Health A-Z Archives: Soy

Soybean PlantBy Mary-Ann Shearer

(for an informative look in detail at the growth and development of the soybean plant click here)

Soy has ancient roots worldwide

Soybeans have been a primary source of protein in the East for centuries and have only been used in the West in the last half of the 1900’s. Soy beans must be cooked before eating as they are mildly poisonous when raw, which most legumes are. Soybeans are high in calcium, B-Complex, phosphorous and potassium. They are extremely versatile and used to make products such as soy flour, lecithin, cooking oils, soy protein, tofu, soymilk, soy nut butter, soy sauce and miso.

The debate around soy has reached new heights recently with many reports  stating that soy is actually detrimental to your health. I will present both sides here and then let you make the decision as to whether you would include it in your diet or not.

Soy and dairy intolerance

For many years now I have been aware that about 40% of people who are dairy intolerant are also soy intolerant and that removing dairy from your diet and replacing with soy products does not always result in improved health.

Soy and thyroid function

I have also known of many babies on soy formula that suffer from constipation and removal of soy corrects the problem. So when research started appearing that soy formula can cause severe thyroid problems I was not surprised as the thyroid controls bowel function and the constipation in some people indicated a problem in this area.

The thyroid also controls calcium levels and bone density so soy could contribute to osteoporosis. Yet here again some researchers believe that these same isoflavones may actually stimulate bone formation. The fact remains that healthy bones result from a diet low in animal protein, with plenty of essential fats, sunshine (for Vit D), physical work (resistance exercise), low salt diet, not smoking, avoiding caffeine and alcohol and not taking vitamin C in supplement form, in other words a healthy lifestyle. Again relying on soy to prevent osteoporosis is like planting apple juice and hoping an apple tree will grow!

I personally use soy products on occasions but fin that my body is not comfortable using it regularly. I used soy milk when making a dairy free ice-cream and as a binder in gluten free baking mixes to make gluten free muffins and pancakes. I sometimes use soy milk in sauces and on occasions tofu. On average I use soy 1-2 times a month and have found no adverse effects. However if I consume soy on a daily basis I do find that I feel mentally sluggish (indicating the thyroid which controls mental clarity and get headaches which indicates an intolerance.

Soy and B12

I have also found that in general vegetarians who rely on soy as their sole source of protein often have digestive problems, are underweight and more prone to Vitamin B12 deficiencies. However fermented soy seems to promote B12 balance

Soy and protein

Soy does contain Trypsin (an important protein digesting enzyme) inhibitors which prevent protein from being digested and this in turn impacts on B12 levels. These inhibitors are believed to be destroyed by cooking for long and intense periods of time, but most literature says it is only destroyed by fermentation such as when making miso and tempeh.

Soy and cancer

Soy is high in phytochemicals called isoflavones, which are oestrogen like compounds believed to prevent degenerative diseases such as cancer. The two most well known being genistein and daidzein. Some researchers swear that these isoflavones prevent cancer and others that they contribute to cancer.

I feel that there are no ‘magic bullets’ and the sooner we stop looking for a miracle food or substance the better. Health comes from healthy living, which includes a natural whole food diet, exercise and emotional and spiritual wellbeing and balance.

Breast cancer is prevented by following an alcohol free lifestyle and eating a diet high in natural whole foods that promotes healthy hormones (see my books Perfect Weight and Perfect Health: The Natural Way), exercising daily and avoiding substances that promote hormone disruption such as the contraceptive pill, caffeine, refined sugar, artificial sweeteners, heated fats and lack of essential fatty acids.

Soy, heart disease and hormones

Some research indicates that people who eat soy regularly have:

  • lower levels of harmful cholesterol and so a lower incidence of heart disease
  • less colon cancer (as soy promotes the growth of the friendly bacteria)
  • less breast cancer (as soy appears to lengthen the menstrual cycle)
  • reduces the symptoms associated with menopause and prevents osteoporosis.

However here again are two differing sides to this story as scientists at the National Institute of Environmental Health Sciences in North Carolina found that mice fed the isoflavones genistein resulted in significant changes to the ovaries.

The problem with this type of research is that we do not eat genistein but the whole soy bean and this comes with other nutrients including fibre.

What is interesting is that I have noticed in pregnant women who suffer from severe nausea from the increased Progesterone levels at this time, is that a natural unprocessed soy milk appears to alleviate the severity of the nausea in a dramatic way. One particular case went from vomiting every few hours to just once in the mornings, when she consume 2-3 glasses of soy milk a day during her first trimester.

Soy and menopause

It is often quoted that Japanese women are less likely to suffer from menopause and this indicates that soy is beneficial. What is never mentioned is hat Japanese women are less sedentary that Western women, eat a less processed diet, with less alcohol and caffeine and manage their stress more effectively.

Soy and anxiety

Again research on rats indicated those given soy isoflavones are more anxious and stressed than those on an isoflavones diet.

Soy and Allergies

Soy is known to contribute to many allergies and intolerances and by some considered to be the most allergic food to consume. However here again some people manage to eat soy products with no problems at all.

