Iodine: sources, risks of too little and too much, and questions for your doctor

The body uses iodine to make thyroid hormones. These hormones affect metabolism, and in pregnancy and early childhood they also affect brain development. Too little and too much iodine can both cause thyroid problems. This is general information, not a diagnosis.

How much and where

The NIH Office of Dietary Supplements lists 150 mcg a day for adults, 220 mcg in pregnancy and 290 mcg while breastfeeding. Sources include sea fish, shellfish, seaweed, dairy, eggs and iodised salt. Seaweed products can contain very different amounts of iodine.

How to check your diet

1. Write down what you eat during a week: fish, dairy, eggs.
2. Check whether you use iodised salt and whether the pack says so.
3. If you do not eat fish and dairy, ask a doctor or dietitian how to meet your needs.
4. Do not take seaweed or kelp products or iodine tablets on your own.

Before a doctor visit prepare a list: what you eat, whether you use iodised salt, whether you take medicines or supplements and whether thyroid disease runs in your family. Also note whether you plan a pregnancy. That helps the doctor decide whether tests are needed and which.

Questions for your doctor

General signs such as tiredness, dry skin or feeling cold are not proof of low iodine and have many causes. If these signs worry you, if you have a swelling in the neck or a thyroid condition, are pregnant or planning a pregnancy, ask: do I need a thyroid check, how is my iodine intake, and are supplements suitable for me. Too much iodine can also cause thyroid problems.

Sources: NIH Office of Dietary Supplements.