You may have read some alarming news stories recently declaring that dairy alternatives such as soya and almond milk may be putting people's health at risk.
According to researchers at the University of Surrey(1), non-dairy milks don't contain nearly enough iodine. After testing 47 alternative milk drinks including hazelnut, coconut, oat, hemp, rice and soy milks, they found that on average they contained around 2 percent of the iodine found in dairy milk.
Dairy alternatives such as nut and soy milks are soaring in popularity as people, for various reasons, decide to reduce or stop consuming dairy and other animal products. However, this doesn't have to mean your iodine levels will rapidly deplete.
While dairy is an excellent source of iodine, if you're lactose intolerant or don't consume dairy products, you are still able to meet your daily iodine requirements from several other food sources.
What is iodine and why we need it
Iodine is a trace mineral which is readily absorbable through the digestive tract and skin (if applied topically). It's involved in growth and cell division, physical and mental development, immunity, hormone balancing and maintenance of healthy brain functioning(2).
Iodine is essential for roles involving the thyroid gland and its hormones. Around 80% of the iodine we absorb from our diet is 'trapped' by the thyroid gland whose primary function is making thyroid hormones T3 and T4. As a component of thyroxine, the thyroid hormone, iodine helps raise metabolic rate which in turn helps the body burn excess fat and stabilise body weight(3)(4).
How much iodine do we need?
The body absorbs around 90% of iodine from food and 10% from water. We only need a tiny amount of iodine to have a huge effect. However, it's important to know how much we need on a daily basis as too much can have a toxic effect on the body.
Current government recommendations advise that for average healthy men and women aged 15 and over, an intake of around 140-150mcg per day should be sufficient. During pregnancy and lactation, slightly more is needed at 220mcg and 290mcg respectively(6). This is because sufficient thyroid hormones are needed to transfer to the growing baby and is especially important for brain development.
Sources of iodine
Now you know how much iodine you need, where are the best places to find it?
Availability of iodine from food is variable and depends largely on the iodine concentration in the soil or water of origination. Good sources include foods grown in or by the sea, e.g. seafood and seaweed(4).
Iodised salt is a useful source, however, this is more common in the US. Currently, the UK doesn't have an iodised salt programme, with only around 5% of salt for domestic use being iodised(5).
The following table provides an indication of the amount of iodine found in different food(7).
Iodine content in food
Note: It is difficult to accurately state how much iodine is found in different foods as it depends largely on the amount of iodine in the soil or animal that it originated from. Because the amount of iodine in seaweed is so variable, it's best not to consume it regularly unless you know the iodine content.
Symptoms of too little iodine
Iodine deficiency directly affects the thyroid gland, making it work harder. Insufficient iodine in the diet can lead to symptoms such as decreased fertility, hypothyroidism, goitre, increased still birth and spontaneous abortion rates, increased perinatal and infant mortality(4).
Cruciferous vegetables such as Brussels sprouts, bok choy, radish, watercress, cabbage, kale, broccoli and cauliflower contain substances called goitrogens. When we eat these vegetables, the goitrogens compete with iodine for uptake by the thyroid gland. This could possibly lead to hypothyroidism.
However, unless you have been diagnosed as having an iodine deficiency or thyroid issues, don't stop eating these highly nutritious vegetables. Just ensure they are lightly cooked and don't consume more than 1-2 servings daily(8). Ideally, eat goitrogen containing foods at a different time to iodine containing foods.
Take note if you're a smoker as this habit also interferes(10) with iodine absorption!
Symptoms of too much iodine
The thyroid gland normally manages iodine levels efficiently but long term Iodine intakes over 2mg per day may lead to toxicity. Some people may be hypersensitive to iodine and experience mild skin conditions, weakness, bad breath, mouth sores, a metallic taste, gastric irritation, diarrhoea, vomiting, enlarged salivary glands or vision problems(4)(9). And more serious conditions include developing autoimmune thyroiditis or Grave's disease(2).
The importance of iodine should not be underestimated. But, while dairy is certainly an excellent source of this mineral, you can meet your needs through other food. It's mainly vegetarians and especially vegans who need to ensure they eat enough foods with iodine or take a supplement to meet their needs so they don't become deficient.
Milk-alternative drinks do not replace the iodine in cows' milk: (https://www.surrey.ac.uk/mediacentre/press/2017/milk-alternative-drinks-do-not-replace-iodine-cows%E2%80%99-milk)
The Nutrient Bible: (H. Osiecki)
The Complete Guide to Nutrients: (Dr. M. Sharon)
Introduction to Human Nutrition: (M. Gibney, S. Lanham-New, A. Cassidy et al.)
Iodine Deficiency in the UK: (http://www.btf-thyroid.org/images/documents/UKISS_poster.pdf)
Factsheets – Iodine: (https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional)
Cruciferous Vegetables, Cancer Killer or Thyroid Killer?: (https://draxe.com/cruciferous-vegetables-cancer-thyroid/)
Prescription for Nutritional Healing: (P. Balch).
Tolerable Upper Intake Levels for Vitamins and Minerals (http://www.efsa.europa.eu/en/ndatopics/docs/ndatolerableuil.pdf)