Hamer DH, Semp?rtegui F, Estrella B, Tucker KL, Rodr?guez A, Egas J, Dallal GE, Selhub J, Griffiths JK, Meydani SN. Micronutrient deficiencies are associated with impaired immune response and higher burden of respiratory infections in elderly Ecuadorians. J Nutr. 2009 Jan; 139(1):113-9.