Oestrogen, Soy Products, and Breast Cancer

31 Aug 2014 by Krystal Barter
Oestrogen, Soy Products, and Breast Cancer

Carolyn McAnlis, a Pink Hope  Ambassador and Dietitian, discusses oestrogen, soy products and breast cancer in this blog post.

The number one risk factor for breast cancer in the general population is lifetime exposure to oestrogen.

Which explains why risk increases if women enter puberty early (before age 12), and enter menopause late (after age 55) as the time in between is when we are producing high levels of hormones.

But, how else are we exposed to oestrogen? In this post I’ll talk about two sources that are somewhat controversial – specifically, pytoestrogens (phyto meaning plant) found in food and chemicals called xenoestrogen (literally “foreign oestrogen”).


Phytoestrogens are naturally occurring compounds that are found in a variety of plant foods such as beans, seeds, and grains, but soybeans and soy products are the major dietary source. The chemical structure resembles oestrogen, and may affect the production and/or the breakdown of oestrogen by the body, as well as the levels of oestrogen carried in the bloodstream. There seems to be a paradox, however, because they can either act like oestrogen, or conversely block oestrogen’s effects.
Unfortunately the result of high phytoestrogen intake is unpredictable, partly due to a poor understanding of exactly how they work in the body. It is interesting to note that women in Japan, a country which consumes a high amount of minimally-processed soy, have about one-third the incidence of breast cancer than in Western countries. Studies have shown varying results, but none have shown a definite increase in risk of breast cancer due to eating soy.

What we do know is that these compounds are weak in comparison to human oestrogen, synthetic oestrogen (HRT), and xenoestrogens, and that moderate amounts are not likely to have any harmful effect. Unfortunately it leaves a lot of questions. It’s important to note that no studies have been done with breast cancer survivors or women taking tamoxifen. If you have any concerns, speak to your doctor, but for most women eating soy a few times a week will not have an effect.

What’s not so uncertain, however, is exposure through chemicals in the environment, called xenoestrogens. Most plastics expose us to the chemical bisphenol A, also called BPA, which is found in the lining of many food cans and containers. It is released from the lining into the food or drink when subjected to high temperatures. Although consumers are exposed to a very low level of these chemicals in any particular product, collectively, the exposures could be harmful. A recent study done by Deakin University found a correlation between BPA and obesity and diabetes. While the direct links have not yet been shown, and therefore BPA is still widely used, common sense suggests that it would be healthier to avoid consuming chemicals.

Pesticides and growth hormones used in food production are a current hot topic as concerns are growing that pesticides, which can also mimic oestrogen, could have detrimental effects on the body. If you are concerned, start incorporating organic food into your weekly shop.

Studies are still being conducted with many of these environmental chemicals that are thought to be dangerous to humans. I think the most important take-home message is to realise how many chemicals we are exposed to every day. Any one exposure is not necessarily going to be harmful, but the accumulative effect could be dangerous. There are some simple things you can do, to be “better safe than sorry.” Small changes like these help you live a less toxic life.



Tips to avoid excess exposure to oestrogens:
• Do not re-use plastic water bottles, as they are only meant to be used once. Buy a BPA-free plastic, glass, or stainless steel reusable water bottle.
• Do not expose plastics to heat – via microwaving or leaving in the sun/a hot car.
• Always transfer food to a ceramic or glass dish when heating.
• Wash all fruits and vegetables before eating to remove as much pesticide residue as possible. Or consider buying organic produce.
• Consider buying organic meat as organic farmers cannot use hormones on the animals.





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