MECHANISMS IN ENDOCRINOLOGY: Estrogens in consumer milk: is there a risk to human reproductive health?

Abstract

Possible effects of xenoestrogens on human health, in particular on male reproductive health, have attracted considerable attention in recent years. Cow's milk was suggested in numerous publications as one of possible sources of xenoestrogens that could affect human health. Although milk has undoubtedly many beneficial health effects and could even have a role in reducing incidence of some cancers, concerns were raised about presumably high levels of estrogens in cow's milk. In intensive farming, concentrations of estrogens in milk are higher due to long milking periods that today extend long into the pregnancy, when concentrations of estrogens in the cow's body rise. Numerous studies examined potential effects of milk on reproductive health and endocrine-related cancers in both experimental studies with laboratory animals, and in human epidemiological studies. In the present review article, we compiled a review of recently published literature about the content of estrogens in cow's milk and potential health effects, in particular on reproductive system, in humans. Although results of published studies are not unequivocal, it seems that there is stronger evidence suggesting that amounts of estrogens in cow's milk are too low to cause health effects in humans.

Impact of Estrogens Present in Environment on Health and Welfare of Animals

“…Estrogens can enter mammals in many ways, not only by ingesting water contaminated with them or through the skin during contact with it [111], but also through the food they eat, an example of which may be the accumulation of estrogens along with trophic levels in consumed foods, e.g., in plants [112,113], fish [114] or even as indicated in the literature in milk, however, in this case the literature reports are contradictory [115]. A very important phenomenon in the context of the threat posed by estrogens is the fact that very often mixtures of these are found in the environment, which in addition to the additive effect of these compounds may also show the synergistic effect mentioned previously [36,116].…”

“…There are a number of potential negative consequences of their action on mammals such as reproductive disorders and lowering the general condition of the body associated with their negative impact at their excessively normal concentrations [117]. There are many reports in the literature indicating an increased risk of carcinogenesis under the influence of estrogens [5,17,115,118]. Słowikowski et al [119] describe two mechanisms that can lead to this, i.e., by destroying the structure of proteins or the structure of the genetic code.…”

“…Słowikowski et al [119] describe two mechanisms that can lead to this, i.e., by destroying the structure of proteins or the structure of the genetic code. The effect of estrogens has been associated with cancers of the prostate, lung, endometrium, and breast [5,17,115,118].…”

Oestrogens in milk and breast cancer: a cause for concern…or not?

“…Since the 1970s there has been a steady stream of original papers (some, sadly, merely repetitive), reviews (of variable quality) and commentaries (of even more variable quality) on the topic. Because of this plethora I will not, therefore, give detailed references in the discussion that follows but simply mention here a list of reviews that provide references plus the other sources I have used (Hamon et al ., 1981; Hamon et al ., 1990; Heap and Hamon, 1979; Heap et al ., 1983; Heap et al ., 1984; Heap et al ., 1986; Janowski et al ., 2002; Kuhl, 2005; Parodi, 2012; Peaker and Neville, 1991; Peaker and Taylor, 1990; Snoj and Majdič, 2018).…”

Resumption of Cyclic Ovarian Activity by Herbal Preparation AyuFertin in Bulgarian Murrah Buffaloes at Early Postpartum

“…The application of hormonal therapy for this purpose provides good results [1][2][3]. However, other than the high cost, the frequent use of exogenous hormones can impair the reproductive system of animals and lead to increased levels of sex hormones in milk, which affects consumer health [4][5][6]. In addition, in organic farms, the use of hormones is prohibited.…”