Teas may assist in regulating bile acid, slow metabolism, and help maintain a healthy weight.

Bile acid has long been suspected to assist in regulating metabolism. We know that these acids are essential in the digestion of fats that we eat in our diet. We know that bile acids saponify and thus increase the surface area of fats to allow enzymes better digest them, but very little research has looked at how they might regulate metabolism.

Experts have long touted the beneficial effects of tea on health and weight loss and maintenance. I have even written several posts on this topic: black tea and green tea. However, teas are not a homogenous group and they differ in preparation. The comparative effects of black, green, white, and oolong teas on weight gain or maintenance are not yet fully understood.

A new study from early 2019 looked at the comparative effects of different teas on weight loss and bile acids in rats​[1]​. Bile acids are shown to be powerful regulators of metabolism, no studies have investigated the effect of tea on bile acid metabolism. The aim of this study was to investigate the modulatory effects that green, black, white, and oolong teas that were prepared from the same raw tea leaves have on the plasma BA profile.

In the study, female rats were dosed with different tea as their sole source of drinking fluid for 28 days. Researchers then investigated their weight and effect on bile acids using liquid chromatography–tandem mass spectrometer. The researchers found levels of murocholic acid, glycochenodeoxycholic acid, glycocholic acid, glycodeoxycholic acid, taurochenodeoxycholic acid, tauroursodeoxycholic acid, taurodeoxycholic acid, tauromuricholic acid, and taurocholic acid were increased in the bile, and levels of taurolithocholic acid and isolithocholic acid were decreased after drinking green, oolong, and white tea types when compared with control. Also, oolong tea significantly influenced the reduction in relative weight compared with control. Unfortunately, black, green, and white teas had no effects on weight compared with control.

The bottom line: Oolong tea appears to be a promising addition to your diet plan to help with weight loss and maintenance. Although maintenance was not studied, it should correlate well. Green, black, oolong and white teas altered the bile acid metabolism and this might be the mechanism. Although only oolong tea was most effective in reducing weight, there are also indications in other studies the others work also. I would not stop drinking other in favor oolong if you prefer the others. I would like to see larger trials and a human trial.