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Effects of green tea extract combined with brisk walking on lipid profiles and the liver function in overweight and obese men: A randomized, double-blinded, placebo-control trial.
Zhang, T, Li, N, Chen, SI, Hou, Z, Saito, A
Anais da Academia Brasileira de Ciencias. 2020;92(4):e20191594
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Studies have shown that green tea extract (GTE) and exercise may help manage obesity. This randomised double-blind placebo-controlled trial study aimed to assess the role of GTE plus exercise on the amount of cholesterol in the blood and in the treatment of chronic diseases in 24 overweight and obese men over 12 weeks. The results showed that although cholesterol levels did not improve with GTE, they were maintained, whereas the placebo groups increased. There was an improvement in liver function in the GTE group, which was not observed with placebo. It was concluded that GTE plus exercise maintained but did not improve cholesterol levels in overweight and obese men contrary to previous study results. This could be due to a lower dose of GTE in the present study. GTE plus exercise did improve liver function. This study could be used by practitioners to recommend GTE supplementation and exercise in the management of cholesterol and to improve liver function in overweight and obese patients.
Abstract
This study was aimed to investigate the effect of green tea extract (GTE) combined with brisk walking on lipid profiles and the liver function in overweight and obese men. Twenty-four participants were randomized to either the GTE group or the placebo group for 12 weeks with a 4-week follow-up. The walking program consisted of four 60-min-sessions/week and all participants were asked to consume two GTE (150mg) or placebo tablets daily. After 12-week intervention, GTE group resulted in a significant difference in the low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) levels when compared to placebo group (P < 0.01). There was also a significant reduction in the aspartate aminotransferase levels (P < 0.01) in the GTE group, but no change in the placebo group (P >0.05). There was no change in the triglyceride or high-density lipoprotein cholesterol (HDL-C) levels in the placebo group, but a significant reduction was noted in the HDL-C levels in the GTE group (P < 0.05). GTE combined with brisk walking resulted in a significant change in the LDL-C and TC levels, however, a significant reduce in HDL-C in the GTE group. The study has a more positive effect on the liver function than brisk walking alone.
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Green tea (Camellia sinensis) for the prevention of cancer.
Filippini, T, Malavolti, M, Borrelli, F, Izzo, AA, Fairweather-Tait, SJ, Horneber, M, Vinceti, M
The Cochrane database of systematic reviews. 2020;3(3):CD005004
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Brewed tea is obtained from the infusion of leaves and buds of Camellia sinensis. The most consumed types of tea are green and black tea. Due to the high content of antioxidant compounds, a great deal of attention has been given to green tea regarding the possible prevention of chronic diseases and cancer, as well as possible beneficial effects on cardiovascular disease, insulin sensitivity and lipid profiles. The main aim of this review was to assess the association between green tea consumption and the risk of developing cancer in epidemiologic studies. This study is an update of a previously published Cochrane review based on studies in which participants consumed green tea orally, either as drinkable tea or as extracts. One hundred and forty-two epidemiological studies of experimental and nonexperimental design were included with a total of 1,100,000 participants. Findings yielded inconsistent results for the effect of green tea consumption on cancer risk, despite some indications of a beneficial effect of green tea on a few site-specific cancers. Authors conclude that the epidemiological evidence appears to be still inadequate to support a beneficial effect of green tea on cancer risk.
