Soy as Goitrogen Foods

Xu Chen1*

1 Xu Chen, University of the Rockies and the College of St. Scholastica. USA

*Corresponding Author:Xu Chen, University of the Rockies and the College of St. Scholastica, USA, Tel: +1 866-621-0124; Fax: +1 866-621-0124;

Citation: Xu Chen (2021) Soy as Goitrogen Foods. Cancer Prog Diagn 5: 124.

Received: April 15, 2021; Accepted: May 19, 2021; Published: May 22, 2021.

Copyright: © 2021 Xu Chen, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Soy product is a common meat substitute among vegetarians. However, soy has its drawbacks. One of the dark sides of soy is that it is a goitrogen. The contents inside soy are not good for thyroid. In fact, American people totally do not know how to eat. The soy in vegan diet is hard to digest, but they think it is healthy; the European gourmet cheese that bugs flying out from are considered not sanitary enough; fermented soy are not considered everyday food on American dinner table. In this review, this author will discuss how to eat soy to benefit thyroid and overall health.


 Soy, Goitrogen, Fermentation, Natto, Vitamin K2, MK7


Soy is a major protein source for vegetarian diet. For instance, if a baby is allergic to caw’s milk, soy can be a great substitute. Protein is very important for human development, and soy is a good source of protein [9]. People use beans in Mexican foods, tofu in Chinese food, and cans of cooked beans in their salad. Soy is supposed to be a good protein source for people of low income. However, with the reputation of being healthy, soy products do not seem to benefit women of metabolism syndrome [11]. On the other hand, Asian people, typically Japanese, who consume a lot of soy, have low body weights [17]. In this paper, this researcher will try to find out whether soy is a healthy protein source, and whether there are different ways in eating soy.


The method of this research will be a literature review. This paper is a synthesis of what is already known and the goal is to answer questions. There will be six research questions:

-Is soy good protein source for weight control?

-If it is soy products that make Japanese people lean, how do Japanese consume soy differently?

-what type of legume is good for the fermentation;

-how long should the fermentation go;

-how to do the fermentation; and what are the nutrition contents of the post-fermentation products?

Result and Discussion

Soy contains phytoestrogens, and phytates, which are both goitrogens [7]. Phytoestrogens have similar structures as human estrogens [15]. One type of phytoestrogen is isoflavone. Some studies show that isoflavone lowers the rates of certain cancers [15]. Phytates affects absorption of some nutrients such as calcium and phosphate [7].

Injecting soy isoflavone subcutaneously to orchidectomized middle-aged (16-month-old) rats causes thyroid angio-follicular changes, reduces thyroid hormone concentration, and increases thyrotropin (TSH) concentration in serum. All these indicate decreased thyroid function [13]. In human subjects, soy isoflavone caused moderate thyroid hormone decrease, which is consistent with animal experiments [8]. Soy contains phytates, which are compounds that control premature germination and store phosphorous in preparation for sprouting. Phytates affect digestive system by interrupting absorption of micro-nutrients. To understand how phytates affect digestion, [7] measured amino acids and calcium and phosphate digestion under three different levels of phytates among pigs. The result showed that phytates interrupt with the absorption of calcium and phosphate, which are essential minerals for human body. One of the solutions is to take in fermented soybeans. Good examples are Natto, tempeh, miso, and soy sauce [3].

Fermentation breaks down phytic acids and some digestive enzymes inhibitors and makes it easy to digest in human body [3]. Natto is a traditional breakfast food in Japan. It smells a like ammonium and has a cheesy look. American people usually cannot accept it because of the taste and smell [2]. Tempeh is a type of fermented soy originally from Java Indonesia, some tempeh has only soy as an ingredient; while others mix into grains [10]. Tempeh has a bland taste with a little nutty flavor and is not good for eating alone without proper seasonings. There are many ways in cooking tempeh. One of the ways is to season tempeh with tamaris and make into Kong Pao Tempeh [4].

Moreover, Fermentation of soy beans produce vitamin K [12]. Vitamin K is a fat-soluble vitamin that has a very low blood concentration. Currently, there is no precise standard for vitamin K blood level and knowledge about vitamin K is limited. Vitamin K metabolism very fast through the body through kidney and bile [12]. Clinically, Vitamin K2 can prevent bone fractures and post-menopausal osteoporosis [5].

