A mixture of extracts of black and green teas and mulberry leaf did not reduce weight gain in rats fed a high-fat diet

Tea extracts are used in many over-the-counter preparations claiming to promote weight loss. The rationale for this usage includes reports that green tea extract increases thermogenesis, and extracts of green and black tea and mulberry leaf inhibit the digestion/absorption of carbohydrate and fat. The investigators in this study tested the potential of increasing doses of a mixture of three extracts (50-percent black tea, 20-percent green tea, and 30-percent mulberry) to induce weight loss, steatorrhea, and blood lipid alterations in rats ingesting a high-fat diet, ad lib. The mixture was incorporated into chow in quantities of 0.5-, 3.0-, and 6.0 percent by weight; a control group received only chow. Food intake and weight were monitored daily, and quantitative fecal fat measurements were obtained weekly for four weeks. The 3.0- and 6.0-percent chows significantly increased fecal fat excretion to 15 percent of dietary fat intake (controls: 5 percent); however, no significant reduction in weight gain was observed. After four weeks of treatment, the 3.0- and 6.0-percent dosages were associated with significant reductions in serum triglycerides and increases in high-density lipoprotein (HDL) cholesterol. However, these chow concentrations were associated with significant increases in serum ALT, and the 6.0-percent chow markedly increased serum alkaline phosphatase. This study does not provide support for the utility of this combination of black tea, green tea, and mulberry extracts in weight-loss regimens and indicates that high doses of this extract combination may be hepatotoxic.