So what to do about Soy…

We need to realize that the world is driven by money and while researching this it appears that there are some organizations whose sole function is to promote soy very clearly for commercial gain, while also realizing that there is a vicious backlash to the promotion of a vegetarian diet by the flesh and meat industry.

So what to do? As I mentioned earlier I eat soy products occasionally and make sure they contain no additives or processing that could be detrimental to my health. For example TVP (textured vegetable protein) which is made as a meat replacement can contain a variety of food additives like MSG that could be detrimental to your health.

It appears that the East consumes mainly fermented soy products and their overall life expectancy is longer and incidence of cancer and heart disease is lower. But we need to take into account that their lifestyle is less sedentary as the tend to walk and cycle everywhere, they are physically active and involved in growing their own food and they eat a high unprocessed plant based diet, and very little processed foods. All this is beneficial to our health.

To claim that soy is the only factor that contributes to their health is misleading. The human body if treated the way it was designed to be treated will respond with health, it is the miracle not the soy bean.


Some by products of the soy bean:

  • Soymilk is made by boiling the soybeans then crushing or blending them, then straining (using cheesecloth) and heating again.

Plain soymilk has less fat than cows milk, but often when fat is added for palatability it is a lot higher than cows milk. The fat added is usually heated and processed vegetable oil. This oil has no taste as has cold pressed oils. Then many times a sweetener and flavourants are added to make the milk more palatable.

The protein is about 1% or similar to that in cows milk. Most soymilk keeps for about 7 days and can be frozen. Soy milk can also be bought in powder form and the best around is the plain unflavoured, no oil variety.

 Soy milk can be used in all recipes requiring milk very successfully, in fact many people say the texture of baked goods is better and lighter.

  • Tofu is a white cake of pressed soy curds made from coagulated soymilk, much as cheese is made from milk. Also known as “soybean cheese”  or “ bean cake”, tofu is sold packed in water or vacuum packed. It is quite bland in flavour and takes on what ever flavour, sweet or salty, you add.

Tofu is made by soaking soybeans in water overnight. They are then blended into a fine puree, which is then heated on a stove for about 20 minutes. The hot liquid, which is then strained off is the soymilk, which can be freshly consumed, frozen or dried to make soymilk powder. The pulp called okara or “honorable hull” in Japan is set aside. The soymilk is then curdled with salts derived naturally from seawater such as calcium sulphate or calcium chloride.

Tofu curds and whey then appear, the curds are pressed in boxes until a large cake is formed. This is then cut into smaller sizes and sold. Tofu keeps for about 2 weeks if you change the water every 2-3 days. It can be frozen but the texture changes considerably.

Tofu contains ‘complete protein’, all 8 Essential Amino acids, with the protein level ranging from 4% for the soft or silken tofu to 10-15% for the very firm or denser style.

The protein is 65% usable, about the same as chicken.

Tofu and soymilk also contain a wide variety of other vitamins, minerals and nutrients, and is easier to digest than the soybean itself.


Soymilk – 2.8%

Soybeans – 16.6%

Tofu – 8.1%

Cow’s milk – 3.3


Soymilk – 4mg

Soybeans – 102mg 

Tofu – 105mg

Cow’s milk – 119mg

(Measured per 100g of edible food)

Fermented soy products

Tempeh (pronounced “tem pay”). Soy beans are mixed with other grains and seeds and a mould culture, then packed in special bags and incubated for 18-24hours. What results is a chunky, white distinct smelling cake, almost like feta cheese. It is used by many as a meat substitute.

Miso & soy sauce

These are closely related products that have been used in the East for many years Soybeans are fermented much the same as grapes to make wine, or milk to make yoghurt and miso (soy bean paste) and soy sauce is produced. Both can be used to flavour savoury foods as they are naturally high in sodium, just look for msg and sugar free products when you do buy.

In Conclusion…

Soy and the isoflavones extracted from them appear to benefit some people, but some people can be intolerant to soy and this may manifest in a variety of ways. Feeding a baby soy milk formula is very unnatural as babies should be breast fed for the first two years of their lives, even goats milk a better option for babies than soy can result in ill health. So to say that all soy is bad based on research feeding children soy formula is misleading as babies should not have any soy and formula is highly processed containing sugar, sweeteners, heated fats and inorganic manmade vitamins and minerals.

I find I am soy intolerant if I consume soy products on a daily basis I get a headache and stuffy nose. However I do use soy products occasionally as mentioned without any detrimental effects.

Soy seems to be like gluten, some people can handle it and even appear to benefit from some products containing gluten like eating oats for example, but in others gluten can cause some sever reactions including acne, diabetes and infertility.

So Soy is not the miracle, your body is but some people do benefit from it, you have to try it out and see how your body responds to it. Just don’t place too much dependence on soy for your nutrients and that includes protein if you are vegetarian. A better source is from raw nuts and seeds, but then of course some people are allergic to nuts! It appears that “one man’s poison is another man’s food” in this instance.

If you do use soy products like milk, only use 100% pure not with added fats and flavourants etc. These fats are heated and carcinogenic and other additives come with a whole host of problems. Avoid smoked tofu as smoked food are high in nitrates and nitrites and both are highly carcinogenic.

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