Oh, it's not just in your soy milk, Roy. It's in your chicken, your beef, and many other foods and products out there:
Many people do not realise that that estrogen and estrogen-mimics are widely found in food and the environment. Synthetic hormones like synthetic estrogens are commonly fed to animals in industrialised countries, and found also in pesticides and herbicides, and these end up on our dinner plates. Stay away from meats and dairy products produced by such commercial farming methods, and canned foods too. There is good reason why organic foods are gaining in popularity, even though they may seem to cost more.
Watch out also for xenoestrogens, chemical compounds with a hormone-like effect on the body. These substances are usually petrochemical-based, and most of them mimic estrogen. Xenoestrogens lurk in everyday items like personal care products / toiletries (soap, artificial fragrances like perfumes and air fresheners, cosmetics etc.), plastics (plastic food wrap, plastic bottles, styrofoam food containers), car exhaust, carpeting, furniture, panelling, paints, solvents and lacquers, household cleaners like detergents, and even medicine.
Xenoestrogens were relatively recently introduced into the environment, produced by industrial, agricultural, and chemical companies. Industrial waste products are loaded with these estrogen mimics.
Then there are phytoestrogens, plants with an estrogen like effect, such as soya and flaxseed.