All you need to know about iodine
by Simone do Carmo
in Blogs

Eating raw kale, by incorporating it in smoothies or salads, is a growing food trend, but what many people don’t realise is that kale in its raw form contains many goitrogens. These are compounds that can interfere with iodine uptake, a vital micronutrient as you’ll see below…

What is iodine and why is it important?

Iodine is a trace element, a key component for the synthesis of our thyroid hormones, thyroxine (T4) and triiodothyronine (T3). Our thyroid hormones are vital for many metabolic and physiological processes; they appear to play a role in our immune response and are determinants of normal growth throughout life and of neurological development in foetuses and infants. Having low iodine levels puts you at a higher risk of having an underactive thyroid. This means a sluggish metabolism, and you’re likely to see an increase in weight.

How much iodine do I need?

Organisations such as the Institute of Medicine (IOM), the World Health Organisation (WHO) and the Iodine Global Network (IGN) provide similar Recommended Dietary Allowances (RDAs). Below is the IOM table for all age groups.

Table 1 iodine

Table 1 – Adapted from the Iodine Fact Sheet for Health Professionals of the National Institutes of Health. Recommended Dietary Allowances (RDAs) for Iodine.

However, we have to be cautious in relation to RDAs since these are based on population studies and aimed at preventing deficiency. They are useful only as a reference because everyone is different. In other words, what one person requires to prevent deficiency might not be enough for another person. Moreover, if a person is seeking to achieve optimal health, higher levels of iodine than the RDAs are probably needed (although still within healthy levels since excessive iodine intake can also cause adverse effects).

Iodine deficiency

Iodine deficiency is considered the most preventable cause of impaired cognitive development in children, but sadly, it is also the most prevalent cause.

Our thyroid function is mainly regulated by the thyroid-stimulating hormone (TSH). When TSH is secreted by the pituitary gland in our brain, this stimulates iodine uptake by the thyroid gland, and thus the production of our thyroid hormones.

When there isn’t enough iodine in our body, TSH levels remain elevated, leading to hypothyroidism, which is commonly accompanied by a condition called goiter. Goiter is when the thyroid gland enlarges to try and ‘trap’ more iodine from our circulation. In adults, this can cause an array of symptoms such as fatigue, impaired mental function, feeling cold, unusual weight gain, depression, constipation, etc.

During pregnancy, iodine deficiency can cause irreversible effects such as growth retardation in utero, major neurodevelopmental deficits, and a host of other physical and neurological abnormalities. In infants and children, iodine deficiency can also cause neurodevelopmental deficits and has been associated with an increased risk of ADHD.

The most reliable ways to check your iodine status include:

  • - Asking your doctor to do some standard tests. Your doctor may also check your thyroid hormones to ensure they are within healthy ranges. Your selenium, vitamin A and iron statuses may also be checked since concurrent deficiencies in these may also exacerbate iodine deficiency.
  • - Asking your functional health practitioner to do certain functional tests such as a Complete Iodine Thyroid Test which assesses the availability of iodine and its ability to be utilised by the body. You can also have a Comprehensive Thyroid Assessment done which provides a comprehensive result and a better individualised understanding of your thyroid function that can then be used to tailor your nutrition (and supplements, if needed).

Iodine food sources

Below is a table of some selected food sources for iodine foods sources. Seaweed is one of the best sources, but the content is highly variable. Seafood is also a good source because marine animals can concentrate the iodine from seawater. Certain foods that are grown or are from animals that have been raised on iodine-rich soil, are also reasonable sources. As I mentioned at the start, certain foods, such as kale, Brussels sprouts and other cruciferous vegetables, as well as soya and cassava, contain goitrogens, which may intensify iodine deficiency as they interfere with iodine uptake, especially when consumed raw and in large amounts. Steaming, cooking and fermenting helps to reduce the goitrogenic content in these foods. The effect of goitrogens will depend on your iodine intake, so if you’re someone who eats good iodine sources, such as fish and seafood, then you probably don’t need to worry. However, if you don’t really include these foods in your diet (e.g. if you’re vegan or a non-fishy person), then goitrogenic foods might be a problem for you.

Table 2 iodine

Table 2 – Adapted from the Iodine Fact Sheet for Health Professionals of the National Institutes of Health and the Micronutrient Information Centre of the Linus Pauling Institute (Oregon University). Selected iodine food sources.

Many countries have implemented programmes to iodise regular table salt in an effort to eliminate iodine deficiency. If you regularly eat iodine food sources, you probably don’t need to include iodised salt in your diet, plus regular table salt is not a good nutritional option. As an alternative, I would opt for some sea salt. Even though it generally has less iodine than regular table salt, sea salt undergoes minimal processing and contains trace amounts of other essential micronutrients such as magnesium and potassium.