Double credit: iron-fortified salt cuts anemia.

A form of table salt manufactured to contain iron can fight off anemia among children, nutrition researchers working in North Africa have shown. That advance could expand the role of salt fortification, already an important global tool against iodine deficiency.

Scientists have long considered salt to be an ideal vehicle for delivering nutrients because it's cheap and nearly all people consume it daily. In recent decades, most governments have required iodization of salt, which has reduced the worldwide prevalence of mental retardation from iodine deficiency.

Adding iron to salt has proved a more enduring challenge. One chemical form, ferrous iron, causes reactions that eliminate iodine, turn salt yellow-brown, and sometimes produce a rusty taste. Ferric iron, the other form of the metal, generally lacks those drawbacks, but its particles are too large to be absorbed well by the body.

To improve the bioavailability of ferric iron, Michael B. Zimmermann of the Swiss Federal Institute of Technology in Zurich and his colleagues ground particles of ferric pyrophosphate to a diameter of about 2.5 micrometers. To keep down manufacturing costs, they used a simple, unpatented milling apparatus. They then mixed the particles with iodized salt.

Working in northern Morocco, the researchers gave the doubly fortified salt to 75 children for 10 months. The blood concentration of iron-rich hemoglobin in kids receiving the iron-fortified salt increased by 16 grams per liter, and the prevalence of anemia fell from 30 percent to 5 percent. A similar group of children that received regular iodized salt didn't show any change in hemoglobin concentration or anemia incidence, the team reports in the October American Journal of Clinical Nutrition.

The results demonstrate that doubly fortified salt could combat anemia and benefit health and economics in poor nations, says food chemist Levente Diosady of the University of Toronto.

An alternative to milling ferric iron is to encapsulate a ferrous compound in digestible shells that prevent changes in salt color or chemistry, Diosady says. He and his colleagues have used that strategy to develop a dual-fortified salt that, with Zimmermann, they are testing in Kenya.

Encapsulating iron raises the cost of the finished product about 4 cents per kilogram, which could nearly double salt's price in some nations, Diosady acknowledges.

Grinding ferric pyrophosphate raises salt's cost by about 3 cents per kg. That's enough to require governments or international groups to subsidize dual-fortified salt if they wish to make it commercially competitive in some places where it's greatly needed to reduce infant mortality and other consequences of anemia, Zimmermann says.