Iodine is a trace element and an essential mineral that is naturally present in plant foods such as cereals and grains, but the levels vary depending on the amount of iodine in the soil where the plants are grown. Iodine is also commonly found naturally in seaweed. The Recommended Daily Amount for Iodine is 150mcg for both males and females in the UK.
Iodine has many functions in the body including its vital role in immunity, inflammation, foetal development and cognitive function during childhood. However, iodine predominantly plays an important role in thyroid function as it is needed for the manufacture of thyroid hormones.
Iodine deficiency has adverse effects on growth and development and may lead to disorders such as goitre (development of an enlarged thyroid gland), mental and growth retardation and cretinism. A deficiency can also cause irreversible effects in pregnancy. Disorders arising from thyroid issues as a result of iodine deficiency are secondary to insufficient iodine intake.
Research has been undertaken on the role of iodine in a number of areas of health including but not limited to foetal and infant development, cognitive function during childhood, fibrocystic breast disease, and radiation-induced thyroid cancer. Through research, iodine supplements have been claimed to assist in the treatment of weight loss, rheumatism, ulcers, hair loss, maintenance of healthy arteries, nervous tissue and nails (1). Iodine in the form of caseinate has been proposed as a treatment for fibrocystic breast disease at doses of 70-90 µg I/kg body weight (2).
Foetal development – Iodine intake is especially important during the early stages of pregnancy as the thyroid in the developing foetus is incomplete at this stage, therefore, the foetus relies entirely on maternal thyroid hormones and iodine intake (3). Neurological growth and maturation are also reliant upon sufficient iodine intake following birth. Even mild-to-moderate iodine insufficiency during pregnancy may subtly affect foetal development (4), (5), (6).
Cognitive development – The effects of severe iodine deficiency on neurological development are well documented. Results from several studies suggest, for example, that chronic, moderate-to-severe iodine deficiency, particularly in children, reduces IQ by about 12–13.5 points (7). A 2004 Cochrane review concluded that iodine supplementation in children living in areas of iodine deficiency appears to both positively affect physical and mental development and decrease mortality with only minor and transient adverse effects (8).
Fibrocystic breast disease- Iodine has been shown to help reduce the pain that is characteristic of fibrocystic breast disease although the mechanisms of action are unclear. In a double-blind study, 56 women with fibrocystic breast disease receiving 70 to 90 mcg I2/kg body weight iodine or placebo over a period of 6 months showed that 65% of the women receiving iodine supplementation reported a reduction in pain compared to the placebo group (9). A further randomized, double-blind, placebo-controlled clinical trial involving111 women aged 18–50 years with fibrosis and a history of breast pain showed a significant reduction in breast pain tenderness and the presence of nodules in women receiving doses of 3,000 or 6,000 mcg iodine per day compared to those receiving placebo or 1,500mcg iodine (10).
Cancer- Research has shown that Iodine-deficient individuals have a particularly high risk of developing radiation-induced thyroid cancer when exposed to radioactive iodine. This is because thyroidal uptake of radioactive iodine is higher in people with iodine deficiency than in people with iodine sufficiency. In areas such as Belarus and Ukraine, where many children were mildly iodine-deficient, the incidence of thyroid cancer was shown to sharply increased among children and adolescents (11).
Inflammation- The anti-inflammatory properties of iodine are also supported by research. Supplementation of 100-300μg iodine in a population of otherwise healthy persons without iodine deficiency was shown to exert anti-inflammatory effects (12).
Stress and related symptoms– Iodine contributes to the normal function of the nervous system. Therefore included in the diet and if necessary a supplement, may help support those who are experiencing stress and low mood.
Fatigue and tiredness– Iodine contributes to normal energy-yielding metabolism. This suggests that a deficiency may be a factor in cases of tiredness and fatigue, and so a supplement may help prevent this. This may also be of value to those participating in sports who wish to ensure the correct functioning of their energy metabolism to maximise performance.
Acne, Eczema and Psoriasis- Iodine contributes to the maintenance of normal skin. This makes a supplement potentially useful for skin problems such as acne, eczema and psoriasis, as a deficiency may lead to poor maintenance of normal skin.
Weight management- Iodine contributes to the normal production of thyroid hormones and normal thyroid function. For thyroid related conditions you should always seek the advice of your GP. Iodine deficiency may lead to impaired thyroid function, which in turn can manifest itself as difficulty in losing weight. A supplement may be useful in helping to prevent any deficiency. This may also be of benefit to those participating in sports, where weight maintenance is a goal.
Iodine is considered to be safe for most people when taken at the appropriate dose, higher intakes may cause thyroid problems. Side effects can include digestive upset, runny nose, headaches and metallic taste have also been reported. For those that are sensitive to iodine, symptoms such as swelling of the lips and face can occur, excessive bleeding and bruising, fever, joint pain and enlargement of the lymph nodes can occur.
The Tolerable Upper Intake Level for Iodine is 1100mcg. It is not recommended for adults to take iodine supplements in excess of 1100mcg per day for extended periods of time without medical supervision.