You’ve probably heard a thing or two about soy protein. The good, the bad, and the ugly.
“Soy protein is bad for you!”
“Soy protein will mess up your hormones!”
We’re here to share information about soy from reliable sources. This scientific guide will help you better understand the most important things you need to know about soy.
Let’s get started.
Why Should I Eat Soy Protein?
Soybeans are nutritional bombs, they contain twice the amount of protein and more oil (healthy unsaturated fat) than other beans, and very little starch. A bunch of years ago, the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) felt the need to assess the quality of all the different proteins you could end up eating, therefore, they established the so-called protein digestibility-corrected amino acid score (PDCAAS).
As you read on our blog about macronutrients, proteins are made of many amino acids and the PDCAAS evaluates the quality of that protein by comparing its amino acid composition to what our body can absorb and use. The highest PDCAAS value that any protein can achieve is 1.0.
This is a list of the best protein sources:
- Whey (1.0)
- Casein (1.0)
- Soy (1.0)
- Pea (0.89)
- Flaxseed (0.61)
- Oats (0.6)
- Rice (0.42)
We gave a chance to different plant-based proteins such as pea, rice, sorghum or hemp, but after seeing soy’s PDCAA’s score of 1.0 we convinced ourselves that this smooth and tasty bean would be the best source of protein for us to use in our products. [1, 2]
You might wonder if we looked at both the so-said health benefits and the health risks of soy protein. That brings us to the following question.
Does soy protein affect hormone levels?
Soy is the main source of dietary isoflavones, which are naturally present in many plants including legumes.
Isoflavones are classified as phytoestrogens: plant-derived compounds with estrogenic activity, where the term ‘phyto’ refers to the fact they are of plant origin.
Soy isoflavones have been consumed by humans for many years without any evidence of adverse effects. They are often related to hormonal activity because their chemical structure shows similarities to the human hormone estrogen.
So, phytoestrogens are estrogen-like compounds found in plants, and isoflavones in soybeans are just one of several classes of phytoestrogens. Although phytoestrogens are chemically similar to estrogen and behave like the hormone in some respects, they are estimated to be between 100 and 100,000 times weaker than the estrogens that occur naturally in humans. 
Studies show that soy isoflavones do not significantly influence circulating thyroid hormones produced in healthy young men. Findings from a recently published meta analysis and later published studies, show that neither isoflavone supplements nor isoflavone-rich soy affects testosterone levels. Similarly, a review of identified clinical studies also concluded that isoflavone exposure does not affect circulating estrogen levels in men.
Men don't need to worry about feminizing effects from eating soy-based foods. Clinical evidence also indicates that isoflavones have no effect on sperm or semen parameters, although only three intervention studies were identified and none were longer than 3 months in duration. [4-6]
Alright, all men can let out a sigh of relieve. Let's move on and consider another serious question about soy.
Can soy protein cause cancer?
Soy foods contain several key nutrients and phytochemicals studied for their cancer prevention properties. Many soy foods also contain dietary fiber, which links to lower risk of colorectal cancer.
Soy foods contain isoflavones, which are structurally similar to your internal estrogens. Because of the high levels of estrogen link to increased breast cancer risk, there was a fear that soy foods – and its isoflavones – may increase risk. Yet overall, human studies show how soy foods do not increase risk and how in some cases, they may even lower it. [7-9]
But then, where did the idea about soy increasing cancer risk came from?
As we just explained in the previous paragraph, isoflavones are plant estrogens, and high levels of estrogen have been linked to an increased risk of breast cancer. However, food sources of soy don't contain levels of isoflavones high enough to increase the risk of cancer, in fact, they may even prevent it when eaten in moderation.
What is moderate usage?
A daily intake that doesn't exceed 50-120mg of isoflavones is considered a moderate consumption of soy. 
This is, in part, confirmed by some well regarded food authorities. The World Cancer Research Fund (WCRF) and the American Institute for Cancer Research (AICR) have concluded that soy foods as part of a healthy diet are perfectly safe.
Also, the European Food Safety Authority (EFSA) conducted an extensive literature review to assess the risk for peri- and post-menopausal women taking soy food supplements containing isolated isoflavones, in which no negative effects were observed even at the highest intake levels of isolated isoflavones, in other words, EFSA recognizes that the consumption of soy foods which naturally contain isoflavones in much lower quantities than soy food supplements, is safe. [11-13]
Next to these well-respected authorities in the area of health and nutrition, there is more evidence. Moreover, the consumption of soy (protein) can have a positive effect.
A six-year prospective cohort study of more than 12,000 men in the US found that those who drank soy milk more than once a day had a 70% lower risk of prostate cancer than those who never drank soy milk.
That’s not the only major study conducted.
A 23-year study of more than 5,000 Japanese American men found no association between tofu consumption and prostate cancer risk.
