This news release was based on a very preliminary four-week study of mice. But readers of the misleading headline — “Black tea may help with weight loss, too” — will assume that the results apply to humans.
The release attempts to quickly clarify the erroneous impression left by the headline, which is good. But then it later quotes a researcher who extrapolates far beyond what a mouse study can tell us when she says: “Our new findings suggest that black tea, through a specific mechanism through the gut microbiome, may also contribute to good health and weight loss in humans.”
Mice are not people, and the results reported here are very unlikely to apply to humans. We have consistently learned, through mounds of research that’s much more relevant to humans than this study, that there’s no single food or nutrient that yields sustainable weight loss in people.
Research that makes small incremental steps in improving our knowledge of the health benefits of various types of foods is useful. This study, done on mice and suggesting that black tea has “strong impact on the gut microbiome” needs to be contextualized in terms of its impact on human health.
The study is very preliminary; it provides little if any support for the suggestion that those who like black tea “may have a new reason to keep drinking it.” And yet the news release framing has already been parroted by numerous news outlets with headlines like these:
There is no discussion of the costs of black, decaffeinated tea.
While one might argue that the cost of tea is relatively well known, remember that this was an animal study. We don’t know how much a person would have to drink in order to achieve the equivalent dosage for humans. The release could have clarified this point.
It’s disappointing that we are left without any idea of the magnitude of the findings. We are told merely that “the weights of the mice that were given green or black tea extracts dropped to the same levels as those of the mice that received the low-fat diet throughout the study.”
No potential harms of consuming black tea were mentioned. Black tea contains caffeine, which can cause a range of adverse effects in high doses.
Of course, the manuscript that’s the basis of the release specifies that the study tested decaffeinated black tea. However, the release doesn’t mention this. Clarifying this point would have been helpful.
Although we do get some detail on the quality of the study and the composition of the different comparator groups, the release never explains the limitations of animal research. Instead of emphasizing the long road to proving an equivalent effect in humans, the release repeatedly suggests the possibility of human application right now.
There is no disease mongering here.
The funders of the study are disclosed and there don’t appear to be any obvious conflicts of interest.
The study was, in a sense, a comparison of alternatives but there were no mentions of any alternatives to reduce weight in mice, other than the two teas in question.
We think the release could have talked briefly about calorie balance as the most accepted way to avoid weight gain, and calorie restriction to encourage weight loss.
Black and green tea are widely available so mentioning that fact is unnecessary.
The release provides some background about previous research in this area and how the black tea hypothesis grew out of that previous research, a 2015 UCLA study.
It’s never justifiable to imply a human effect based entirely on mouse research. Moreover, the release further suggests that it’s already been proven that green tea induces weight loss — something that certainly has not been conclusively established.