Estrogenic activity of commercial milk as revealed in immature hamster uterotrophic assay – pilot study.

Background: The risk for public health posed by endocrine disruptors present in food is relatively new issue. Our current understanding of human exposure is mainly based on the residue analysis of selected compounds. With such approach potential, effects of mixtures, including so-far unidentified compounds are not taken into consideration. Therefore, the knowledge of overall hormonal activity in food samples is of big importance.

Objective: Milk and dairy products are a rich source of estrogens but very rarely undergo testing for estrogenic activity. For this reason the rodent uterotrophic bioassay is one of the most useful tool. This preliminary study was conducted in immature hamsters to assess commercially available milk. The endpoint measured was uterine weight increase.

Material And Methods: Fifteen-day old females received ad libitum throughout 7 days commercially available milk i.e. raw goat’s, raw cow’s, processed 3.2% UHT, and for comparison soy milk. The animals of negative control group received water but positive control group got 17β - estradiol (E2) at the concentration of 100 ng/ml.

Results: All samples of milk showed estrogenic activity as follow: goat’s >cow’s >soy >processed milk. Significant increase of uteri weights were recorded in goat’s (p<0.001) and cow’s milk (p<0.01). However, the activity was approximately 5-fold lower than induced by 17β-estradiol. The ratio uterine weight/body weight (%) in negative control was 0.096%, in milk experimental groups ranged from 0.112% to 0.153% and in positive control this value was 0.493%.

Conclusion: The results suggest that commercially available milk has a weak uterotrophic activity. Further in vivo and in vitro studies are warranted to gain more insight into the estrogenic risk from milk and other dairy products.