IF you have a daughter in secondary school, have her checked out for iron deficiency. Researchers at John Hopkins University School of Medicine have found that iron pills may help teenage girls with mild deficiency to remember more and learn more easily. The girl does not have to be actually anaemic to be affected; low iron stores are enough. It is thought that low iron concentrations in the brain may impair brain functionally decreasing the activity of iron dependent enzymes needed for the synthesis and processing of neurotransmitters, The Lancet reported. Iron deficiency is the most common nutritional disorder, affecting about one in seven teenage girls, and the recent vogue for vegetarianism hasn't helped matters.