Health effects of green tea catechins in overweight and obese men: a randomised controlled cross-over trial
What this study found
Green tea catechin supplementation increased circulating and urinary catechins, confirming absorption, but did not lower blood pressure or improve metabolic biomarkers over 6 weeks. Plasma EGCG was detectable after DGT treatment at a mean of 98 ng/ml, while baseline levels were undetectable; urinary EGC increased 28-fold and 4'-O-methyl EGC increased 34-fold in the DGT group. A period-by-treatment interaction suggested less weight gain in the first intervention period: body-weight change was -0.64 kg with DGT versus +0.53 kg with placebo, P=0.025. LDL-cholesterol decreased with DGT and…
- Study & population
- Randomized controlled cross-over trial in sedentary, non-smoking overweight or obese men aged 40 to 69 years with BMI 28 to 38 kg/m2.
- Intervention
- Decaffeinated green tea extract (DGT; Sunphenon 90LB) was given orally as 530 mg per capsule, two capsules per day, taken 1 hour before breakfast and 1 hour before the evening meal for 6 weeks.
- Key limitation
- The trial was short and included only middle-aged men, limiting generalizability.
View source
Open PDFOriginal abstract
Regular consumption of green tea may be cardioprotective. In the present study we investigated the health effects of dietary supplementation with green tea catechins and the potential modifying effect of the catechol-O-methyltransferase (COMT) Val/Met genotype. Subjects (sedentary males, aged 40–69 years, with BMI ≥ 28 and ≤ 38 kg/m2) were randomly assigned to consume decaffeinated green tea extract (DGT; 530 mg containing about 400 mg total catechins/capsule, twice daily) and placebo in a complete cross-over design. Ambulatory blood pressure and biomarkers of metabolic function (cholesterol, TAG, glucose and insulin) were measured at weeks 0 and 6. Although a marked increase in the concentration of plasma epigallocatechin gallate (EGCG), urinary epigallocatechin (EGC) and urinary 4′-O-methyl EGC was found after DGT treatment, no effect on blood pressure or biomarkers of metabolic function was observed. However, a period × treatment interaction (P < 0·05) was detected for body-weight change. Despite a similar increase in estimated energy intake during intervention period 1, body weight decreased by 0·64 (sd 2·2) kg and increased by 0·53 (sd 1·9) kg in the DGT and placebo groups, respectively (P = 0·025), suggesting a protective effect of green tea catechins on weight gain. Additionally, the COMT Val/Met genotype influenced urinary accumulation of EGC and 4′-O-methyl EGC (P < 0·01). Mean concentrations were lower in individuals homozygous for the high-activity G-allele, possibly reflecting increased metabolic flux and a more rapid conversion to downstream metabolic species, compared with individuals carrying at least one copy of the low-activity A-allele. Additional studies are needed to confirm these findings and further explore the modifying effect of genotype.