A new study shows that dairy alternatives could be leaving you deficient in this essential mineral. From its importance to iodine-rich foods and how to boost your intake on a dairy-free diet, registered nutritionist Rob Hobson shares his advice
So, you’ve all heard about certain nutrients and their importance in our diet such as calcium and vitamin D (bone health), omega 3 (heart health), iron (tiredness and fatigue), zinc (immunity) and B vitamins (energy), but how familiar are you with iodine?
We need iodine to make thyroid hormones. These hormones, which include the ‘master’ hormone thyroxine, control all metabolic processes including your metabolic rate. Maintaining a good intake of iodine is essential to produce thyroxine and low levels of this hormone are associated with weight gain and a lower metabolic rate (symptoms of an underactive thyroid).
A very low intake of iodine can cause your thyroid to work extra hard to maintain enough thyroxine in the blood. (This can cause swelling also known as goitre as your thyroid increases in size to trap iodine, but intakes in the UK rarely reach such low levels so this is uncommon).
The recommended daily intake of iodine is set at 150 micrograms (mcg) for adults and 200mcg for pregnant and breastfeeding women. In pregnancy and during breastfeeding, your body has a greater need for iodine so you can make enough of the thyroid hormones to transfer to your baby and insure their brain develops correctly. Research published in the Lancet showed a positive association between maternal prenatal iodine levels and both the child’s IQ and their reading ability at aged 8-9 years. This same study also showed that many women in the UK have a lower level of iodine than is optimum for their child’s development.
According to the latest published findings from the National Diet and Nutrition Survey , women appear to be more likely than men to have a shortfall in their diet for this mineral. According to this survey, 26 per cent of girls and 12 per cent of women have very low intakes of iodine. Further findings have even suggested that 70 per cent of UK teenage girls could be deficient in iodine (the key issue here being pregnancy, especially among teenagers and unplanned pregnancies).
Dairy products, especially milk, are the main dietary source of iodine, providing around 40 per cent of the overall intake. The high iodine content in milk is due to the addition of this mineral to cattle feed and the iodophor sanitising agents used to clean milking equipment. Interestingly, organic milk has been shown to provide a third less iodine than conventionally farmed milks, which may be due to differences in the iodine content of winter feeds or different practices in cleaning cow teats prior to milking.
the trend to cut out dairy foods and switch to fashionable, non-dairy alternatives may be increasing the risk of iodine deficiency
Current food trends have had a big impact on milk consumption in the UK. The popularity of ‘clean eating’ and other such dietary regimes that promote the exclusion of dairy foods has seen a dramatic decrease in the number of people that drink milk and eat dairy foods. The effect of these diets, combined with a supermarket price war has wiped £240 million off the value of milk sales over the past two years.
A recent study carried out by the University of Surrey has warned that the trend to cut out dairy foods and switch to fashionable, non-dairy alternatives may be increasing the risk of iodine deficiency, especially among women. In the first study of its kind in the United Kingdom, researchers examined the iodine content of 47 milk-alternative drinks (including soya, almond, coconut, oat, rice, hazelnut and hemp) and compared it with that 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 per cent of that found in cow’s milk. The findings from the study showed that most milk-alternative drinks are not an adequate substitute. While many non-dairy milk alternatives are fortified with calcium, B12 and vitamin D, they all lack adequate iodine. A glass of a milk-alternative drink would only provide around 2mcg of iodine which is a very small proportion of the adult recommended iodine intake of 150mcg/day. The equivalent glass of cow’s milk can provide up to 100mcg, which is a third of the recommended daily intake.
Professor Margaret Rayman, an expert in nutritional medicine at the University of Surrey, said: “Many people are unaware of the need for this vital dietary mineral and it is important that people who consume milk-alternative drinks realise that they will not be replacing the iodine from cow’s milk which is the main UK source of iodine.”
Some people need to omit dairy foods from their diet such as vegans or those with a milk allergy or lactose intolerance. It’s likely in this case that these people have received guidance and information from qualified health professionals such as dietitians on the modifications that need to be made to their diet to fill any shortfalls from the exclusion of dairy foods (including milk). However, for those that have self-diagnosed or cut out dairy foods off the back of a diet trend, it’s less likely they understand how to change their diet to account for these shortfalls.
These food trends don’t seem to be going away anytime soon and more so, the supermarket shelves are brimming with new ‘dairy-free’ food products to support these types of diets. Unfortunately, the effect of this is that exclusion diets such as ‘dairy-free’ or ‘gluten-free’ are starting to be accepted as a healthier way to eat, when they have traditionally been thought of as special diets recommended for those with allergies, intolerances and autoimmune conditions such as coeliac disease.
I would recommend that if you don’t have any negative symptoms associated with eating dairy foods, (bloating, stomach upset, nausea) then there is no real reason to cut them out of your diet and no added health benefit from doing so. However, if this is what you want to do then you need to be mindful of the adjustments you need to make to your diet to accommodate the nutrient shortfalls. As far as the vital nutrients in dairy are concerned, then calcium, vitamin D and B12 are easy to find by choosing dairy-free milk alternatives that are fortified. However, iodine is a little trickier but not difficult to adjust when you know how to get more of this mineral into your diet.
Other sources of iodine
The iodine content of milk can vary depending on the time of year, production or feeding and sanitising practices. Seafood can also vary depending on the season and breed of fish. This table taken from the British Dietetic Association fact sheet on iodine provides a useful estimate.
Food GroupFoodPortion sizeAverage iodine content (mcg)Milk and dairy productsCow's milk200ml50-100 Organic cow's milk200ml30-60 Yoghurt150g50-100 Cheese40g15 FishHaddock120g390 Cod120g230 Plaice130g30-60 Salmon fillet100g14 Canned tuna100g12 ShellfishPrawns60g6 Scampi170g160 OtherEggs1 egg (50g)25 Meat/poultry100g10 Nuts25g5 Bread1 slice (35g)5 Fruits and vegetables1 portion (80g)3
Tips to boost your iodine intake on a dairy-free diet
1. Take a daily multivitamin and mineral supplement that also contains iodine such as Healthspan Multivitality Gold (£5.95 for 90 tablets). Most supplements contain 100 per cent of your recommended intake. If you are pregnant or breastfeeding, then make sure you seek professional advice before taking any supplements as certain nutrients can harm your baby if taken in excess. If you have thyroid disease, are taking other medication, or have experienced iodine deficiency over many years, you should speak to your GP before taking additional iodine. According to NHS Choices, taking too much iodine may be harmful but 500mcg or less is unlikely to cause any harm.
2. Include at least one serving of white fish such as cod or haddock each week. These foods are one of the richest sources of iodine. Try grilling or baking. You could also make a delicious fish-pie or kedgeree from cod or haddock.
3. Explore the use of sea vegetables in your diet. Sushi is great and you can add seaweed to miso soup and salads. You can also buy dried seaweed thins in the snack aisles of supermarkets and health food shops. Pregnant women are advised to limit seaweed in their diet to one serving per week as it is very high in iodine content.
4. Try eating eggs for breakfast. Two eggs provide around one-third of your recommended intake. Omelettes and other egg dishes make healthy quick lunch or supper options.
There is no reason to cut dairy foods (including milk) from your diet if you don’t need too. Eating three servings of dairy foods each day can provide you with enough iodine to meet your daily requirement alongside other foods in your diet. If you need to go dairy-free or choose to do so, then be mindful of your iodine intake by taking a supplement or including other iodine-rich foods in your diet.