Our subject for today is table salt, or more specifically, iodised table salt. We are commemorating the work of David Marine, an American pathologist who died on this day back in 1976.

Marine did research on the treatment of goiter (swelling of the thyroid gland in the neck) with iodine. Between 1917 and 1922 he ran medical trials on a large sample of school girls, showing that iodine supplementation significantly reduced the incidence of goiter. Recognising the potential health benefits of iodine supplementation, Marine worked on the World Health Organisation’s salt iodisation programme.

Adding trace amounts of various iodine salts to regular table salt is an easy and effective way of preventing iodine deficiency in people. Worldwide, iodine deficiency is said to affect almost 2 billion people, causing mental retardation and various thyroid problems including goiter. While people in some regions, for example near the coast, can potentially get enough iodine from their general diet, the majority of the world has low natural iodine levels, resulting in the need for artificial supplementation.

Over the years there has been some opposition to iodisation of salt, mainly from fringe groups such as small salt producers concerned about the added production expense, manufacturers of iodine supplements who are obviously at risk of losing their market, and health groups concerned that the promotion of iodised salt will lead to excessive salt intake. Of course there will always be lobbies (rightly) promoting foods and food products that are as ‘natural’ and ‘pure’ as possible, and who would prefer to rather get their iodine in some more natural way. For this reason, most countries allow both iodised and non-iodised salt to be sold to consumers.

While the iodisation of salt has contributed a great deal to improve global iodine deficiency levels, there are indications in many countries, including new Zealand, of a re-emergence of iodine deficiency. This is due in part to the increased consumption of commercially prepared foods made with cheaper, non-iodised salt, and because of decreased general use of salt (iodised and not) as a response to health programmes recommending reduced salt intake.

Of course using less salt, iodised or not, is a good thing, as we discussed previously. But the key message from most health bodies, in terms of iodine intake, is to opt for iodised salt when we do use salt, and to generally give preference to freshly prepared, non-processed foods. Non-vegetarians can boost their iodine intake with iodine rich foodsources like seafood, milk, eggs and meat, but vegetarians may well consider an iodine supplement.

Just remember that the iodine in iodised salt disappears over time due to evaporation and oxidation, so even when you do use iodised salt, that bag of salt that’s been sitting in the cupboard for years may not be of much use as an iodine supplement anymore.