Nut602 Research Methods in Nutrition and Food Science Intervention Studies PDF

NUT602: Research Methods in Nutrition and Food Science Fall Intervention 2024 Studies  Intervention Studies 2 ▪ Experimental studies ▪ Hypothesis driven ▪ Have a strong evidence basis ▪ Short term ➔ immediate effect of i...

NUT602: Research Methods in Nutrition and Food Science Fall Intervention 2024 Studies  Intervention Studies 2 ▪ Experimental studies ▪ Hypothesis driven ▪ Have a strong evidence basis ▪ Short term ➔ immediate effect of intervention is measured ▪ Long term ➔ effect of intervention is evaluated over weeks, months, years ▪ Pilot studies ▪ Randomized controlled trials ▪ Quasi-experimental studies ▪ Population-based fortification studies Pilot studies 3 ▪ Feasibility or exploratory study ▪ Implemented on a small scale in order to test whether all the study processes operate as anticipated before undertaking a full-scale trial ▪ Provide data on the distribution/variability and timescale of outcome responses ➔ power calculations ▪ May test all, or only some, aspects of a full-scale study ▪ May be single-arm (before and after) studies with no control group ▪ Cost and time-effective to assess potential effects ▪ Data reported in descriptive terms & caution should be exercised when interpreting any statistical tests of significance ▪ Cannot determine the effect of intervention Pilot studies 4 ▪ Inform studies with greater rigor ▪ Randomizing participants to study groups ▪ Increasing the range of populations studied ▪ Using new and/or longer-term outcome measures ▪ Assessing the minimum effective amount (or ‘dose’) to be consumed ▪ Evaluating different forms of presentation or delivery of the nutrient or food… Controlled Studies 5 ▪ Measuring outcomes in participants receiving the active intervention ▪ Measuring outcome in a control group (placebo or no intervention) ▪ Increased confidence that changes observed are directly attributable to the intervention → cause-and-effect statements ▪ Allows seasonal variations to be taken into account ▪ Allows to assess the ‘placebo effect’ can be assessed RCTs: Parallel Design 6 ▪ Each participant receives one intervention ▪ Comparisons between groups made on a between-participant basis RCTs: Cross-over design 7 ▪ Participants receive all interventions under comparison & the design specifies the order of interventions: participants act as their own controls ▪ Comparisons between interventions made on a within-participant basis ▪ Improvement in the precision of comparisons (power of the study) ▪ Reduction in required sample size ▪ A washout period may be required between intervention periods ▪ Avoid contamination or carry-over ▪ A run-in period may be desirable to minimize order effects Parallel or Cross-over design? 8 ▪ Parallel studies ▪ Longer-term interventions ▪ Where a washout period may be ineffective at returning outcome measures to baseline ▪ Where intentionally returning to baseline may be unethical ▪ Cross-over studies ▪ Where participant availability may be restricted and in very short-term studies ▪ Choice of study design depends also on: ▪ Time frame, availability of other resources, and potential roles of confounding factors, such as seasonal variations  Quasi-experimental studies 9 ▪ Similar to RCTs but they lack key features of a true experiment ▪ Random assignment to the intervention or control group is absent ▪ Control group is lacking altogether ▪ Often used in public health (community food-based interventions) ▪ Provide valuable information about potential usefulness of an intervention, but their internal validity will be compromised  Quasi-experimental studies 10 ▪ Before-and-after study without a control group ▪ Data are collected before and after an intervention takes place ▪ No control group for comparison ▪ Impossible to be certain that any differences that have occurred between the start and end of the study are directly attributable to the intervention ▪ Before-and-after study with a non-equivalent groups ▪ One group is assigned to the intervention and another group acts as control group ▪ Groups are not created through random assignment → they may not be similar in all key aspects at the start of the study ▪ May affect the outcome of the study and its internal validity (impossible to conclude that the intervention was causally related to the study outcome)  Population-based fortification studies 11 ▪ Implemented as part of public health policy to correct dietary deficiencies ▪ Require careful planning and consideration of a wide range of background scientific data ▪ Examination of high-quality data on the dietary intake (usual food intake and dietary patterns) and nutritional status of the population ▪ Calculation of the dose and most appropriate form of micronutrient to add Methodological Considerations 12 Ethical approval & study Hypothesis Duration registration Intervention Amount nutrient, food, Control consumed diet Recruitment & Outcome Eligibility participant flow measure  Data Collection 13 Background Background diet & health, lifestyle change in diet status & change Adverse events Compliance  14 Documenting participant flow Unique study number for each participant  Statistical Considerations 15 Randomization Concealment Blinding Analysis Size Per protocol Intention-to-treat Planning a dietary 16 intervention 17 Take-home message 18 Randomized Clinical Trials of Nutritional Interventions – YouTube  Recap 19 Aschengrau, A., Seage, G. R. (2020). Essentials of Epidemiology in Public Health. United States: Jones & Bartlett Learning.