Firstly, I want to start off by looking at some of the research and why it has been misinterpreted… and why soy has a bad name in the first place.
1. Approximately 90-95% Soy in the USA is genetically modified to result yield a greater amount of crop during harvest, however even that appears to be debatable (1, 2). The majority of this Non-Organic/Genetically Modified Soy is fed to cattle who are then consumed by humans or used to make milk which is also consumed by humans. I only recommend eating Organic/Non-GMO Soy. GMO, in general, pose a risk to our health as they can withstand massive amounts of herbicides, pesticides, etc. which you are also no doubt consuming.
2. Studies showing side effects of soy consumption have looked at subjects consuming up to 12 servings of soy a day (3). That’s a ridiculous way to look at the effect of any food – I would never recommend consuming one food this frequently. It’s important to note that even in these studies, when the subjects discontinued such excessive soy consumption, their health returned to normal (4).
3. Most of the negative research and public scaring has been pushed by animal-backed bodies to discredit soy and cause confusion. Confusion means consumers stick to their animal products – it’s the animal industry’s way of trying to slow down the growth of soy consumption which affects their bottom line ($$$).
Most people assume soy causes breast cancer/man boobs because research links excess oestrogen to these (5). Firstly, soy does not contain oestrogen (animal hormone). Rather, soy, along with chickpeas & other legumes, contains isoflavones/phytoestrogens (plant hormone) which have been shown to be 1,000 x weaker than animal oestrogen. These isoflavones have actually been shown to lower cholesterol and help regulate cell growth – reducing some cancers. In particular, studies have shown soy to actually reduce breast cancer risk – & some of the lowest incidences of breast cancer in the world are in Asian countries where the most soy is consumed.
There is also evidence to support soy consumption for reducing the risk of prostate cancer and coronary heart disease. This paper in particular, which draws on 20 years of soy research, had the below to say (6,7).
Finally, other than allergic reactions, there is almost no credible evidence to suggest traditional soyfoods exert clinically relevant adverse effects in healthy individuals when consumed in amounts consistent with Asian intake.
This evidence from observational studies shows a statistically significant association between soy consumption and decreased Prostate Cancer risk
“As reviewed, the evidence indicates that, with the exception of those individuals allergic to soy protein, soyfoods can play a beneficial role in the diets of vegetarians. Concerns about adverse effects are not supported by clinical or epidemiologic literature. Based on the soy intake associated with health benefits in the epidemiologic studies and the benefits noted in clinical trials, optimal adult soy intake would appear to be between two and four servings per day.”
If you have a normal functioning thyroid gland, there is no compelling research to suggest that soy will negatively affect thyroid function. If you have an existing thyroid issue then soy may affect the absorption of your medications so you should consult your GP. A good tip is to only consume soy a few hours after you’ve had your medications.
The only subset (very small group of people) who should avoid soy is anyone with hypothyroidism (clinically diagnosed) or is deficient in iodine. In these cases, these individuals should correct these issues before commencing/resuming soy consumption (9).
It’s worth pointing out that in 2019, a systematic review and meta-analysis concluded that soy has no effect on the thyroid hormones and only modestly stimulates thyroid-stimulating hormone (TSH) – with the authors declaring that the latter may have little, if any, clinical significance. (11)
While it is true that the scale of soy production has contributed to mass deforestation, particularly in Brazil and Argentina and the USA, more than 80% of the soy is produced as feed for livestock, not human consumption. So don’t worry about consuming some tofu – its environmental impact is way lower than any other animal food! (10)
If Soy is not unhealthy & actually has health benefits, practically speaking how can we incorporate it into our plant-based diets best?
1.When speaking of the health benefits of soy foods, keep in mind this applies to soy in its most natural forms: tempeh, natto, miso, tofu and soy milk – NOT to soy isolates or other heavily processed forms of soy.
2. Therefore, stick to as much ‘whole food’ soy products as you can. Processed foods like tofu are not unhealthy (still far healthier than animal protein sources) however during the processing you do lose around 50% of the nutrients. Given soybeans pack a tonne of nutrients, don’t be too concerned but worth noting.
2. Unprocessed soybeans like Edamame and Tempeh products should be your main sources of soy. These are nutrient powerhouses. Tempeh also has amazing probiotics to help with gut health.
3. Choose organic soy milks and, where possible, short shelf life ones as they contain less preservatives & are not packaged under immense heat, which no doubt kills many vitamins.
4. Read labels! If the soy is artificially coloured or flavoured or contains artificial preservatives, give it a miss! You want Non-GMO Soy with no artificial ingredients.
5. Miso soup is another healthy, soy-based food. You may ask, but Miso is incredibly high in salt & this can’t be good for high blood pressure, cancer, etc.? Research has shown that when the salt is consumed with soy (I.e miso soup) they seem to balance one another out so you do not get the negative effects of high salt consumption.
6. Add soy in within your balanced diet. I probably have 4-5x a week & then around that I eat a lot of other beans & different forms of Tempeh like Organic Village Tempeh.
Pretty cool how soy, a frequently ‘hated on’ bean, is so misunderstood by the masses. Back to my earlier point – if soy is misunderstood & there is confusion around its effect on the body, a large percentage of people won’t look into it and will just stick with their current animal protein sources… which is a win for the industries that started the confusion in the first place.
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