There’s a lot of online advice about eliminating certain foods to “heal” your thyroid. However, much of this advice is unlikely to help. Let’s discuss the main foods patients often ask about:
1️⃣ Gluten
The idea that gluten impacts thyroid function or decreases antibodies is mostly anecdotal. A widely cited study showed that people with confirmed celiac disease who eliminated gluten saw improved thyroid function. However, this study involved a specific population with a different clinical scenario. Using it as evidence for the general population is misleading.
2️⃣ Soy
Animal studies suggest that soy may decrease iodine absorption in the thyroid. Before iodine fortification, there were rare cases of babies on soy formula developing an enlarged thyroid (goitre) and hypothyroidism. A study of 60 people with sub-clinical hypothyroidism given high doses of soy supplements showed an increased likelihood of developing hypothyroidism. However, large studies and meta-analyses show that soy consumption does not increase the risk of hypothyroidism. In summary, consuming soy is fine for thyroid health unless you are iodine deficient and your diet is very high in soy.
3️⃣ Cruciferous Vegetables
Vegetables like broccoli, kale, and Asian greens have been suggested to impact the enzymes that make thyroid hormones based on animal data. There is a case report of someone eating 1.5 kg of raw bok choy daily for months who presented in a hypothyroid coma. However, randomized controlled trials (RCTs) of 450g kale juice vs. placebo and similar studies with broccoli sprouts showed no impact on thyroid function, despite some evidence of impacting iodine absorption. Cruciferous vegetables are very good for us and do not cause low thyroid function unless you are iodine deficient.
4️⃣ Animal Products
There is an association between lactose intolerance and hypothyroidism. Not adhering to a lactose-free diet can impair the absorption of nutrients and thyroxine medication. However, a study in Seventh-day Adventists showed no difference in rates of thyroid disease between vegans and dairy consumers, but meat consumption was associated with an increased risk of hyperthyroidism.