Iodine;an overlooked micronutrient

Iodine, one of the most important micronutrient required at all stages of life. Iodine is essential for the synthesis of Thyroid hormone, triidothyronine (T3 )and thyroxine (T4) which regulates body metabolism. Thyroid hormones receptors are presents in almost every cell of the body, so they are important regulators of many physiological processes includes brain development, growth, metabolism and cardiac function. Iodine plays a vital role in brain development during early pregnacy till childhood. Many brain structures and systems appear to be affected with iodine deficiency, including areas such as the hippocampus, microstructures such as myelin, and neurotransmitters.

25 -30mg of iodine present in a healthy body, 80% of which is stored in the thyroid gland. The non hormonal iodine is found in a variety of body tissues including mammary glands, eye, gastric mucosa, cervix and salivary glands.

How much Iodine Do we Need

In the UK, the recommended daily intake of iodine for a healthy adult (male and female) is140 microgram and there is no specific recommendation for pregnant and breastfeeding women. As during pregnancy, iodine requirement increases so the British Dietetic Association (BDA) suggested 200 microgramm of iodine per day for pregnant and breastfeeding women.

dietary sources of iodine

Milk and dairy products fish and eggs are a major source of iodine. In the UK, milk and dairy products provide as much as 34% of iodine intake. Fortified milk is recommended for those who are using non dairy milk alternative. however, a study conducted by the University of surry revealed that only a few plant based milk brands in UK are fortified with iodine.

Fruits and vegetables also contain iodine but the amount varies depending on the iodine content of the soil, fertilizers use up and irrigation practice. The table below produced by BDA shows the iodine content of food in the UK.

Some vegetables impair absorption of iodine like cruciferous vegetables (broccoli, cauliflower, cabbage and soya) and cause swelling of the thyroid gland (goitre) due to low levels of thyroid hormones. However, normal consumption of cruciferous vegetable does not appear to increase the risk of hypothyroidism unless accompanied by iodine deficiency. 

iodine deficiency

  • Pregnant and lactating women; The iodine requirement in pregnant women is 50% higher as compared to non preganant women as; maternal iodine production increases by 50% in eraly pregnancy.At this stage fetal thyroid is not fully active so, additional iodine is rquired for fetus toproduce its own thyroid hormones.
  • vegetarian /vegans
  • People with food allergies; milk or fish allergies
  • Lactose intolerance

Globally, iodine deficiency is a serious public health issue and it is estimated that around 2 billion people all over the world are iodine deficient. iodine deficiency leads to hypothyroidism which causes impair neurodevelopment in early childhood.

It is claimed by WHO that iodine deficiency is the most significant preventable cause of brain damage and mental retardation. Severe iodine deficiency during pregnancy causes Endemic cretenism( congenital hypothyroidism) in the newborn which is marked by gross mental retardation, deaf mutism, short stature.

iodine deficiency causes a spectrum of disorders in different age groups collectively known as iodine deficiency disorders ( DIDs). The effects of IDD in humans at different stages of life are presented in the following pyramid.

Iodine deficiency can be corrected by adding iodine to dietary media like salt, oil, water, sauces etc. The methods of proven value for mass use are iodized salt and iodized oil. To this end, fortification of salt with iodine has been identified and considered to be the most suitable method of fortification.

universal iodized salt is recommended intervention by WHO for iodine deficiency however, in the UK there is no iodized fortification program and most sale salts are not fortified. it is better to meet iodine requirement through diet.

TAKE HOME MESSAGE;

Iodine is essential for thyroid hormone production and its deficiency may impair body metabolism and brain development.

The best way to meet your daily iodine requirement is eating a healthy well balanced diet. People with different dietary choices like vegan and vegetraian are increased risk of developing iodine deficiency.

vegans should check their iodine levels and in case of iodine deficiency, consume iodine supplements but always consult GP, dietitian or nutritionist before using iodine supplements.

Strong evidence is still needed to conclude the efficacy of iodine supplementation in mild to moderate iodine deficient women on the cognitive function of their children.

Avoid seaweed based supplements as they may cause iodine intoxication.

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