Is soybean a problem?

Is soybean problem?articles

It seems lots of discussions are going on about soybean after some scientific studies are published.

Is soybean a problem for your health?


No. Actually, no problem at all.

Comparing to thousands of years of soybean history in Asian countries, soybean is still new for western countries. Fear about soybean appeared obviously in western countries, not in Asian countries. A human has a tendency to have fear of new thing, especially to food even billions of Asians enjoy the food for everyday diet.


The reason why I decided to write this post is that one lady gave me a comment on my previous post and questioned if soy is good or bad. I hope this post helps you to alleviate your fear and worry about soybean.

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Does soybean really have a negative effect on cognitive function?

There is a study in 2000. They asked old Japanese-American in Hawaii how much they were eating tofu when they are younger. And, the scientist claimed men who ate more tofu when they are younger had more problem with cognitive functions. The data relies on old people’s memory about a younger age, who may already have a memory problem.

Is the study really trustworthy?

Based on a review paper in 2017, half of the studies found supplementation of soy isoflavone, daidzein can improve cognitive function, other half studies found no benefit.

So, actually, the effect of soybean on cognitive function is not clear. But, some blog writers love to magnify the only negative data and say soybean is bad. I don’t know why. I think they should research more and be responsible for what they write. Otherwise, people trust the writer believe the fearful information as truth. Somehow, fearful and negative information tends to attract more audience. As you know the majority of TV shows still love to show negative news and gossip to get more people’s attention.


Does soybean really make thyroid problems worse?

Soybean contains a high concentration of isoflavones, a phytoestrogen. Scientists suspect phytoestrogen interfere with human estrogen function. The study took place with sixty subclinical hypothyroidism patients.

The article states, in short, group 1 consumed 30g soy protein with 2mg soy isoflavones, which is the amount you get from a western diet for 8 weeks. Group 2 consumed 30g soy protein with 16mg soy isoflavones for 8 weeks. They found soybean may reduce absorbing thyroid medication. However, they also found the benefit that higher isoflavones intake reduced cardiovascular risk, insulin resistance, inflammation, and blood pressure.

Although isoflavones may reduce the absorption of thyroid medication, it doesn’t cause a thyroid problem.

I don’t recommend people take “extracted” phytoestrogen (isoflavones) even if a health food company claims they are beneficial for your heart, insulin level, inflammation, and blood pressure. Why? It is simply you can’t get purified isoflavones in nature. If you want to get them, you have to chemically process with other chemical substances to extract. It is not natural. And, I don’t want to feed it to my daughter. On the contrary, I happily give my daughter miso, natto, tofu, soybean sprout, and soymilk. They contain crude nutrients from superfood soybean.

It is like white sugar and fruits. Will you stop eating fruits because purified white sugar is not good for your body? Carbohydrates in fresh fruits and chemically purified white sugar are completely different. Soy isoflavones in traditional soy products and chemically purified Isoflavones are completely different.

I have another question for the experiment. Is the chemical compound used for the study is extracted from organic non-GMO soybean or GMO soybean? I don’t want to eat GMO soybean. Do you want to?

I want scientists to do a study with not extracted compounds but with non-GMO and organic soybean products such as tofu, soymilk, miso, and natto which you can get a variety of soybean nutrients.

By the way, there are also clinical studies finding that soy products don’t cause hypothyroidism.


Does soybean really make breast cancer worse?

The study didn’t take place with a human, but an animal with human cells instead. Scientists implanted human breast cancer cells into mice and kept feeding the mice high dosage of isoflavone (a kind of compound found in soybean) or isolated soybean protein. And, they killed and measured how much cancer cells grew. And, they found breast cancer cells increased.

First of all, I feel the experiment cruel. How do you feel? You know, The EU countries and other 8 countries already banned animal testing. Although the study was much before the ban, still I don’t know how they decided to do this experiment. Can you do that kind of research with your hands? By the way, if you want to do research in university, you need funding. So, usually, the research needs to match the research funder’s interest. I don’t know who funded that kind of research and for what???

Let me talk more about the study.

You know, mice with human breast cancer cells will never happen in nature. And, It is also not natural that they didn’t give whole soybean foods that are rich in healthy nutrition but gave only two kinds of extracted compounds from soybean. It will never happen in nature, too. I don’t encourage people to put into your daily diet this kind of extracted compounds. It is similar I don’t want to eat purified white sugar with zero nutrient, but love to drink a cup of fresh sugarcane juice which contains crude beneficial nutrients that I can buy on a street in Taiwan. We should eat whole foods.

There is a 7 years study with 73,223 Chinese women. They found the highest soy consuming women has a 59% lower risk of premenopausal breast cancer than the lowest soy consuming women. Additionally, when women eat soy during adolescence, the risk was 43% lower.

Not only the study above, but there also are more studies which found soybean product can reduce the risk of breast cancer. You can verify by doing a Pubmed search yourself.


