Nutrition: Raspberry ketones

Could raspberry ketones be magic? Popular television doctor Mehmet Oz certainly thinks so: he proclaimed last year on The Dr Oz Show that the raspberry compound was "the miracle fat burner in a bottle". Since then, the dietary supplement, which costs an average of US$20 a bottle, has been selling out in health food stores in the US and Britain.

Search online and you'll find many testimonials from happy customers - some even claiming to have seen results in as few as five days. But you'll also find many doctors warning against putting your money and faith in this latest weight-loss short cut.

There have been no major human studies to support the touted fat-burning feats of raspberry ketones. A few studies, however, have been done in vitro and on mice put on a high-fat diet.

Japanese researchers reported in 2005 that the compound "prevents and improves obesity and fatty liver" by enhancing the break-up of fat cells. Korean researchers reported in 2010 that raspberry ketone increased fat cells' secretion of a hormone called adiponectin that regulates the processing of sugars and fats in the blood.

Raspberry ketone is the primary aromatic compound of red raspberries. It has been speculated that the compounds increase metabolism generally in a similar way to that of capsaicin found in chilli peppers. Weight management expert Caroline Cederquist, writing in a blog for The Huffington Post, says the chemical structure of the compound shares some similarities with synephrine, which is a stimulant, a quality being looked at continuously for weight loss.