More recently, a prospective study in a cohort of 43,509 Japanese men found that the consumption of soy foods was associated with a decreased risk of localized prostate cancer in men older than 60 years.
Whatever the latest results show us, further clinical trials are needed. Researchers have to further determine the relationship between prostate cancer risk and soy consumption. 
Since we’ve considered these major questions, let’s move down to other topics.
Can soy protein affect my thyroid health?
Your thyroid is a small, butterfly-shaped gland situated at the base of the front of your neck, just below that stuck apple in your throat.
Hormones produced by the thyroid gland are called triiodothyronine and thyroxine. These are also known as T3 and T4. They have a huge impact on your health, mainly your metabolism and vital functions, such as body temperature, digestion and heart rate.
Moderate consumption of soy protein won’t have an affect on your thyroid that would negatively affect your thyroid health.
It can happen that your body doesn’t produce enough hormones from the thyroid, a health condition called hypothyroidism. Hypothyroidism and isoflavones in soy can be problematic for some people with an underactive thyroid because they can block the function of the main enzyme needed by the thyroid gland to be able to produce the T3 and T4 hormones. Therefore, if you have been diagnosed with hypothyroidism, we strongly advise you to speak with your doctor about the consumption of isoflavone-containing foods such as soy, and to make sure that you are consuming enough iodine, one of the main deficiencies caused by hypothyroidism. 
“A handful of case reports have indicated that soy might interfere with the absorption of thyroid medicine.” Reason to which it has been concluded that people with normal thyroid function who aren't taking thyroid medicine don't have to worry about soy suppressing their thyroid levels. [4, 16]
Soy and naturally occurring toxins.
You might not know this yet, but toxic compounds are produced by a variety of plants and animals as part of their growth.
This happens especially as a chemical defense against predators, insects or microorganisms. These chemicals have diverse chemical structures and are vastly different in toxicity, all of which can be controlled through appropriate handling and production processes. The scientific literature states that cooking or steaming soybeans for at least 5 minutes at a minimum of 100°C is required to ensure the removal of Leucine, the main toxin found in soybeans.
To be on the safe side, the soybeans found in our products are heated between 100 - 120°C for approximately 30 minutes. 
Does soy protein affect fertility?
Interest in phytoestrogens has increased dramatically over the last decade. As we mentioned earlier, soy is believed to behave in a similar way as certain compounds in our body because of having a similar structure, nevertheless, soy phytoestrogens are far less strong.
The concerns raised are based on animal experiments which suggest that phytoestrogens can affect sexual development and reproduction function, but these experiments can be inaccurate when relating them to human health. Rodents metabolise isoflavones differently compared to humans. Besides this, animals in these studies were exposed to excessively high amounts of isoflavones. [18, 19]
A study, reviewing all the available scientific studies on soy isoflavones and their possible effect on male hormones and reproductive functions, concluded that there is essentially no basis for concern. Isoflavone exposure at levels even greatly exceeding reasonable dietary intakes did not affect sex hormones in men. 
Moreover, the UK Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment conducted an in-depth analysis of soy effects on human health. They acknowledged that there is no evidence that populations which regularly eat high quantities of soy, such as the Chinese and Japanese, have altered sexual development or impaired fertility. 
Is soy protein bad for the environment?
Much of the concern about soy’s impact on the environment is attributed to the way on how ethically are soybeans harvested, produced and distributed. So let’s dive a little bit deeper.
More than 90% of the soy consumed in Europe is imported from South America, one of the reasons for which we chose to obtain our tasty soy from a Dutch local producer, located just 2 hours away from Amsterdam.
Did you know that Europe’s current agricultural systems depend on soy? Yes! The consumption of this humble beans in Europe rose from the equivalent of 2.7 million tonnes in 1960 to the booming amount of 43.5 million tonnes in 2016. 
Our soy provider has over two centuries of experience in processing beans and specialty grains in a NON-GMO way, taking into account the required aspects to ensure food safety and accordingly working with the following certified quality standards: FSCC2200, Riskplaza, SKAL, NOP, GMP+ and Valid IT.
Fun fact: Soy plants themselves are naturally fixing nitrogen, which reduces the need for use of energy-intensive artificial fertilizers used in the harvesting of other crops.
Another fun fact: Producing 1 litre of soy drink requires three times less land, less water and emits less CO2 than 1 liter of milk.
Crops account for 12% of the earth's surface. 75% of these crops are used for animal feed. So instead of using crops for food, the industry feeds them to livestock such as cows, which is very ineffective in our opinion.
Livestock such as cattle occupy 26% of the earth's surface and are actually the main cause of deforestation.
Moreover, methane-rich gases produced during their digestion processes are known to be destructive to the ozone layer and contributors to global warming. It is estimated that cows release between 250 and 500 liters of methane per day.
