Thrive expert and qualified nutritionist Anne Lecomber looks at the importance of iodine in your diet and how you can ensure that you get the right balance.
Iodine is a micronutrient essential for production of the hormones, thyroxine (T4) and triiodothyronine (T3) produced by the thyroid gland. These hormones are needed throughout our life for the regulation of our growth, metabolism, heart rate and temperature, but are of vital importance during the critical stages of development in the womb through to early childhood.
An iodine deficient diet can lead to a variety of iodine deficiency disorders (IDD) including congenital abnormalities, stunted growth, and impaired hearing. Sadly, miscarriages and stillbirths can also happen. Organs that grow quickly are affected greatly, with the brain as the most susceptible organ; mild intellectual disabilities are common. Intervention studies have shown improved IQ in iodine-sufficient groups compared to iodine deficient groups.
Not enough iodine in your diet can lead to hypothyroidism – an underactive thyroid caused by a lack of thyroid hormones. But too much iodine in your diet is also unhealthy, causing hyperthyroidism – an overactive thyroid.
Each condition has a whole host of non-specific symptoms, and the only test for thyroid dysfunction is a blood test measuring your thyroid hormone levels. But one shared specific symptom is a goitre. Goitres are a swelling of the thyroid. In hypothyroidism and hyperthyroidism, the thyroid becomes enlarged from essentially being overworked from trying to produce enough hormone or from producing too much hormone respectively.
Luckily in the UK, iodine deficiency is not an issue, and goitres normally show after long exposure to excess iodine or iodine deficiency. Whilst we know the effects of deficiency, there is some evidence that suggests that teenage girls, young women of childbearing age, and pregnant women in the UK are not getting sufficient iodine in their diet. We need larger studies to investigate this further.
Sources of Iodine
Our bodies can’t produce iodine therefore we must get this trace element through our diet. This isn’t always simple. There is huge variation of iodine content in soils and water with the bulk of the earth’s iodine found in our vast oceans. The content found in crops increases as the soil gets closer to the ocean.
Most of us could do with eating more fish for heart health, and with fish being the best natural source of iodine, what a perfect way to kill two birds with one stone! Dairy is also a good source, due to livestock eating fortified animal feed. Seaweed can be a good vegan, concentrated source of iodine, but the bioavailability may not be as good as that in fish.
Dairy and iodine content can also differ greatly between seaweed varieties.
Therefore, the British Dietetics Association recommends that people eat seaweed only once a week, especially if you are pregnant to avoid accidental excessive consumption.
The type of milk you consume affects your iodine intake considerably! Milk alternatives are often not fortified with iodine – check the label. There are so many innovative milk products on the market, so have a look out for iodine-fortified milk products. Some studies show that organic milk has half the iodine of conventional cows’ milk. Something to be aware of when choosing your milk.
How much iodine do I need?
• Adults: 150μg per day
• Pregnant Women: 200 μg per day
• Breastfeeding Women: 200 μg per day
The European Food Safety Authority (2014)
If you have read this and are now worrying you may not be getting enough iodine in your diet, or that you are concerned about your new baby, use this as an opportunity to think about your diet. It may be that you cannot eat any of these sources in which case speak to your GP or dietitian and they may recommend supplements if you have concerns.
1) Agostoni et al (2014). Scientific Opinion on Dietary Reference Values for iodine. EFSA Journal. 12. 10.2903/j.efsa.2014.3660.
2) Bath, S., Button, S., & Rayman, M. (2012). Iodine concentration of organic and conventional milk: Implications for iodine intake. British Journal of Nutrition, 107(7), 935-940. doi:10.1017/S0007114511003059
3) Jiang, H., Powers, H., & Rossetto, G. (2019). A systematic review of iodine deficiency among women in the UK. Public Health Nutrition, 22(6), 1138-1147. doi:10.1017/S1368980018003506
Anne Lecomber has a firstclass honours (BSc) degree in Human Nutrition from the University of Greenwich and is one of our Thrive Experts. And has over 15 years’ experience working in the fitness industry as a Personal Trainer and Bodybuilder.