Food and Behaviour Research

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Most milk substitutes are low in iodine – here’s why it matters

Sarah Bath, Lecturer in Public Health Nutrition, University of Surrey, and Margaret Rayman, Professor of Nutritional Medicine, University of Surrey

milk substitute

We found that most milk substitutes were naturally low in iodine; their concentration was around 2% of that of cows’ milk. And only three of the 47 drinks were fortified with iodine.


The use of non-dairy milk substitutes has been growing in recent years, along with the increasing promotion of vegan or 'plant-based' diets.  Furthermore, such products (and 'plant-based' diets in general) are often promoted as 'healthy' choices.

Milk and dairy products are rich sources of most essential nutrients - and in the case of iodine, milk has become the main dietary source in the UK and many other developed countries as consumption of fish and seafood has declined.

This study confirmed that milk subsitutes available in the UK are an extrenely poor source of iodine (providing only around 2% of the amounts found in cows' milk), as only 3 of 47 brands sampled were fortified with this nutrient.

Public awareness of iodine remains very low - and yet this mineral is an essential component of thyroid hormones, which have a major influence on general health and metabolism. Adequate supplies of iodine are particularly important during pregnancy to support normal brain development in the unborn child, as: 

Iodine deficiencies during pregnancy can cause profound and irreversable mental and physical impairments in the offspring - and as these authors note, their previous research showed that even mild to moderate iodine deficiency during pregnancy (affecting around 2/3 of UK mothers-to-be) predicted lower intelligence and reading ability in the resulting children.

The current findings highlight the importance of improving public awareness of iodine, and the consequences of even mild deficiencies in this essential mineral - particularly among vegans and other consumers of plant-based milk substitutes. 

Public health authorities also need to help improve both public and professional awareness of these issues - and to improve the regulation of supplemets containing iodine, so that people wishing to avoid animal products can safely ensure adequate intakes.

See the underlying research:

See also:

And for more information on the critical importance of iodine, please see the following lists, which are regulary updated:

From 'The Conversation' - 26/09/2017 - By Dr Sarah Bath and Professor Margaet Rayman

Milk and dairy products are the main source of iodine in many diets, and an important iodine source in many countries. However, our latest research found that the iodine concentration of most alternatives to cows’ milk – such as soy and almond “milk” – is very low. This matters because deficiency of iodine, especially during pregnancy, affects brain development and is linked to lower intelligence.

As people increasingly switch from cows’ milk to alternative drinks, and their sales grow, we wanted to know if consumers of these products would be able to match the amount of iodine in cows’ milk. To do this we measured the iodine concentration of 47 milk substitutes available in the UK, including a range of different types: soya, almond, oat, rice, coconut, hazelnut and hemp (but excluding those marketed for infants and children).

We found that most milk substitutes were naturally low in iodine; their concentration was around 2% of that of cows’ milk. And only three of the 47 drinks were fortified with iodine. While some manufacturers replace the calcium found in cows’ milk, the vast majority, including big brands, do not replace the iodine.

We are aware that consumers may choose these alternatives for a variety of reasons, including allergy or intolerance to cows’ milk, so it is important that they are aware of the low iodine content of milk substitutes and the potential health consequences.

Iodine matters

Most people don’t know that iodine is found in cows’ milk and are unaware that they need a certain amount in their diet. In the UK, iodine is not listed on the nutrition information labels on milk containers, and there is little knowledge that iodine intake matters – even among pregnant women.

Cows’ milk is an excellent source of iodine, with a glass (200g) providing around 70μg (micrograms), a considerable proportion of the 150μg iodine intake recommended for European adults every day. By contrast, our study found that a glass of milk substitute would provide only around two micrograms.

The drinks with added iodine (as stated on the ingredients label) provided a reasonable amount of iodine (between 45μg and 60μg per glass). But, as these drinks were not from a market leader, most consumers will probably not get enough iodine in their diet from this source.

Severe iodine deficiency during pregnancy is well known to cause impaired brain development and lead to lower IQ in the infant. It is for that reason that many countries have added iodine to table salt (iodised salt) in order to improve iodine intake and reduce the impact of deficiency on population health. As a result, the number of countries with severe iodine deficiency has been reduced, but some countries are still classified as mildly-to-moderately iodine deficient.

But as our earlier research has shown, even mild-to-moderate iodine deficiency in pregnant women is linked to lower IQ and reading scores in their children, up to nine years of age.

Other dietary sources

Of course, milk is not the only source of iodine. Other rich sources include seafood – particularly white fish, such as cod. Eggs are also a good source of iodine.

For people who cannot or will not eat these alternative sources – such as vegans or those who dislike fish – it can be hard to meet the recommended iodine intake. Some people may therefore need to consider a suitable iodine supplement to ensure that their intake is adequate.

It is very important that kelp supplements – often sold as an iodine source in health food shops – are not used, as they can provide excessive amounts of iodine.

Unfortunately, there is no test for iodine deficiency. To know if you’re getting enough iodine, you need to consider whether iodine sources are part of your diet. We have written a fact sheet on iodine, available through the British Dietetic Association, that can help you understand how to meet the recommendations.