw milk before the age of 1 or if they drank it daily. Asthma rates were not lower in these children.
Importantly, when raw milk was boiled at home - to kill bacteria - it completely canceled out these effects.
Unsurprisingly, the researchers found much higher levels of bacteria in raw milk consumed by the children in this study. However, it was not possible to determine whether or not these bacteria were the factors that provided the protection.
Allergies in adults
A recent study by researchers from the National Institutes of Health (NIH) shows that the risk of having allergies later in life was reduced in adults in the United States who grew up in a farming environment, therefore drinking mostly raw milk.
The same was not true for asthma.
In this particular study, it is difficult to look at the effect of raw milk consumption in isolation, because the study specifically looked at individuals who grew up in a farming environment.
Therefore, raw milk may not have been the only factor that contributed to the reduced rates of allergy in this study population.
Raw milk: Yes or no?
With more than 50 million U.S. individuals suffering from allergies and nearly 25 million from asthma, could raw milk protect the next generation from these debilitating conditions?
Loss and his colleagues urge caution, saying, "[...] on the basis of current knowledge, raw milk consumption cannot be recommended because it might contain pathogens."
Instead, the team hopes that "once the mechanisms underlying the protective farm milk effect are better understood, ways of processing and preserving a safe and preventative milk can be developed."
The CDC are clear in their recommendation. They say, "If you want to keep milk in your family's diet, protect them by not giving them raw milk."
Scientists are pursuing different avenues of research to get to the bottom of what makes raw milk so good at preventing allergy and possibly asthma.
Drinking raw milk is a personal choice, and for those undecided about raw milk, it may be worth watching this space and waiting for a safe alternative.