Abstract
BACKGROUND This review is an update of a previously published review in the Cochrane Database of Systematic Reviews (2009, Issue 3).Tea is one of the most commonly consumed beverages worldwide. Teas from the plant Camellia sinensis can be grouped into green, black and oolong tea, and drinking habits vary cross-culturally. C sinensis contains polyphenols, one subgroup being catechins. Catechins are powerful antioxidants, and laboratory studies have suggested that these compounds may inhibit cancer cell proliferation. Some experimental and nonexperimental epidemiological studies have suggested that green tea may have cancer-preventative effects. OBJECTIVES To assess possible associations between green tea consumption and the risk of cancer incidence and mortality as primary outcomes, and safety data and quality of life as secondary outcomes. SEARCH METHODS We searched eligible studies up to January 2019 in CENTRAL, MEDLINE, Embase, ClinicalTrials.gov, and reference lists of previous reviews and included studies. SELECTION CRITERIA We included all epidemiological studies, experimental (i.e. randomised controlled trials (RCTs)) and nonexperimental (non-randomised studies, i.e. observational studies with both cohort and case-control design) that investigated the association of green tea consumption with cancer risk or quality of life, or both. DATA COLLECTION AND ANALYSIS Two or more review authors independently applied the study criteria, extracted data and assessed methodological quality of studies. We summarised the results according to diagnosis of cancer type. MAIN RESULTS In this review update, we included in total 142 completed studies (11 experimental and 131 nonexperimental) and two ongoing studies. This is an additional 10 experimental and 85 nonexperimental studies from those included in the previous version of the review. Eleven experimental studies allocated a total of 1795 participants to either green tea extract or placebo, all demonstrating an overall high methodological quality based on 'Risk of bias' assessment. For incident prostate cancer, the summary risk ratio (RR) in the green tea-supplemented participants was 0.50 (95% confidence interval (CI) 0.18 to 1.36), based on three studies and involving 201 participants (low-certainty evidence). The summary RR for gynaecological cancer was 1.50 (95% CI 0.41 to 5.48; 2 studies, 1157 participants; low-certainty evidence). No evidence of effect of non-melanoma skin cancer emerged (summary RR 1.00, 95% CI 0.06 to 15.92; 1 study, 1075 participants; low-certainty evidence). In addition, adverse effects of green tea extract intake were reported, including gastrointestinal disorders, elevation of liver enzymes, and, more rarely, insomnia, raised blood pressure and skin/subcutaneous reactions. Consumption of green tea extracts induced a slight improvement in quality of life, compared with placebo, based on three experimental studies. In nonexperimental studies, we included over 1,100,000 participants from 46 cohort studies and 85 case-control studies, which were on average of intermediate to high methodological quality based on Newcastle-Ottawa Scale 'Risk of bias' assessment. When comparing the highest intake of green tea with the lowest, we found a lower overall cancer incidence (summary RR 0.83, 95% CI 0.65 to 1.07), based on three studies, involving 52,479 participants (low-certainty evidence). Conversely, we found no association between green tea consumption and cancer-related mortality (summary RR 0.99, 95% CI 0.91 to 1.07), based on eight studies and 504,366 participants (low-certainty evidence). For most of the site-specific cancers we observed a decreased RR in the highest category of green tea consumption compared with the lowest one. After stratifying the analysis according to study design, we found strongly conflicting results for some cancer sites: oesophageal, prostate and urinary tract cancer, and leukaemia showed an increased RR in cohort studies and a decreased RR or no difference in case-control studies. AUTHORS' CONCLUSIONS Overall, findings from experimental and nonexperimental epidemiological studies yielded inconsistent results, thus providing limited evidence for the beneficial effect of green tea consumption on the overall risk of cancer or on specific cancer sites. Some evidence of a beneficial effect of green tea at some cancer sites emerged from the RCTs and from case-control studies, but their methodological limitations, such as the low number and size of the studies, and the inconsistencies with the results of cohort studies, limit the interpretability of the RR estimates. The studies also indicated the occurrence of several side effects associated with high intakes of green tea. In addition, the majority of included studies were carried out in Asian populations characterised by a high intake of green tea, thus limiting the generalisability of the findings to other populations. Well conducted and adequately powered RCTs would be needed to draw conclusions on the possible beneficial effects of green tea consumption on cancer risk.
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Combined epigallocatechin-3-gallate and resveratrol supplementation for 12 wk increases mitochondrial capacity and fat oxidation, but not insulin sensitivity, in obese humans: a randomized controlled trial.
