💊 What it does
Iodine is essential for the production of thyroid hormones (T3 and T4), which regulate metabolism, growth, brain development, and body temperature. Adequate iodine during pregnancy is critical — deficiency is the leading preventable cause of intellectual disability worldwide. In adults, iodine deficiency causes hypothyroidism (underactive thyroid), with symptoms including fatigue, weight gain, feeling cold, brain fog, and hair loss.
👤 Who needs it
Vegans and plant-based eaters are at significant risk — the main dietary sources of iodine in the UK are dairy products and white fish, both absent from a vegan diet. Seaweed is not a reliable substitute — iodine content varies enormously and some varieties (particularly kelp) can provide dangerously excessive amounts. Pregnant and breastfeeding women have higher requirements. People living in iodine-depleted soil regions (much of inland UK).
🥦 Food sources first
Dairy products (milk, yoghurt) are the primary UK source. White fish (cod, haddock). Eggs. Seaweed — but content is highly variable and potentially unsafe in large amounts. Iodised salt (widely used in continental Europe and the US, but not standard in the UK). For vegans avoiding dairy and fish, reliable food sources are very limited.
🗓 When to supplement
Any vegan or plant-based eater should assess their iodine intake carefully. If dairy and fish are absent from the diet, a 150 µg supplement provides the full UK recommended intake. Do not use seaweed as an alternative without knowing its iodine content — kelp in particular can provide 1,000–10,000 µg per gram.
🏷 Best form to look for
Potassium iodide is the standard supplement form — stable, well absorbed, and consistent in dose. Avoid organic seaweed supplements for iodine due to unpredictable content.
⏰ When to take it
Can be taken at any time. Some people prefer to take it away from thyroid medications if relevant.