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Consumers Being Misled Over Bioavailabity of Resveratrol

Longevinex(R) One Of Few Dietary Supplements To Provide Quercetin To

Improve Instant Availability of Resveratrol

SAN DIMAS, Calif., Jan. 9 /PRNewswire/ -- In response to consumer inquiries emanating from a misleading press release issued by a competing dietary supplement company, which falsely claims quercetin inhibits the bioavailability of resveratrol, Longevinex(R) provides the following information.

"Quercetin is one of the secrets of red wine. It works in tandem with resveratrol to make it more instantly available to tissues throughout the body," says Bill Sardi, spokesperson for Longevinex(R), maker of a leading brand resveratrol dietary supplement.

A recently issued press release by a competing dietary supplement company, falsely claims quercetin inhibits bioavailability of resveratrol. "With no scientific substantiation for their claim, they are misleading many consumers," says Sardi.

"This distorts the science," says Sardi. Eight years ago researchers in Italy showed that quercetin is about ten times better at inhibiting immediate attachment of resveratrol to sulfur and glucuronate molecules in the liver than other molecules found in red wine and therefore "improves the bioavailability of resveratrol." Interested consumers can examine the evidence for themselves at the National Library of Medicine, here: [Xenobiotica 2000 Sep; 30(9):857-66 ( m2. PEntrez.Pubmed.Pubmed_ResultsPanel.Pubm); 2000 Nov; 30(11):1047-54 ( m2. PEntrez.Pubmed.Pubmed_ResultsPanel.Pubm); 2000 Jun; 30(6):609-17 ( m2. PEntrez.Pubmed.Pubmed_ResultsPanel.Pubm)]

Sardi asks: "If there is a question over bioavailability of resveratrol when provided with quercetin, then how did Longevinex(R), which provides both molecules, produce measurable declines in markers of oxidation and inflammation in endurance athletes in the first successful human study of a resveratrol supplement, at doses far lower than recommended by producers of resveratrol supplements that contain resveratrol only?" A press release describing the study is found here (

In that study, Longevinex(R) was found to be biologically active at dose (~120 milligrams) far less than what was used in a recent mouse study (1565 mg equivalent human dose), and far less than is recommended by other brands of resveratrol that do not contain quercetin.
"This is no surprise, since numerous studies indicate quercetin works synergistically to enhance the biological action of resveratrol. The effect is both additive and multiple," says Sardi. [Cancer Letters 2005 Feb 10; 218(2):141-51 ( PEntrez.Pubmed.Pubmed_ResultsPanel.Pubm); Journal Agriculture Food Chemistry 2005 Mar 23; 53(6):2015-21 ( .PEntrez.Pubmed.Pubmed_ResultsPanel.Pub).

What's to hide?

While there is scientific evidence that quercetin makes resveratrol more immediately available, there is no evidence for a claim by a competing company that their undisclosed technology doubles the absorption and utilization of resveratrol. Consumers need to be wary unless independent laboratory tests confirm this claim. "Research studies already estimate about 70% of resveratrol is absorbed, so I don't know how you double that number?" asks Sardi. [Drug Metabolism Disposition 2004 Dec; 32(12):1377-82 ( m2. PEntrez.Pubmed.Pubmed_ResultsPanel.Pubm)]

Instant and long-term bioavailability

Interested consumers need to distinguish between instant and long-term bioavailability of resveratrol.

"Quercetin can be mischaracterized," says Sardi, "since it allows resveratrol more passes through the liver before it is finally conjugated (attached to) sulfur and glucuronate molecules. Eventually, all resveratrol is metabolized in the liver. Once bound to these molecules, resveratrol is, for a time, not biologically active, but this process prolongs the life of resveratrol in the blood circulation up to 9 hours. Otherwise, resveratrol has a short half life (time it takes for 50% to degrade), about 14 minutes."

"Nature takes over from there, producing an unlocking enzyme called glucuronidase, which is abundant at sites of inflammation, infection and malignancy. This enzyme releases unbound (free) resveratrol at the right time and place. It is nature's drug delivery system," says Sardi. This was all explained back in 2003-2004. [Biochemical Journal 374 (Pt 1):157-63, 2003 (; J Pharmaceutical Sciences 93:2448-2457, 2004 ( bin/abstract/109572576/ABSTRACT?CRETRY=1&SRETRY=0)]

Dosage concerns

Citing a recent human study where a single high-dose (500-5000 milligrams) of resveratrol did not produce a serious side effect, Biotivia claims their recommendation to take mega-dose resveratrol should be of no concern, but high-dose resveratrol like Biotivia recommends was not absolutely safe. There were side effects with just one mega-dose. There were 51 reported side effects (all transient and reversible) among 40 healthy volunteers, 12 of them at the 500 mg dose, and 20 at the 1000 mg dose. These side effects included abnormal blood tests, over-thinning of the blood, loose stool, headache, and anxiety reactions. [Cancer Epidemiology Biomarkers Prevention 2007 Jun; 16(6):1246-52

For more answers to questions about potency and bioavailability of resveratrol, consumers are invited to visit:

SOURCE Resveratrol Partners LLC
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