A dietary supplement containing compounds from red raspberries has become nearly impossible to find in stores since Dr. Mehmet Oz proclaimed it a fat-buster and "The No. 1 Miracle in a Bottle" on his television show.
"I never understood how powerful it could be," Oz told his studio and television audience in comments that some nutritionists have attacked as hype, unsupported by any human studies.
The raspberry ketones that give the characteristic raspberry aroma and flavor to soft drinks, puddings and ice creams, also can melt away the pounds, according to Lisa Lynn, a personal trainer and fitness expert who promoted them on an episode of "The Dr. Oz Show" that aired in early February and re-ran last week.
Lynn, who sells her own line of LynFit Nutrition supplements (one of which contains raspberry ketones) described the compounds as "very healthy" with "no side effects" and said she's seen them produce results in her clients in as few as five days. The pills enable the body to "burn fat easier."
That was enough to send TV viewers running to local health food stores in search of a bottle. But many found empty shelves. The General Nutrition Center (GNC) store in the busy Santa Monica Place shopping center in California was holding its last bottle Sunday for a customer, which disappointed an environmental consultant who came up empty-handed after searching at several health and nutrition stores, which typically sell the pills for about $12 to $20 a bottle, depending on quantity and dosage.
"I'm interested because it seems like it might give a bit of a jump start to the challenge of losing weight and it seems to be just a condensed version of raspberries, which are good for you in general anyway," said the consultant, who asked not to be identified.
Apparently, many weight-conscious people who follow a healthy diet came away with the same message about getting better results from the pills. But dietary experts maintain there's no substitute for long-lasting dietary changes and increased physical activity; they also worry about the absence of human studies establishing raspberry ketones' effectiveness as well as safety.
For now, the reputations of products like Raspberry Ketone Plus and Raspberry Ketone Ultra rest on anecdotes and two studies conducted on mice put on a high-fat diet. Japanese researchers reported in 2005 that raspberry ketone "prevents and improves obesity and fatty liver," by boosting the breakup 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.
Dr. Robert H. Lustig , a neuroendocrinologist and UC San Francisco pediatrics professor who is among top experts in the nation's obesity epidemic, said that animal studies alone are insufficient for scientists to say how raspberry ketones work in people.
"Until there are human studies I won't weigh in," he said.
"People are willing to take chances. It's amazing how many people look for a miracle instead of looking at what they're eating and how much they're moving and fixing whatever is broken," said Mary Hartley, a registered dietitian and clinical nutritionist in Brooklyn, N.Y.