Guest post by our Elements Dietitian – Dr William Cook
Do you ever consider how much iodine you are getting in your diet? Whilst not being a nutrient that receives much headline coverage, iodine is crucial for good health and rather worryingly is a nutrient that many of us in the UK are not getting enough of which research shows can have profound affects on our health.
Iodine is an element named from the Greek for ‘violet’ and is a mineral that is an essential part of the hormones produced by the thyroid gland. Thyroid hormones, and therefore iodine, are essential in humans and are required for the regulation of growth and metabolism as well as playing an important role in foetal brain development.
An insufficient intake of iodine impairs the function of the thyroid gland and leads to a range of disorders including goitre (when the thyroid gland swells causing a lump to appear on the neck), impaired brain development and congenital abnormalities. The World Health Organisation considers iodine deficiency to be ‘the single most important preventable cause of brain damage worldwide’ and two billion people worldwide are at risk of iodine deficiency.
Whilst we often consider ourselves in the UK to be immune for nutritional deficiencies and more prone to symptoms of excessive food intake, it makes for alarming reading that one recent study showed that 51% of teenage girls had mild iodine deficiency, 16% moderate deficiency and 1% severe deficiency. 10% of woman aged 19-64 were shown to have daily intakes of iodine less than the minimum recommended intake. These findings may well be explained by the fact that teenage girls consume low levels of dairy products and data suggests that this group generally have a poor diet, with a low intake of fruit, vegetables and oily fish as well as having a poor intake of other nutrients such as iron and calcium. To put this estimate of iodine deficiency into perspective, the UK lies between Angola and Mozambique in the list of top ten countries with the greatest number of school aged children with insufficient iodine intake.
In general, the iodine content of most foods and beverages is low, with most foods containing 3-80 micrograms per serving. Marine plants and animals are rich sources of iodine and population groups consuming large amounts of these foods can have very high iodine intakes. Plant-based foods are generally low in iodine and their iodine content is affected by soil content, irrigation and the use of fertilizers. In the UK, iodine is naturally present in cow’s milk although levels can vary depending on the season.
Which foods contain iodine
In the UK, milk and dairy foods are the major contributors to iodine intake, providing 33 per cent of the daily iodine intake for adults. Dairy products that are derived from cattle that are pasture fed have a lower iodine content than those from cattle that are fed ‘cattle cakes’. This explains why organic milk has a lower iodine content as organic cows are usually grass fed. The table below shows the iodine content of foods.
|Food||Portion||Average iodine content per portion (micrograms)|
|Cow’s Milk||200 ml||50-80*|
|Organic cow’s milk||200 ml||30-65*|
|Eggs||1 egg (50 g)||20|
|White fish||100 g||115|
|Oily fish||100 g||50|
|Bread||1 slice (36 g)||5|
|Fruit and vegetables||1 portion (80 g)||3|
*Value depends on the season, higher iodine content in winter
Vegetarians and vegans may be at greater risk of iodine deficiency as they may not eat many of the iodine rich food sources such as meat, fish and dairy. It is also important to be aware that non-dairy milk alternatives such as soya milk are often not fortified with iodine.
The Scientific Advisory Committee on Nutrition (SACN) are currently reviewing iodine deficiency in the UK in order to consider whether there is sufficient evidence to judge if iodine intakes are inadequate in the UK and potentially to set new iodine intake levels for pregnant and lactating woman (iodine is essential for normal brain development in infants).