Consumers of milk-alternative drinks may be at of risk iodine deficiency, according to the findings of a new study in the British Journal of Nutrition.

In the first study of its kind in the U.K., researchers from the University of Surrey examined the iodine content of 47 milk-alternative drinks (including soy, almond, coconut, oat, rice, hazelnut and hemp but excluding those marketed specifically at infants and children) and compared it with the iodine content of cow's milk.

Researchers discovered that the majority of milk-alternative drinks did not have adequate levels of iodine, with concentration levels found to be around 2% of those in cow's milk. Cow's milk and dairy products are the main source of iodine in the typical diet in the U.K., but findings from the study show that most milk-alternative drinks are not an adequate substitute.

Iodine is required to make thyroid hormones and is particularly important during pregnancy because it is essential for normal fetal brain development. Previous research in this area by the University of Surrey has shown that low iodine status in pregnant mothers is linked to lower IQ and reading scores in their children (up to nine years of age).

"Many people are unaware of the need for this vital dietary mineral, and it is important that people who consume milk-alternative drinks realize that they will not be replacing the iodine from cow's milk, which is the main U.K. source of iodine,” University of Surrey professor of nutritional medicine Margaret Rayman said. “This is particularly important for pregnant women and those planning a pregnancy.

"A glass of a milk-alternative drink would only provide around 2 micrograms of iodine, which is a very small proportion of the adult recommended iodine intake of 150 micrograms per day. In pregnancy, that recommendation goes up to 200 micrograms per day," she noted.

Dr. Sarah Bath, lecturer in public health nutrition at the University of Surrey and a registered dietitian, said milk-alternative drinks are increasingly being used as a replacement for cow's milk for a number of reasons, include an allergy or intolerance to cow's milk.

"Worryingly, most milk-alternative drinks are not fortified with iodine, and their iodine content is very low,” Bath said. “If avoiding milk and dairy products, consumers need to ensure that they have iodine from other dietary sources, where possible.”

Iodine can be found in foods such as white fish, kelp, yogurt, corn, milk, bananas and prunes, to name a few.

Bath added, “If considering taking an iodine supplement, they should avoid kelp, which can provide excessive amounts of iodine."

Milk-alternative samples were analyzed at LGC, the U.K.'s National Measurement Laboratory for chemical and bio-measurement.

"Reliable methods to test food samples for minerals, such as iodine, are invaluable to nutrition research,” said Dr. Sarah Hill, science leader in inorganic analysis at LGC. “As a metrology institute, one of our key missions is the provision of reference methods and materials that underpin validation of field laboratory measurements. This ensures that high-quality data are generated to support researchers in these important studies."