Why you should never eat soy protein powder

Protein powders are becoming increasingly sought-after. Even those not involved in strenuous physical exercise or strength training are discovering their numerous benefits. However, there are several disadvantages associated with animal-based, whey protein powders, which is why more and more consumers are switching to vegetable protein powders instead. In this blog, you’ll discover why soy protein powder is definitely NOT a healthy vegetarian alternative to whey protein powder.

Why you should never eat soy protein powder

Why is soy protein powder unhealthy?

Protein powders have been popular for decades. They are a firm favourite with strength athletes, as they contain amino acids that promote the repair of damaged muscle tissue and stimulate the production of new muscle tissue. Yet protein powders are not only a useful supplement for those wanting to build muscle; they’re also prized by vegetarians and vegans (who use them as an additional source of protein), and those wishing to lose weight or maintain a healthy body weight (who stir them into green smoothies, in order to make them more filling).

Whilst whey protein powders were once the protein powders of choice, plant based alternatives are rapidly overtaking these in terms of popularity. That’s because protein powders made from dairy products are often less healthy than vegetarian ones; they’re typically brimming with artificial flavours, colours and preservatives for example. You can read more about the drawbacks of whey protein powders in: "Can whey protein powder be replaced with hemp protein or brown rice protein powder?". Many people mistakenly believe that soy protein powder is a sensible alternative to whey protein powder. But this is far from true. In fact, even though soy is rich in protein, it also contains a number of substances that can greatly undermine your health. 

Soy protein powder is made from unfermented soybeans - soybeans that, unlike tempeh and soy sauce, haven't undergone fermentation. This means that they have an extremely high phytic acid and phytoestrogen content. Most soy has also been genetically modified, and the health consequences linked to consuming genetically modified food products are still far from clear.

The adverse effects of phytic acid

Phytic acid (also known as inositol hexakisphosphatase (IP6) and phytate) is a saturated cyclic acid that is the principal storage form of phosphorus in many plant tissues. As this acid cannot be digested by humans, it is not a dietary source of phosphorus.

Furthermore, phytic acid binds to the minerals zinc, iron, calcium and magnesium (Dendougui et al., 2004[1]), making these less absorbable by the human body. If you ingest a considerable amount of of phytic acid on a daily basis, you therefore run the risk of a mineral deficiency (Oberleas, 1973[2]; Hurrell, 2003[3]). Phytic acid can thus be regarded as an "anti-nutrient" that depletes essential nutrients from the body. Yet despite being an anti-nutrient, it also has some beneficial properties. Indeed, phytic acid is a powerful antioxidant that can help to slow down the oxidising effect during an iron surplus (which often occurs in men) (Graf et al., 1990[4]). In addition, phytic acid may inhibit tumour growth in certain types of cancer, including colon cancer (Graf et al., 1993[5]), helps stabilise blood sugar levels (Thompson et al., 1987[6]), lowers cholesterol (Urbano et al., 2000[7]) and, thanks to its cleansing effect, can support detoxification (Cheryan et al., 1980[8]). So, phytic acid is not necessarily bad by definition. If you consume soy protein powder on a regular basis, however, you will ingest excessive quantities of phytic acid and run the risk of a vitamin B3, zinc, iron, calcium and / or magnesium deficiency. 

The dangers of phytoestrogens

Soy protein powder also contains a considerable amount of phytoestrogens - plant-based, oestrogen-like substances that structurally resemble the human hormone estradiol (17-β-estradiol), and are therefore capable of binding to oestrogen receptors within both the male and female body. At a molecular level, phytoestrogens are extremely similar to human oestrogen, and are therefore able to 'trick' the body and imitate human oestrogen. They can also stimulate the body’s oestrogen production (Yildiz et al., 2005[9]). Indeed, a major effect of phytoestrogens, is that they can increase oestrogen levels within the body, which can in turn affect hormonal balance and potentially lead to oestrogen dominance in both women and men (Hall, 2001[10]). Oestrogen dominance occurs when the body contains too much oestrogen relative to progesterone (in women) or testosterone (in men).

