<正>Micronutrient deficiencies(MNDs) result from chronic inadequacy in dietary quality that can adversely affect health,development and survival.Infants,young children and women of reproductive age in poor,undernourished regions of the developing world are at high risk of MNDs.Among deficiencies of known public health consequence are those of vitamin A,zinc, iron and iodine.Vitamin A deficiency,estimated to affect 190 million children,increases risks of childhood blindness,and mortality by compromising host defenses.Zinc deficiency depresses immunity and increases risks of childhood diarrhea,pneumonia and mortality.While widespread,numbers affected remain difficult to estimate.Iron deficiency remains the world’s leading cause of anemia,but needs to be identified from other causes to effectively and safely prevent.Iodine deficiency,by its environmental origin,spans the world’s socio-economic gradients,but is proving difficult to prevent in poor societies.Other vitamin and mineral deficiencies form part of the complex syndrome of undernutrition,but their extent,severity or public health consequences remain largely unknown.Assessment and prevention of individual MNDs have historically been motivated by goals to prevent specific,short-acting(eg, xerophthalmia due to vitamin A deficiency) or longer-acting(eg,goiter due to iodine deficiency) clinical consequences.However,it is increasingly clear that mild-to-moderate micronutrient deficiencies can also exact less-specific,short-term(eg increasing severity infections and mortality risk) and longer-acting(eg,mild impairments in cognition,growth and development) tolls on children and mothers.In particular,fetal,post-natal and early childhood exposures to MNDs may increase risks of chronic disease or disability in undernourished settings,discernable by longitudinal study.Yet,despite their public health importance for enabling full human potential,MNDs remain incompletely understood and quantified in most populations.They represent "hidden hunger" due to inadequate means of assessment,and a historically narrow view toward prevention.Emerging concepts are that there are(a) a potentially large number of nutrient deficiencies relevant to public health,(b) a spectrum of health consequences for each deficiency that depend on life-stage and other co-existing conditions,and(c) geographic and temporal differences in extent and health impact of nutrient deficiencies that should be considered in prevention.These concepts are motivating development of simpler methods to assess more MNDs,a wider range of complementary interventions(eg,supplementation, fortification,dietary diversification and biofortification),and a realized need for evidence-based approaches that can assure their sustained,effective,equitable and safe prevention.