Tier 2 — strong

Effect of fruit juice intake on urinary quercetin excretion and biomarkers of antioxidative status

J F Young, S E Nielsen, J Haraldsdóttir, B Daneshvar, S T Lauridsen, P Knuthsen, A Crozier, B Sandström, L O Dragsted
The American journal of clinical nutrition 1999 69(1):87-94

Bibliography

PubMed
PMID 9925128
DOI
10.1093/ajcn/69.1.87
Funding
Funding was not specified in the indexed record or the disclosure metadata available for this entry.
Competing interests
A competing-interest declaration was not available in the indexed record or the disclosure metadata used for this entry.

Study snapshot

DesignCrossover juice dose-response study
ModelHuman intervention research
Sample5 healthy volunteers
InterventionBlackcurrant and apple juice 750, 1,000, or 1,500 mL/day
Duration1 week per juice dose
EndpointsOxidative-stress measures; Exposure and pharmacokinetics

What the study showed, in plain terms

Published in 1999, this source examined forms, absorption and food sources. Design: Crossover juice dose-response study. Sample/model: 5 healthy volunteers. The exposure or intervention was Blackcurrant and apple juice 750, 1,000, or 1,500 mL/day. Follow-up or treatment period: 1 week per juice dose.

Urinary quercetin increased, while oxidative-stress measures showed mixed directions, including increased protein oxidation.

Very small whole-juice study with several active nutrients. Neither antioxidant benefit nor prooxidant effects can be assigned specifically to quercetin.

Continue with Quercetin Data Center

For topic-level interpretation, read Quercetin Forms: Dihydrate, Phytosome, Liposomal and Glycosides. This is a related guide; the citation panel separately identifies articles that directly cite this paper.

Key findings

  • Urinary quercetin increased, while oxidative-stress measures showed mixed directions, including increased protein oxidation.
  • The recorded outcome domains were Oxidative-stress measures; Exposure and pharmacokinetics.
  • The result applies to the tested exposure: Blackcurrant and apple juice 750, 1,000, or 1,500 mL/day; 1 week per juice dose.

What this study can and cannot tell us

  • Very small whole-juice study with several active nutrients. Neither antioxidant benefit nor prooxidant effects can be assigned specifically to quercetin.
  • An individual controlled trial must be interpreted alongside its comparator, sample size, endpoint selection and independent replication. It does not validate a different commercial formulation or a general longevity claim.
  • Source basis: Source check: PubMed abstract and indexed metadata; full methods were not independently confirmed for this entry. Missing method details, funding information or participant denominators are not inferred.

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Editorial review

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Dr. Khaled Mahmoud, MBBChCritical Care Medicine, Longevity Science & Editorial Direction Dr. Amr Yasser, PhDCardiometabolic, Musculoskeletal, Gut & Bioavailability Dr. Abdulla Mostafa, PhDCellular Senescence, Neurological, Mitochondrial & Brain-Ageing Biology