Health effects of green tea catechins in overweight and obese men: A randomised controlled cross-over trial
– Source: Journal of Human and Clinical Nutrition, Jun 7, 2011
By A Louise Brown, et al.
[Note: In 6 weeks with no dietary change except supplementation with decaffeinated green tea EGCG extract, the green tea takers were down an average of 2.58 pounds versus the control group (an average loss of 1.41 pounds vs starting weight, plus average weight-gain avoidance of 1.17 pounds) - "suggesting a protective effect of green tea catechins on weight gain," the researchers conclude.]
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 or greater and 38 kg/m2 or less) 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 x 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.
Source: Journal of Human and Clinical Nutrition, Jun 7, 2011. Brown AL, Land J, Holyoak C, Nicol B, Mayes AE, Dadd T. Unilever R&D, Shambrook, Bedfordshire, UK