What is iodine and why do we need it in our daily diet?


A nationwide study found almost half of Malaysian pupils in the eight to 10 age group were deficient in iodine. — 123rf.com

Most people know we need many types of minerals for our body to function.

They are familiar with calcium, which is important for strong bones and teeth. They know iron is important to make red blood cells in the body.

But many do not know about iodine – an important trace mineral needed in daily diet.

Iodine is now being highlighted as the Health Ministry (MOH) announced last week that all fine salt or salt that weighs 20kg or less must be fortified with iodine before it can be sold in the country i.e. Universal Salt Iodisation (USI).

This new ruling is aimed at tackling iodine deficiency among children after almost half of the pupils aged eight to 10 in Malaysia were found to lack the essential nutrient.

What is iodine and what foods are rich sources?

Most of the earth’s iodine is found in the ocean – sea water and marine products. The foods that are highest in iodine are therefore marine fish and shell fish, including mussels, clam, cockles and prawns. I see some people chewing dried seaweeds as snacks; it is important to note that these are very high in iodine!

Eggs, milk and milk products are good sources, too. Meats may provide a fair amount of this mineral.

And now, you can get it from any type of salt sold in this country!

What are the functions of iodine in the human body?

Iodine is an essential nutrient that helps the body to make the hormone, thyroxine (often referred as T4), by the thyroid gland.

This is an important hormone that regulates various metabolic processes. T4 is particularly important during early growth and development of many organs, especially the developing brain.

We need very small amounts of this mineral (hence the name “trace” mineral) – about 100mcg (microgramme) or 0.0001g (gramme) per person per day, which we can obtain by consuming 30g of fish.

Pregnant and lactating women need additional amounts, up to twice the amount, to meet the needs of the developing foetus and to produce breast milk. She would then have to consume fish with other foods such as milk and egg to meet the total amount needed.

What happens if a person is deficient in iodine?

Deficiency of iodine brings about iodine deficiency disorders (IDD).

Since the main role of the mineral is in the formation of T4 in the thyroid gland, insufficient intake leads to insufficient thyroid function (or hypothyroidism).

Persons with severe iodine insufficiency may experience reduced metabolic rate, fatigue and weakness, cold intolerance, weight gain and other symptoms.

IDD can be seen at all stages of development but the most serious is probably during pregnancy and infancy.

IDD during pregnancy results in foetal iodine deficiency with serious implications.

Such women will also have a higher rate of stillbirths, abortions and congenital abnormalities. It may result in serious effects on brain development of the foetus, affecting physical and mental retardation, and resulting in lower cognitive and motor performance in later life.

In areas with severe IDD, a condition called cretinism has been observed, wherein children are severely stunted and experience retarded physical and mental development.

Foods that are highest in iodine are found in marine fish and shell fish, including mussels, clam, cockles and prawns. — FilepicFoods that are highest in iodine are found in marine fish and shell fish, including mussels, clam, cockles and prawns. — Filepic

In iodine deficiency, the body cannot make enough T4 for use. As a result, the thyroid gland works harder to produce more of this hormone. If this deficiency becomes prolonged, the thyroid gland becomes enlarged and results in goitre, where there is a visible swelling in front of the neck.

How do we prevent suffering from IDD?

To prevent from nutrient deficiencies, including iodine deficiency, just remember the principles of healthy eating which includes taking balanced meals, consuming a variety of foods from each food group, and eating meals in moderate amounts.

This way, it is likely that we will be able to obtain most of the nutrients that we need.

In this case, just remember to include seafoods, milk, eggs in the daily diet!

Since iodine is so important, should I take more of it?

No, like all nutrients, more is not necessarily better.

There is an optimal amount of iodine which is needed and excessive intakes are to be avoided.

Too much intake of iodine can bring about hyperthyroidism when the thyroid gland produces too much T4. This can result in increased body metabolism, causing unintentional weight loss or irregular heartbeat.

Long term excessive intake of iodine can bring about some of the same symptoms as iodine deficiency. This includes goitre (enlarged thyroid gland), thyroid gland inflammation and thyroid cancer.

Why is the government adding iodine to all salt in the country?

They are doing so to help the community have access to enough intake of daily iodine, especially for those who do not have access to iodine-rich foods.

Fortification of foods with iodine is one approach used.

The fortification of salt with iodine has been found to be an effective approach to increase iodine intake of population groups, to prevent IDD.

Salt is consumed by everyone, and the intake of salt is self-limiting, hence the intake of iodine is controlled.

When large population groups are at risk of IDD, to make sure that everyone has access to iodised salt, an approach called USI has been used.

This means that all salt available in the market must be fortified with iodine.

World Health Organization and many health authorities globally have been advocating this approach.

MOH has gazetted USI because there is significant IDD in the country. This is based on nationwide studies of urinary iodine among school children, which is a good indicator of IDD.

Surveys of iodine intake among pregnant women and school children also showed intake below the recommended amounts.

In addition, MOH has successfully used USI to reduce significantly the IDD and goitre problem in Sabah in the past.

MOH has implemented USI to prevent the whole population in the country from suffering from IDD.

A law was gazetted in 2018 (Regulation 285) to require all salt at retail level to be added with iodine, and this law has been enforced on December 31,2020, after a grace period of two years.

All salts available for retail in the country must now be fortified with iodine. — Photos.comAll salts available for retail in the country must now be fortified with iodine. — Photos.com

What does this USI law mean to consumers?

It does not mean that because there is iodine in the salt, we should increase our salt intake. It certainly does not mean that parents should start giving your child more iodine in the hope that your child’s brain will develop better (and become smarter!). This will certainly not happen.

It has been well established that excessive intake of salt will increase risk to high blood pressure.

The consumer need not be unduly concerned that he may be taking too much iodine now that all salt is iodised, and his diet includes seafoods, milk and eggs.

It is unlikely that the consumer has excessive intake of iodine if he follows the dietary advice of keeping salt intake to the minimum.

Excessive intake of iodine is unlikely to happen from consuming foods alone.

It is however possible if someone takes an iodine supplement.

It you suspect you have an iodine deficiency, consult your family physician and don't start taking iodine supplements on your own.

Dr Tee E Siong is the president of the Nutrition Society of Malaysia. For more information, email starhealth@thestar.com.my. The information provided is for educational purposes only and should not be considered as medical advice. The Star does not give any warranty on accuracy, completeness, functionality, usefulness or other assurances as to the content appearing in this column. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.

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Iodine , Salt , Thyroid

   

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