How was it discovered?
The element iodine was discovered by Bernard Courtois in 1811. Like most of the other elements,
iodine was discovered by accident. The most accurate historical explanation is that Courtois was
hired as a new chemist by the French government while Napoleon was in power and fighting wars in
many different places. His job was to try and create a new type of gun powder. In the process he
added an acidic mixture to a sample of seaweed and it exploded into a purple gas which is why he
named it after the Greek word "iodes" meaning violet. After some simple tests he proved his
hypothesis that the purple gas was an element.
How is it obtained?
Iodine is never found as an element in nature. It is obtained in various ways such as extracting it
from seaweed and brines in the ocean. The iodine found in most manufactured goods is harvested
from saltpeter deposits in Chile.
What is the current UK iodine status?
Of all the World Health Organisation regions, Europe continues to have the lowest coverage of
iodised salt and nearly half of all school-age children have inadequate iodine intakes. 1 Although the
UK had historically been considered to be a country of sufficient iodine intake, 2 concern has been
previously expressed about the UK iodine status. 3 At the 20-year follow-up of the Whickham survey
in 1995, 4 the median urinary iodine excretion for a random sample of 101 subjects aged 38 years and
over was 102μg/g creatinine (range 44-990), which did not suggest that iodine deficiency was
present in the survivors of this cohort.
Concern was expressed about the iodine status of UK women following a more recent survey in
Middlesbrough. 5 In this study of 227 women at 15 weeks gestation and 227 non-pregnant agematched controls, 3.5% of the pregnant women had evidence of iodine deficiency and 40% were
borderline iodine deficient. This has been supported from data reported in a study of pregnant
women in Dundee 6 and Wales. 7 A recent study of a small sample of 26 women recruited from the
University of Surrey found that the median value for urine iodine was 66μg/L and 20% were
classified as iodine deficient. 8 Thus, up to 50% of pregnant women in the UK could be significantly
iodine deficient during gestation.
1 A further and recent study measured the iodine content in 36 different salt preparations from nine
major national supermarkets in Cardiff. 9 Iodine concentrations varied from undetectable in 32
samples to trace quantities in two. Only two samples contained meaningful concentrations of iodine
(20mg/Kg) related to the prevention of iodine deficiency. A similar pattern of iodine deficiency has
been seen in Ireland, with iodine intake being particularly low in the summer months. 10
How to test for Iodine Status?
Urinary analysis of urinary iodine status has been employed for many years as a comparative based
test against many large population values.
In more recent times a “24-hour iodine/iodide load test” has become a useful analysis for
practitioners.
A specified oral dose of iodine/iodide is given and urine is collected for the
subsequent twenty-four hours. The test is based on the concept that the body has specific and
saturable mechanisms to take up iodine/iodide. When maximal retention is attained, the percentage
of an iodine/iodide load that is retained decreases and the percentage urinary excretion increases.
The percentage excretion is calculated by dividing the patient’s mg/24-hour iodine results by the oral
iodine/iodide dosage (mg) provided on the requisition form by the practitioner, then multiplied by
100. The iodine excretion value represents iodine plus iodide oxidised to iodine. The load test
requires a complete twenty-four hour urine collection.
References:
1
International Council for Control of Iodine Deficiency Disorders. IDD Newsletter Volume 29, No 3, August 2008.
Read Iodine Newsletter
2
Lee SM, Lewis J, Buss DH, et al. Iodine in British foods and diets. Br J Nutr 1994;72:435-446 View Abstract
3 Lazarus JH, Phillips DIW, Parkes AB, at al. Status of iodine nutrition in the United Kingdom. in Iodine Deficiency in
Europe - A Continuing Concern. F Delange, JT Dunn and D Glinoer eds. NATO ASI Series, Plenum Press (New York)
1993: 323.
4
Vanderpump MPJ, Tunbridge WMG, French JM, et al. (1995). The incidence of thyroid disorders in the community: A
twenty-year follow-up of the Whickham Survey. Clin Endocrinol 1995;43:55-69. View Abstract
5
Kibridge MS, Hutchison S, Owen CJ, et al. Prevalence of maternal dietary iodine insufficiency in the north easy of
England: implications for the fetus. Arch Dis Child Fetal Neonatal. Ed 2004;89:436-439. View Abstract
6
Lazarus JH, Parkes AB, Smyth PPA, et al. Iodine status in early pregnancy :relation to thyroid function. 13th
International Thyroid Congress, Buenos Aires, Argentina. Thyroid Abstracts 2005;15:218.
7
Barnett CA, Visser TJ, Williams F, et al. Inadequate iodine intake of 40% of pregnant women from a region in
Scotland. J Endocrinol Invest 2002;25(Suppl):90
8
Bath S, Walter A, Taylor A, et al. Iodine status of UK women of child-bearing age. J Human Nutr Dietetics
2008;21:379-380.
9
Lazarus JH and Smyth PPA. Iodine deficiency in the UK and Ireland. Lancet 2008;372:888 View Abstract
10
Nawoor Z, Burns R, Smith DF, et al. Iodine intake in pregnancy in Ireland - a cause for concern? Ir J Med Sci.
2006;175:21-4 View Abstract
2