Does Soy foods Affect Kelp?

Amount or timing may matter

The short answer

Kelp is primarily taken for iodine content. Soy isoflavones inhibit thyroid peroxidase, reducing the thyroid benefit of kelp-derived iodine.

How to arrange timing

Separate kelp supplements from soy products by at least 4 hours if using for thyroid support.

Reference

Reference noted for this food and supplement combination: Doerge & Sheehan, Clin Chem 2002; NIH ODS 2024

Important context

The effect can also change with food amount, supplement dose, product formulation, health conditions, and medication use. Ask a doctor or pharmacist first if you take medication, are pregnant or breastfeeding, or have a chronic condition.