diet, cross sectional studies provide a snapshot of the frequency of disease in a population at a given point in time. Cross-sectional studies offer advantages such as the ability to measure multiple outcomes and exposures and, in the planning, and allocation of health resources as it assesses the burden of disease in a specified population. The measure of the outcome is however heavily reliant on population responses. Non-response results in responder bias and therefore unreliable results. Case control study A case-control study is an observational-individual study that is defined by the outcome (i.e. measures outcomes in the present and past exposure is established). It involves two groups controls and cases (diseased), both which have two treatments; exposed and unexposed. Case-control studies can be used to study diseases that are rare and over long periods of time however are limited to examining one outcome and are also susceptible to the effects of bias if selected control groups are no representative of the population, so give rise to misleading results. Cohort study A cohort study is an observational-individual study that measures exposure in the present over long periods of time and the outcome is determined in the future. Cohort studies allow for multiple outcomes to be measure per one exposure. In nutritional epidemiological studies it is advantageous in measuring outcomes that occur after exposure and can measure both incidence and prevalence. Cohort studies are however costly and time consuming. As outcome is determined in the future, any issues pertaining to the collection of information or confounders cannot be resolved back in time. Clinical and community trails Clinical and community trails are experimental studies that involve active intervention in either individuals (clinical) or populations (community). Clinical trials often involve test and procedures carried on subjects placed in different treatment groups. Clinical trials allow for the evaluation of new therapies, drugs and procedures. Clinical trials however risk subject to experience side effects and inadvertent harm from the intervention therefore should only be considered when supporting evidence is strong. Community trials involve assigning groups of individuals with and without disease to different interventions. This allows for larger scale findings however does not account for individual variability. Social impact The impact nutritional epidemiology had in the past has led to social, physical and economic changes. Nutritional epidemiological findings guide dietary recommendations including the prevention of certain disease and cancers. They play a role in policies on