Estrogens in the daily diet: in vitro analysis indicates that estrogenic activity is omnipresent in foodstuff and infant formula

Food is a main source of exposure to endocrine active compounds, many of which have been linked to adverse health effects. Phytoestrogens, especially from soy, are the major dietary source of estrogenicity. However, foodstuff contains a variety of estrogen-like compounds that might not be detected analytically. To assess the total estrogenic activity of foodstuff, we employed the Yeast Estrogen Screen (YES). We analyzed 18 food samples and five milk-based infant formulas. Soy-based products contained potent estrogenicity of 100-1500ng estradiol equivalents per kilogram (EEQ/kg). The estrogenicity in soy-free products was far lower (10-40ng EEQ/kg). We also detected significant estrogenic activity in three infant formulas (14-22ng EEQ/kg). Furthermore, we found soy lecithin to be strongly estrogenic. It might, therefore, be a major contributor to total estrogenicity. We conclude that dietary estrogens are omnipresent and not limited to soy-based food. In an exposure assessment we calculated a total dietary intake of 27.5 and 34.0ng EEQ/d for adults and 1.46ng EEQ/d for infants. While the dietary exposure to estrogenic activity is lower than previously estimated, our results demonstrate that many food types are a source of unidentified estrogen-like compounds still awaiting toxicological evaluation.