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Recent studies suggest that chlorogenic acids, which are the main components of the polyphenol class in coffee, decrease blood pressure, and that hydroxyhydroquinone (HHQ), which is generated by roasting coffee beans, inhibits the antihypertensive effect of chlorogenic acids in brewed coffee. Here, we examined the vasoreactivity and antihypertensive effects of HHQ-reduced coffee in mild hypertension. The study design was a double blind, randomized, placebo-controlled intervention study, with a 4-week run-in period, followed by an 8-week test beverage ingestion period. The subjects were Japanese men and women with mild hypertension and vascular failure, who were not taking any antihypertensive drugs. During the test beverage ingestion period, the subjects ingested either active or placebo HHQ-reduced coffee (chlorogenic acids per 184 ml of coffee: active, 300 mg; and placebo, 0 mg) daily. Subjects were randomly divided into two groups: active group (n¼9) and placebo group (n¼12). In the active beverage group, endothelium-dependent, flow-mediated vasodilation impairment was significantly ameliorated and systolic blood pressure was significantly decreased from the baseline, but not in the placebo group. There were no test beverage consumption-related changes in other parameters that may influence blood pressure, such as pulse, cardiac output, body weight or 24-h urine volume. Ingestion of the active beverage significantly decreased urinary isoprostane levels, suggesting a reduced oxidative stress. These findings indicate that HHQ-reduced coffee decreased blood pressure in subjects with mild hypertension. The decreased blood pressure was associated with improved vascular endothelial function.

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The long-term ingestion of tea catechins has been reported to reduce body fat. The aim of this study was to investigate the effect of the long-term ingestion of tea catechins on postprandial energy expenditure and dietary fat oxidation. Twelve healthy men aged 27-48 years participated in the study. The subjects consumed 350 ml of a test beverage/day that contained either a high dose of catechin (592.9 mg) or a low dose of catechin (77.7 mg) for a period of 12 weeks. Respiratory analyses were conducted before and at 4, 8, and 12 weeks during the test period, in which oxygen consumption and the excretion of 13 CO 2 were monitored over 8 hr after a single ingestion of a test meal containing 13 C labeled triglyceride. The excretion of 13 CO 2 in the high dose catechin group (the HC group) was significantly increased at 4 and 12 weeks of the test period compared to that for the low dose catechin group (the LC group) (p < 0.05), and this elevation persisted at 8.9% at week 0 to 12.9% at week 12. Dietary induced thermogenesis (DIT), defined as an increased energy expenditure from the fasting baseline for 8 hr after the single ingestion of a test meal, was significantly higher in the HC group at 8 and 12 weeks compared to that in the LC group (p < 0.05) with elevation to 90.3 kcal at week 12 from 51.4 kcal at week 0. In conclusion, enhanced dietary fat oxidation and an increased DIT may play an important role in the mechanism of the anti-obesity effect of tea catechins.

The influence of hydroxyhydroquinone (HHQ) on the antihypertensive effects of chlorogenic acids in coffee was evaluated in a double-blind, randomized controlled trial of high-normotensive and mild hypertensive adult men and women. The subjects were randomly assigned to either an active group that ingested HHQ-reduced coffee (0.05 mg/184 ml) containing chlorogenic acids (299 mg/184 ml) or a control group that ingested coffee containing HHQ (1.69 mg/184 ml) and chlorogenic acids (299 mg/184 ml), corresponding to commercially available products. Each subject was instructed to continuously ingest one can of test beverage (coffee) daily for 12 weeks. A linear mixed-model repeated-measures analysis of covariance of 38 high-normotensives and 60 mild hypertensives showed that systolic blood pressure (SBP) was significantly lower in the active group (n = 51) than in the control group (n = 47) throughout the intake period (Group effect; p = 0.031). A stratified analysis suggested that the antihypertensive effect was greater in the mild hypertensives (Group effect; p = 0.013 in SBP and p = 0.015 in diastolic blood pressure) than in the high-normotensives. Safety assessment revealed no adverse effects associated with the reduction of HHQ to a level lower than the amounts in commercially available coffee products. These results suggest that HHQ-reduced coffee containing chlorogenic acids can be safely ingested to improve hypertension.