Several types of studies can be used to elucidate various aspects of the effect of food on human health. The main categories are:
• Epidemiological (observational) studies with humans. These can be prospective, where the diet is recorded and health indicators are moni-tored after the first recording, or retrospective, where people who have a disease are identified and it is then investigated if their diet has been different from those who did not get the same disease.
• Intervention studies with animals or humans, where the outcome is differences in indicators of health between groups eating different controlled diets.
• In vitro studies, where specific aspects of the mechanisms of the effects of food or food com-ponents are studied in cell cultures, isolated or-gans or on enzyme activities.
Each type of study is useful for elucidation of certain types or aspects of hypotheses. They also differ in terms of sensitivity (precision) and accuracy (risk of confounding with other influences than the food it-self). A thorough understanding of the effect of a food on human health requires that all three types of stud-ies give corresponding and predictable results
