Iodine deficiency disorder

Posted on 23 October 2013

Endocrinologist and paediatrician Dr David Segal, from the Wits Donald Gordon Medical Centre hospital, answers questions about this essential mineral.

What does iodine do for the human body?
Iodine is an essential mineral required for normal production of thyroid hormone. Adequate amounts of thyroid hormone are essential for early brain development: deficiency of thyroid hormones results in lower IQ scores. In addition, thyroid hormones assist in maintaining a normal metabolic rate within the body.

Is iodine deficiency a third-world problem, or is it prevalent across the world?
Iodine deficiency affects two billion people and not only in third world countries. But third world countries may be at an increased risk because of poorer awareness and education. In addition, there may not be adequate government-initiated programmes to supplement iodine. Even first world countries are seeing an increase in iodine deficiency related to a lower consumption of natural iodine in seafoods and lower fortified iodised salt intake, due to increases in fast food consumption (which has a high salt content but low iodine content) and recommendations of health authorities to limit salt intake.

What can iodine deficiency cause, from mild to extreme cases?
Mild cases may be undetectable: as the deficiency progresses, the thyroid hormone levels drop, leading to a compensatory increase in the thyroid gland. With worsening deficiency, the thyroid will under-function, leading to poor brain development, thyroid enlargement (called a goiter), and symptoms of hypothyroidism (tiredness, lethargy, constipation). In the most severe cases babies and young children can develop cretinism (severe hypothyroidism), mental retardation, deaf-mutism, show nerve damage and stunted growth.

Is it true that iodine deficiencies have been linked to brain and nervous system disorders, like Alzheimer’s?
Iodine deficiencies are well known to cause brain problems, mostly in developing brains, with IQ deficits of 15 or more points possible. There may be some associations between Alzheimer’s and iodine deficiency, but there’s no proven causative link that deficiency causes Alzheimer’s. There are reports of people with Alzheimer’s showing dramatic improvement with iodine supplementation, suggesting that both conditions probably co-exist.

Given that certain raw foods block iodine absorption, and that iodine is found in salt, is there a relationship between dieting and iodine deficiency?
Certain raw foods and calcium can block iodine absorption, while other vegan and vegetarian foods contain very little dietary iodine. Excessive salt intake has been linked to the development and exacerbation of high blood pressure. The fact is that the majority of the ‘bad’ salt comes from processed foods and non-iodised table salt. Iodine supplementation can’t help weight-loss. This myth may have come about because of the weight gain related to the hypothyroid state present with iodine deficiency, which resolves with iodine replacement.

A lack or iodine can lead to stillbirths and miscarriages. But can too much iodine be dangerous for pregnant/nursing women?
It is very difficult to consume too much iodine and the benefits of iodine supplementation far outweigh the risks of iodine excess.

Should we all have out iodine levels tested, and if so, is this something we can do ourselves?
Iodine levels can be tested either on a 24-hour urine collection or a spot urine sample. It may be more appropriate to ensure an adequate supply of iodine than to have one’s levels tested. Pregnant women, vegans and vegetarians, as well as those living in high-lying areas, should ensure an adequate iodine intake.

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Published in Endocrinology

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