Why Salt Is Fortified With Iodine

For more than 70 years, iodised salt has been the most efficient means of providing iodine to iodine-deficient populations. The World Health Organization (WHO) encourages it as part of their Universal Salt Iodisation (USI) initiative, to help prevent and control Iodine Deficiency Disorders (IDDs).

Fortifying salt with iodine does not affect its smell or taste, which makes it acceptable among consumers, yet many do not understand its reasoning. So, let’s unpack the iodisation of salt.

What is iodine and why is it important?

Iodine is a vital micronutrient that aids in thyroid hormone synthesis, which plays an important role in the body’s growth and development. Adequate iodine intake from foetal development through adolescence is essential for lifelong health.

The thyroid requires iodine to synthesise thyroid hormones. The prime thyroid hormone that’s secreted by the thyroid gland is thyroxine. This is taken up by cells and converted into triiodothyronine – a vital element in developmental and metabolic processes.

The insufficient and excess intake of iodine can have negative effects on thyroid function. The recommended daily intake for iodine is:

• 90 mg for preschool children (0 to 59 months)
• 120 mg for children aged six to 12 years
• 150 mg for adolescents (above 12 years) and adults
• 250 mg for pregnant and lactating women

When the body’s iodine intake is inadequate, the thyroid gland may no longer be able to synthesise enough thyroid hormone. This leads to low levels of thyroid hormones in the blood – a condition referred to as hypothyroidism. Hypothyroidism is responsible for damage to the developing brain as well as a whole range of IDDs.

Iodine Deficiency Disorders (IDDs)

A shortage of iodine over a long period of time leads to iodine deficiency, which could cause irreparable damage to the developing brain as well as other issues collectively known as Iodine Deficiency Disorders (IDDs). These disorders affect almost 1.9 billion people worldwide and are a major public health concern in many countries. The areas most affected by include South-East Asia, the Western Pacific, Africa, the Eastern Mediterranean, and Eastern/Western Europe.

IDDs include a range of preventable conditions, including impaired mental functioning, hypothyroidism, cretinism, abnormal physical development, and goitre, which is recognised by the swelling of an ill-functioning thyroid gland.

Pregnant women, lactating women, women of reproductive age, and children under 3 are at the highest risk of iodine deficiency. Further health issues include decreased fertility, miscarriages, stillbirths, and congenital abnormalities.

Although problems from excess consumption of iodine are rare, iodine‐induced hyperthyroidism can occur, and there have been reports of toxicity – but these numbers are limited.

Why iodise food, especially salt?

Iodine is mainly found in soil, water, seaweed, seafood, dairy products, and certain crops such as soy and cruciferous vegetables like cabbage, broccoli, cauliflower and brussels sprouts. Seaweed and seafood are the richest natural sources of iodine. In contrast, the iodine content of plant-based foods depends on soil quality, which varies globally. Most of the soil used today contains insufficient iodine due to leaching by glaciation and flooding.

Iodine in food is absorbed through the gastrointestinal tract but acquiring a sufficient amount through natural food alone is almost impossible nowadays. This is why interventions have been made in the form of food fortification.

Foods that are typically fortified with iodine include salt, tea, water, fish paste, bread, soya sauce, dairy, and poultry. But the most widespread and mature option is salt iodisation. Salt iodisation is one of the primary means of increasing the global population's iodine intake to reduce the risk of IDDs. Thus far, it has resulted in an average 13-point increase in IQ levels in developing countries where iodisation was introduced.

Salt is the vehicle of choice because:

• It’s consumed year-round by nearly everyone, at almost equal amounts
• It’s a general staple in most households
• Its production is typically limited to a few centres, which aids quality control
• Iodising salt doesn’t affect its taste or smell
• It’s affordable, which makes it more accessible

Salt iodisation in South Africa

Before the introduction of salt iodisation, South Africa was one of the many countries in the world with low-iodine consumption, so there was a need for a salt iodisation programme. To comply with the WHO’s goal of iodising salt globally, South Africa introduced the compulsory iodisation of all table salt on 1 December 1995. Consequently, the majority of our salt products are iodised today. Its formulation is regulated to ensure that it doesn’t cause a large increase in cost and is suitable for coarse, unrefined salt as well.

The WHO’s recommended levels of iodine to be added to salt fall between 40 mg/kg and 20 mg/kg. This is based on an estimated average salt consumption in adult populations, which is between 5 and 10 grams per day. These iodine levels are considered safe with salt intakes of around 25 gram per day when iodine from dietary sources is low – as it typically is across the world.

There is a strong correlation between high salt (sodium) intake and elevated blood pressure (hypertension), which is a major contributor to cardiovascular diseases and stroke. To reduce the prevalence of high blood pressure and related health issues, South African and International Hypertension Guidelines Committees recommend a low sodium intake, along with a healthy diet, for the prevention and/or management of hypertension.

South Africa is a global leader in addressing salt reduction and was the first country to mandate maximum salt targets, especially in processed foods. The National Department of Health’s (NDoH) aim is to reduce the mean population’s salt intake to less than 5 g per day. This amounts to one teaspoon of salt, and includes the salt already found in foods as well as the raw salt that’s added.

So, even with the added iodine, salt should be consumed in moderation.

Conclusion

The best way to prevent and control any kind of micronutrient deficiency is by following a balanced, nutrient-rich diet, but in modern times, this is often difficult. Even more so in rural areas. To this end, the WHO strongly encourages all kinds of food fortification – including the iodisation of salt – as a comprehensive strategy for the prevention and control of deficiencies.

FAQs

• What is iodine and why is it important?

  Iodine is a vital micronutrient that aids in thyroid hormone synthesis, which plays an important role in the body’s growth and development. Adequate iodine intake from foetal development through adolescence is essential for lifelong health.

• What does iodisation mean?

  Iodisation is a form of food fortification in which iodine is added to specific food items. Foods that are typically fortified with iodine include salt, tea, water, fish paste, bread, soya sauce, dairy, and poultry. But the most widespread and mature option is salt iodisation.

• Why iodise salt?

  Salt is the vehicle of choice for iodisation because:

  • It’s consumed year-round by nearly everyone at almost equal amounts
  • It’s a general staple in most households
  • Its production is generally limited to a few centres, which aids quality control
  • Iodising salt doesn’t affect its taste or smell
  • It’s affordable, which makes it more accessible
• Do we have iodised salt in South Africa?

  Yes. South Africa introduced the compulsory iodisation of all table salt on 1 December 1995. So, the majority of our salt products are iodised today.