Having a healthy thyroid is essential to keep you full of energy, at a healthy weight and feeling your best, but lots of people don't know much at all about the key element that makes having a healthy thyroid possible: Iodine! Today let's learn about this essential element, what makes it so special and how you can up your intake.
Iodine is a trace element that is needed to make the thyroid hormones (thyroxine T4 and triiodothyronine T3) which studies show are essential for normal development and function of the brain and the nervous system, and for maintenance of body heat and energy. Iodine deficiency is considered to be the most common cause of brain damage in the world.
According to the WHO (World Health Organisation) 800 million people are affected by iodine deficiency disorders (IDD) including hypothyroidism, hyperthyroidism, impaired mental function and stillbirth. Many countries in Africa and South Asia are the most affected. However, 50% of the population in Europe remains mildly iodine deficient, and iodine intake in other industrialised countries such as the United States and Australia have fallen considerably in recent years.
The best way to determine iodine deficiency across a population is to measure the amount of iodine in urine samples. If the iodine concentration is less than 100 μg/L in a non-pregnant population, (or <150 μg/L in a population of pregnant women) then that specific population is iodine deficient. Adults are recommended to have 150 μg of iodine, and pregnant women are recommended to have 200-250 μg of iodine.
In particular, pregnant women and school-age children are a high-risk group of the population: research shows that insufficient intake of iodine during pregnancy can adversely affect both maternal thyroid health and the infant's neurological development. In its extreme form, severe deficiency can lead to cretinism and growth retardation. Children born to moderately iodine deficient mothers can have neurological problems and lower IQ scores.
The most common conditions that affect the thyroid hormones (and are often caused by a lack of iodine) are hypothyroidism and goiter, so let's explore those together.
Hypothyroidism makes your thyroid gland unable to produce thyroid hormones. It is generally caused by iodine insufficiency, but it can also be caused by a chronic condition known as autoimmune thyroiditis in which the body interprets the thyroid glands as a threat, and as a result produces antibodies that destroy the thyroid’s cells. Hypothyroidism usually develops gradually, and it causes a general slowing down of the body’s function. Common symptoms are tiredness, increased awareness of the cold, increase in weight, slow heartbeat or slightly raised blood pressure.
Goiter is a condition characterised by having a thyroid gland bigger than normal due to a low production of thyroid hormones. This is determined by an increased production of the THS (thyroid stimulating hormone). THS is produced more than usual because the pituitary gland located in the brain detects the low thyroid hormone level and makes more of its controlling hormone, which is THS. As a result, THS makes the thyroid gland work harder, causing an enlargement.
On the other hand, an excess iodine intake causes a condition called hyperthyroidism or Graves disease.
Hyperthyroidism indicates an increased thyroid hormone synthesis. In other words, the thyroid gland is overactive. The most common cause is an overproduction of thyroid hormones by the entire thyroid gland. Common symptoms include weight loss, sweating and a rapid heartbeat.
This condition is common among people living in the northern coastal regions of Japan that have been found to have iodine intakes ranging from 50,000 to 80,000 mcg (50-80 mg) of iodine/day due to a large amount of seaweed in the diet. Seaweed (along with fish and other seafood) is one of the best sources of iodine. This is because they can concentrate iodine from seawater (which is a great source of iodine).
Elemental iodine in the ocean rises into the atmosphere and returns to the soil through rainfall. Mountainous areas like the Alps, Andes and Himalayas (areas with frequent flooding) typically have iodine-deficient soil.
We can find iodine in a range of foods in our diet, the richest sources being fish, seafood, iodised salt, seaweed, milk and dairy products. In general, white fish (haddock, cod) contains more iodine than oily fish (tuna, salmon). However products like plant-based milks are not fortified with iodine and therefore have a low iodine content.
In general, plant-based food (with the exception of seaweed and sea vegetables) does not provide an adequate dietary iodine intake, and quite often vegan and vegetarians can develop iodine deficiency (even if they live in iodine-sufficient areas). Furthermore, pregnant women are still a high-risk group for iodine deficiency. In the UK, 60% of pregnant women do not meet the WHO recommended intake (see above).
To address this issue, more than 120 countries have implemented salt iodisation and food fortification strategies. It is the main method of iodine prophylaxis worldwide, first proposed in 1820. However, in some countries like the UK, salt iodisation is voluntary.
The final goal of worldwide salt iodisation programmes is to ensure that 90% of households consume iodised salt. Currently, an estimated 70% of households use iodised salt. The percentage of households using iodised salt varies from country to country, from a low of 50% coverage in Europe to a high of 86% in Latin America and the Caribbean.
Therefore, to address IDD and increase iodine in your diet, we recommend you consume iodised salt along with fish and seafood. We recommend trying to consume fish twice a week (ideally only one of which being oily fish) and trying out a pescatarian diet. For vegan or vegetarians, we recommend a diet rich in sea vegetables such as nori, kelp and wakame, along with some iodine supplements if you know that you're not hitting that ideal iodine intake!