In the UK, demand for dairy products, particularly cow’s milk, is in steady decline. Defra’s Family Food survey shows a 17.9 per cent drop in milk consumption since 2021, and Mintel research reveals that 26 per cent of under-35s now avoid dairy.
This isn’t good news for our intake of an important mineral: iodine. Dairy products are the main source of iodine in the UK diet, which is needed by our bodies to produce thyroid hormones. The shift away from cow’s milk and other dairy products has resulted in iodine deficiency becoming increasingly common. The National Diet and Nutrition Survey found that up to 30 per cent of women of childbearing age have low iodine, and a recent report identified iodine deficiency as a significant public health concern.
So what exactly is iodine, why do we need it – and how do we get more of it?
What is iodine?
“Iodine is a vital trace element we absorb from our food,” explains Dr Camilla Stokholm, a functional medicine doctor at Mosaic Medical and author of What Your Doctor Eats. “It’s best known for its role in thyroid hormone production, and it also plays an important role in brain development, cognition and skin health.”
An iodine deficiency may cause symptoms of an under-active thyroid. “These include a ‘goitre’, or a swelling at the base of the neck, weight gain, dry skin, constipation, cold intolerance, brain fog, severe fatigue and hair loss, especially from the outer parts of your eyebrows,” says Dr Stokholm.
How can I get more of it?
Other countries support iodine intake with iodised salt, table salt containing a small amount of the mineral. First introduced in Switzerland in 1922, before hitting the shelves in the US, iodised salt has been credited as one of the most effective public health interventions in history; as iodine supports brain development, it reportedly raised the average population IQ by 15 points.
In Australia, it’s been mandatory to add iodised salt to nearly all types of bread since 2009, but its use has never been recommended in the UK. Instead, NHS guidelines state that people should be able to get all the iodine they need by eating a varied and balanced diet.
How much iodine do I need each day?
The World Health Organisation recommends the following amounts:
- Children aged 0-5 years: 90 micrograms (mcg)
- Children aged 6-12 years: 120mcg
- Adults and teenagers: 150mcg
- When pregnant and breastfeeding: 250mcg
The top 10 foods for iodine
So how can you increase the amount of iodine in your diet? Here are 10 of the best foods to top up your iodine levels and help prevent deficiency.
Seaweed
Up to 3,000mcg per sheet
Seaweed is the top source because it absorbs natural iodine from seawater. Kombu kelp, which is used to make a Japanese stock called dashi, contains the most iodine, but even a 2g sheet of dried nori, which is used to make sushi, contains an impressive 42mcg of iodine. “I like sushi, seaweed crisps or nori furikake sprinkled on top of any Asian-inspired meals,” says Dr Stokholm.
Cod
225mcg per 150g serving
Seafood is one of the best sources of iodine as fish that are low in fat, such as cod, contain the highest amounts. Wild-caught cod contains more iodine than farmed varieties due to its natural diet, and cod caught in the Norwegian Sea often contains higher levels than Atlantic cod because it swims in cold, nutrient-rich Arctic waters. Halibut and pollock are also good sources.
Cottage cheese
50-60mcg per 100g serving
One of the best dairy sources of iodine, cottage cheese is also a good source of protein. Try serving it on toast or a jacket potato or serve it with fruit and chopped nuts for breakfast. “To optimise your iodine absorption, make sure you’re also getting enough selenium in your diet – Brazil nuts are the best source, with just one or two nuts providing the recommended daily amount,” says Dr Stokholm.
Greek yogurt
63mcg per 150g serving
As yogurt is denser than milk, it contains a higher concentration of iodine. Both full-fat and low-fat options contain roughly the same amount of iodine, so opt for low-fat if you need to manage your cholesterol.
Prawns
30-50mcg per 100g serving
Like other fish and shellfish, prawns absorb some of the iodine that is naturally present in seawater. To preserve the highest iodine levels, it’s best to cook them in their shells and peel them when you’re ready to eat. If you’re not keen on prawns, choose lobster, scallops, mussels, oysters or crab.
Iodised salt
30mcg per 1.5g serving
Iodised salt isn’t widely available in the UK but can be found in bigger supermarkets and health food shops. However, too much salt can lead to high blood pressure and a raised risk of heart disease, with the average person in the UK eating 8.4g per day – more than 2g over the recommended amount. Due to government recommendations to reduce salt intake, it’s not recommended as a way to boost iodine levels.
Cow’s milk
25-50mcg per 100ml
As the primary source of iodine in the UK, milk accounts for up to half of our daily intake. The iodine content varies through the year, with winter milk having higher levels due to cows being kept indoors and being fed supplemented feed rather than grazing pasture. Organic milk often has lower iodine levels as organic farming standards restrict the use of these supplements and don’t rely on iodine-based disinfectants.
Eggs
25mcg per egg
Most of the iodine in eggs is found in the yolk, with the highest levels coming from birds that have been fed an iodine-enriched diet. “For most people, eating a few eggs a day shouldn’t be an issue, but if you have stubbornly-high cholesterol it might be worth cutting back to see if it makes a difference,” says Dr Stokholm.
Liver
16mcg per 100g
A good meat-based source of iodine, beef liver has one of the highest iodine levels of any organ meat and is also a good source of iron and vitamins A and B12. Limit consumption to once per week, and avoid it if you are pregnant as too much vitamin A can harm the unborn baby.
Cheddar cheese
9mcg per 30g serving
A moderate source of iodine, cheddar also contains calcium and vitamin K2, which supports bone health. Limit serving size to 30g daily as cheddar is high in sodium and saturated fat, and choose low-fat options if you have high cholesterol or heart health concerns.
Should you take iodine supplements?
Many pregnancy vitamins and minerals contain trace amounts of iodine, but most of us should be able to get what we need from a balanced diet. If you’re vegan or don’t eat fish, eggs or dairy, opt for plant milks that are fortified with iodine, which is often listed on the label as “potassium iodide” or “potassium iodate”.
“I always champion a ‘food-first’ approach and only support evidence-based supplementation when absolutely necessary,” says Dr Stokholm. “Please don’t take iodine supplements without medical guidance.”
FAQs
Which groups of people are most likely to be iodine deficient?
Pregnant and breastfeeding women are at risk of iodine deficiency, as their requirements increase to support the growing baby. Vegans may also be deficient, as iodine is mainly found in seafood and dairy.
Is iodine deficiency dangerous?
“Iodine deficiency in adults isn’t usually dangerous, but it can be unpleasant and lead to hypothyroidism,” says Dr Stokholm. “However it can be serious during pregnancy and early development, potentially causing irreversible damage to the child’s growth and brain development.”
Can you have too much iodine?
“Yes, iodine is known as a ‘Goldilocks nutrient’: you don’t want too little but you don’t want too much,” says Dr Stokholm. “A couple of my colleagues have seen patients trigger thyroid disease simply by taking excessive iodine supplements.”
How do I test my iodine levels?
“It’s not a routine test offered on the NHS,” says Dr Stokholm. “Functional medicine doctors can arrange a 24-hour urine test for the most accurate level, particularly when the root cause of thyroid disease is unclear, but there’s no quick finger-prick blood test we can access just yet.”