Most, J, Timmers, S, Warnke, I, Jocken, JW, van Boekschoten, M, de Groot, P, Bendik, I, Schrauwen, P, Goossens, GH, Blaak, EE
The American journal of clinical nutrition. 2016;104(1):215-27
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The prevalence of obesity and related chronic diseases is continuously increasing. Insulin resistance is a major risk factor for the progression of obesity toward chronic metabolic diseases, including cardiovascular disease and type 2 diabetes. Polyphenols were identified as dietary ingredients with antioxidant properties decades ago. Epigallocatechin-3-gallate (EGCG), which is most abundant in green tea, and resveratrol (RS), which is present in grape skins, have been implicated in the prevention of body weight gain and improvements in markers of insulin sensitivity in human and animal studies. The aim of this randomised control study was to investigate the longer-term effect of EGCG and RES (EGCG+RES) supplementation on metabolic profile, mitochondrial capacity, fat oxidation, lipolysis, and tissue-specific insulin sensitivity. 38 overweight and obese men and women received supplementation with either EGCG+RES (282 and 80 mg/d, respectively) or a placebo for 12 weeks. Before and after the intervention, oxidative capacity, lipid metabolism and insulin sensitivity were measured. EGCG+RES supplementation did not affect the fasting plasma metabolic profile. Although whole-body fat mass was not affected, visceral adipose tissue mass decreased after the intervention compared with placebo. EGCG+RES supplementation significantly increased oxidative capacity in muscle fibres. Fat oxidation and energy expenditure were not significantly affected by EGCG+RES. Finally, EGCG+RES had no effect on insulin-stimulated glucose disposal, suppression of endogenous glucose production, or lipolysis. The authors concluded that 12 weeks of EGCG+RES supplementation increased mitochondrial capacity and stimulated fat oxidation compared with placebo, and this may improve physical condition and play a role in the prevention of weight gain and worsening of insulin resistance in the long term.
Expert Review
Conflicts of interest:
None
Take Home Message:
- 12 wks of EGCG+RES intake increased skeletal muscle oxidative capacity as well as upregulating mitochondrial pathways, which may translate into an improved metabolic risk profile over time because greater mitochondrial capacity has been associated with higher insulin sensitivity in other studies
- The fat oxidation alterations in those taking the active ingredients vs. the placebo group suggests that this intervention could lead to metabolic adaptation towards lipids instead of CHOs as a fuel source, over time.
- EGCG+RES intake attenuated the increase in plasma triacylglycerol levels during the HFMM test, while the levels were significantly increased in the placebo group after 12 wks. This suggests that the intervention may provide positive support for individuals with high triacylglcerol (triglyceride) levels
- The ratio of total cholesterol to HDL cholesterol tended to decrease after EGCG+RES supplementation but not after placebo. Increased total & HDL cholesterol marker for myocardial infarction risk, so this intervention could help with persons who have disordered cholesterol values, and perhaps contribute to reducing their MI risk over time.
Evidence Category:
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X
A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
- This randomised controlled trial investigated the effect of 12-wk supplementation of combined epigallocatechin-3-gallate and resveratrol (EGCG+RES) on metabolic profile, mitochondrial capacity, fat oxidation, lipolysis, and insulin sensitivity.
- 38 overweight and obese subjects (active ingredient cohort n = 18; placebo n = 20) received 282 mg/d EGCG and 80 mg/d resveratrol; one capsule of each was taken at breakfast and dinner. Subjects were medically screened 10 times in total, including: 3 times before starting supplementation, 3 times during the supplementation period, and 3 in the last week of supplementation.
- EGCG capsules contained 94% epigallocatechin-3-gallate (141 mg/capsule) and resveratrol capsules contained 20% trans-resveratrol (40 mg trans-resveratrol in Polygonum cuspidatum extract/capsule).
- Medical screening included skeletal muscle biopsies (Vastus lateralis), with various tests done to measure oxidative capacity, X-ray absorptionmetry, a high-fat mixed meal (HFMM) test, and an insulin test via hyperinsulinemic-euglycemic clamp; meal intake before screening was standardised.
- Blood probes were also taken, and subjects completed food records; exact kcals per macronutrient were calculated.
Clinical practice applications:
The results of the study, which relate to clinical practice, highlight:
- 12 weeks of ECGC+RES supplementation increased mitochondrial capacity.
- EGCG+RES increased skeletal muscle oxidative capacity as well as protein expression of OxPhos complexes in skeletal muscle.
- EGCG+RES supplementation significantly affected fasting substrate oxidation, whereas fat oxidation declined in the placebo group; this suggests that it could help to improve fat metabolism.
