Members of the UK Iodine Group - Dr Sarah Bath, Lecturer in Public Health Nutrition and Prof Margaret Rayman, Professor of Nutritional Medicine, University of Surrey respond to the following questions from one of our members about iodine in the diet.

It is important to point out that iodine supplements are not recommended for those with thyroid disease. There is more information about this on the UKI website.

I am involved in various online groups through Facebook, such as breast-feeding networks, parenting and ‘foodie’ groups. Over the last few years I have been increasingly aware that more and more people are becoming vegan and many at least try ‘vegananuary.’ We have observed that this is becoming a fashionable trend and are also concerned that people who become vegan are generally unaware of the potential risks they run in adopting a diet that contains no iodine sources, except, perhaps, seaweed. 

I became aware of the importance of iodine to thyroid health, and issues with getting too little or too much, and especially the importance of iodine during pregnancy and breast-feeding. As a key constituent of the thyroid hormones, iodine is required for development in early life, particularly of the brain. Pregnant and lactating women are at high risk of iodine deficiency as their intake requirements are almost twice as high as in the pre-pregnant state. This puts their developing infants at risk, as the mother is the baby’s sole source of iodine for thyroid hormone production during both pregnancy and breast-feeding.

In the USA iodine is supplemented in common foods such as salt. The UK Vegan Society references the need for iodine, but not the increased need during pregnancy and breast-feeding. I have also been aware that some vegans are dismissive of too many vitamin pills. Some feel seaweed is a good thing to try. The UK Vegan Society has a supplement that contains 140mcg iodine (along with B12, selenium and folic acid), which is certainly adequate for non-pregnant women.

Ideally pregnant and breast-feeding women should have an intake of around 200-250mcg per day.

Nori, green seaweed, has a lower iodine concentration than brown seaweed. One sheet (at 2.5g) would provide around 100mcg of iodine. The Vegan Society also warns against excessive consumption of seaweeds such as kelp but people may not see the need to consult the Vegan Society website and may put themselves at risk of excess iodine intake. A potential problem is that vegans who consume brown seaweed (kelp or kombu) as an iodine source (readily available in health-food shops) may very well be overdosing; for instance breast-feeding mothers who consumed seaweed soup (popular in mothers of Japanese and Korean origin) had babies who developed neonatal hypothyroidism.

Mothers who have to go dairy free due to their babies having intolerance issues, and their children subsequently, are often dairy-free for some time. Presumably iodine is in breast milk but not all mothers continue feeding their dairy-free children and this will potential impact on their personal health if they are not taking any supplements.Mothers who are breast-feeding and have to give up dairy-product consumption should ideally continue with an iodine-containing supplement after pregnancy unless they consume a lot of seafood (especially white fish such as cod and haddock). Infants of mothers who are not breast-feeding may be given a milk-alternative formula; they need to check that it contains iodine. Once beyond that stage, they need to ensure an adequate iodine source in the child’s diet. Hopefully in the future more manufacturers of milk alternatives may fortify with iodine.

Dr Sarah Bath and Prof Margaret Rayman have written an Iodine Food Fact Sheet that the British Dietetic Association (BDA) has endorsed which is a source of good advice on iodine for women of childbearing age, pregnant and lactating women.

The BDA has also recently published a Food Fact Sheet on plant-based diets. This also has information on iodine