Nutrition Hot Topic - The importance of a grain of salt

Iodised salt is the best salt to use at home.

There is concern that New Zealanders' intake of iodine, an essential nutrient, is falling below the necessary level. Evidence that there is re-occurrence of iodine deficiency in New Zealand is increasing and the Ministry of Health is monitoring the iodine status of children and other groups.

New Zealand soils are low in iodine and in the early years of the 20th Century, goitre (an iodine deficiency disorder) was widespread with many people showing the associated thickened neck. The most damaging effect of iodine deficiency is on the developing brain and iodine deficiency is the world's biggest single cause of preventable brain damage and mental retardation. The term 'cretin' refers to an individual affected by the mother's low iodine status.

In 1924, New Zealand followed Switzerland's example of iodising salt for domestic use. However, more recently the evidence that salt (sodium chloride) contributes to high blood pressure led to the recommendation "eat less salt." Heeding this advice makes it especially important that the small amount of salt used at home is iodised. Salt used in food processing and manufacturing is usually not iodised and eating more pre-prepared foods and meals away from home are thought to have contributed to New Zealanders' declining iodine intake. Also contributing is less use of iodophors as sanitisers in the dairy industry, a practice that boosted the iodine content of milk products. 

All salt is derived from sea water with rock salt being mined from anciently evaporated seas. Rock salt is promoted as having the edge on flavour, but lacks the specific advantage of added iodine. For the New Zealand population, iodised salt provides an example of nature being improved upon. 

The best food sources of iodine are:

  • milk and low fat milk products
  • eggs
  • fish and shellfish, sushi and other foods containing seaweed.

Kelp tablets, concentrated seaweed or other iodine-containing dietary supplements are not recommended as they may increase intake above a safe level.