Superfoods Research & Evidence-Based Practice 5 — Questions and Answers
Question 1: In a crossover trial comparing chia seeds to flaxseeds for omega-3 status, a 'washout period' between phases is included to:
- Eliminate carryover effects from the first treatment before beginning the second (Correct answer)
- Prevent participants from dropping out
- Allow researchers to analyze interim data
- Satisfy FDA regulatory requirements for food studies
Correct answer: Eliminate carryover effects from the first treatment before beginning the second
A washout period allows any physiological or biochemical changes from the first intervention to return to baseline before participants begin the second, ensuring clean comparisons.
Question 2: The concept of 'nutrigenomics' is most relevant to superfood research because it examines how:
- Individual genetic variation affects responses to dietary bioactive compounds (Correct answer)
- Superfoods can alter DNA structure permanently
- Genomic sequencing can identify new superfood candidates
- Nutrition labels must disclose genetic modification
Correct answer: Individual genetic variation affects responses to dietary bioactive compounds
Nutrigenomics studies interactions between genes and nutrients, explaining why individuals with different SNPs (e.g., in MTHFR or COMT) may respond differently to the same superfood.
Question 3: A study shows that participants who ate kale daily for 8 weeks had significantly lower LDL cholesterol. The study had no control group. The most significant methodological concern is:
- Regression to the mean — participants may have had unusually high LDL at baseline that would improve regardless (Correct answer)
- The study duration was too long for dietary changes
- Kale's cholesterol effect is already scientifically proven
- Blood cholesterol cannot be reliably measured in outpatient settings
Correct answer: Regression to the mean — participants may have had unusually high LDL at baseline that would improve regardless
Without a control group, it is impossible to distinguish the effect of kale from natural fluctuation back toward average values (regression to the mean) or other concurrent lifestyle changes.
Question 4: Which scientific body publishes the Dietary Reference Intakes (DRIs) that researchers use to contextualize superfood nutrient findings in the US?
- National Academies of Sciences, Engineering, and Medicine (Correct answer)
- American Heart Association
- US Food and Drug Administration
- Centers for Disease Control and Prevention
Correct answer: National Academies of Sciences, Engineering, and Medicine
The National Academies of Sciences, Engineering, and Medicine establishes DRIs (including RDAs, AIs, and ULs) through expert panels reviewing the available evidence base.
Question 5: A researcher wants to study the long-term effect of pomegranate juice on cardiovascular disease incidence over 20 years. The most feasible design is:
- Prospective cohort study with dietary assessment at baseline and follow-up (Correct answer)
- Double-blind RCT with pomegranate juice vs. placebo
- N-of-1 trial repeated across many individuals
- Laboratory analysis of pomegranate polyphenol content
Correct answer: Prospective cohort study with dietary assessment at baseline and follow-up
A 20-year RCT with a food is impractical; a prospective cohort can follow large groups naturally over decades, measuring dietary habits and tracking cardiovascular outcomes.
Question 6: When reviewing a meta-analysis on ginger and nausea, a 'funnel plot asymmetry' suggests:
- Possible publication bias — small negative studies may not have been published (Correct answer)
- The studies used different doses of ginger
- The meta-analysis included too few studies
- Ginger has no effect on nausea
Correct answer: Possible publication bias — small negative studies may not have been published
Funnel plot asymmetry often indicates that small studies showing null or negative results were not published, inflating the apparent overall effect in the meta-analysis.
Question 7: A health claim on a US superfood product stating 'may reduce the risk of heart disease' requires, at minimum, which type of regulatory support?
- Significant scientific agreement among qualified experts, as reviewed by the FDA (Correct answer)
- One peer-reviewed study published in any journal
- A patent on the active ingredient
- Approval from the USDA Agricultural Research Service
Correct answer: Significant scientific agreement among qualified experts, as reviewed by the FDA
FDA-authorized health claims (not qualified claims) require substantial scientific agreement; qualified health claims require credible but less definitive evidence and must carry a qualifying disclaimer.
Superfoods Research & Evidence-Based Practice 5
In a crossover trial comparing chia seeds to flaxseeds for omega-3 status, a 'washout period' between phases is included to: