GHM summative practice

Portions of Fruits and Vegetables Recommendation & Rationale

The recommended intake of fruits and vegetables varies based on guidelines from different health organizations, but generally:

• The World Health Organization (WHO) recommends at least 400g/day (5 portions of 80g each) to reduce the risk of non-communicable diseases (NCDs) such as heart disease, stroke, and cancer.

• Higher intakes (e.g., 800g/day or 10 portions) are associated with even lower risks of premature mortality and cardiovascular diseases (Aune et al., 2017).

Number of Cohort Studies

• The meta-analysis by Aune et al. (2017) included 95 cohort studies evaluating fruit and vegetable consumption and health outcomes.

What is I² (I-squared)?

• I² is a statistical measure of heterogeneity in meta-analyses.

• It quantifies the percentage of variation across studies due to heterogeneity rather than chance.

• I² values interpretation:

  • 0-25%: Low heterogeneity

  • 25-50%: Moderate heterogeneity

  • 50-75%: Substantial heterogeneity

  • >75%: Considerable heterogeneity

What is a Systematic Review?

• A systematic review is a research method that collects, evaluates, and synthesizes evidence from multiple studies on a specific topic.

• It follows a structured and reproducible methodology to minimize bias.

What is Relative Risk (RR)?

• Relative Risk (RR) is a measure of association between exposure and outcome in cohort studies.

• It compares the risk of an event (e.g., mortality) between an exposed and unexposed group.

• Formula:

  RR=Risk in exposed groupRisk in unexposed groupRR=Risk in unexposed groupRisk in exposed group​

  • RR > 1: Increased risk in exposed group

  • RR = 1: No difference in risk

  • RR < 1: Reduced risk in exposed group

WHO Recommendation for Fruit and Vegetable Intake

• The WHO recommends consuming at least 400g/day (5 portions) to reduce risks of NCDs.

Components in Fruits & Vegetables That Decrease Premature Mortality

• Fiber: Improves gut health, lowers cholesterol, and reduces CVD risk.

• Antioxidants (Vitamin C, polyphenols, flavonoids, carotenoids): Reduce oxidative stress and inflammation.

• Potassium: Helps regulate blood pressure.

What is a Prospective Cohort Study?

• A longitudinal study where participants are followed over time to examine the relationship between an exposure(e.g., fruit intake) and an outcome (e.g., stroke or mortality).

• Reduces recall bias since exposure is recorded before outcomes occur.

Why is Strawberry “Bad” for You?

• There is limited evidence suggesting strawberries have significant health benefits.

• Some studies indicate lower effects on CVD risk reduction compared to other berries (e.g., blueberries).

• Strawberries contain pesticide residues, which may have health concerns.

• However, the number of studies on strawberries is small, so findings are not conclusive.

Fruit with the Least Beneficial Effect on Stroke?

• Tinned fruits (canned fruits)

• Some studies suggest an increased risk of mortality due to added sugars and preservatives.

Fraction of All-Cause Mortality Globally Attributable to Low Fruit & Vegetable Intake?

• 11.3% of global mortality is attributed to low fruit and vegetable intake (Aune et al., 2017).

Beneficial Effect of Dried Fruits

• Dried fruits contain high concentrations of fiber, polyphenols, and antioxidants.

• Studies show they reduce the risk of CVD and metabolic diseases (Ellis et al., 2022).

• They have low glycemic index, despite high sugar content.

Do Fruits or Vegetables Have a Greater Beneficial Effect on Stroke?

• Vegetables have a greater protective effect against stroke than fruits.

• Leafy green vegetables (e.g., spinach, kale) are especially beneficial due to high nitrate content (Aune et al., 2017).

What Is NOT an Advantage of Meta-Analysis?

• Publication Bias: Meta-analyses may overestimate effects if only positive results are published.

• Heterogeneity: Studies may differ in methods, populations, and measurements, making comparisons difficult.

• Quality Dependence: A meta-analysis cannot fix the limitations of individual studies; poor-quality studies can still influence results.