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Brent Bauer, an internist at the Mayo Clinic, noticed something strange in recent years about the clinic's arthritis patients. Some reported no longer needing their steroid medications after drinking a juice produced from an obscure fruit.

Bauer began wondering whether there really is something to the mangosteen. This tropical berry is used in expensive supplement beverages sold through multilevel marketing programs, including Utah's XanGo, that claim anti-inflammatory properties and other health benefits.

Under Bauer's supervision, Mayo is now organizing a randomized 250-patient clinical trial on XanGo's flagship product, but without the company's funding or influence.

"We initiated the study because of patient interest," said Bauer, director of the Complementary and Integrative Medicine program at the famed research clinic in Rochester, Minn. He is recruiting patients for the study, which will be double-blind and placebo controlled.

But not every inquiry into XanGo's products hews to this gold standard of clinical science, in which some patients take a placebo, and neither patients nor researchers know who is getting what. And some studies' results are widely touted but never published so consumers don't know how the research was done.

One company-sponsored trial into XanGo's new Eleviv supplement is particularly suspect, yet the company touts it in promoting the product's vigor-boosting claims. Officials concede this study was little more than a "proof-of-concept" inquiry, setting the direction for subsequent studies.

"XanGo is proud of its commitment to advance scientific research that is credible and, in many cases, validates the experience of millions of consumers worldwide," spokesman Jeff Chandler wrote in an email.

Studies by Mayo and others are part of rising tide of clinical trials into possible health benefits of nutritional supplements, which represents a $6 billion industry in Utah. Some research is independently funded, but much is sponsored by the industry itself and is conducted on university campuses and in contract-research labs, such as Medicus Research in Northridge, Calif.

"They want to scientifically demonstrate efficacy: Does it work?" said Jay Udani, director of Medicus, which XanGo has hired for juice studies. "The second thing is for the consumer, so they can understand the benefits and how it applies to them."

Japan's Kyowa Hakko and Utah's USANA Health Sciences are funding ongoing research at Utah universities into the health benefits of their products.

"This is a sign that these companies are stepping up to put sound science behind their product," said Michael Lefevre, director of Utah State University's Applied Nutrition Research team, which is researching whether a USANA supplement can reduce airway inflammation.

Still, consumers should remain wary, particularly when companies make claims based on "borrowed research." Sometimes they cite studies that demonstrate the benefits of a nutrient or ingredient, say ginger, without noting whether it's the same ginger in their product, Udani said.

"You don't know if your ginger will have the same effect," he said. Multiple active ingredients in combination may actually reduce efficacy because they compete for the same metabolic pathways.

Udani advises companies to first run pilot studies on their products, followed by larger clinical trials to confirm positive results. But such inquiries aren't cheap if they follow scientific standards. A pilot study can cost up to $75,000 and trials from $50,000 to $300,000, depending on the protocols, and can take up to three years to complete.

Medicus last year published a pilot study on XanGo's mangosteen juice affirming its promise for reducing one marker for inflammation, C-reactive protein, but not other markers.

Another reason such studies are a smart investment: The Federal Trade Commission has been stepping up enforcement of rules against making health claims with no scientific basis, Udani says.

One of the FTC's past targets was weight-less formula CortiSlim, developed by Shawn Talbott when he was a University of Utah instructor. Now XanGo's science adviser, Talbott is back with a new supplement, the XanGo-marketed Eleviv, a formulation of herbs found in traditional Chinese medicine.

Where's the rigor? • Unlike the Mayo study, the Eleviv study did not adhere to the gold standard protocols — randomized, double-blind and placebo-controlled — required to demonstrate causal relationships between a substance and its benefits. Yet, the company cites its study as "astoundingly affirmative" proof that Eleviv promotes broad health benefits that include lowered levels of the hormone cortisol and increased energy and focus.

"We're confident in this research and what it has shown. The study was intended as a benchmark for ongoing research that may be published in the future," said an email from spokesman Jeff Chandler.

Published by Talbott last year in a peer-reviewed journal, the study does not disclose Talbott's ties to the product or XanGo. Talbott helped devise Eleviv's recipe of camellia leaves used in green tea, the herb eurycoma, citrus peel and the amino acid L-theanine. A month's supply of Eleviv, which Talbott's bio says generates more than $20 million in annual sales, retails for $70.

He tested the product through his Draper firm SupplementWatch, publishing the results under the title "Ancient wisdom meets modern ailment — Traditional Asian medicine improves psychological Vigor in stressed subjects," in the journal Progress in Nutrition.

All 82 subjects took the supplement in concert with a lifestyle "intervention" that included recommendations to eat a balanced diet and follow moderate exercise. At the end of eight-week and 12-week regimens, the participants demonstrated dramatic improvement on tests gauging mood and energy, as well as improved hormone ratios between cortisol and testosterone, the study reported.

But those benefits could have been the exclusive result of improved diet and exercise. Had the study measured hormone and mood levels in a randomized control group that took a placebo, the results could have separated effects associated with the supplement from those associated with the lifestyle changes, notes Roberta Anding, a spokeswoman for the American Dietetic Association.

Yet the study concludes that "the addition of a 'balancing' dietary supplement based on traditional Asian medicine is effective in balancing metabolic hormone profile, reducing stress and improving mood state."

Based on these preliminary findings, Talbott said, he moved forward with a placebo-controlled, double-blind study on XanGo juice and Eleviv in combination. He claims it demonstrated anti-inflammatory and anti-stress effects, but XanGo declined to publish the study even though Talbott has been presenting its conclusions at conferences.

"Sometimes supplement companies don't want to publish their work for proprietary reasons," he said. "Once they get the data, they just want it for marketing purposes."

What about apples? • Anding does not doubt XanGo products are healthy because they are based on plants rich in polyphenols and other antioxidants. But research, flawed or not, may simply be a marketing tool to persuade people to buy high-priced novel juices when they could spend less on apples or broccoli.

"Could I do the same thing with blueberry juice?" asked Anding, director of sports nutrition at Texas Children's Hospital. "The science is compelling that a plant-based diet is associated with a lower [body-mass index], lower cardiovascular disease, but the money is made on the marketing of the nutrients found in the individual components of a particular food."

Udani of Medicus Research says that criticism is easily rebutted.

"When two-thirds of our country is overweight and not getting access to the right types of foods, the role of dietary supplements and functional foods is exactly to supplement the diet of those who don't have a lifestyle to go to farmers markets and create home-cooked meals every day," he said.

All the subjects in the Mayo study have a history of atrial fibrillation, a form of cardiac arrhythmia often caused by inflammation-induced fibrosis in the upper chambers of the heart. But the team is excluding people who have undergone recent surgery, suffer from heart attack, vascular disease, or an active infection, or are on corticosteroids.

"We chose a difficult population to recruit," Bauer said.

The treatment group will consume six ounces of mangosteen juice a day for three months, while the control groups will take a placebo juice. At three months and six months, researchers screen the participants for a host of immune-function and inflammation markers, as well as quality of life indicators.

"Based on pre-clinical trial data there is something there," Bauer said. "XanGo is supplying the product, but they have no say in the research. At the end of the day, it's our science."