According to a 2019 meta-analysis, soy supplements can raise thyroid-stimulating hormones slightly, but there is no effect on the actual thyroid hormone production. People with healthy thyroids and adequate iodine intake don’t have to be concerned about any disadvantages when consuming soy! However, one clinical trial found that the risk of clinical hypothyroidism was increased in people with already existing mild hypothyroidism when taking a high-dose soy supplement. To this day, research on the topic still isn’t conclusive. But until we know more, people with mild hypothyroidism might want to limit their soy intake and monitor their thyroid function carefully.