Does soybean really affect fertility?

It seems people worry about soy reduce fertility.

I am 42 years old and became the father of a baby girl 6 months ago. I have been eating soy products from childhood in every meal. I have been a vegetarian for 9 years and a vegan for 3 years. I had no problem with my fertility.

Studies about men and women found soybean has no negative effect on reproductive health. On another study, infants who were fed with soy formula had no problem with fertility just like babies fed with cow milk formula when they turned adult.


Does soybean have a negative effect on male hormones?

A study also showed isoflavones supplement and soy product didn’t affect to male hormone level. Also, scientists found that people who take more soybean products were 26% less at risk for prostate cancer.


Should you stop eating soybean?

You can get the best benefit through whole and crude soybeans products such as soybean sprouts, green young soybeans, tofu, soymilk, miso, natto, soy yogurt, and so on. But, I don’t recommend you to take extracted soy protein or soy isoflavones supplement. They are not in their natural form.

I also recommend checking if the soybean product is non-GMO. It is better to avoid them.

If you still fear for soybean, you don’t need to eat them. If you are interested in a vegan diet, you can get sufficient protein and nutrition from various kinds of plants. Soy is not the only plant on the planet.

By the way, I will keep eating soybean products because I love them and feel the benefit through my body. I ate tofu today too.

Here is another post which talks about soybean benefits and history.

Is soybean good for you?
Do you know the benefit of soybean? Is soybean good for you? We have been using soybean as a daily diet in Japan ...

If you have any questions or a comment, please send me a message into a box below. Thank you!






de Lemos ML. Effects of soy phytoestrogens genistein and daidzein on breast cancer growth. Annals of Pharmacotherapy. 2001 Sep;35(9):1118-21.

Allred CD, Allred KF, Ju YH, Virant SM, Helferich WG. Soy diets containing varying amounts of genistein stimulate growth of estrogen-dependent (MCF-7) tumors in a dose-dependent manner. Cancer research. 2001 Jul 1;61(13):5045-50.

Sathyapalan T, Manuchehri AM, Thatcher NJ, Rigby AS, Chapman T, Kilpatrick ES, Atkin SL. The effect of soy phytoestrogen supplementation on thyroid status and cardiovascular risk markers in patients with subclinical hypothyroidism: a randomized, double-blind, crossover study. The Journal of Clinical Endocrinology & Metabolism. 2011 May 1;96(5):1442-9.

Thaung Zaw JJ, Howe PR, Wong RH. Does phytoestrogen supplementation improve cognition in humans? A systematic review. Annals of the New York Academy of Sciences. 2017 Sep 1;1403(1):150-63.

White LR, Petrovitch H, Ross GW, Masaki K, Hardman J, Nelson J, Davis D, Markesbery W. Brain aging and midlife tofu consumption. Journal of the American College of Nutrition. 2000 Apr 1;19(2):242-55.

Mitchell JH, Cawood E, Kinniburgh D, Provan A, Collins AR, Irvine DS. Effect of a phytoestrogen food supplement on reproductive health in normal males. Clin Sci (Lond). 2001;100:613-618.

Kurzer MS. Hormonal effects of soy in premenopausal women and men. J Nutr. 2002;132:570S-573S.

Strom BL, Schinnar R, Ziegler EE, et al. Exposure to soy-based formula in infancy and endocrinological and reproductive outcomes in young adulthood. JAMA. 2001;286:807-814.


  1. April says:

    You have lots of information about soybeans that I had no idea about. I have hypothyroid and didn’t know that soybeans interfere with medication absorption. I think I’m going to have to stop eating them. Thank you for this post. And by the way, it’s beautifully done and easy to read.

    • Koichi says:

      Hi, April. Thank you for reading my article. I hope you get better with your thyroid issue and enjoy amazing superfood soybean again. As English is my second language, your comment confirmed that my writing is ok.Thank you again!

  2. Samta says:

    Hi Koichi. Nice to read your blog. There is a lot of negative information on the internet about soybean. It is like a lot of negative information about eating wheat and gluten related allergies. They are both large scale produced products. Especially because they are used to feed animals. The spraying of glycosulphate could be the reason, I think, relating to the studies. What about genetic seed modification? Can that affect nutrition content of the food?

    • Koichi says:

      Hi, Samta. Thank you for your comment. And, I am sorry for my late reply. I was with my daughter on a mountain.
      Glyphosate is carcinogenic. And, glyphosate is to be sprayed on glyphosate-resistant GMO corn and soybean. It is better to avoid GMO crops.
      Also, eating GMO is not natural. I believe, if we are farther from the natural ecosystem, we get a negative effect on our health. GMO soybeans can’t appear in nature but only from a laboratory.
      GMO soybean usually is grown in the monocropping system or grown together with GMO corn. Comparing to a biologically diversified cropping system, the soil has fewer minerals and nutrients, and less diversified microbes. So, these crops are less nutritious than a natural farming system.

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