Polyphenol-enriched oolong tea increases fecal lipid excretion

Antiobesity effects of green tea catechins: a mechanistic review

Green tea catechins (GTC) are polyphenolic compounds present in the unfermented dried leaves of the plant, Camellia sinensis. Results from a number of randomized, controlled intervention trials have shown that consumption of GTC (270 mg to 1200 mg/day) may reduce body weight and fat. There are several proposed mechanisms whereby GTC may influence body weight and composition. The predominating hypothesis is that GTC influences sympathetic nervous system (SNS) activity, increasing energy expenditure and promoting the oxidation of fat. Caffeine, naturally present in green tea, also influences SNS activity, and may act synergistically with GTC to increase energy expenditure and fat oxidation. Other potential mechanisms include modifications in appetite, up-regulation of enzymes involved in hepatic fat oxidation, and decreased nutrient absorption. This article reviews the evidence for each of these purported mechanisms, with particular reference to studies in humans.

Structured triacylglycerol containing behenic and oleic acids suppresses triacylglycerol absorption and prevents obesity in rats

Background

Dietary 1(3)-behenoyl-2,3(1)-dioleoyl-rac-glycerol (BOO) has been reported to inhibit pancreatic lipase activity in vitro and suppress postprandial hypertriacylglycerolemia in humans. In the present study, the anti-obesity activities of BOO and its inhibitory effects on lymphatic triacylglycerol (TAG) absorption were investigated in rats.

Methods

In Experiment 1, rats were fed either BOO or soybean oil (SO) diet for 6 weeks. In the BOO diet, 20% of SO was replaced with an experimental oil rich in BOO. In Experiments 2 and 3, rats cannulated in the thoracic duct were administered an emulsions containing trioleoylglycerol (OOO) or an oil mixture (OOO:BOO, 9:1). Tri[1-¹⁴C]oleoylglycerol (¹⁴C-OOO) was added to the emulsions administered in Experiment 3.

Results

No observable differences were detected in food intake or body weight gain between the BOO and SO groups in Experiment 1. Plasma and liver TAG concentrations and visceral fat weights were significantly lower in the BOO group than in the SO group. The apparent absorption rate of fat was significantly lower in the BOO group than in the SO group. In Experiment 2, the lymphatic recovery of oleic and behenic acids was significantly lower at 5 and 6 h after BOO administration than after OOO administration. In Experiment 3, the lymphatic recovery of ¹⁴C-OOO was significantly lower at 5 and 6 h after BOO administration than after OOO administration.

Conclusions

These results suggest that BOO prevents deposition of visceral fat and hepatic TAG by lowering and delaying intestinal absorption of TAG.

The role of lipid and carbohydrate digestive enzyme inhibitors in the management of obesity: a review of current and emerging therapeutic agents

Obesity is a global epidemic associated with significant morbidity and mortality in adults and ill health in children. A proven successful approach in weight management has been the disruption of nutrient digestion, with orlistat having been used to treat obesity for the last 10 years. Although orlistat-induced weight loss remains modest, it produces meaningful reductions in risk factors for obesity-related conditions such as diabetes and cardiovascular disease. Moreover, this lipase inhibitor is free of the serious side effects that have dogged appetite-suppressing drugs. This success had driven investigation into new generation nutraceuticals, supplements and pharmaceutical agents that inhibit the breakdown of complex carbohydrates and fats within the gut. This review focuses on agents purported to inhibit intestinal enzymes responsible for macronutrient digestion. Except for some synthetic products, the majority of agents reviewed are either botanical extracts or bacterial products. Currently, carbohydrate digestion inhibitors are under development to improve glycemic control and these may also induce some weight loss. However, colonic fermentation induced side effects, such as excess gas production, remain an issue for these compounds. The α-glucosidase inhibitor acarbose, and the α-amylase inhibitor phaseolamine, have been used in humans with some promising results relating to weight loss. Nonetheless, few of these agents have made it into clinical studies and without any clinical proof of concept or proven efficacy it is unlikely any will enter the market soon.

