Basic medicine pursues studies of the universal biological phenomenon of life on cellular, molecular and genetic levels and clinical medicine bases its focus on the process of the disease and its results in an individual .
Epidemiology focuses on human groups, individuals and ecosystems .
Instead of the effects or results of disease, epidemiology examines origins and causes of diseases and association to disease prevention. Nutritional characteristics of an individual, a component of the population under study, are comprehensively assessed by dietary intake, physical activity, anthropometry, biochemical compo- nents in urine and blood specimens and immunological examinations. The occurrence of stroke, ischemic heart disease and cancer in the cohorts is determined using both active surveillance and registry . In the determination of nutritional etiology, findings from ecological studies lead to the formation of a hypothesis. The hypothesis is then tested in sequence by case control studies and cohort studies.