Irrelevant 'evidence'

Mike spotted a product in his local Holland & Barrett which made some bold claims about helping with weight management and detoxification. It also suggested that "for maximum effect" it should be taken for 2 weeks.

Mike used the site to Ask for Evidence and received a very personable reply from one of the nutritionists at the head office.

“A main ingredient in the Bootea Daytime tea is oolong tea, a type of green tea derived from the leaves of the Camellia Sinensis plant. Some evidence suggests that the combined effect of phytochemicals called catechins alongside naturally occurring caffeine provided by teas made from the leaves of the Camellia Sinensis plant may aid weight loss. Since green tea typically contains higher levels of catechins compared to black tea this type of tea has been the main focus for studies examining this issue. I have provided a link to a meta-analysis on this subject published in the International Journal of Obesity which I hope you find useful.”

Mike was pleasantly surprised to get a reply linking to a piece of published research. As we cover in our ‘What’s reliable evidence?’ section, this is a good indicator that it has been peer-reviewed, meaning other scientific experts have checked the paper for validity, significance and originality.

Of course peer-review is certainly not fool-proof, but it’s a good start. And a meta-analysis (also covered in our help centre) means that this paper in particular looked at all of the research in this area, not just one isolated study. So far so good.

Mike isn’t a scientist so decided a second pair of eyes would help him decide whether the paper counted as good evidence or not. Mike hit ‘request more help’ and we contacted Emeritus Professor Edzard Ernst for his take on whether this paper supported the claims made about weight management and detox.

"This product contains Chinese Oolong tea, Maté leaves, Ginger root, Fennel seeds, Lemongrass, Dandelion leaf, Ginseng root, Gotu Kola leaves, and Nettle leaves at non-disclosed dosages. The cited meta-analysis is on green tea only and thus totally irrelevant. As far as I can see, there is no proof that this product generates weight loss. If that is so, the claims made for it are not backed up by evidence."

It seems that Oolong tea isn’t actually a type of green tea - whilst they are both made from Camellia Sinensis leaves they are treated and processed quite differently. Considering the meta-analysis only looked at green tea, you can see why Professor Ernst considers it ‘totally irrelevant’. Not to mention the fact that the product has a whole host of other ingredients in unknown quantities. It’s quite a leap to go and make these claims about weight management.  

Mike has decided the evidence doesn’t stack up and he’s contacted Holland & Barrett to let them know.

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