ω-3 fatty acids contribute to the asthma-protective effect of unprocessed cow's milk.

BACKGROUND: Living on a farm has repeatedly been shown to protect children from asthma and allergies. A major factor involved in this effect is consumption of unprocessed cow's milk obtained directly from a farm. However, this phenomenon has never been shown in a longitudinal design, and the responsible milk components are still unknown. OBJECTIVES: We sought to assess the asthma-protective effect of unprocessed cow's milk consumption in a birth cohort and to determine whether the differences in the fatty acid (FA) composition of unprocessed farm milk and industrially processed milk contributed to this effect. METHODS: The Protection Against Allergy-Study in Rural Environments (PASTURE) study followed 1133 children living in rural areas in 5 European countries from birth to age 6 years. In 934 children milk consumption was assessed by using yearly questionnaires, and samples of the "usually" consumed milk and serum samples of the children were collected at age 4 years. Doctor-diagnosed asthma was parent reported at age 6 years. In a nested case-control study of 35 asthmatic and 49 nonasthmatic children, 42 FAs were quantified in milk samples. RESULTS: The risk of asthma at 6 years of age was reduced by previous consumption of unprocessed farm milk compared with shop milk (adjusted odds ratio for consumption at 4 years, 0.26; 95% CI, 0.10-0.67). Part of the effect was explained by the higher fat content of farm milk, particularly the higher levels of ω-3 polyunsaturated FAs (adjusted odds ratio, 0.29; 95% CI, 0.11-0.81). CONCLUSION: Continuous farm milk consumption in childhood protects against asthma at school age partially by means of higher intake of ω-3 polyunsaturated FAs, which are precursors of anti-inflammatory mediators.

Bioavailability and allergoprotective capacity of milk-associated conjugated linoleic acid in a murine model of allergic airway inflammation.

BACKGROUND: Cross-sectional epidemiological studies have demonstrated that farm milk from traditional farm settings possesses allergoprotective properties. Up to now, it has not been clarified which milk ingredient is responsible for protection against allergic diseases. As farm milk is rich in conjugated linoleic acids (CLA), it is hypothesized that this n-3 polyunsaturated fatty acid family contributes to the allergoprotective capacity of farm milk. We aim to prove this hypothesis in a murine model of allergic airway inflammation. METHODS: To prove the bioavailability and allergoprotective capacity of milk-associated CLA in a standardized protocol, milk batches that differed significantly in terms of their CLA content were spray dried and incorporated into a basic diet by substituting the regular sunflower fat fraction. Initially, the milk CLA uptake from the diet was monitored via measurement of the CLA content in plasma and erythrocyte membranes obtained from supplemented mice. To determine whether a milk CLA-enriched diet possesses allergoprotective properties, female Balb/c mice were fed the milk CLA-enriched diet ahead of sensitization and a challenge with ovalbumin (OVA) and the parameters of airway inflammation and eisosanoid pattern were measured. RESULTS: In animals, supplementation with a diet rich in milk CLA resulted in elevated CLA levels in plasma and erythrocyte membranes, indicating bioavailability of milk fatty acids. Though membrane-associated phospholipid patterns were affected by supplementation with milk CLA, this application neither reduced the hallmarks of allergic airway inflammation in sensitized and OVA-challenged mice nor modified the eiconsanoid pattern in the bronchoalveolar lavage fluid of these animals. CONCLUSION: Milk-associated CLA was not capable of preventing murine allergic airway inflammation in an animal model of OVA-induced allergic airway inflammation.

Development and validation of a combined method for the biomonitoring of omega-3/-6 fatty acids and conjugated linoleic acids in different matrices from human and nutritional sources.

BACKGROUND: During the last decade, the contribution of omega-3 and -6 long chain-polyunsaturated fatty acids (LC-PUFA) and conjugated linoleic acids (CLA) to the prevention and development of many inflammatory and cardiovascular diseases has been of growing interest. In order to investigate the etiology of these diseases, rapid, combined and comparable methods are invaluable for monitoring both the intake and the incorporation of these fatty acids (FA). METHODS: The fatty acid methyl esters (FAME) were analyzed using a gas chromatography/flame ionization detector (GC-FID) system and quantified with an internal standard (C18:0 iso). RESULTS: An effective and rapid protocol for sample preparation and the analysis of FAME was developed and validated. The comparison of different extraction methods showed that the Hara and Radin method gave the best results for serum and erythrocyte membranes. Excellent mean within-day and day-to-day precisions for serum, erythrocytes and cow's milk LC-PUFAs demonstrated the high reproducibility of the method. Recovery rates for FAMEs in serum and milk were close to 100%. In addition, high mean method linearity (R(2)) (>0.99) was shown for serum, erythrocytes and cow's milk. The sensitivity for FA achieved by GC analysis was acceptable. CONCLUSION: With the newly adapted protocols, combined and rapid analyses of up to 46 FAMEs, including CLAs and omega-3/-6 LC-PUFAs, can be conducted with high reliability and reproducibility using serum, erythrocyte membranes or cow's milk. This provides a novel tool that can be easily implemented in epidemiological studies or clinical diagnostics.