The fortification of salt with iodine is a global success story: with two out of three households in the developing world now consuming iodized salt, an estimated 82 million children are protected from thyroid disease and resultant learning disabilities every year. Still, people suffer from a lack of other micronutrients.
For years, food scientists have looked for a way to fortify iodized salt to combat iron-deficiency anemia, which affects some two billion people, as well as vitamin A deficiency, which afflicts at least 100 million children in poor countries and is the leading cause of blindness among them. Canadian researchers have now developed a practical way to double- and triple-fortify salt, which might also be more acceptable to people than genetically modified foods in tackling malnutrition.
Adding iron to iodized salt is a simple idea that has proved difficult to execute. The chemicals are incompatible: when mixed together, iodine vaporizes and iron degrades. After more than a decade, Levente Diosady, a chemical engineer at the University of Toronto, finally solved the problem by borrowing a technique from the food industry referred to as microencapsulation. The process involves spraying iron particles with stearine, a vegetable fat, which creates a protective coat and prevents the iron from reacting with the iodine.
Encapsulating the iron, however, was only part of the solution. Diosady’s team also had to change the appearance of the iron particles—which are dark brown and much smaller than salt grains. “The iron can’t look like mice droppings in the salt,” Diosady says. “This is important in developing countries where food contamination is a problem.”
So to make the iron resemble salt, Diosady first sprays the microscopic iron granules with maltodextrin, a modified food starch that acts like a glue to bind the iron particles together until they form spheres about the size of salt crystals. He then spray-coats the iron clusters with hot vegetable fat containing food-grade titanium dioxide, a whitening pigment. When mixed with iodized salt, the modified iron capsules are nearly imperceptible. Vitamin A can also be added using a similar method to create triple-fortified salt.
Field tests in Nigeria and Kenya showed that the double- and triple-fortified salts are stable in humid and hot climates and acceptable to the locals. The Micronutrient Initiative, an Ottawa-based nongovernmental organization, tested iron-enriched salt in Ghana, where in eight months the number of anemic children dropped by 23 percent without any other iron supplementation. The technology has been scaled up in two large plants in India, and the initiative is currently leading a study with 3.6 million schoolchildren.
Salt is an ideal vehicle for providing micronutrients, Diosady notes, because almost everyone consumes it and it is relatively inexpensive to fortify—about 1.7 cents per kilogram of salt for double-fortified salt. “Even the poorest of the poor have to barter or buy salt. There’s no person in the world so poor that they have to make their own salt,” he says. Also, the amount of salt eaten in a given population is about the same, making dosage easier to control. People might also accept fortified salt more readily than genetically modified foods such as Golden Rice, which contains beta-carotene, a precursor to vitamin A. The rice has yet to be introduced into developing countries amid fears about its safety and concerns that the crops may not have high enough concentrations of micronutrients.
But fortified salt cannot supply all the critical nutrients. For instance, vitamin C is needed in such large quantities that it would end up carrying the salt, not the other way around. And because, on average, the daily intake of salt is 10 grams, the fortified version could only supplement a person’s nutritional requirements, not supply all of them.