Department of Production Animal Medicine, University of Helsinki, Helsinki, Finland.
Br J Nutr. 2009 Dec;102(11):1552-6. doi: 10.1017/S0007114509990857. Epub 2009 Jul 22.
The intake of isoflavones and the resulting equol contents of both plasma and milk of the same red clover-fed cows are reported for the first time in cyclic change-over design study. Cows were fed four different red clover silages and two timothy-meadow fescue silages as controls. The red clover silages contained daidzein, formononetin, biochanin A and genistein, whereas the timothy-meadow fescue silages contained no isoflavones. We found a strong association (y = 0.071x+2.75, R 2 0.71) between the formononetin intake (x) and equol concentration (y) in the plasma, while the formononetin intake and milk equol concentration were weakly associated (y = 0.0035x+0.358, R 2 0.20). This means that a small part of the total formononetin in the silage is secreted into milk as equol. The mean equol contents in plasma and milk of cows fed red clover silage diets were in the range of 4.6-8.4 mg/l and 458-643 microg/l, respectively, while the respective values for the control diets were in the range of 0.8-1.5 mg/l and 171-287 microg/l. We showed that shorter growing periods of red clover resulted in higher silage formononetin contents and plasma and milk equol contents, suggesting that the equol content of milk can be manipulated by varying the harvesting strategy of red clover. We conclude that milk equol is derived from the formononetin of red clover silage and that milk from red clover-fed cows can be considered as a source of equol in human nutrition.
首次在周期性交叉设计研究中报告了同一红三叶草喂养的奶牛的异黄酮摄入量及其导致的血浆和牛奶中的黄豆苷元含量。奶牛被喂食四种不同的红三叶草青贮饲料和两种提莫西-草地羊茅青贮饲料作为对照。红三叶草青贮饲料中含有大豆甙元、芒柄花素、大豆黄素和染料木黄酮，而提莫西-草地羊茅青贮饲料中不含异黄酮。我们发现血浆中黄豆苷元浓度（y）与芒柄花素摄入量（x）之间存在很强的相关性（y = 0.071x+2.75，R 2 0.71），而芒柄花素摄入量与牛奶黄豆苷元浓度的相关性较弱（y = 0.0035x+0.358，R 2 0.20）。这意味着青贮饲料中总芒柄花素的一小部分被分泌为黄豆苷元进入牛奶。饲喂红三叶草青贮饲料的奶牛的血浆和牛奶中黄豆苷元含量分别在 4.6-8.4mg/L 和 458-643μg/L 的范围内，而对照饲料的相应值在 0.8-1.5mg/L 和 171-287μg/L 的范围内。我们表明，红三叶草较短的生长周期导致青贮饲料中更高的芒柄花素含量以及血浆和牛奶中的黄豆苷元含量，这表明通过改变红三叶草的收割策略可以控制牛奶中的黄豆苷元含量。我们得出结论，牛奶中的黄豆苷元源自红三叶草青贮饲料中的芒柄花素，并且来自红三叶草喂养奶牛的牛奶可以被认为是人类营养中黄豆苷元的来源。