There have been a number of conflicting reports about phytoestrogens in recent years. According to some studies, the consumption of foods rich in phytoestrogens may promote the growth of tumours in breast cancer and other hormone-related cancers (e.g. Martin et al., 1978[11]), while other studies have concluded that phytoestrogens actually provide protection against breast cancer (Ingram et al., 1997[12]). In the past, women who have or have had breast cancer were advised to minimise their consumption of foods that contain phytoestrogens (De Lemos, 2001[13]). However, based on recent epidemiological studies, it is now being claimed that moderate phytoestrogen consumption is safe for women who have (had) breast cancer, and may even extend life expectancy and reduce the likelihood of recidivism (the return of cancer) (Shu et al., 2009[14]). There are also reports of phytoestrogen rich foods helping to reduce menopausal symptoms, such as hot flashes. However, a large-scale study recently demonstrated that soy products, soy meat substitutes and other phytoestrogen-rich foods, do not help to combat menopausal problems (Lethaby et al., 2007[15]).

Further research into the exact effects of dietary phytoestrogens on different types of cancer is still required. In lieu of this, it’s best to avoid consuming soy protein powders altogether, as these have a disproportionately high phytoestrogen content.

The risks of genetically modified soy

The soy used for the preparation of soy protein powder has often been genetically modified. With this type of soy, which is also known as GMO soy or genetically engineered soy, the genetic structure of the plant has been modified using genetic technology, in order to make it more resistant to certain pesticides. This allows the soy plant to be sprayed with herbicides that contain the highly toxic, glyphosate, without them being killed. Many types of GMO soy have also had the addition of specific genes, which secrete substances that are toxic to insects. A good example of this is Bacillus thuringiensis (BT), an organic pesticide that naturally occurs in certain plants, soil and dung. The genetic makeup of soy has now been modified to such an extent that the soy plant can manufacture BT toxins themselves, thus preventing them from being eaten by insects.

The main disadvantage of GMO soy is that it contains glyphosates and BT-toxins, two toxic substances that can cause a variety of diseases and disorders in the human body, including stomach inflammation, leaky gut, autoimmune diseases, various forms of cancer, liver damage and cardiovascular disease (e.g. Pusztai et al, 2003[16]). Glyphosate, the pesticide to which GMO soy is resistant, can also cause hormonal imbalance, leading to a higher risk of infertility, miscarriage and birth defects (Richard et al., 2005[17]). Glyphosates may additionally increase the risk of neurological disorders, such as learning disabilities, attention deficit disorder, autism, Alzheimer's disease, bipolar disorder, dementia, schizophrenia and other neurological conditions. Scientists have demonstrated that there is a direct link between the increasing number of autism cases and an increased consumption of genetically modified soy and maize, and the number of children and adults with chronic diseases and conditions, such as asthma, learning disabilities and obesity, has risen 25% since the introduction of genetically modified soy into the consumer market (D'Brant, 2014[18]). And the long term effects of consuming genetically modified soy and other GMO products are not yet known. Recent scientific studies indicate that DNA fragments, which enter the human body via food, can transport complete genes into the human circulation system (Spisák et al., 2013[19]) and thus penetrate and alter "good" bacteria within the intestines, (Netherwood et al., 2004[20]).

The effect this will have on our health and that of our offspring in the next 20 to 40 years, is still not fully understood. Genetically modified food has only existed since 1994, so scientists are only able to investigate its short-term effects. Well-known Canadian geneticist, David Suzuki, recently expressed concern and claimed that humanity is currently part of a "massive genetic experiment", in which thousands of people and animals are consuming GMO food products without knowing the long term health effects. According to Suzuki, just one small genetic change can have a huge impact on the human body, meaning that it’s impossible to predict the future consequences of GMO food.

What is the best vegetarian alternative to soy protein powder? 

