Institute for Prevention and Cancer Epidemiology, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany.
Department of Epidemiology, Fielding School of Public Health, University of California, Los Angeles, CA.
Am J Clin Nutr. 2019 Feb 1;109(2):402-410. doi: 10.1093/ajcn/nqy279.
Current cow milk production practices introduce considerable levels of pregnancy hormones into the milk. Humans are exposed to these hormones when cow milk is consumed, and this may explain the observed association between cow milk consumption and several hormone-sensitive cancers.
The aim of the study was to evaluate whether cow milk consumption is associated with an increase in urinary excretion of sex steroid hormones and their metabolites in humans.
We conducted a randomized crossover intervention feeding experiment. A total of 109 postmenopausal women consumed 1 L of semiskimmed milk (1.5% fat) per day for 4 d and 1 L of whole milk (3.5% fat) per day for 4 d, intersected by 4-d wash-out periods. Sex steroid hormone levels were measured in 24-h urine samples collected at the end of each intervention and wash-out period.
Estrogens, androgens, and progesterone were detected in the examined milk samples used for our intervention. Although a very high proportion of the estrogens were conjugated, only small proportions of the androgens and progesterone were conjugated. Milk consumption resulted in a significant increase in urinary estrone (E1) excretion, whereas estradiol (E2), estriol (E3), and 16ketoE2 excretion only increased after semiskimmed milk consumption. Urinary pregnanediol glucuronide excretion was not significantly affected.
Cow milk consumption increases urinary excretion of E1 in humans. Ingestion of semiskimmed milk appears also to raise E2, E3, and 16ketoE2 excretion, but future studies need to confirm these associations. This trial was registered at https://www.drks.de as DRKS00003377.
目前的牛奶生产实践将相当水平的妊娠激素引入牛奶中。当人类饮用牛奶时，会接触到这些激素，这可能解释了观察到的牛奶消费与几种激素敏感型癌症之间的关联。
本研究旨在评估牛奶消费是否与人类尿液中性激素及其代谢物的排泄增加有关。
我们进行了一项随机交叉干预喂养实验。共有 109 名绝经后妇女每天饮用 1 升半脱脂牛奶（1.5%脂肪）连续 4 天，然后每天饮用 1 升全脂牛奶（3.5%脂肪）连续 4 天，中间穿插 4 天的洗脱期。在每个干预和洗脱期结束时收集 24 小时尿液样本，测量其中的性激素水平。
在所使用的干预牛奶样本中检测到雌激素、雄激素和孕激素。尽管大部分雌激素都被共轭化，但只有小部分雄激素和孕激素被共轭化。牛奶消费导致尿液中雌酮（E1）排泄显著增加，而雌二醇（E2）、雌三醇（E3）和 16ketoE2 排泄仅在摄入半脱脂牛奶后增加。尿孕烷二醇葡萄糖醛酸苷排泄没有显著影响。
牛奶消费增加了人类尿液中 E1 的排泄。摄入半脱脂牛奶似乎也会增加 E2、E3 和 16ketoE2 的排泄，但需要进一步的研究来证实这些关联。本试验在 https://www.drks.de 注册，编号为 DRKS00003377。
