Almost everyone in the world consumes salt, regardless of culture, religion or socioeconomic status

Venkatash Mannar, Micronutrient Initiative

The deficiency can lower a child's IQ by between 10 and 15 points, which, if repeated across large swathes of the population, can severely hamper the economic development of nations.

However, the introduction and widespread use of salt containing iodine in recent decades has dramatically cut the numbers of babies born this way.

The percentage of households in developing countries using iodised salt has risen from one in five in 1990 to 70% this year.

It is estimated that 91m newborns around the world are protected from iodine deficiency by iodised salt.

At the United Nations General Assembly on Children in New York, a new body was launched to almost completely eliminate the problem by 2005.

Werner Schultink of Unicef said: "From start to finish, the global effort to eliminate iodine deficiency by universal salt iodisation will have taken only 15 years to achieve, making it one of the most effective international public health campaigns in history."

Improvements

Some countries in particular have substantially increased the use of iodised salt.

China has moved from 50% use to more than 95%.

However, in parts of central and Eastern Europe, only approximately a quarter of households use iodised salt.

Venkatesh Mannar, President of the Micronutrient Initiative, said: "Almost everyone in the world consumes salt, regardless of culture, religion or socioeconomic status.

"The combination of its universal use and the relative ease of fortifying it make salt an excellent vehicle for providing essential nutrients to large populations."