- 12 weeks of ECGC+RES supplementation preserved fasting and postprandial fat oxidation compared with placebo.
- Plasma triacylglycerol levels were not significantly increased in the EGCG+RES cohort on being given an HFMM test after 12 wks, whereas they went up in the placebo group, indicating that this intervention preserved fasting and post-prandial fat oxidation.
- EGCG+RES group tended to decrease visceral adipose tissue mass by ~11% vs. placebo,
- These findings suggest that combined ECGC+RES supplementation might support mitochondrial function and weight loss/insulin sensitivity over a longer period of time
Considerations for future research:
- The EGCG+RES supplementation had no effect on postprandial glucose, insulin and FFA concentrations or local interstitial glucose and glycerol concentrations. Altering the study parameters in the future might identify changes of these markers.
- There was a tendency toward visceral adipose tissue mass decrease that was not considered significant, but altering dosage and length of time of a similar study might result in a more notable outcome related to weight loss, which was a targeted endpoint
- The combined supplements were not found to affect energy expenditure, contrary to a previous study by the same team, which was for a much shorter time period. It would be interesting to identify why this was.
- Complex and numerous gene set enrichment analyses were performed indicating that the most upregulated pathways after EGCG+RES supplementation were related to the Krebs cycle and electron transport chain, whereas pathways related to CHO metabolism were upregulated in the placebo group. This was taken to indicate that the increased mitochondrial capacity after EGCG +RES supplementation is accompanied by changes at the transcriptional and translational levels; further follow-up of this would be useful to know what clinical impact this has longer term
Abstract
BACKGROUND The obese insulin-resistant state is characterized by impairments in lipid metabolism. We previously showed that 3-d supplementation of combined epigallocatechin-3-gallate and resveratrol (EGCG+RES) increased energy expenditure and improved the capacity to switch from fat toward carbohydrate oxidation with a high-fat mixed meal (HFMM) test in men. OBJECTIVE The present study aimed to investigate the longer-term effect of EGCG+RES supplementation on metabolic profile, mitochondrial capacity, fat oxidation, lipolysis, and tissue-specific insulin sensitivity. DESIGN In this randomized double-blind study, 38 overweight and obese subjects [18 men; aged 38 ± 2 y; body mass index (kg/m(2)): 29.7 ± 0.5] received either EGCG+RES (282 and 80 mg/d, respectively) or placebo for 12 wk. Before and after the intervention, oxidative capacity and gene expression were assessed in skeletal muscle. Fasting and postprandial (HFMM) lipid metabolism was assessed by using indirect calorimetry, blood sampling, and microdialysis. Tissue-specific insulin sensitivity was assessed by a hyperinsulinemic-euglycemic clamp with [6,6-(2)H2]-glucose infusion. RESULTS EGCG+RES supplementation did not affect the fasting plasma metabolic profile. Although whole-body fat mass was not affected, visceral adipose tissue mass tended to decrease after the intervention compared with placebo (P-time × treatment = 0.09). EGCG+RES supplementation significantly increased oxidative capacity in permeabilized muscle fibers (P-time × treatment < 0.05, P-EGCG+RES < 0.05). Moreover, EGCG+RES reduced fasting (P-time × treatment = 0.03) and postprandial respiratory quotient (P-time × treatment = 0.01) compared with placebo. Fasting and postprandial fat oxidation was not significantly affected by EGCG+RES (P-EGCG+RES = 0.46 and 0.38, respectively) but declined after placebo (P-placebo = 0.05 and 0.03, respectively). Energy expenditure was not altered (P-time × treatment = 0.96). Furthermore, EGCG+RES supplementation attenuated the increase in plasma triacylglycerol concentrations during the HFMM test that was observed after placebo (P-time × treatment = 0.04, P-placebo = 0.01). Finally, EGCG+RES had no effect on insulin-stimulated glucose disposal, suppression of endogenous glucose production, or lipolysis. CONCLUSION Twelve weeks of EGCG+RES supplementation increased mitochondrial capacity and stimulated fat oxidation compared with placebo, but this did not translate into increased tissue-specific insulin sensitivity in overweight and obese subjects. This trial was registered at clinicaltrials.gov as NCT02381145.