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Ask the Herbalist: Is Soy a Health Food?


Q: I keep hearing conflicting reports about whether I should be consuming soy. Is soy a health food or should I avoid it?

A: The soybean (Glycine max) is a member of the legume family, which, due to its hardy nature and high protein content, has been a staple of Asian diets for centuries, and has become one of the most widely produced food crops in the world. Soy can be found on grocery store shelves in many traditional forms such as tofu, tempeh and soymilk. It is also the main protein source in a majority of vegetarian meat alternatives and protein bars. Additionally, soy is fed to many of the animals you may eventually consume. And it doesn’t stop there! Because of the overproduction and inexpensiveness of soy, it is used as an emulsifier in many food products, and is now making its way into body products.

There are health benefits associated with using soy as a supplement. The most well-known soy benefit may be the hormone balancing effect of certain phytoestrogens (estogen-like plant compounds) found in soy known as isoflavones, which when taken in supplement form, can play a role in relieving menopausal symptoms. Soy isoflavones are weak estrogen mimickers, and two in particular, genestein and diadzein, can bind to the body’s estrogen receptors, allowing the body’s natural estrogen to remain in the body longer. This is one of the reasons why soy helps menopausal women.

What has come to light recently, however, is a wide range of adverse effects associated with using and consuming large amounts of soy over a length of time. Several studies show that the phytoestrogens found in soy may lead to hormonal disruption in men, women and children, thyroid problems and potential increases in anxiety and stress.

Unfermented soy also contains chemicals that are toxic, such as phytic acid, protease inhibitors and soy lectins. Continual intake of these toxins can lead to hormonal and thyroid issues. These toxins also reduce your body’s ability to absorb necessary nutrients from food and supplements. Fermenting soy changes its chemical composition, making it more digestible and less likely to cause problems.

One place where soy shows up frequently is in baby formula. This can be problematic because infants’ bodily systems are just beginning to develop, and exposure to large amounts of soy can disrupt healthy development. Unfortunately, many mothers who do not breast feed their babies feed them soy-based infant formulas. Hormonal, thyroid and nutritional absorption issues due to soy intake have been documented in adults — imagine what infants have to deal with. Chen and Donovan performed a study in 2004 which showed that infants fed soy-based formula had a reduction in intestinal cell growth and a change in their intestinal cell function, which could lead to a compromised digestive system, and hence a compromised immune system for the rest of these infants’ lives.

Soy is consumed in many Asian countries. However, it is primarily consumed in traditional, fermented forms (like tamari, miso, tempeh and natto), and in small amounts, often more as a condiment. In America, on the other hand, soy is typically eaten in unfermented and highly processed forms — often even when you don’t know you’re eating it. Remember, the animals you eat have been fed soy, unless you specifically purchase all grass-fed or free-range animal products. The conventional products you use on your skin may contain small amounts of soy as well. More and more people continue to develop soy allergies, thyroid issues, hormonal disruption and weight gain, which may all be related to excessive soy consumption.

So, what can you do about it? Being aware of what you are consuming is the first step. Read labels, and if you do not understand an ingredient, research it or ask a knowledgeable person about it. Buy all natural, minimally processed food products made with clean ingredients you can understand, so that you are not unknowingly consuming soy ingredients. Purchase grass-fed or free-range meats, eggs and dairy products, directly from a farm or farmer’s market whenever possible.

The bottom line is that soy in large amounts can have harmful effects on health for men, women and children, and due to its prevalence in our food system, it’s best to make a conscious effort to minimize its role in your diet. The fermented soy foods that are part of traditional Asian diets are a safer bet, if you’d like to include soy in your diet.

Soy isoflavones in supplement form may offer women significant relief from symptoms of menopause. However, if you are a women still of reproductive age, have a family history of estrogen-dominant cancer, or have estrogen-dominant cancer yourself (whether you are male or female), you should consider avoiding soy as much as possible.


  1. Chen, AC, Donovan, SM (2004). Genestein at a concentration present in soy infant formula inhibits CACO-2BBe cell proliferation by causing G2/M cell cycle arrests. Journal of Nutrition, 134(6), 1303:1308
  2. Jefferson, WN, Padilla-Banks, E, Newbold, RR (2007). Disruption of the developing female reproductive system by phytoestrogens: genestein is an example. Molecular Nutrition Food Research. 51(7), 832:844
  3. Lopez, HW, Coudray, C, Bellanger, J, Younes, H, et al. (1998). Intestinal fermentation lessens the inhibitory effect of phytic acid on mineral utilization in rats. The Journal of Nutrition. 178(7), 1192:1198
  4. “Phytoestrogens and Your Baby”. Retrieved on June 11, 2009 from
  5. “Soy and Menopause”. Retrieved on June 11, 2009 from
  6. “Soy Toxins”. Retrieved on June 11, 2009 from
  7. “Soy: The Unsuspected Cause of Thyroid Problems”. Retrieved on June 11, 2009 from

Lissa’s passion for educating people about the healing powers of herbs led her to obtain a Masters of Science in Herbal Medicine from the Tai Sophia School of the Healing Arts. She has also studied nutrition and women’s health extensively, and has trained as a doula.

Have a question for Lissa? Send her an email and she’ll get back to you!

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15 responses to “Ask the Herbalist: Is Soy a Health Food?”

