Właściwie mam w nosie to, czy herbatki działają odchudzająco, czy nie. Będę je i tak piła litrami, bo lubię. I zapewne słuszne jest stwierdzenie, że jeśli ktoś chce się odchudzić, to tak naprawdę niezastąpiona jest dieta MŻ, czyli mniej żreć (oraz jej modyfikacje) plus ruch. Nikogo też nie zamierzam ani zachęcać, ani też zniechęcać do stosowania jakichkolwiek (rozsądnych) diet, bo to nie moja sprawa.
Ale pani docent z WUM mówi: Jednak żadna herbata nie jest środkiem odchudzającym. Do tej pory nie przeprowadzono żadnych badań klinicznych potwierdzających skuteczność herbaty zielonej, czerwonej czy yerba mate w redukcji masy ciała. O czym jak zwykle radośnie informuje pani Bosacka, w artykuliku zatytułowanym Herbata nie odchudza. Oczyszcza głównie portfele.
Może zamiast „powtarzać to jak mantrę”, warto czasem zajrzeć do jakichś publikacji. Fakt, niektóre pokazują efekt działania pewnych składników zawartych w herbatach nie na ludziach, ale na zwierzakach, np.:
The stimulation of hepatic lipid metabolism might be a factor responsible for the anti-obesity effects of tea catechins. The present results suggest that long-term consumption of tea catechins is beneficial for the suppression of diet-induced obesity, and it may reduce the risk of associated diseases including diabetes and coronary heart disease.
(Beneficial effects of tea catechins on diet-induced obesity: stimulation of lipid catabolism in the liver. Murase T et al, Int J Obes Relat Metab Disord. 2002 Nov;26(11):1459-64.)
Visceral fat deposition and the concentration of hepatic triacylglycerol were significantly lower in the tea catechin and heat-treated tea catechin groups than in the control group. The activities of fatty acid synthase and the malic enzyme in the liver cytosol were significantly lower in the two catechin groups than in the control group. In contrast, the activities of carnitine palmitoyltransferase and acyl-CoA oxidase in the liver homogenate were not significantly different among the three groups. These results suggest that the reduction in activities of enzymes related to hepatic fatty acid synthesis by the feeding of tea catechins or heat-treated tea catechins can cause reductions of hepatic triacylglycerol and possibly of visceral fat deposition.
(Dietary gallate esters of tea catechins reduce deposition of visceral fat, hepatic triacylglycerol, and activities of hepatic enzymes related to fatty acid synthesis in rats. Ikeda I et al, Biosci Biotechnol Biochem. 2005 May;69(5):1049-53.)
Ale i badania na ludziach się zdarzają:
Body weight, BMI, waist circumference, body fat mass, and subcutaneous fat area were significantly lower in the green tea extract group than in the control group. Changes in the concentrations of malondialdehyde-modified LDL were positively associated with changes in body fat mass and total fat area in the green tea extract group. Daily consumption of tea containing 690 mg catechins for 12 wk reduced body fat, which suggests that the ingestion of catechins might be useful in the prevention and improvement of lifestyle-related diseases, mainly obesity.
(Ingestion of a tea rich in catechins leads to a reduction in body fat and malondialdehyde-modified LDL in men. Nagao T et al, Am J Clin Nutr. 2005 Jan;81(1):122-9.)
Green tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine content per se. The green tea extract may play a role in the control of body composition via sympathetic activation of thermogenesis, fat oxidation, or both.
(Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Dulloo AG et al, Am J Clin Nutr. 2000 Nov;72(5):1232-4.)
These findings suggest that EGCG alone has the potential to increase fat oxidation in men and may thereby contribute to the anti-obesity effects of green tea. However, more studies with a greater sample size and a broader range of age and BMI are needed to define the optimum dose.
(The effects of epigallocatechin-3-gallate on thermogenesis and fat oxidation in obese men: a pilot study. Boschmann M, Thielecke F. J Am Coll Nutr. 2007 Aug;26(4):389S-395S.)
A nawet przeglądówki można sobie obejrzeć:
Tea has been found to possess widespread biological functions based on a variety of laboratory data. The effects of tea on obesity and diabetes have received increasing attention. This paper reviews the evidence for the connections among tea catechins, and obesity and diabetes. Tea catechins, especially (-)-epigallocatechin gallate (EGCG), appear to have antiobesity and antidiabetic effects. While few epidemiological and clinical studies show the health benefits of EGCG on obesity and diabetes, the mechanisms of its actions are emerging based on the various laboratory data. These mechanisms may be related to certain pathways, such as through the modulations of energy balance, endocrine systems, food intake, lipid and carbohydrate metabolism, the redox status, and activities of different types of cells (i. e., fat, liver, muscle, and beta-pancreatic cells). Because the EGCG receptor, the so-called 67-kDa laminin receptor (LR), has been discovered with colocalization of other types of LR and cytoskeleton in both cancer cells and normal cells, this may explain that EGCG possesses numerous actions. The mechanistic results of this review may possibly be utilized in the treatment of obesity, diabetes, and other related diseases using tea- and EGCG-based folk medicines.
(Tea, obesity, and diabetes. Kao YH et al, Mol Nutr Food Res. 2006 Feb;50(2):188-210.)