Iodine is needed to make thyroid hormones, and adults need about 140 micrograms a day, according to the NHS. Milk and dairy, eggs, sea fish and shellfish are the main sources, and the WHO recommends using iodised salt. Vegans and people who are pregnant should check their intake with a health professional.
Key takeaways
- Iodine is needed to make thyroid hormones; adults need about 140 µg a day (NHS).
- Milk and dairy, eggs, sea fish and shellfish are the main food sources.
- Plant foods vary with the soil, so vegans may need fortified foods or a supplement.
- The WHO recommends eating less salt overall and making the salt you use iodised.
- High-dose iodine supplements can affect the thyroid; check with a doctor first.
What does iodine do?
Iodine is a mineral your thyroid gland uses to make thyroid hormones, which help keep your cells healthy and your metabolic rate steady. Your body cannot make iodine, so it has to come from food, drinks or iodised salt. It is especially important before birth and in early childhood: the WHO notes that iodine is essential for healthy brain development in the foetus and young child, which is why it recommends that all salt people consume should be iodised.
Most people never think about iodine, and most can meet their needs from a varied diet. It becomes worth a closer look when you cut out whole food groups, such as dairy and fish, or when you are pregnant or planning a pregnancy.
How much iodine do you need?
The NHS says adults need about 140 micrograms (µg) of iodine a day. A microgram is a millionth of a gram, so this is a tiny amount, but it needs to be supplied regularly. Recommended amounts differ slightly between countries, and needs are not the same in pregnancy and breastfeeding, so if you are in one of those groups, ask your midwife, doctor or a registered dietitian what applies to you.
Which foods contain iodine?
Iodine is not spread evenly across foods. The main sources the NHS lists are:
| Food group | Examples | Notes |
|---|---|---|
| Milk and dairy | Cow's milk, yogurt, cheese | A main source in many diets |
| Eggs | Boiled, scrambled, omelettes | An easy everyday source |
| Sea fish | Cod, haddock, sea bream, sardines, tuna | Sea fish rather than freshwater fish |
| Shellfish | Prawns, mussels | A good occasional source |
| Plant foods | Grains, cereals, vegetables | Contain some iodine, but the amount depends on the soil they grew in |
| Iodised salt | Table salt labelled "iodised" | Recommended by the WHO for the salt you do use |
| Fortified plant drinks | Some soya and oat drinks | Only if iodine is added; check the label |
Because plant foods vary so much with the soil, people who eat little dairy, eggs or fish rely more heavily on iodised salt, fortified foods or a supplement. The guide to dairy milk versus plant milks explains why it is worth checking the label of your plant drink.
Who is more likely to fall short?
- Vegans and people who avoid dairy, eggs and fish. The NHS suggests considering fortified foods or a supplement, and speaking to a healthcare professional before starting one.
- People who are pregnant, planning a pregnancy or breastfeeding. Iodine matters for the baby's brain development, so ask your midwife or doctor whether your diet covers it or whether a supplement suits you.
- People who switched entirely to non-iodised salt. Only salt labelled iodised contains added iodine. If you use flaky sea salt, rock salt or speciality salts, check the pack.
- People on a restrictive diet. Very low-calorie plans or diets that drop milk and fish entirely can leave gaps in several minerals, iodine among them.
Does a calorie deficit affect iodine intake?
It can, but only indirectly. Iodine itself has no calories, so the question is whether the foods that supply it stay on your plate. When people cut calories, they sometimes drop milk, cheese and yogurt, skip eggs at breakfast, or avoid fish because it feels like more effort. Keeping a few of these foods in your week is usually enough. The article on vitamins and minerals in a calorie deficit covers the wider picture.
Here are some meals from Sporty's catalog that include iodine-containing foods, with Sporty's per-serving estimates for calories and protein (real values depend on recipe and portion):
| Meal | Iodine-containing foods | Calories | Protein |
|---|---|---|---|
| Yogurt and fruit | Yogurt | 230 kcal | 16 g |
| Spinach omelette | Eggs | 300 kcal | 21 g |
| Shrimp casserole | Shellfish | 380 kcal | 30 g |
| Oats, yogurt and fruit | Yogurt (and milk, if used) | 390 kcal | 22 g |
| Baked sea bream | Sea fish | 400 kcal | 42 g |
| Grilled fish and vegetables | Sea fish | 450 kcal | 48 g |
| Tuna salad and yogurt | Sea fish and yogurt | 480 kcal | 52 g |
A handy bonus: many of these are also high in protein for their calories, which helps you feel full while you eat less. A dish like baked sea bream gives 42 g of protein for about 400 kcal. For ideas on how often to eat fish, see fish and seafood nutrition.
Iodised salt or less salt?
Both, and they do not conflict. The WHO recommends adults eat less than 5 g of salt a day, yet the global average is about 11 g, more than double. At the same time, it recommends that the salt people do use should be iodised. In practice, that means using iodised salt in small amounts at home rather than adding more salt for the sake of iodine. Much of the salt people eat comes from bread, processed meat, snacks and sauces, so cutting those is usually the bigger step. The guide to salt and sodium limits has practical tips.
Can you have too much iodine?
Yes. The NHS warns that taking high doses of iodine for long periods could change the way your thyroid gland works, and says supplements of 0.5 mg (500 µg) or less a day are unlikely to cause harm. Food rarely causes problems; concentrated supplements are where the risk lies. If you already take a multivitamin, check how much iodine it contains before adding another product, and never take iodine supplements to "boost metabolism" or speed up weight loss.
If you have a thyroid condition, such as an underactive or overactive thyroid, or you take thyroid medication, do not change your iodine intake with supplements without talking to your doctor first.
Simple ways to cover your iodine
- Include dairy or a fortified alternative most days. Milk in coffee or porridge, yogurt as a snack or a piece of cheese.
- Eat eggs a few times a week if they suit you.
- Have sea fish or shellfish regularly. Fish once or twice a week is a common recommendation for overall health.
- Use iodised salt for the salt you add at home, while keeping total salt low.
- If you are vegan or pregnant, talk to a healthcare professional about fortified foods or a supplement.
This article is general information, not medical advice. If you are pregnant, planning a pregnancy or breastfeeding, have a thyroid condition, take regular medication or are under 18, talk to a doctor or registered dietitian before changing your diet or taking supplements.
Frequently asked questions
How much iodine do adults need a day?
The NHS says adults need about 140 micrograms of iodine a day. Recommendations differ slightly by country and are different in pregnancy and breastfeeding.
What foods are highest in iodine?
Cow's milk and dairy, eggs, sea fish and shellfish are the main sources. Plant foods contain some iodine, but the amount depends on the soil they grew in.
Do vegans need an iodine supplement?
Vegans may not get enough iodine from food alone. The NHS suggests fortified foods or a supplement and recommends speaking to a healthcare professional before starting one.
Should I use iodised salt if I am cutting salt?
Yes. The WHO recommends less than 5 g of salt a day and that the salt you do use is iodised. Use it sparingly rather than adding more for the iodine.
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This article is general information, not medical advice. If you have a health condition, are pregnant or under 18, talk to a doctor or registered dietitian before changing your diet.