Minerals (Leaving Cert Home Economics): Revision Notes
Iodine
Where can we find iodine?
Natural food sources
The ocean and earth's soil contain natural iodine, which makes its way into our food chain. Marine foods are particularly rich sources because they absorb iodine directly from seawater. The best natural sources include:
- Seafood - Fish, seaweed, and shellfish contain high levels of iodine
- Dairy products - Milk, cheese, and yoghurt provide iodine, partly because cattle consume iodine-rich feed
- Eggs - Another reliable source, especially if hens have been fed iodine-supplemented feed
Fortified foods
Many countries have introduced iodine fortification programmes to prevent deficiency in their populations. The most common approach is adding iodine to table salt, creating what we call iodised salt.
This simple public health measure has been extremely effective at reducing iodine deficiency worldwide, making fortified salt one of the most successful nutritional interventions in history.
Supplements
When people cannot get enough iodine from their diet, or have specific dietary restrictions, doctors may recommend iodine supplements.
Medical Supervision Required
Iodine supplements should always be taken under medical supervision to avoid consuming too much, as excessive iodine can also cause health problems.
Why do we need iodine?
Thyroid hormone production
Iodine serves as a building block for two crucial thyroid hormones that control many body functions. These hormones are called thyroxine (T4) and triiodothyronine (T3).
Critical Function of Thyroid Hormones
Thyroid hormones regulate metabolism (how fast your body uses energy), support normal growth patterns, and ensure proper development throughout life.
Without adequate iodine, the thyroid gland simply cannot manufacture enough of these essential hormones, leading to various health problems.
Brain development
Iodine plays a particularly critical role during pregnancy and early childhood. The developing brain requires sufficient thyroid hormones to form properly. During these crucial periods, even mild iodine deficiency can have lasting effects on cognitive development and learning abilities.
What happens when we don't get enough iodine?
Goitre
When the body lacks iodine, the thyroid gland works harder to try to produce enough hormones. This extra effort causes the gland to enlarge, creating a visible swelling in the neck area.
Goitre Definition
Goitre is the enlargement of the thyroid gland, which appears as a swelling in the front of the neck.
Hypothyroidism
Without enough iodine to make sufficient thyroid hormones, the body's metabolism slows down significantly. People with hypothyroidism often experience:
- Persistent tiredness and fatigue
- Unexplained weight gain
- Feeling cold even in warm environments
- Difficulty concentrating
These symptoms develop because the body's metabolic processes cannot function properly without adequate thyroid hormones.
Developmental problems
In severe cases of iodine deficiency during infancy, a condition called cretinism can develop. This serious disorder involves:
- Stunted physical growth
- Impaired mental development
- Delayed learning abilities
Pregnancy complications
Pregnant women with iodine deficiency face increased risks of:
- Miscarriage
- Stillbirth
- Birth defects
- Poor brain development in the unborn child
Critical Period Alert
The first trimester of pregnancy is especially critical, as this is when the baby's brain and nervous system begin to develop.
How much iodine do we need?
The amount of iodine required varies depending on age, gender, and life stage. Generally, healthy adults need approximately 150 micrograms each day to maintain proper thyroid function.
Special Requirements
- Pregnant women need higher amounts to support both their own needs and their developing baby
- Breastfeeding mothers require extra iodine as it passes into breast milk
- Children and teenagers may need varying amounts depending on their growth stage
Properties of iodine
Chemical characteristics
Iodine belongs to a group of elements called halogens and is classified as a non-metallic element. This classification helps explain some of its behaviour in food and in the body.
Stability in food
One advantage of iodine is its stability during food preparation. Unlike some other nutrients, iodine remains largely intact when foods are cooked or processed.
This means that cooking seafood or heating iodised salt doesn't significantly reduce the iodine content, making it a reliable nutrient source even after food preparation.
Factors that affect iodine absorption
Goitrogens
Certain foods contain natural substances that can interfere with iodine absorption and utilisation. These are called goitrogens, and they're found mainly in cruciferous vegetables such as:
- Cabbage
- Broccoli
- Cauliflower
- Brussels sprouts
However, cooking these vegetables reduces their goitrogenic effects, and they remain healthy choices as part of a balanced diet.
Mineral interactions
Sometimes other minerals can compete with iodine for absorption in the digestive system. Taking very high amounts of calcium or iron supplements may reduce how well the body absorbs iodine from food.
Supplement Timing
If you take multiple mineral supplements, consider spacing them apart or consulting with a healthcare provider about optimal timing.
Health conditions
Certain autoimmune thyroid diseases can affect how efficiently the body uses iodine, even when intake is adequate. People with these conditions may need special monitoring and treatment approaches.
Summary
Key Points to Remember:
- Iodine is essential for making thyroid hormones that control metabolism, growth, and brain development
- Best sources include seafood, dairy products, eggs, and iodised salt
- Deficiency causes goitre, hypothyroidism, and serious developmental problems, especially during pregnancy
- Adults need about 150 micrograms daily, with pregnant and breastfeeding women requiring more
- Iodine is stable in food and isn't easily destroyed by cooking or processing