A lack of iron lowers children's IQ by an average five to seven points, the study said. A deficiency in iodine cuts it another 13 points, said Venkatesh Mannar, president of the Micronutrient Initiative, which produced the report along with U.N. children's fund. Birth defects increase when mothers don't get enough folic acid, and a shortage of vitamin A makes children 25 to 30 percent more likely to die of disease.