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Next miracle fat blocker? Grapefruit derivative promotes weight loss, stabilizes blood sugar in mice

July 13, 2009 |  3:55 pm

The sciences of weight control and longevity creep along on little mice feet. And the breathless marketing of dietary supplements that purport to stem from such science often follows close behind.

So let us be the first to suggest what botanical extract will be close on the heels of resveratrol as the next anti-aging and weight-loss "miracle": naringenin.

Why? A study published in the journal Diabetes, published by the American Diabetes Assn., has found that naringenin (pronounced NAR-en-GEN-in), a flavenoid derived from grapefruit, reverses the signs of impending diabetes in mice fed a high-fat "Western" diet, including high cholesterol, insulin insensitivity and blood sugar irregularities. And, with no change in diet but for the addition of naringenin, the overfed mice did not develop the "marked obesity" that such mice generally develop, researchers said.

The researchers determined that naringenin tweaked the genes of the overfed mice to reprogram their livers so that they burned off excess fat rather than storing it. The naringenin didn't suppress their appetites at all: They ate just as much; they just didn't get fat or develop the metabolic disturbances that generally presage the development of Type 2 diabetes.

Murray Huff, a professor of medicine and biochemistry at the University of Western Ontario, said he plans to explore next whether naringenin might also prevent the development of cardiovascular disease in mice who eat a diet high in fat and calories. From there, he hopes to explore the possibility of clinical trials using human subjects. If naringenin proves successful at preventing obesity in animals and people at risk, Huff suggested it might also prove effective as a treatment for obesity and metabolic syndrome, sometimes called pre-diabetes.

In laboratory experiments using human cancer cells, naringenin, an anti-oxidant, also has been found to inhibit tumor growth. Huff said that the mechanisms by which naringenin appears to suppress cancerous growth and right metabolic disturbance are different. Such multitasking suggests that the stuff concentrated in grapefruit peels will be in line for a future "superfood" label.

But before you strip your local produce bins of grapefruit or rush out to your local vitamin store to look for a dietary supplement that includes naringenin (I found it online in one product only, marketed for "healthy vision support"), here are some things to consider:

-- We're talking about mice here. And as they say in the world of pharmacology, only at Disney World do mice closely approximate humans. 

-- The doses that effectively headed off obesity and diabetes were probably larger than it would be practical or maybe even healthy to eat every day. Huff said a roughly equivalent dosage to that fed to the mice who stayed healthy (always an imprecise calculation) would be six to eight glasses of grapefruit juice a day. That's a lot of sugar, a lot of acid, and Florida would be stripped of grapefruit in no time at all if drinking that much grapefruit juice became a trend. Plus, the naringenin fed to the mice was in purefied form -- without the variables you'd probably find in fruit from different sources or in supplements.

-- Drinking grapefruit juice is a definite no-no for many of the same people who might well think they could benefit from the goodness of naringenin: people who take statin medications (simvastatin, lovastatin, atorvastatin) to lower their high cholesterol or calcium-channel blockers (filodepine, nifedepine, nimodepine and nisoldepine) for high blood pressure or amiodorone for heart arrhythmia. It also is not recommended for those taking some immunosuppressive drugs, HIV medications, anti-seizure drugs and antidepressants. The body's metabolizing of grapefruit juice interferes with the breakdown of these drugs, leaving to a great concentration in the blood, with possibly dangerous side effects. The Mayo Clinic has posted a list of drugs that interact badly with grapefruit juice.

-- Finally, Huff underscores that the research on naringenin is largely valuable: a) for the light it casts on the mechanisms of metabolic syndrome; and  b) for the possibility that it will point the way to pharmaceuticals that can exert these powerful effects precisely and with as few dangerous side effects as possible.

 "Everyone wants instant gratification," says Huff. But rather than flock to the produce counter and stock up on grapefruits or order a naringenin supplement, he says people would do better to exercise and eat and drink healthy foods--including a reasonable amount of citrus fruit and its juice--and let science figure out just how much of a "miracle" naringenin is.

-- Melissa Healy