Kelp
Kelp is a type of large brown seaweed and a common dietary supplement. It is naturally very high in iodine and is sometimes marketed as a “thyroid booster” for this reason.
Why Kelp Is Problematic for Thyroid Patients
- Hyperthyroidism: Excess iodine worsens hyperthyroidism by further stimulating thyroid hormone production. Kelp supplementation can interfere with thyroid function and overall wellbeing.
- Antithyroid medications: The extra iodine from kelp can counteract the benefits of antithyroid drugs.
- Healthy thyroid: No health benefit from kelp supplementation in people with diagnosed thyroid conditions.
- Sea moss also falls into this category.
Dietary Context
Kelp and seaweed (nori, wakame, etc.) are common in Japanese and East Asian diets. High dietary seaweed intake has been associated with changes in thyroid function, particularly in populations consuming large amounts.
Foods made with seaweed-derived ingredients (e.g., carrageenan, certain sushi rolls) are also restricted on a low-iodine-diet.
Recommendation
Avoid kelp and sea moss supplements if you have any diagnosed thyroid condition.