Effects of catechin enriched green tea on body composition

Obesity is a major health problem in the developed and developing world. Many "functional" foods and ingredients are advocated for their effects on body composition but few have consistent scientific support for their efficacy. However, an increasing amount of mechanistic and clinical evidence is building for green tea (GT). This experiment was therefore undertaken to study the effects of a high-catechin GT on body composition in a moderately overweight Chinese population. In a randomized placebo-controlled trial, 182 moderately overweight Chinese subjects, consumed either two servings of a control drink (C; 30 mg catechins, 10 mg caffeine/day), one serving of the control drink and one serving of an extra high-catechin GT1 (458 mg catechins, 104 mg caffeine/day), two servings of a high-catechin GT2 (468 mg catechins, 126 mg caffeine/day) or two servings of the extra high-catechin GT3 (886 mg catechins, 198 mg caffeine/day) for 90 days. Data were collected at 0, 30, 60, and 90 days. We observed a decrease in estimated intra-abdominal fat (IAF) area of 5.6 cm(2) in the GT3 group. In addition, we found decreases of 1.9 cm in waist circumference and 1.2 kg body weight in the GT3 group vs. C (P < 0.05). We also observed reductions in total body fat (GT2, 0.7 kg, P < 0.05) and body fat % (GT1, 0.6%, P < 0.05). We conclude that consumption of two servings of an extra high-catechin GT leads to improvements in body composition and reduces abdominal fatness in moderately overweight Chinese subjects.

Purified black tea theaflavins and theaflavins/catechin supplements did not affect serum lipids in healthy individuals with mildly to moderately elevated cholesterol concentrations

BACKGROUND

Ingestion of tea flavonoids found in both green and black tea is linked to cardiovascular health benefits such as lowering serum lipids. Evidence for a cholesterol-lowering benefit of green or black tea consumption from human intervention studies is, however, conflicting and active components responsible for the effect have not yet been clearly identified.

AIM OF THE STUDY

In a randomized, double-blind, placebo-controlled, parallel design study the effects of ingesting a purified black tea theaflavins (TFs) powder alone or in combination with catechin (TFs/catechins) on lowering serum total (TC) and LDL-cholesterol (LDL-c) were assessed.

METHODS

In total, 102 mildly to moderately hypercholesterolemic (TC and LDL-c: 5.70 +/- 0.74 and 3.97 +/- 0.61 mmol/L, respectively) subjects (67 men and 35 women) were randomly assigned to consume once daily one capsule of one of the 3 treatments: TFs (providing 77.5 mg), TFs/catechins (providing 75.0 mg TFs plus 150.0 mg catechins and 195.0 mg of other polyphenols), or placebo (cellulose).

RESULTS

Serum TC and LDL-c concentrations did not differ significantly among the 3 treatments as assessed at 4, 8, and 11 weeks using analysis of covariance (p = 0.1187 and p = 0.1063, respectively). Although changes over time from baseline to week 11 were significant for TC and LDL-c (p = 0.0311 and p = 0.0269, respectively), this decrease over time was seen in the TFs and placebo groups.

CONCLUSION

In this human intervention study, no statistically significant LDL-c lowering effect was seen with either TFs alone or the TFs/catechins combination as compared to placebo. Based on these findings it cannot be concluded that tea flavonoids such as theaflavins and catechins are responsible for a putative cholesterol-lowering effect of black tea, at least not with the daily dose applied in the present study.

Effect of moderate intakes of different tea catechins and caffeine on acute measures of energy metabolism under sedentary conditions

