Plant-based nutrition › Iodine
Iodine on a plant-based diet
Iodine is often low on a plant-based diet because dairy and fish are the main UK sources. Plant options are limited: a little nori, and iodine-fortified plant milks (not all are). Kelp is not a safe fix: it can massively overshoot, so a modest iodine supplement is often the sensible route. UK adults need 140µg a day.
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Iodine keeps your thyroid and metabolism working, and is especially important before and during pregnancy for a baby’s brain development. Both too little and too much cause thyroid problems, so the aim is steady, moderate intake.
Why plant-based diets fall short
In the UK, milk and white fish supply most people’s iodine, so cutting them out leaves a gap. Plant levels depend on the soil and are unreliable, iodised salt is uncommon here, and seaweed swings wildly, from useful to dangerously high.
How to get enough
A sheet or two of nori a week, or a genuinely iodine-fortified plant milk, can help, but check the carton, as many are not fortified with iodine. Avoid kelp and high-dose seaweed supplements, which can deliver many times a safe dose. For most plant-based eaters, a modest supplement providing around 150µg is the reliable, controllable option.
Could you be low?
Iodine is not part of routine blood tests. If you are pregnant, trying to conceive, or breastfeeding, iodine is a priority: speak to a midwife or dietitian about a suitable supplement rather than relying on seaweed.
How much do you need?
| Group | Per day |
|---|---|
| Adults (19–50) | 140µg |
| Adults (51+) | 140µg |
| Breastfeeding | no UK figure |
Source: NHS; SACN/COMA DRV.
Best plant-based and fortified sources
| Food | Serving | Amount | % of RNI |
|---|---|---|---|
| Dried nori seaweed | 1 sheet (3g) | 70µg | 50% |
| Fortified soya milk | 1 cup (240ml) | 54µg | 39% |
| Fortified oat milk | 1 cup (240ml) | 54µg | 39% |
| Fortified almond milk | 1 cup (240ml) | 54µg | 39% |
| Fortified pea milk | 1 cup (240ml) | 54µg | 39% |
| Fortified coconut milk drink | 1 cup (240ml) | 54µg | 39% |
| Wakame seaweed | 2 tbsp rehydrated (10g) | 42µg | 30% |
Common questions
Do vegans need an iodine supplement?
Often, yes. Without dairy or fish, and with seaweed being unreliable and easy to overdo, a modest supplement (around 150µg) is the safest steady source for many plant-based eaters.
Is seaweed a good source of iodine?
A little nori is fine, but kelp and many seaweed supplements contain enormous, variable amounts that can harm the thyroid. Do not use kelp to top up iodine.
How much iodine do I need?
UK adults need 140µg a day; needs are higher in pregnancy and breastfeeding, when getting it right matters most.