Summary
Researchers explored how polyphenol-rich fruit juices affect antioxidant status, immune function, and DNA integrity in healthy men following a low-polyphenol diet. In this randomized crossover study, participants consumed 330 mL per day of two different polyphenol-rich juices—one high in cyanidin glycosides and the other in epigallocatechin gallate—for two weeks each. Despite the substantial polyphenol content, fasting plasma polyphenol levels did not rise, suggesting rapid metabolism or clearance. Even so, both juices produced meaningful physiological benefits: plasma malondialdehyde, a marker of lipid peroxidation, steadily declined; lymphocyte proliferation and natural killer cell activity increased; and interleukin-2 secretion from activated lymphocytes improved. While the juices did not affect baseline DNA strand breaks, they significantly reduced oxidative DNA damage in lymphocytes, with a notable delay between consumption and measurable improvement. Overall, the study shows that regular intake of these polyphenol-rich juices enhances antioxidant defenses, boosts immune responsiveness, and protects DNA from oxidative injury, even without detectable increases in circulating polyphenols after overnight fasting.
PMID: 12667600
DOI: 10.1016/s0955-2863(02)00255-3
Abstract
Polyphenolic compounds exert a variety of physiological effects in vitro including antioxidative, immunomodulatory and antigenotoxic effects. In a randomized crossover study in healthy men on a low-polyphenol diet, we determined the effects of 2 polyphenol-rich juices (330 ml/d) supplemented for 2 weeks on bioavailability of polyphenols, markers of antioxidative and immune status, and reduction of DNA damage. Juices provided 236 mg (A) and 226 mg (B) polyphenols with cyanidin glycosides (A) and epigallocatechin gallate (B) as major polyphenolic ingredients. There was no accumulation of plasma polyphenols after two weeks of juice supplementation. In contrast, plasma malondialdehyde decreased with time during juice interventions. Moreover, juice consumption also increased lymphocyte proliferative responsiveness, with no difference between the two juices. Interleukin-2 secretion by activated lymphocytes and the lytic activity of natural killer cells were significantly increased by both juices. Juice intervention had no effect on single DNA strand breaks, but significantly reduced oxidative DNA damage in lymphocytes. A time-delay was observed between the intake of fruit juice and the reduction of oxidative DNA damage and the increase in interleukin-2 secretion. We conclude that consumption of either juice enhanced antioxidant status, reduced oxidative DNA damage and stimulated immune cell functions. However, fruit juice consumption for 2 weeks did not result in elevated plasma polyphenols in subjects after overnight fasting. Further studies should focus on the time-delay between juice intake and changes in measured physiological functions, as well as on active polyphenolic metabolites mediating the observed effects.
Bub A, Watzl B, Blockhaus M, Briviba K, Liegibel U, Müller H, Pool-Zobel BL, Rechkemmer G. Fruit juice consumption modulates antioxidative status, immune status and DNA damage. J Nutr Biochem. 2003 Feb;14(2):90-8. doi: 10.1016/s0955-2863(02)00255-3. PMID: 12667600.