Nutrition Research Overview

1. Nutrition Research Overview • Nutrition Research • Primary vs. Secondary Sources • 7 Steps of the Scientific Method • 2 Main Types of Research Design • Observational • Experimental • One Study Doesn’t Prove a Finding

2. Primary vs Secondary Sources • Secondary Sources: • Scientific magazines based on primary source • Science writing in newspaper, magazine, TV news, internet, etc. • Position papers or commentary in peer-reviewed journals • Primary Sources: • Original Research • Usually published in peer-reviewed journals • As scientific information gets interpreted by others, less detail is provided and more opinion and sensationalism is introduced

4. Scientific Method • Process of gaining scientific knowledge through the observation of measurable evidence. • Steps used by scientists to explain observations.

5. Scientific Steps: • Question or observation • Purpose of study or hypothesis (testable statement) • Design: • 2 main types: observational & experimental • Implement the research design • Collect & analyze data • Interpret results • State results or accept/reject hypothesis

6. Scientific Step: Design • Base design on whether study is determining correlation or cause & effect • Correlation (Association): When a change in one variable is RELATED to a change in another variable. • Cause and Effect: When a change in one variable CAUSES a change in another variable • 2 Main Types of Research Design • Observational • Epidemiological, Retrospective, Prospective • Experimental • Intervention, Clinical Trial

7. Observational Study • Scientists do NOT ask people to change their behaviors or undergo any treatment. • Data collected by recording observations & data • Minimal risk to participants • Suggests correlation (association), NOT cause & effect • Risk factors: conditions that increase the likelihood that a particular disease or condition will develop. • 2 Types of Observational Studies • Prospective study • Retrospective study

8. Prospective Study • Pro-spective – looking ahead • “What will happen to me”? • Also called “cohort” study (study a group) • Follow a group of healthy people with different levels of exposure and observe effects on health or disease. • Disadvantages: expensive, time-consuming, may lose subjects • Advantages: ethical • Framingham Study • Began in 1948 to determine relationship between diet, lifestyle and heart disease. • Nurses Health Study • Following cohort of nurses over 25 years with regular questionnaires.

9. Prospective study

10. Retrospective Study • Retrospective (looking back) • “why me” study • Also called a “case-control” study • Investigates prior exposure of individuals with particular condition and those without it to understand why the “cases” became ill and the “controls” did not. • Advantages: quick, cost-effective and no loss of subjects • Disadvantages: potential for bias

11. Retrospective study

12. Experimental Study • Researchers intervene -some exposed to “treatment”, others in control group (no treatment) • Random assignment • The subjects have an equal chance to be in experimental or control groups • Factors that may affect the outcome are distributed equally among groups • Single-blind: • Participants in control group are given a placebo • The subjects do not know who receives treatment but researchers do know • Some bias may occur: researcher may treat subjects differently

13. Experimental Study, cont. • Double Blind • Neither the researcher nor subjects knows whether treatment or placebo is given • A member of research team holds code for group assignments and does not participate in data collection • Laboratory (animal) and Clinical Trial (people) • “Gold Standard” clinical trials that are randomized and double blind • Suggests cause & effect - if differences found between groups at end of study - treatment caused the effect

14. Observation vs Experimental

15. Starvation Study • The Purpose: • Gain insight into the physical & psychological effects of starvation • Determine how to rehabilitate people who are starving from the food shortage during WWII in Europe. • The study can last no longer than 1 year. • What kind of study design would you use; Observational or Experimental? WHY? • How would you find participants? Are they randomly assigned to groups?

16. Scientific Steps: • Question or Observation • Purpose or Hypothesis (testable statement) • Design: • Develop a plan to test the hypothesis • 2 main types: observational & experimental • Implement the research design • Collect & analyze data • Interpret results • State results or accept/reject hypothesis

17. Scientific Steps: Implement, Analyze, Interpretation • Data collected on each participant • Analyze data to see if the difference between “Group A and Group B” is “statistically significant” • Statistical significance • The difference between groups did not happen by chance.

18. Scientific Step: State results or accept/reject hypothesis • If there is a “significant difference”, then results show a correlation or cause and effect • Findings submitted to boards of scientists for review. If conclusions are accurate, study results are published in a scientific journal. • One study doesn’t prove a finding. Findings need to be repeated in several kinds of experiments, by different researchers. • News media may report new findings before confirmed by other research.