Drinking farm milk can protect children against asthma and hayfever, according to a study of nearly 15,000 children published in the May issue of Clinical and Experimental Allergy.
But consuming farm milk that hasn't been boiled poses serious health risks and further research is needed to develop a safe product that still provides good protection against these common childhood diseases.
Researchers from Europe and the USA studied 14,893 children aged between five and 13 in Austria, Germany, the Netherlands, Sweden and Switzerland.
The children were drawn from farm children, rural and suburban communities and Rudolph Steiner schools, which primarily cater for families with anthroposcopic lifestyles, who restrict their use of antibiotics, vaccinations, fever-reducing drugs and often follow a biodynamic diet.
Parents were asked to complete detailed questionnaires about their child's consumption of milk, butter, yoghurt, eggs and fruit and vegetables and whether they were farm-produced or shop-bought.
They also answered questions about their child's height and weight, whether they were breastfed and any allergies or asthma problems affecting the child or their family.
Allergy- related blood tests were also carried out on just under 4,000 children from across the five countries and the questionnaire results were validated with random telephone interviews with 493 respondents
The researchers discovered that children who drank farm milk were much less likely to suffer from hayfever and asthma.
Lower levels of diagnosed asthma were also observed for all farm-produced dairy products and eating farm eggs also provided protection against hayfever. However, these foods only provided increased protection when the children also drank unpasteurised farm milk , not in isolation.
None of the farm products had any effect on eczema levels.
"All the children drinking unpasteurised farm milk and eating other farm-related dairy products showed the same level of protection against asthma and allergies, regardless of whether they were living on a farm or not" says lead author Marco Waser, a doctor in natural sciences from the Institute of Social and Preventative Medicine at the University of Basel, Switzerland.
"This is an important finding as it rules out other protective factors that farm life may provide, such as exposure to microbial compounds in animal shed and farm homes. For example, earlier studies have shown that farm children are less likely to be affected by pollen.
"Our research showed that the children who enjoyed the best protection from asthma and allergies had been drinking farm milk since their first year of life."
About half of the parents who told researchers that their child regularly drank farm milk said that they did not boil the milk before giving it to them. The protective results were the same, regardless of whether milk was boiled or not.