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Soy protein : Enemy (or) Comrade?

Soy protein isolate is the dry protein powder ingredient that is extracted or isolated, from the remaining hull and oil of the soybean

So, is soy consumption good or bad? And what is actually better for gaining protein – whey protein or soy protein? Well, as always, it depends.

There is a lot of hullabaloo associated with soy as to why it gets so much of positive hype. It is important to know whether it is super-healthy or super-detrimental to health. Further, we will also look into the deal with the infamous soy estrogens.



Soy protein is extracted from the soybean leguminous plant, and is considered to be the only plant-based protein which is of high-quality and contains all nine of essential amino acids in the required ratios for supporting growth and development. Soy consists of 36% protein, 30% carbs, 19% oil, and 14% moisture. The provision consists of a sufficient amount of phosphorus, potassium, iron, zinc, and vitamin E, which are some of the other nutritional functions of soy. It also provides for the full provision of B complex.

The controversy

There have been a lot of studies which have been on both sides of the debate supporting the sides of soy being good or bad for health.

Soy is bad?

A few studies have suggested that the phytoestrogens present in soy protein cause a decrease in the levels of testosterone and an increase in estrogen. Soy is actually rich in estrogenic compounds, such as daidzein and genistein, which are known as phytoestrogens. The number of phytoestrogens available in plants has been known to be over 300 and have varying effects on the potency and physiology of animals as well as humans. A change in the ratio of testosterone and estrogen, favoring estrogen, can lead to an increase in the fat content in the body and can also have an impact on strength. Further, a phytoestrogen called isoflavones which are abundant in soy are known to imbalance the hormone ratios and result in the above mentioned unnecessary changes in estrogen and testosterone. Thyroid problems have also been reported as a consequence of their consumption. The following is a chart showing the amount of phytoestrogens present in various soy-containing foods:

Food Serving Total PEs(mg)
Soy protein concentrate, Water wash 3.5 oz 102
Soy protein concentrate,

Aclohol wash

3.5 oz 12
Miso 1/2 Cup 59
Soybeans,cooked 1/2 Cup 47
Tempeh 3 ounces 37
9Soy milk 1 cup 30
Tofu based yogurt 1/2 cup 21
Tofu 3 ounces 20
Soy beans, green, cooked


1/2 cup 12
Soy hot dog 1 hot dog 11
Soy sausage 3 Links 3
Soy cheese, mozzarella 1 oz 2



Soy proteins contain antinutrients which block the absorption and digestion of other nutrients. Protease inhibitors and lectins are two of the antinutrients present in soy.

Lectins are undesired containments of plants and can lead to a variety of problems, which vary from their interference in the absorption of important nutrients to causing intestinal damage. Further, the enzymes which aid in protein digestion are known as proteases. Protease inhibitors, as their name suggests, interfere and inhibit the functioning of the trypsin and chymotrypsin enzymes, which are important in the absorbing and digesting of proteins in the intestinal tract.

Quite a few researchers in the field of nutrition have begun to blame soy for low energy, hypothyroidism, infertility, digestive disturbances, and other problems.

However, on the other side, many scientists are strong in their belief that soy is in fact substantially beneficial for a varying range of physical ailments.

Soy Protein Isolate

The previously mentioned problem of the presence of antinutrients in soy has now been taken care of as the producers of good-quality soy protein isolates have removed or significantly reduced their presence/activity during processing, which totally removes the concern associated with the presence of antinutrients in soy. Therefore, soy protein isolates give you the good parts of soy removing its bad ones.

Estrogen and Thyroid Hormone

There are studies which have concluded that soy effects hormone levels, but there are those which also suggest that they do not increase estrogen or decrease testosterone. Studies suggest that even though soy contains these phytoestrogens, they are tissue specific in nature and do not necessarily have an impact on hormones. Such studies suggest that phytoestrogens in fact do not have any estrogenic effects such as increase in body fat.

Further, soy has been proven to show an increase in the output of thyroid hormone, which is good news for people trying to shed fat. The intake of other types of proteins has been associated with an increase in the levels of thyroid hormone, but soy seems to have a unique ability when compared to those, it affects the T-4 hormone, whereas other affect the T-3 hormone.

Apart from the above, there are a plethora of benefits associated with soy

  • It enhances the nutritional value of other foods owing to the complete amino acid profile available in soy
  • Soy has been proven to aid in the maintenance of healthy levels of cholesterol.
  • The isoflavones present in soy protein produce antioxidant effects, which aid in the improvement of athletic performance.

As seen from the above, the good of soy overwhelms the bad, especially when it comes to isolates, which provide the benefits of soy, without its associated negative impacts. Research is on-going to provide a much clearer answer for this debate, until then we know what to look for!

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