So basically, we’re cutting down huge parts of the world’s forests to make room for methane-producing cows that also consume 75% of our crops. Not cool at all. 
Food science is an ever-evolving field of science that we continue to monitor with great care to deliver the healthiest meal possible. We mention sources below so you can monitor these too.
- Nadathur, Sudarshan R., Janitha P. D. Wanasundara, and Laurie Scanlin. 2016. Sustainable protein sources. http://site.ebrary.com/id/11275745.
- Gorissen, S., Crombag, J., Senden, J., Waterval, W., Bierau, J., Verdijk, L. B., & van Loon, L. (2018). Protein content and amino acid composition of commercially available plant-based protein isolates. Amino acids, 50(12), 1685–1695. doi:10.1007/s00726-018-2640-5
- Messina M, Redmond G, 2006. Effects of soy protein and soybean isoflavones on thyroid function in healthy adults and hypothyroid patients: a review of the relevant literature. Thyroid. 16(3): 249-258.
- Harvard Health. (2010). An update on soy: It's just so-so - Harvard Health. [online] Available at: https://www.health.harvard.edu/newsletter_article/an-update-on-soy-its-just-so-so
- Barbara L. Dillingham, Brianne L. McVeigh, Johanna W. Lampe, and Alison M. Duncan.Thyroid.Feb 2007.ahead of printhttp://doi.org/10.1089/thy.2006.0206
- Messina, Mark. Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence. Fertility and Sterility, Volume 93, Issue 7, 2095 - 2104
- American Institute for Cancer Research. (2019). Soy. [online] Available at: https://www.aicr.org/foods-that-fight-cancer/soy.html
- Messina MJ. Emerging evidence on the role of soy in reducing prostate cancer risk. Nutr Rev. 2003;61(4):117-131.12795445
- Sirtori CR. Risks and benefits of soy phytoestrogens in cardiovascular diseases, cancer, climacteric symptoms and osteoporosis. Drug Saf. 2001;24(9):665-682.11522120
- Williams, V. (2016). Does Soy Increase Breast Cancer Risk?. [online] https://newsnetwork.mayoclinic.org. Available at: https://newsnetwork.mayoclinic.org/discussion/mayo-clinic-minute-does-soy-increase-breast-cancer-risk/
- American Institute for Cancer Research (AICR). Cancer Research Update: Soy is Safe for Breast Cancer Survivors [Internet]. 2012 [cited 8/20/2018]. Available from: http://www.aicr.org/cancer-research-update/2012/november_21_2012/cru-soy-safe.html EFSA.
- Risk assessment for peri- and post-menopausal women taking food supplements containing isolated isoflavones. EFSA Journal 2015;13(10):4246 [342 pp.]. 2015.
- WCRF Intern. Continuous Update Project. Breast cancer survivors: how diet, nutrition and physical activity affect breast cancer survival [Internet]. 2018 [cited 7/24/2018]. Available from: https://www.wcrf.org/dietandcancer/breast-cancer-survivors
- Higdon, J., Drake, V. and Anderson, J. (2009). Legumes. [online] Linus Pauling Institute. Available at: https://lpi.oregonstate.edu/mic/food-beverages/legumes
- Mayo Clinic. (2018). Hypothyroidism - Symptoms and causes. [online] Available at: https://www.mayoclinic.org/diseases-conditions/hypothyroidism/symptoms-causes/syc-20350284 [Accessed 10 Dec. 2019].
- American Thyroid Association. (n.d.). Low Iodine Diet. [online] Available at: https://www.thyroid.org/low-iodine-diet/
- Pusztai, Arpad & Grant, George. (1998). Assessment of Lectin Inactivation by Heat and Digestion. Methods in molecular medicine. 9. 505-14. 10.1385/0-89603-396-1:505.
- Viva! - The Vegan Charity. (n.d.). Fact Sheet: The Safety of Soya. [online] Available at: https://www.viva.org.uk/resources/the-safety-of-soya-factsheet [Accessed 10 Dec. 2019].
- Messina M, 2010. Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence. Fertility and Sterility. 93(7): 2095-2104.
- COT, 2003. Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment. Phytoestrogens and Health. London: The Food Standards Agency, FSA/0826/0503.
- Donau Soja. The Donau Soja Institute. [online] Available at: https://www.donausoja.org/en/about-us/the-association/?fbclid=IwAR0Oux8ZJp5deDxFHXe_71QSoJY3vF-datcfenG0K4oBGfUpmo-ORpZMvMk
- Pittman, A. (2016). How Planting Crops Used to Feed Livestock is Contributing to Habitat Destruction. [online] One Green Planet. Available at: https://www.onegreenplanet.org/environment/livestock-feed-and-habitat-destruction/