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Tè verde: effetti antiossidanti sul colesterolo LDL
Hirano-Ohmori R, Takahashi R, Momiyama Y, Taniguchi H, Yonemura A, Tamai S,
Umegaki K, Nakamura H, Kondo K, Ohsuzu F
J Am Coll Nutr. 2005 Oct;24 (5):342-6
Il tè verde, grazie soprattutto al contenuto in polifenoli, viene comunemente accreditato di proprietà antiossidanti e in generale di benefici effetti sulla salute. In questo studio è stata studiata la capacità del tè verde di inibire in vivo l’ossidazione delle LDL, meccanismo coinvolto nell’aterogenesi, attraverso la misurazione delle concentrazioni di MDA-LDL, un prodotto dell’ossidazione delle LDL stesse, nelle urine di 22 maschi sani non fumatori. I soggetti hanno assunto per 2 settimane 7 tazze al giorno di tè verde e hanno mostrato una riduzione significativa dei livelli di MDA-LDL. I risultati suggeriscono che il consumo di alte dosi di tè verde potrebbe inibire l’ossidazione delle LDL in vivo.
Green tea consumption and serum malondialdehyde-modified LDL concentrations in healthy subjects
OBJECTIVE: Green tea was shown to inhibit LDL oxidation, platelet aggregation, and matrix metalloproteinases (MMPs) activities in vitro. We tried to elucidate whether or not green tea consumption may have these effects in vivo, which may be protective against atherosclerotic disease. METHODS: We measured serum malondialdehyde-modified LDL (MDA-LDL) concentrations and urine 8-epi-prostaglandin (PG) F(2alpha) in 22 healthy male nonsmokers. They drank 7 cups/day of water for 2 weeks and drank 7 cups/day of green tea for the next 2 weeks. Regarding platelet aggregation, plasma thromboxane B(2) (TXB(2)) and 6-keto-PGF(1alpha) concentrations and ex vivo platelet aggregation were evaluated. Plasma MMP-2 and -9 concentrations were also measured. RESULTS: Of the 22 subjects, 20 had been in the habit of drinking green tea before the study. Plasma catechins concentrations significantly decreased at the end of the water period and then increased at the end of the green tea period. Although no change in plasma LDL-cholesterol concentrations (110 +/- 33 vs. 113 +/- 28 mg/dL, p = NS) was found, MDA-LDL concentrations (84 +/- 45 vs. 76 +/- 40 IU/L, p < 0.05) and the ratio of MDA-LDL/LDL-cholesterol (0.74 +/- 0.21 vs. 0.65 +/-
0.20, p < 0.02) significantly decreased at the end of the green tea period. However, no significant changes were observed in urine 8-epi-PGF(2alpha) concentrations, in platelet aggregation, nor in plasma TXB(2), 6-keto-PGF(1alpha) or MMP concentrations. CONCLUSION: Daily consumption of green tea decreased serum MDA-LDL concentrations, but it had no significant effects on platelet aggregation, platelet TX production or plasma MMPs concentrations. Our results suggest that green tea consumption may inhibit LDL oxidation in vivo.
