Flavonoid-Rich Apples Improve Endothelial Function in Individuals at Risk for Cardiovascular Disease
Identifier: 38792149-Bondonno
Study Type: Randomized Controlled Cross-Over Trial (2017)
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## Abstract
The cardioprotective effects of apples are primarily attributed to flavonoids, found predominantly in the skin. This study aimed to determine whether acute and/or chronic (4 weeks) ingestion of flavonoid-rich apples improves endothelial function, blood pressure, and arterial stiffness in individuals at risk for cardiovascular disease (CVD). In this randomized, controlled cross-over trial, 30 participants consumed either a high-flavonoid apple (with skin) or a low-flavonoid apple (flesh only). The primary outcome was endothelial function measured by flow-mediated dilation (FMD). Compared to the low-flavonoid control, the high-flavonoid apple significantly increased FMD both acutely (0.8%, p<0.001) and after 4 weeks (0.5%, p<0.001), alongside increases in plasma flavonoid metabolites. Other outcomes were not significantly altered. The authors conclude that the lower risk of CVD associated with higher apple consumption may be mediated by the beneficial effects of apple-skin flavonoids on endothelial function.
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## Key Findings
### 1. Study Design
- Randomized, controlled, cross-over trial.
- 30 adults at risk for cardiovascular disease.
- Compared high-flavonoid apples (with skin) vs. low-flavonoid apples (flesh only).
- Acute and 4‑week chronic phases.
### 2. Primary Outcome: Endothelial Function (FMD)
- High-flavonoid apples significantly improved FMD:
- Acute: +0.8% (p<0.001)
- Chronic (4 weeks): +0.5% (p<0.001)
- Indicates improved nitric‑oxide–mediated vascular responsiveness.
### 3. Plasma Flavonoid Metabolites
- Significant increases in circulating flavonoid metabolites after high-flavonoid apple intake (p<0.0001).
- Confirms systemic absorption of apple-skin polyphenols.
### 4. Blood Pressure and Arterial Stiffness
- No significant changes in 24‑hour ambulatory blood pressure.
- No significant changes in arterial stiffness indices.
### 5. Additional Biomarkers
No significant changes in:
- Fasting glucose
- Lipoprotein profile
- Hmox‑1
- F2‑isoprostanes
- Plasma/salivary nitrate or nitrite
### 6. Interpretation
- The primary cardiovascular benefit observed was improved endothelial function.
- Effects were driven specifically by apple-skin flavonoids, not apple flesh.
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## Mechanisms of Action
### Nitric Oxide–Mediated Vasodilation
Flavonoids enhance endothelial nitric oxide (NO) bioavailability, improving FMD.
### Antioxidant Activity
Apple-skin polyphenols reduce oxidative stress, protecting endothelial cells from ROS-mediated dysfunction.
### Improved Vascular Responsiveness
Enhanced endothelial signaling supports healthier vascular tone regulation.
### Polyphenol Bioavailability
Increased plasma flavonoid metabolites confirm systemic uptake of active compounds.
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## Relevance to Apple Poly Products
### Apple Poly
This study directly supports the cardiovascular relevance of apple-derived polyphenols. Apple Poly contains concentrated apple-skin flavonoids—the same class of compounds shown here to improve endothelial function both acutely and chronically. The observed increases in plasma flavonoid metabolites and improved FMD align with the polyphenol-driven vascular support provided by Apple Poly.
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## Conclusion
This randomized controlled trial demonstrates that flavonoid-rich apples—specifically those containing the skin—significantly improve endothelial function in individuals at risk for cardiovascular disease. The benefits occur both acutely and after 4 weeks of daily intake and are accompanied by increases in plasma flavonoid metabolites. These findings support the role of apple-skin polyphenols in vascular health and provide mechanistic insight into the cardioprotective associations observed in epidemiological studies.
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## Reference
Bondonno NP, et al. Flavonoid-rich apples improve endothelial function in individuals at risk for cardiovascular disease. Mol Nutr Food Res. 2017.