Green tea may stimulate energy metabolism; however, it is unclear if acute effects are caused by specific catechins, caffeine or their combination. The objective of the present study was to examine the separate and combined effects of different catechins and caffeine on energy expenditure (EE) and fat oxidation over a single day. Fifteen healthy, normal-weight males received capsules containing placebo, caffeine alone (150 mg), or caffeine plus a catechin mixture (600 mg) enriched in either epigallocatechin-3-gallate (EGCG), epigallocatechin or a mix of catechins, in a randomised cross-over double-blinded design. On each test day EE, respiratory quotient (RQ) and substrate oxidation were measured under sedentary conditions in a respiratory chamber for 13·5 h. We found no significant treatment effect on EE (P = 0·20) or RQ (P = 0·68). EGCG with caffeine insignificantly raised EE and fat oxidation v. caffeine-only and placebo (EE 5·71 (se 0·12) v. 5·68 (se 0·14) v. 5·59 (se 0·13) MJ/12·5 h, respectively; fat oxidation 84·8 (se 5·2) v. 80·7 (se 4·7) v. 76·8 (se 4·0) g/12·5 h). Catechin/caffeine combinations at these dosages and mode of application had non-significant acute effects on EE and fat oxidation. The maximum observed effect on EE of about 2 % could still be meaningful for energy balance over much longer period of exposure. However, higher short-term effects reported in the literature may reflect variations in green tea extracts, added caffeine, or synergies with physical activity. The specific mechanisms and conditions that may underpin observed longer-term benefits of catechin-enriched green tea consumption on body composition remain to be confirmed.

Effect of polyphenol-rich extract from walnut on diet-induced hypertriglyceridemia in mice via enhancement of fatty acid oxidation in the liver

The kernel pellicles of walnut are rich in ellagitannins with antioxidative activity. A polyphenol-rich extract from walnuts (WP, 45% polyphenol) was prepared and evaluated for its hypolipidemic effect in high fat diet fed mice. Oral administration of WP (100 and 200 mg/kg) significantly reduced liver weight and liver and serum triglycerides (TG). Hepatic beta-oxidation in cytosol, including peroxisome, was enhanced by WP (50-200 mg/kg). mRNA expressions of hepatic peroxisome proliferator-activated receptor (PPAR) alpha and acyl coenzyme A oxidase (ACOX) 1 were enhanced by WP (50-200 mg/kg). With respect to the hypotriglyceridemic mechanism of WP, it suppressed neither olive oil induced serum TG elevation in mice nor oleic acid induced TG accumulation in HepG2 cells. On the other hand, mRNA expressions of PPARalpha, ACOX1, and carnitine palmitoyltransferase (CPT) 1A in HepG2 cells were significantly enhanced by addition of WP (100 microg/mL). Moreover, tellimagrandin I, a polyphenolic constituent in WP, enhanced ACOX1 expression at 1-100 microg/mL. In conclusion, WP was found to possess hypotriglyceridemic activity via enhancement of peroxisomal fatty acid beta-oxidation in the liver. These results suggest that tellimagrandin I is involved in the hypotriglyceridemic mechanism of WP.

Tea and health: preventive and therapeutic usefulness in the elderly?

PURPOSE OF REVIEW

To update the growing literature suggesting that tea and its constituent flavonoids are inversely related to the risk of chronic diseases common among the elderly.

RECENT FINDINGS

Results are provided from recent observational studies and clinical trials on the relationship of tea and tea catechins to body weight control and energy metabolism, impaired glucose tolerance and diabetes, cardiovascular disease, bone mineral density, cognitive function and neurodegenerative disease, and cancer. The evidence for the efficacy and potency of tea and tea extracts in benefiting these outcomes ranges from compelling for cardiovascular disease to equivocal at best for some forms of cancer.

SUMMARY

Although randomized clinical trials of tea have generally been of short duration and with small sample sizes, together with experimental and epidemiological studies, the totality of the data suggests a role for tea in health promotion as a beverage absent in calories and rich in phytochemicals. Further research is warranted on the putative benefits of tea and the potential for synergy among its constituent flavonoids, L-theanine, and caffeine.

Current developments on the inhibitory effects of berry polyphenols on digestive enzymes

The recent developments and evidence for the effect of polyphenol components of berries on digestive enzymes has been reviewed. Certain plant polyphenols can inhibit starch digestive enzymes in the gastrointestinal tract and modulate blood glucose control in vivo. Certain berry polyphenol components can inhibit protease activities at levels which could affect protein digestion in the gastrointestinal tract. In addition, other polyphenol components show potential for the inhibition of gastrointestinal lipase activity, which is a proven therapeutic target for the control of obesity through reduced fat digestion. Taking into account the potential synergies for inhibition of starch and lipid digestion by the spectrum of polyphenol components present within berry species, the inhibition of digestive enzymes by dietary polyphenols may be another important mechanism for the health benefits attributed to a diet rich in fruit and vegetables.