RAWALPINDI, Pakistan

Travelers to Africa and Asia all have their favorite forms of foreign aid to “make a difference.” One of mine is a miracle substance that is cheap and actually makes people smarter.

Unfortunately, it has one appalling side effect. No, it doesn’t make you sterile, but it is just about the least sexy substance in the world. Indeed, because it’s so numbingly boring, few people pay attention to it or invest in it. (Or dare write about it!)

It’s iodized salt.

Almost one-third of the world’s people don’t get enough iodine from food and water. The result in extreme cases is large goiters that swell their necks, or other obvious impairments such as dwarfism or cretinism. But far more common is mental slowness.

When a pregnant woman doesn’t have enough iodine in her body, her child may suffer irreversible brain damage and could have an I.Q. that is 10 to 15 points lower than it would otherwise be. An educated guess is that iodine deficiency results in a needless loss of more than 1 billion I.Q. points around the world.