Abstract
Pure fruit juices provide nutritional value with evidence suggesting some of their benefits on biomarkers of cardiovascular disease risk may be derived from their constituent polyphenols, particularly flavonoids. However, few data from clinical trials are available on the dose-response relationship of fruit juice flavonoids to these outcomes. Utilizing the results of clinical trials testing single doses, we have analyzed data from studies of 100% Concord grape juice by placing its flavonoid content in the context of results from randomized clinical trials of other polyphenol-rich foods and beverages describing the same outcomes but covering a broader range of intake. We selected established biomarkers determined by similar methods for measuring flow-mediated vasodilation (FMD), blood pressure, platelet aggregation, and the resistance of low density lipoprotein cholesterol (LDL) to oxidation. Despite differences among the clinical trials in the treatment, subjects, and duration, correlations were observed between the dose and FMD. Inverse dose-response relationships, albeit with lower correlation coefficients, were also noted for the other outcomes. These results suggest a clear relationship between consumption of even modest serving sizes of Concord grape juice, flavonoid intake, and effects on risk factors for cardiovascular disease. This approach to dose-response relationships may prove useful for testing other individual foods and beverages.
Highlights
The consumption of 100% fruit juice is positively associated with improved diet quality in children and adults [1] and with essential nutrient adequacy in children, and can contribute to a healthy diet [2]
In addition to its phenolic constituents, it is worthwhile noting that some 100% grape juices may be fortified with vitamin C which has been shown to act in synergy with flavonoids to increase the resistance of low density lipoprotein cholesterol (LDL) to oxidation and may contribute to some of the outcomes achieved in clinical studies [17]
We plotted the relative change in flow-mediated vasodilation (FMD) versus daily polyphenol dose from 16 chronic studies of other beverages and foods and from 4 studies of purple grape juice
Summary
The consumption of 100% fruit juice is positively associated with improved diet quality in children and adults [1] and with essential nutrient adequacy in children, and can contribute to a healthy diet [2]. Absent a framework like the Dietary Reference Intakes for essential nutrients, Lupton et al [4] have recently described an evaluative process for substantiating the relationship between dietary bioactive components such as the polyphenols and enhanced health outcomes or reduced risk of chronic disease. Criteria defined for this process include validated methods of analysis of the bioactives, databases quantifying the presence of these compounds in diets, human studies characterizing their pharmacokinetic profiles, and a biological plausibility for their efficacy in promoting health. There is an opportunity to explore the available data from these research studies to learn more about the effect of a specific food, here 100% Concord grape juice, and extract information useful for generating dose-response data applicable to elucidating information about serving sizes effective for health outcomes
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