Seasonal variation in contents of phytoestrogens in Danish dairy milk lines of different farm management systems

Abstract

Farm management systems and seasonal variation are suggested to affect the concentrations of phytoestrogens in milk. The present study analyses the concentrations of phytoestrogens and their relative composition in distinct milk lines from six Danish dairies representing three management systems (conventional, organic and biodynamic) in five sampling periods (P1–P5) over one year. A highly selective and sensitive liquid chromatography-triple quadrupole mass spectrometry method was applied to determine absolute concentrations of phytoestrogens in the different milk lines over the period. Biodynamic dairy milk lines contained higher levels of most isoflavones compared with milk from conventional systems. This may be explained by the differences in feeding strategies and, more specifically, botanical composition of feed. In relation to season, the concentration of the mammalian derived isoflavone, equol, was highest during the indoor period in biodynamic milk. Compared with the isoflavones, concentrations of lignans were less affected by farm management system.