Loss et al (J Allergy Clin Immunol 2011;128:766-773) report on results from an extensive study in rural Germany, Austria and Switzerland that collected questionnaire data from parents of over 8,000 children, with over 7000 consenting to provide serum samples for specific IgE levels. Additionally, 800 cow’s milk samples from the children’s homes were analyzed for viable bacteria, whey protein levels, and total fat content.
The GABRIELA protocol divided milk consumption into two categories: “shop” milk and “farm” milk. Farm milk consumption was further divided into “only boiled farm milk drinkers” and “any unboiled farm milk drinkers.” Children drinking exclusively farm milk had significantly lower risk for asthma, current asthma, atopy and hay fever as compared to children exclusively drinking shop milk. This relationship held for consumption of any unboiled farm milk. Consumption of farm milk was also inversely correlated to food allergen sensitization.
Loss et al. describe microbiological analysis of shop milk and heated farm milk, which detected microorganisms in only a few samples. Raw farm milk, in contrast, contained significant amounts of micrococci, staphylococci, and lactobacilli as well as other bacteria. Only 3 milk samples contained human pathogens, Listeria innocua and Listeria ivanovii. Consumption of the analyzed raw farm milk was inversely correlated with asthma and current asthma, but not with atopy as compared to heated shop milk. Total fat and viable bacterial load did not associate with any health outcomes; however, increased levels of whey proteins were inversely associated with asthma, but not atopy. Specific significant associations were found for α-lactalbumin, β-lactoglobulin and bovine serum albumin and protection from asthma.
Loss et al. comment that higher bacterial load in raw farm milk might be expected to cause the protective effects, but instead, no association was observed between viable bacteria counts and any of the health outcomes. Surprisingly, the authors found that some whey proteins were inversely associated with asthma. They state that this finding is perplexing given that two of the three proteins inversely associated with asthma, α-lactalbumin and β-lactoglobulin, are the major allergens in milk. Loss et al. note that the inverse relationship of bovine serum albumin, α-lactalbumin and β-lactoglobulin to asthma does not apply to atopy and speculate that other milk components may be responsible for epidemiologic data that demonstrate inverse association between farm milk consumption and atopy.