Every so often a health topic comes up that creates a lot of buzz, confusion, and controversy in the media. Soy is one of those topics! Soy consumption has come under a lot of scrutiny – most people avoid it out of fear it will give them breast cancer. If that’s true, how come Asian populations eat it and are some of the healthiest races? The answers lie in eating the right amount and kind of soy while avoiding the bad.
Why is Soy so Confusing?
There is no black and white answer to if soy is bad for you because it depends on multiple factors such as:
- The type of soy eaten. i.e., soybean, soymilk, tofu, soy protein powder, etc.,
- The amount of soy eaten
- Your metabolic condition
- Hormonal status and gender
In a large majority of studies performed the amount of soy used was much higher than what a typical daily amount would be — The average dose of soy was equivalent to one pound of tofu or three soy protein shakes/day. This means that the results of those studies don’t reflect the average daily consumption of soy.
Soy and Estrogen
The hormonal effects of soy are complex. Soybeans contain isoflavones that are known as phytoestrogens that can mimic estrogen in the body. It’s important to note that the way our body utilizes estrogen is complicated. Our body has different types of estrogen receptors that bind estrogen. Once stimulated, these receptors can either be pro-cancerous or cancer-protective. Soy’s phytoestrogens can stimulate both receptors but have a 100-fold stronger affinity to the protective cancer receptors. (1, 2)
Soy’s other key compounds (i.e., Alpha-linolenic Acid and Phytic acid) have conflicting positive and negative health effects which must be understood in greater detail.
Deconstructing The Soybean
These are the 3 key constituents in soy that have an effect on our body:
- Soybeans primarily contain the isoflavones, genistein and daidzein, and glycerin in a smaller amount which are all phytoestrogen compounds.
- Phytoestrogen compounds can act like estrogen in the body which have both positive and negative effects.
2. Alpha-Linolenic Acid
- Soybean oil contains both omega-3 (anti-inflammatory) and omega-6 (pro-inflammatory) fatty acids.
- It has a higher omega 6 : omega-3 ratio meaning it has a higher pro-inflammatory effect. (3)
3. Phytic Acid
- Soybeans contain a high level of phytic acid, which can bind minerals in the gut before they are absorbed and influence digestive enzymes. (4)
- When phytic acid binds minerals in the gut, it prevents the formation of free radicals, making it an antioxidant. It also seems to bind heavy metals helping to prevent their accumulation in the body. (5)
Is Soy Bad for You? What The Experts Are Saying
According to the American Cancer Society, “Studies in humans have not shown harm from eating soy foods. Moderate consumption of soy foods appears safe for both breast cancer survivors and the general population, and may even lower breast cancer risk.” They caution, however, that soy supplements should be avoided. (6)
Don’t worry about soy’s effect on breast cancer if you eat it in the forms and amounts listed below.
Another popular concern about soy’s safety is its effect on the brain. This 2000 research study is often cited as evidence that soy consumption is linked to brain aging, but upon closer inspection, the study isn’t as sound as one might think. Researchers did not specify a control group to compare the results too, and furthermore, it was not a controlled study. This means that many other uncontrolled variables were at play to impact participants’ brain function, including their age.
YES – 1-2 Servings Of:
Fermented soybean proteins are more easily digested and absorbed, have reduced phytic acid and additional nutrients and probiotics.
- Foods include miso, tempeh, or natto
- Organic/non-GMO tofu
- Certain brands of soy milk
- Organic/non-GMO edamame
NO – Processed/Non-Organic Soy
Processed soy has been stripped from the majority of its nutrient, and faux-soy products are often loaded with added sugars, fats, and refined flours.
- Soy protein isolate and concentrates
- Genetically engineered soy foods and soy supplements
- Soy junk foods like soy cheese, soy ice cream, and soy burgers
- Soy oil should be replaced with olive oil, fish oil, nuts, and seeds
** Foods containing soy lecithin which includes soy sauce, should not be counted among soy foods. Foods containing soy lecithin (an emulsifier used in lots of processed foods) should not be considered a source of isoflavones. (7)
The Bottom Line
As with everything moderation is key, and your overall diet and lifestyle factors are the big picture. Whole soy foods can be a source of high-quality protein and plant compounds that help promote health. Eat only organic soy and stay away from genetically modified versions.
- Kostelac D, Rechkemmer G, Briviba K, 2003 Phytoestrogens modulate binding response of estrogen receptors α and β to the estrogen response element. J Agric Food Chem 51: 7632-7635.
- Harris DM, Besselink E, Henning SM, Go VLW, Heber D, 2005 Phytoestrogens induce differential estrogen receptor alpha- or beta-mediated responses in transfected breast cancer cells. Exp Biol Med 230: 558-568.
- Daly, J. (2012). Substitution of Standard Soybean Oil with Olive Oil-Based Lipid Emulsion in Parenteral Nutrition: Comparison of Vascular, Metabolic, and Inflammatory Effects. Yearbook of Surgery, 2012, 212-213. doi:10.1016/j.ysur.2012.03.044
- Sandberg A. Bioavailability of minerals in legumes. British Journal of Nutrition 2002;88(Suppl 3):S281-S285.
- Schlemmer U, et al. Phytate in foods and significance for humans: Food sources, intake, processing, bioavailability, protective role and analysis. Mol Nutr Food res 2009;53:S330-S375.
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