It is now undisputed that meat and other animal products should be significantly reduced due to their adverse environmental effects. An ideal sustainable alternative is protein-rich legumes. Soybeans stand out because they contain exceptionally high amounts of high-quality protein. However, many people are unsure because of contradictory statements about their health effects. We are therefore subjecting the versatile legume to a fact check: How healthy are tofu, soy milk, and the like?
What nutrients does soy provide?
With an impressive 38 percent protein content, soybeans are one of the plant foods with the highest protein content. In addition, the protein is characterized by a high biological value. It can, therefore, be used by humans to produce the body’s own protein. The fatty acid pattern is also favorable: it contains many unsaturated fatty acids, including valuable omega-3 fatty acids, and only a few of the more undesirable saturated fatty acids. In addition, soybeans provide significant amounts of iron, calcium, and zinc, some B vitamins, and a lot of fiber. All of this makes soy an excellent source of nutrients.
Does soy have hormonal effects on men?
In the past, concerns have been raised that soy could have a feminizing effect on men and lead to libido and fertility problems. In a meta-analysis published in 2021, all studies conducted on this topic were considered and analyzed together. The result is clear: neither the consumption of soy protein nor the intake of isolated isoflavones has an effect on men’s testosterone or estrogen levels – regardless of the amount taken and the duration of intake (Reed et al. 2021).
Does soy interfere with thyroid function?
The all-clear can also be given with regard to the thyroid. In theory, isoflavones can reduce the production of thyroid hormones, but this inhibition is reversible in the presence of iodine (Mörixbauer 2019b). In healthy people with sufficient iodine supply, soy isoflavones have no negative effects on the thyroid People who take thyroid medication can also continue to consume soy products but should consult a doctor or dietician and monitor their thyroid hormones
Which soy products are recommended?
A healthy plant-based diet should consist primarily of unprocessed and minimally processed foods. In addition to other valuable ingredients such as vitamins, minerals, and fiber, these provide a particularly high level of secondary plant substances. The isoflavone content in soy foods also varies greatly: depending on the degree of processing, it can decrease by up to 90 percent (Rizzo & Baroni 2018). Whole soybeans such as edamame and soy nuts are particularly recommended, as are minimally processed products such as tofu and soy milk. Fermented products such as tempeh and miso can also have a positive effect. Soy isoflavones from fermented products are probably more easily absorbed and could, therefore, have a stronger effect.
How much soy is healthy?
To benefit from the positive effects of soy isoflavones, an intake of at least 60–100 mg per day should be sensible (Rizzo & Baroni 2018). This corresponds to 2.5–4 servings of soy, each containing around 25 mg of isoflavones. One serving is, for example, 100 g of tofu, 250 ml of soy milk, or 20 g of soy nuts, i.e., roasted soybeans. This intake is considered safe (EFSA 2015; AICR 2021). Two to three servings per day also correspond to the amounts usually consumed in Asian studies in which positive effects were associated with soy consumption