Content of omega-3 fatty acids partially explains the asthma-protective effect of unprocessed cow's milk

Abstract

Living on farms has repeatedly been shown to protect children from asthma and allergies. A major factor involved in this effect is consumption of unprocessed cow9s milk directly obtained from a farm (Loss, G. et al. JACI 2011;128:766-773). In contrast to farm milk, industrially processed cow9s milk is subjected to heat-treatment and alteration of fat fraction and fat globule size. Aim of this analysis was to assess whether the composition of fatty acids (FA) differed between unprocessed farm milk and industrially processed milk and, if so, whether this contributed to the protective effect of farm milk on asthma. The PASTURE study followed 934 children living in rural areas in 5 European countries from birth to age 6 years. During this time, their milk consumption was assessed by questionnaires. Samples of the usually consumed milk were taken at the age of 4.5 years. Doctor-diagnosed asthma was parent-reported at age 6 years. In a random sample of 35 asthma cases and 49 controls, the content of 46 FA was quantified. Proportions of omega-3 FA were highest in raw farm milk and lowest in UHT milk. The risk of asthma was reduced when consuming raw farm milk as compared to shop milk (OR=0.31 [0.14-0.69]). Part of the effect was explained by the higher fat content of farm milk (OR high vs. low fat 0.59 [0.33-1.05]). Half of this effect was attributable to the contents of omega-3 FA (CIE=56%), which had significant inverse association with asthma after adjustment for milk fat content (OR=0.2 [0.04-0.91]). The asthma-protective effect of unprocessed farm milk is partially attributable to omega-3-FA, which counterbalance the synthesis of pro-inflammatory leukotriens and prostaglandins.