Raspberry ketone aka frambinone or (4-(4-hydroxyphenyl) butan-2-one) is a chemical compound naturally found in raspberries, as well as other plants.
Raspberry ketone is that which gives raspberries their unique flavor and aroma. This compound is both naturally and synthetically produced in the laboratory and is primarily used by the flavor and fragrance industry. It is often added to soft drinks, candy and ice cream for this purpose.
Topically, raspberry ketone has been shown to have a skin whitening effect and is added to cosmetics for this effect.
Because of its structural similarity to capsaicin (from cayenne pepper) and synephrine (from bitter orange peel) -- two other compounds known to exert anti-obese actions and alter the lipid metabolism -- raspberry ketone has been studied in both animals and in vitro ( test-tube) for these effects. The evidence for this purpose is limited but hopeful.
Recently raspberry ketone was mentioned on the Dr. Oz Show as a weight loss aid. After doing a little investigative work of my own, I am able to report that raspberry ketone is lacking in human studies.
The few studies that I found were on animals and in vitro (in a test tube). In one small study, mice fed a high fat diet received either 0.5 percent, 1 percent or 2 percent of their diet as raspberry ketone -- this was fed intragastrically (directly into the stomach through a feeding tube) for 10 weeks.
Compared to mice not fed the raspberry ketone, the experimental mice showed evidence of improved insulin sensitivity.
In vitro, raspberry ketone was found to increase both the expression and the secretion of adiponectin, an adipocytokine (fat cell hormone) mainly expressed and secreted by adipose (fat) tissue.
In addition, treatment with raspberry ketone increased fatty acid oxidation ("fat burning") and suppressed fat accumulation in fat cells.
Lipolysis is the process by which fats are broken down so they can be used for fuel. A lipolytic is a substance which increases the rate of lipolysis.
In a comparison of raspberry ketone to eight different kinds of citrus peel extracts, citrus peels showed a more profound lipolytic effect.
Of the compounds tested, limonene showed the third highest lipolytic activity. D-limonene from orange peel is widely available as an effective and clinically tested remedy for heartburn in many natural food stores. This product may therefore be even more effective for fat-burning than raspberry ketone, according to this study.
While there seems to be only hopeful, limited evidence for this natural compound as a weight loss aid, I could find no evidence of any toxicity and it is apparently safe.
Time will tell if human studies will confirm the limited data that is available on this substance to date.
As a final note, given the research above, I would guess that drinking plenty of water with lemon juice (a rich source of limonene) would give the same lipolytic effect. It would certainly be a more cost effective solution.