Iodine status in the UK deserves our attention, but dairy is not the ‘solution’

The latest sensationalist story from the Daily Mail implies that switching to plant-based milks could lead to miscarriage, stillbirth, irreversible brain damage and lower IQs in younger generations. They may as well say it might cause the next pandemic or World War III! Like most of these headline-grabbing stories, they fix on a nutrient that is of some concern – but claiming “the surge in veganism contributes to this decline” is simply not true.

Iodine levels are measured in urine. The latest National Diet and Nutrition Survey (NDNS) 2019 to 2023 data show that in most people in the UK, urinary iodine concentration (UIC) exceeds the World Health Organisation threshold of 100 µg/L, meaning that most people get enough. However, some girls aged 11 to 18 and women of reproductive age have insufficient levels. For example, UK women aged 16 to 49 have a median UIC of 82 µg/L (mild deficiency), comparable to those in Ireland (~75 µg/L) or New Zealand (~60 to 85 µg/L), so not the “lowest globally” – this claim is alarmist and inaccurate, exaggerating UK iodine status to imply a crisis.

Studies linking iodine deficiency to an IQ drop of eight to 10 points, for example, apply in cases of severe, chronic deficiency across unfortified populations. Applying this to UK women is misleading, wrongly equating our mild deficiency with the profound intellectual disability seen in severely deficient regions of the world.

Why are UK iodine levels dropping?

There are several reasons but placing the blame on “the surge in veganism” is blatantly ridiculous as lower levels are seen on a population-wide basis in girls and women. Furthermore, only around 10 per cent of people in the latest NDNS reported that they consumed plant-based milk during the survey period.

Other reasons include:

• animal feed regulation: in 2005, the maximum permitted level of iodine in livestock feed was halved to prevent human toxicity; this lowered the iodine content of milk
• rising popularity of organic milk: organic standards restrict the use of mineral supplements and often use clover pastures, which can further reduce iodine levels in cattle so organic milk contains 25 to 40 per cent less iodine than conventional milk
• processing changes: The transition away from iodine-based disinfectants (iodophors) in milking parlours has reduced ‘accidental’ iodine contamination that previously boosted levels in the food chain

Universal salt iodisation has worked well in many countries but can be problematic when we are trying to cut our salt intake – according to the British Heart Foundation, Brits eat the equivalent of 22 packets of crisps a day in salt.

What is the solution?

Dairy is not the answer. Suggesting that we should drink cow’s milk for iodine ignores the changes in farming practices that have led to the drop in levels. The author of the Daily Mail feature told Viva! she was aware of these changes in farming practices and said the Daily Mail had edited her statements significantly.

Promoting dairy also ignores those who are lactose intolerant, have cow’s milk allergy or want to avoid the inherent cruelty of the dairy industry – all cow’s milk comes from cows that have recently given birth. Find out what happens to the calves here.

Many plant milks are now fortified with iodine (often listed as potassium iodide); for example, Oatly, Alpro Original Soya, ASDA’s own brand (soya, oat, almond, etc) and M&S now fortify their products with iodine. Choosing iodine‑fortified plant milks will provide intakes comparable to or greater than cow’s milk, without relying on animal products. These plant milks usually contain vitamins B12 and D too – cow’s milk in the UK is not a reliable source of vitamin D.

Iodised salt, consumed in moderation, can also be an effective way to ensure a sufficient intake. Adults need 140 µg of iodine per day. A quarter teaspoon (~1.25 grams) of iodised salt delivers ~50 to 80 µg iodine, fitting well within UK 6g/day salt limits. Much of the salt consumed in the UK comes from processed foods – so reducing those while selecting iodised salt could be an effective strategy. Find out more about iodine and where to get it here.

The UK Scientific Advisory Committee on Nutrition (SACN) is currently conducting a risk assessment on nutrition and maternal health, which includes considering the effects of iodine intake during pregnancy and lactation. In summary, the UK may need to look into updating policy, especially for pregnant women, but misrepresenting the UK’s position in articles such as this does women no favours.