Iodine concentration of milk-alternative drinks available in the UK in comparison with cows' milk

Abstract

Iodine deficiency is present in certain groups of the UK population, notably in pregnant women; this is of concern as iodine is required for fetal brain development. UK milk is rich in iodine and is the principal dietary iodine source. UK sales of milk-alternative drinks are increasing but data are lacking on their iodine content. As consumers may replace iodine-rich milk with milk-alternative drinks, we aimed to measure the iodine concentration of those available in the UK. Using inductively coupled plasma-MS, we determined the iodine concentration of seven types of milk-alternative drink (soya, almond, coconut, oat, rice, hazelnut and hemp) by analysing forty-seven products purchased in November/December 2015. For comparison, winter samples of conventional (n 5) and organic (n 5) cows' milk were included. The median iodine concentration of all of the unfortified milk-alternative drinks (n 44) was low, at 7·3 μg/kg, just 1·7 % of our value for winter conventional cows' milk (median 438 μg/kg). One brand (not the market leader), fortified its soya, oat and rice drinks with iodine and those drinks had a higher iodine concentration than unfortified drinks, at 280, 287 and 266 μg/kg, respectively. The iodine concentration of organic milk (median 324 μg/kg) was lower than that of conventional milk. Although many milk-alternative drinks are fortified with Ca, at the time of this study, just three of forty-seven drinks were fortified with iodine. Individuals who consume milk-alternative drinks that are not fortified with iodine in place of cows' milk may be at risk of iodine deficiency unless they consume alternative dietary iodine sources.

Keywords: TMAH tetramethylammonium hydroxide; Diets; Iodine; Iodine deficiency; Milk; Pregnancy; Public health; United Kingdom.

Figure 1

Median (25^th, 75^th percentile shown as error bars) iodine concentration (μg/kg) in milk-alternative drinks in the UK in comparison to all-season conventional (344 μg/kg) and all-season organic cows’ milk (234 μg/kg); figures for both conventional and organic milk averaged from the median values from summer samples [from our previous publication(29)], and winter samples (from Table 2). Hatched bars represent milk-alternative drinks fortified with iodine. Error bars are not shown for hazelnut, hemp or iodine-fortified drinks as a result of the small sample size (n≤3). For information on the number of samples, statistical significance, and further details see Table 1.