Iodine is an essential component of the thyroid hormones which are required for brain and neurological development during fetal and early life(Reference Glinoer1). Milk is the main contributor to iodine intake in the United Kingdom (UK)(2). In recent years, there has been an increase in the consumption of milk-alternative drinks (e.g., soya, almond, rice drinks), particularly by women and younger age groups(3,Reference Chambers4) . These milk-alternatives, however, unless fortified, have a lower iodine content than cows’ milk (median 7 vs 438 μg/kg, respectively)(Reference Bath, Hill and Infante5). This is of concern because the consumers of milk-alternative drinks might be at risk of iodine deficiency. The aim of this study, therefore, was to investigate the iodine intake and status of milk-alternative consumers in the UK.
We used data from the National Diet and Nutrition Survey collected between 2014/15 and 2016/17 (Years 7–9) (i.e., prior to several manufacturers fortifying their milk-alternative drinks with iodine). Data on the consumption of milk-alternative drinks and cows’ milk were derived from four-day food diaries. Daily iodine intake (μg/day) was also estimated from the food diaries. Iodine status was assessed using urinary iodine concentration (UIC, μg/L) measured in spot-urine samples.
A total of 3976 individuals were included [1353 from Year 7 (2014/15), 1370 from Year 8 (2015/16) and 1253 from Year 9 (2016/17)]. Milk-alternative drinks were consumed by 4.6% (n = 185) of individuals; 2.2% (n = 88) of those consumed these drinks exclusively while 2.4% (n = 97) also consumed cows’ milk. There was a non-significant increase in the proportion of milk-alternative consumers from 3.9% in 2014/15 to 5.0% and 5.1% in 2015/16 and 2016/17, respectively (P = 0.282). Females were more likely to consume these drinks than males (5.4 vs 3.8%, P = 0.015) and the highest proportion of milk-alternative consumers was in the 16–49-year age group (6.3%, n = 85). Those who consumed milk-alternatives exclusively (n = 62) had a significantly lower UIC than cows’-milk consumers (n = 2426) [median (25–75th percentile): 79 (38–135) μg/L vs 132 (80–209) μg/L; P < 0.001]. When comparing to the median-UIC cut-off defined by the World Health Organisation for iodine sufficiency in populations or groups (i.e., median-UIC > 100 μg/L), only the group of cows’-milk consumers was iodine-sufficient. Those who exclusively used milk-alternatives had a lower dietary iodine intake than those who consumed only cows’ milk [median (25–75th percentile): 94 (63–158) μg/day (n = 88) vs 129 (92–181) μg/day (n = 3399), respectively; P < 0.001)].
These data, collected prior to manufacturers fortifying their milk-alternative drinks with iodine, show that consumers of unfortified milk-alternatives are at risk of iodine deficiency. With the continuing rise in consumption of milk-alternative drinks, it is important for manufacturers to fortify them appropriately with iodine (i.e., with potassium iodide) to provide a similar iodine content to that of cows’ milk and thus reduce the risk of iodine deficiency in milk-alternative consumers.