It’s clear that you should avoid consuming soy protein powder, or other soy-based products made from unfermented soy, such as soy milk, tofu and soy based meat substitutes. The best vegetarian alternative to soy protein powder is organic hemp protein powder or brown rice protein powder. You can read about the numerous benefits of these delicious vegetable protein powders in the following blogs: "Can whey protein powder be replaced with hemp protein or brown rice protein powder?", “How many protein shakes a day is still healthy?” and “What is the best protein powder for women”. 


[1] Dendougui, Ferial, and Georg Schwedt. "In vitro analysis of binding capacities of calcium to phytic acid in different food samples." European food research and technology 219.4 (2004): 409-415.

[2] Oberleas, Donald. "Phytates." Toxicants occurring naturally in food. Committee on Food Protection (Ed.) National Academy of Sciences (1973): 363-371.

[3] Hurrell, Richard F., et al. "Degradation of phytic acid in cereal porridges improves iron absorption by human subjects." The American journal of clinical nutrition 77.5 (2003): 1213-1219.

[4] Graf, Ernst, and John W. Eaton. "Antioxidant functions of phytic acid." Free Radical Biology and Medicine 8.1 (1990): 61-69.

[5] Graf, Ernst, and John W. Eaton. "Suppression of colonic cancer by dietary phytic acid." Nutrition and cancer 19.1 (1993): 11-19.

[6] Thompson, Lilian U., Cheryl L. Button, and D. J. Jenkins. "Phytic acid and calcium affect the in vitro rate of navy bean starch digestion and blood glucose response in humans." The American journal of clinical nutrition 46.3 (1987): 467-473.

[7] Urbano, G., et al. "The role of phytic acid in legumes: antinutrient or beneficial function?" Journal of physiology and biochemistry 56.3 (2000): 283-294.

[8] Cheryan, Munir, and Joseph J. Rackis. "Phytic acid interactions in food systems." Critical Reviews in Food Science & Nutrition 13.4 (1980): 297-335.

[9] Yildiz, Fatih, ed. Phytoestrogens in functional foods. CRC Press, 2005.

[10] Hall, D. "Nutritional influences on estrogen metabolism." Applied nutritional science reports 1 (2001): 1-8.

[11] Martin, Pierre M., et al. "Phytoestrogen Interaction with Estrogen Receptors in Human Breast Cancer Cells*." Endocrinology 103.5 (1978): 1860-1867.

[12] Ingram, David, et al. "Case-control study of phyto-oestrogens and breast cancer." The Lancet 350.9083 (1997): 990-994.

[13] de Lemos, Mário L. "Effects of soy phytoestrogens genistein and daidzein on breast cancer growth." Annals of Pharmacotherapy 35.9 (2001): 1118-1121.

[14] Shu, Xiao Ou, et al. "Soy food intake and breast cancer survival." Jama 302.22 (2009): 2437-2443.

[15] Lethaby, A. E., et al. "Phytoestrogens for vasomotor menopausal symptoms." Cochrane Database Syst Rev 4.4 (2007).

[16] Pusztai, A., S. Bardocz, and S. W. B. Ewen. "16 Genetically Modified Foods: Potential Human Health Effects." Food Safety (2003): 347.

[17] Richard, Sophie, et al. "Differential effects of glyphosate and roundup on human placental cells and aromatase." Environmental health perspectives (2005): 716-720.

[18] D'Brant, Jeanne. "GMOs, Gut Flora, the Shikimate Pathway and Cytochrome Dysregulation." Nutritional Perspectives: Journal of the Council on Nutrition 37.1 (2014).

[19] Spisák, Sándor, et al. "Complete genes may pass from food to human blood." PLoS One 8.7 (2013): e69805.

[20] Netherwood, Trudy, et al. "Assessing the survival of transgenic plant DNA in the human gastrointestinal tract." Nature biotechnology 22.2 (2004): 204-209.

Dangers of soy protein powdersThe adverse effects of phytic acidThe benefits of brown rice protein powderThe benefits of hemp protein powderThe benefits of vegan protein powdersThe dangers of phytoestrogensThe risks of genetically modified soyWhat is the best vegetarian alternative to soy protein powder?Why is soy protein powder unhealthy?Why you should never eat soy protein powder

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