There is more than one form of Vitamin K2. MK4 and MK7 are two of them. The structures of Vitamin K1, MK4, and MK7 are as follows [14].

Between MK4 and MK7, MK7 has a higher effect than MK4. The dose of MK7 in treating rheumatoid Arthritis is 100ng/day, while the dose of MK4 is 45mg per day. If MK7 is much more potent than MK4, and Natto contains big amount of MK7, how to make Natto to maximize the MK7 content will become significant [1].

According to [12], 24-hour fermentation can yield 39.039 ng/g of MK7. If one portion of Natto is 70g, it should give about 3mg of MK7. The optimum temperature is 37 Celsius. To understand what type of legume is good for natto making, this researcher made her own natto. This researcher inoculated overcooked boiled beans. The following picture is fermentation of 24 hours at room temperature:

The following picture is from fermentation for 24 hours at 37 Celsius:

The following picture is from fermenting black beans for 24 hours under 37 Celsius:

The pictures illustrated that black beans made the best natto. However, personally, this researcher believes that yellow soy bean natto taste better than others.

Vitamin K2 rich vegetables are as follows in (mcg/100g)

cooked spinach – 540.7 mcg; cooked kale – 418.5 mcg; cooked mustard greens – 592.7 mcg; cooked collard greens – 623.2mcg; cooked beet greens – 484 mcg; raw swiss chard – 830 mcg; raw dandelion greens – 778.4 mcg; cooked turnip greens – 518.9 mcg; broccoli – 141.1 mcg; cooked cabbage – 108.7 mcg; raw arugula – 108.6 mcg; dried basil –1714.5 mcg; dried sage – 1714.5 mcg; dried thyme – 1714.5 mcg; dried marjoram – 621.7 mcg; dried oregano – 621.7 mcg; fresh parsley – 1640 mcg; dried coriander leaf – 1359.5 mcg; endives –231 mcg; chives – 212.7 mcg; raw cress – 541.9 mcg; cooked brussel sprouts – 193.5 mcg; red leaf lettuce – 140.3 mcg; green leaf lettuce –126.3 mcg; soybean oil – 183.9 mcg; mayonnaise – 163 mcg; margarine – 101.3 mcg; Share on Pinterest

100 g of the following foods contain high levels of vitamin K-2.

natto – 939 mcg; goose liver – 369 mcg; beef liver –106 mcg; turkey sausage – 36.6 mcg; chicken meat –35.7 mcg; turkey frankfurter – 31.2 mcg; salami – 28 mcg; pepperoni – 41.7 mcg; soft cheese – 506 mcg; blue cheese – 440 mcg; hard cheese – 282 mcg; full-fat milk – 38.1 mcg; bacon – 35 mcg

Therefore, the veggies that are rich in VitK2 are parsley and other spices alike. The food that are rich in Vitamin K2 are Natto, cheese, and livers. However, since Vitamin K2 has many forms, and MK4 and MK7 functions differently, further research will focus on what different foods contain most of which kind of Vitamin K2. Also, how MK4 ,5, 6, 7…., 10 function differently.


For research question number one: Is soy a good protein source for weight control? The answer is that it is a good protein source, but the ways of preparing is important. Question number two: If it is soy products that make Japanese people lean, how do Japanese consume soy differently? The answer is fermented soy. Eating soy can be healthy, but the ways to eat soy is crucial in weight control. Soy contains phytates that affect absorption of other nutrients such as calcium and phosphate. Soy also contains isoflavon which is a goitrogen. To prevent these problems, people should eat fermented soy. Fermented soy includes natto, tempeh, miso, and soy sauce. Yellow soy bean is traditionally most popular one for Natto. One of the most important nutrients in fermented soy is Vitamin K2 Which includes many forms of menaquinone (MK). The best legume for natto making is black soybean. The fermentation should last at least 24 hours to achieve the high amount of MK7, and the fermentation temperature is about 37 Celsius. To get enough Vitamin K2, people should eat fermented foods and spice up when they cook.


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