Lack of oestrogen-like activity in commercially refined vegetable oils

Commercially refined corn, safflower, sunflower and soya-bean oils, as well as well as lard and beef tallow, were fed to pre-pubertal female mice at a level of 5 or 20% of a semi-synthetic diet to assess whether they exhibited any oestrogen-like activity, as measured by changes in uterine weight or in the ratio of uterine weight to body weight. No measurable oestrogen-like activity was observed, in contrast to the effects in positive-control animals treated with 5, 10 or 15 ppb diethylstilboestrol. This finding contradicts an earlier report in the literature. It also shows that oestrogen-like activity in a commercially refined oil is not likely to be a variable in the complex mechanism of the dietary modulation of induced breast-tumour growth.