Exploring the potential of apple (poly)phenols:

A systematic review of randomized controlled trials on metabolic diseases prevention

Publication Date:
2024-03-01

Institutions involved:

Department of Food Science and Nutrition, University of Shizuoka, Japan
Faculty of Agriculture, Shinshu University, Japan
Department of Food and Nutritional Sciences, University of Shizuoka
Institute of Nutrition and Functional Foods (INAF), Université Laval, Canada

Participants:
The authors reviewed RCTs involving adult humans with metabolic risk factors or diagnosed metabolic disorders.

Duration:
Included trials had an intervention duration of at least one week, with most lasting 4–12 weeks.

Dosage:
Effective interventions typically used apple polyphenol doses of ~800 mg/day

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Key Takeaways:

This review highlights the emerging consensus that apple polyphenols are potent modulators of human physiology, and clinically relevant in cardiometabolic health.

30 years of RCTs with apple polyphenols (~800 mg/day) consistently showed improvements in LDL, fasting glucose, insulin sensitivity, and key inflammatory markers.

From the authors: “Apple polyphenols have the potential to serve as safe and effective agents for the prevention or alleviation of metabolic diseases.”

Apple Poly Summary:

Why is this study important? This review synthesizes 30 years of randomized, controlled clinical trials to evaluate whether apple polyphenols can prevent or improve metabolic diseases. It highlights consistent benefits on inflammation, lipid profiles, and glycemic control—positioning apple-derived polyphenols as promising agents in cardiometabolic health strategies.

In Plain English: Scientists looked at many studies where people ate apples or apple extracts to see if it helped with things like cholesterol, blood sugar, and inflammation. They found that eating enough apple polyphenols—about 800 mg a day—can help improve these health markers, especially if done for at least a month.

For Medical Professionals: This systematic review of RCTs (n=unspecified) found that daily intake of ~800 mg apple polyphenols for ≥4 weeks was associated with improvements in LDL-C, CRP, fasting glucose, and insulin sensitivity. Mechanisms include antioxidant activity, modulation of gut microbiota, and improved endothelial function. However, heterogeneity in study design and limited sample sizes warrant cautious interpretation.

Abstract:

Background:
Emerging evidence underscores the significance of fruits and vegetables in ameliorating metabolic disorders. However, a comprehensive understanding of the specific role of apple (poly)phenols, a major component of apples, in preventing and treating metabolic diseases remains to be fully elucidated.

Scope and approach:
This study aimed to conduct a systematic review of Randomized Controlled Trials (RCTs) investigating the therapeutic potential of apple (poly)phenols in the context of metabolic diseases among adults. It also focused on the analysis of recent findings suggesting that polyphenol consumption may modulate gut microbiota composition and thereby impart protection against metabolic disorders. Guided by the preferred reporting items for systematic reviews and meta-analyses (PRISMA) 2020 guideline, we carried out an exhaustive search of the literature within PubMed, Medline, Cochrane, and Web of Science databases, encompassing English-language publications spanning 30 years, until December 31, 2022. Eligible studies were RCTs with an intervention period of over one week, utilizing apple or apple (poly)phenols as the intervention and with primary outcome measures encompassing aspects of metabolic diseases, including plasma lipids, plasma glucose, HbA1c, insulin, gastric inhibitory peptide, C-peptide, systolic and diastolic blood pressure, and C-reactive protein levels.

Key findings and conclusions:
The reviewed literature suggests a protective role of apple (poly)phenols, at an intake of approximately 800 mg/day for 4 weeks or more, against chronic metabolic diseases. Nevertheless, limitations such as the small sample sizes in human studies and the limited number of pertinent studies necessitate further research to substantiate these findings conclusively.

Shoji, Toshihiko, et al. “Exploring the Potential of Apple (Poly)phenols: A Systematic Review of Randomized Controlled Trials on Metabolic Diseases Prevention.” Trends in Food Science & Technology, vol. 144, 2024, p. 104419. Elsevier, https://doi.org/10.1016/j.tifs.2024.104419.