3. Thyroid Disruption
Tofu is made from soy, and soy contains goitrogenic compounds, specifically the soy isoflavone genistein. These goitrogens are thyroid hormone blockers that can interfere with thyroid hormone production and specifically cause hypothyroidism.
Many parents think they’re making a healthy choice when they opt for soy formula for their babies. Unfortunately, this couldn’t be further from the truth. A study published in the Archives of Disease in Childhood shows how the intake of soy products can negatively affect us starting at a very early age, especially for people born with congenital hypothyroidism. As this 2004 study shows, infants fed soy formula have a prolonged increase of thyroid stimulating hormone compared to infants fed non-soy formula. (7)
An earlier study in 1994 showed similarly concerning results. A patient with congenital hypothyroidism continued to be “persistently hypothyroid” while on a soy formula diet even though the patient was receiving large doses of L-thyroxine (T4). (8) T4 is a standard conventional treatment for hypothyroidism.
Tofu contains phytate, which science has shown contributes to the firm texture of tofu. (9) Phytate is essentially phytic acid bound to a mineral. What’s the problem with phytate? Well, phytate and phytic acid are known antinutrients, and they aren’t the only antinutrients in tofu. Soy products like tofu contain several highly concerning antinutrients, including: (10)
- Lectins and saponins — linked to leaky gut syndrome as well as other gastrointestinal and immune problems
- Oligosaccharides — gas-promoting, which is why soy is sometimes called the “king of musical fruits”
- Oxalates — known to promote kidney stones and vulvodynia
- Protease inhibitors — interfere with protein digestion and have caused malnutrition, poor growth, digestive distress and pancreatitis
- Phytates — block mineral absorption, causing zinc, iron and calcium deficiencies
When it comes to tofu, cooking it does not seem to reduce the level of phytates and other antinutrients. What does reduce these antinutrients is fermentation.