Micronutrient deficiency conditions are widespread among 2 billion people in developing and in developed countries. These are silent epidemics of vitamin and mineral deficiencies affecting people of all genders and ages, as well as certain risk groups. They not only cause specific diseases, but they act as exacerbating factors in infectious and chronic diseases, greatly impacting morbidity, mortality, and quality of life. Deficiencies in some groups of people at special risk require supplementation, but the most effective way to meet community health needs safely is by population based approaches involving food fortification. These complementary methods, along with food security, education, and monitoring, are challenges for public health and for clinical medicine. Micronutrient deficiency conditions relate to many chronic diseases, such as osteoporosis osteomalacia, thyroid deficiency colorectal cancer and cardiovascular diseases. Fortification has a nearly century long record of success and safety, proven effective for prevention of specific diseases, including birth defects. They increase the severity of infectious diseases, such as measles, HIV/AIDS and tuberculosis. Understanding the pathophysiology and epidemiology of micronutrient deficiencies, and implementing successful methods of prevention, both play a key part in the New Public Health as discussed in this section, citing the examples of folic acid, vitamin B12, and vitamin D.