Historical iodine status in the UK
- Iodine deficiency was once common in the UK in the 1800s and early part of the 20th century.
- Goitre (the physical symptom of iodine deficiency) was found in several regions – including the South West, Wales and the Peak District.
- In the Peak District, it was so common it was called Derbyshire neck.
- Cretinism (individuals with extreme learning difficulties) was also found in some areas of the UK
How was goitre eradicated in the UK?
- Unlike many countries, the UK did not introduce a formal iodine-fortification programme. In many countries, iodine was added to table salt (called iodised salt) and this increased iodine intake. An iodised salt programme was not introduced in the UK.
- In the UK, iodine intake increased as a result of changes in the dairy-farming industry. In the 1930s, farmers began to add iodine to cattle feed in order to improve cattle health – it was not done for human health or to improve iodine intake in the general population.
- The additional iodine in the cattle feed increased the iodine concentration of milk.
- In addition, disinfectants in the dairy industry contained iodine (called iodophor disinfectants). This increased the iodine concentration of milk.
- Therefore milk-iodine concentration increased and milk and dairy products became an important source of iodine.
- At the same time, milk consumption was encouraged. This was especially true in the post-war years. For example, The 1946 School Milk Act provided 1/3 pint of milk to under 18 year olds and in the 1950s there was a marketing campaign to “Drinka Pinta Milka Day”.
- The combined effect of increased milk-iodine concentration and increased milk consumption was a three-fold increase in iodine intake. this was enough to eradicate goitre.
Iodine sufficiency in the UK in the late 20th century
- For many years, the UK was considered to be an iodine-sufficient country.
- However, there was very little monitoring of the population’s iodine status.
Current iodine status
- Most salt on sale in the UK is not iodised and iodised salt is not used in food processing; there is a poor availability of iodised salt in UK supermarkets and it is not stocked by the two major chains.
- Without a formal iodine-fortification policy, iodine intake is dependent on an individual’s food choice leaving certain sub-groups vulnerable to iodine deficiency.
- In 2009, a nationwide study was conducted to measure iodine status 14-15 year old schoolgirls – over 700 girls were included in the study.
- This was the first nationwide study for over 60 years
- The study revealed that the group were classified as mildly iodine deficient, according to WHO criteria.
- Other, studies of women of childbearing age have noted a degree of deficiency
- However, a recent study of UK schoolchildren aged 8-10 years has found that this age group are not at risk of iodine deficiency. This could be because children drink more milk than adults and are therefore more protected against deficiency in the UK.
- The National Diet and Nutrition Survey now includes assessment of iodine status through measurement of spot-urine iodine concentration.
- The median urinary iodine concentration shows that children and adults in the UK meet the WHO criteria for iodine sufficiency
- However, in women of childbearing age (16-49 years), the median urinary iodine concentration is close to the adult cut-off of 100 mcg/L (at 102 mcg/L) would “not meet the criterion for iodine sufficiency in pregnant and lactating women (i.e. median urinary iodine concentration within 150-249µg/L).
Current status in UK pregnant women
- There is no nationwide study of iodine status in pregnant women. However, ten studies that recruited women at various locations around the UK and have all found that the groups of pregnant women are classified as mildly-to-moderately iodine deficient.
- There is more information about iodine in pregnancy here.
Text written by Dr Mark Vanderpump and Dr Sarah Bath (November 2015, updated April 2019)