  1. Joshua says:

    Lissa – Thanks for the great information. As a vegetarian going on 10+ years, I am concerned about how much soy I consume. I recently replaced soymilk with almond milk to cut down on my soy intake. I've also been trying to better track my overall daily consumption.

    Until recently, I wasn't aware of the differences between fermented and unfermented soy, or the fact that overall, soy can be harmful in high levels. I am definitely going to read up on this more. Again – Thanks for the great info!

    • MaryJane says:

      Thanks for explaining the difference between fermented and unfermented soy. Ive always wondered what the importance was when I would read labels. I love soy products but since I am in my “child bearing” years, Ill cut it down for the kids.

  2. Danielle says:

    Hi Lissa –

    What would you suggest as some good alternative sources of protein for vegans? I have been a vegan for almost a year now, and am really enjoying the way I feel on this diet. I don't eat a ton of soy, but I do include soy foods in my diet pretty regularly just to make sure I am getting enough protein. I'd like to eliminate it, but am concerned about getting sufficient protein.


    • Lissa says:

      Hi Danielle, I understand what you mean. Eating soy occasionally as tofu and tempeh is great. I also suggest incorporating more beans in the diet: kidney beans, red beans, black beans for example. Consider sprouting the beans to reduce flatulence or digestive upset. Sprouting makes them easier to digest and often has higher amount of nutrients than legumes and grains that are not sprouted. If you are not allergic to nuts, nuts provide a great protein source. Grains to consider that are rich in protein: brown rice, quinoa, amaranth, kamut grains, barley, etc. Combining nuts, grains, and beans work well too.

      As for frozen foods, there are now some that are made without soy, but with rice instead. Because you are vegan, the important thing to remember is to combine protein sources to make up a complete protein such as beans with rice or chickpeas with couscous. It may take some practice and making some dishes from scratch. Here's a website of vegan recipes worth looking into:

      • Danielle says:

        Thanks so much for your helpful reply! :)

        • CasieT says:

          And to elaborate on Lissa's answer, be sure to be aware of complementary proteins. Since I tend to be a “flexitarian,” whenever I give up meats for periods of time (be it a cleansing or whatever), I pay special attention to this. Plus I love soy milk so I find it hard to include a variety. Most meat-eaters don’t have to worry about this since meat, dairy eggs and fish provide the essential amino acids in sufficient amounts. But since beans, nuts and grains only provide some of the essential amino acids, or all but in insufficient amounts, it’s important to pair them in a way to meet your protein needs. Some examples of complementary proteins include peanut butter on whole wheat bread, beans and brown rice and hummus with pita bread. While a little in-depth, I think this webpage helps a lot…

          • Ellen says:

            On the contrary, I respectfully disagree on the issue of protein combining as a matter of necessity for vegans or vegetarians. The theory behind it has in fact now been largely discredited by most nutrition experts, medical professionals and even the ADA.

            As long as you are eating a variety of healthy foods throughout the day, you don't need to mix and match foods to get “complete proteins” in the each meal. Research has shown that our bodies are capable of assembling, storing and releasing amino acids as necessary. From Dr. Andrew Weil:

          • CasieT says:

            Certainly I would agree to an extent. The ADA does say that ” Recent studies suggest that eating a good variety of plant-based protein throughout the day will provide all of the essential amino acids your body needs… it would be wise to meet with a registered dietitian to help you plan your meals to meet your calorie and protein needs.”

            If one's diet is varied enough then protein assimilation will not be a concern however to be prudent (and perhaps I’m old school in that sense) I like to double up on my assurance.
            It takes, in my opinion, a very cautious eater to be certain. And since I, like most Americans, use a little less caution in this sense, I always practice and advise the “better safe than sorry” approach

        • Lissa says:

          You're welcome.

  3. BethF says:

    How does edamame fall into the continuum with all this? Since they are soybeans, should they be avoided (or eaten in small quantities) as well?

    What about steamed edamames versus the roasted ones?

    • Lissa says:

      That's a great question. Compared to isolated soy protein and soy isoflavones, edamame is a whole food and therefore contains chemical compounds not found in isolated soy products that protect the body. Because edamame is soybeans that are immature, they contain less toxins than mature soybeans. Although edamame has less toxins and is healthier than other processed soy products and isolates, as is the case with all foods, it should be eaten in moderation.

  4. Sue says:

    Very interesting article. I was wondering Lissa, how much soy can I consume per day? I have heard it's 25mg, but I am not sure that is correct. What about men and women? Can women consume more soy than men because of the estrogen?

    • Lissa says:

      Hi Sue, the recommended soy intake is 25 mg daily, however this is based on the belief that soy is healthy for everyone and we are now learning that is not true. Soy is also in almost everything now so if you add the 25 mg daily with what you are getting through conventional meats (for meat eaters), processed foods, frozen meals, and some supplements, you will definitely exceed the 25 mg daily. I personally stick to eating primarily whole foods and desserts I can make myself. If I decide to purchase cookies for example instead of make them myself, I check the ingredients. If I see soy flour or soy lecithin, I almost always put them back. Our bodies are sensitive once we tune in. Even though we may feel healthy for years eating “toxic foods”, at some point, our bodies will say ENOUGH and begin to break down. This is my opinion anyway.

      Both men and women should limit their intake of soy. The soy phytoestrogens displace the body's natural estrogen which may lead to estrogen dominance and hence estrogen related health issues. Estrogen aside, soy also disrupts thyroid and other hormones in the body. In this case, less is more.

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