(HealthScoutNews) -- What you see may not be what you get, and what you get may not be what you need -- when shopping for the popular herbal supplement St. John's wort.

That's the finding of a new study that reports sizeable discrepancies in label claims and compounds found in eight popular brands of the popular yet controversial herb commonly used to treat mild-to-moderate depression.

In research published in the new edition of the American Journal of Health System Pharmacists, scientists from the University of Southern California's School of Pharmacy report that manufacturers of at least some versions of St. John's wort may be concentrating their formulas on the wrong components of the herb. Also, these same companies may not be so accurate in listing the percentages of the compounds the products contain.

"Most manufacturers test their products for levels of hypericin, while ignoring the compound hyperforin, even though there is good evidence that hyperforin may have the most therapeutic benefits," says lead study author Gerlie de los Reyes, a researcher at USC's Department of Pharmaceutical Sciences.

Complicating matters further, manufacturers that do test for hypericin and put the results on the product label aren't always accurate in their claims. The study also found that those that significantly mislabeled hypericin levels were also more likely to include too little hyperforin -- to the point where only two of the eight products tested got the researchers' approval.

"We concluded that manufacturers need to accurately assay [test levels] their products and ensure levels of both hypericin and hyperforin if the product is going to be effective," de los Reyes says.

Alternative medicine specialist Dr. James Dillard says that conclusion is important, if for no other reason that we still don't know what it is about St. John's wort that helps us feel better.

"The latest information is that we don't know whether hypericin or hyperforin is the key ingredient. And, in reality, we don't know if either one is having the effect independently, or if they must work in harmony to achieve the results," says Dillard, medical advisor at the Rosenthal Center of Alternative and Complementary Medicine at Columbia University.

In fact, Dillard says, it may be that all the compounds found in St. John's wort are necessary to combat depression.

"This is why products need to be standardized for as many of the compounds as possible -- to ensure that the product is of high quality and that it will yield the therapeutic effects," Dillard says.

The USC study examined eight brands of St. John's wort: PNC (Pharmacists Nutrition Center, Wilsonville, Ore.); Brite Life (Bergin Brunswig, Orange, Calif.); ShopKo (ShoptKo Stores, Green Bay, Wisc.); Shurfine (Shurfine International, Northlake, Ill.); Your Life (Leiner Health Products, Carson, Calif.); Nature's Balance (Vitamin Classics, Calabasas, Calif.); and Natrol (Natrol, Chatsworth, Calif.), and Hyperifin (Finzelberg, Birkenweg, Germany).

First the researchers checked the levels of hypericin and compared them to the amounts printed on the label. The result: Only Hyperifin (with 98 percent of its label claim) and Your Life (with 95 percent of its label claim) were considered "accurate."

PNC contained approximately 80 percent of its label claim; Natrol, approximately 82 percent, and Shurfine tested at just 56 percent of its label claim. Nature's Balance, which had no label claim for hypericin, came in with the lowest amount -- 0.03 percent.

While two of the products exceeded label claims -- Britelife with 110 percent and ShopKo with 130 percent -- de los Reyes says this isn't necessarily a good thing.

"The further away you get from the amount listed on the label -- high or low -- the less likely that the product is being carefully examined and tested," says de los Reyes. What's more, she says, discrepancies in one compound often mean discrepancies in ingredients that may not listed.

And that's what the researchers found when they tested for hyperforin. While research shows hyperforin should be present in amounts ranging from 1 percent to 6 percent, des los Reyes says few companies standardize for this ingredient. Amounts found in the products she tested ranged from a low of 0.01 percent (Nature's Balance) to a high of 1.89 percent (Hyperifin).

Percentages of hyperforin found in the other products were: ShopKo, 0.05; Your Life, 0.19; PNC, 0.20; Shurfine, 0.29; Natrol, 0.48; and Brite Life, 1.16.

"Only two of the brands we measured [for hyperforin] went over the 1 percent mark -- Hyperifin and Brite Life," de los Reyes says.

These were the same two products that came the closest in accuracy to label claims for hypericin.

The product with the least hyperforin -- Nature's Balance -- also had the lowest level of hypericin, according to de los Reyes.

"The point of our study is that all St. John's wort products should be standardized for both hypericin and hyperforin, in order for consumers to get a product that really works," she says.

Dillard agrees: "The long answer is that we need better regulations of herbal products with more standardization. The short answer is to buy products from known manufacturers, with supplements imported from Germany usually among the most reliable."

The Council for Responsible Nutrition is a science-based trade organization of the dietary supplementary industry.

Asked to respond to the USC study, John Cardellina, vice president of botanical science and regulatory affairs, says, "This study has analyzed for content of components that aren't listed or claimed on the label. Based on that, they are concluding that the products are not appropriately manufactured. The flaw here is that the researchers are not taking into account the continuing debate regarding which of the components in St. John's wort are responsible for providing the antidepressant activity.

"At best, hyperforin is one of three chemical components of St. John's wort that contributes to the antidepressant activity of the plant. So St. John's wort could very well be an effective product without containing hyperforin. In fact, there is a substantial evidence base derived from over 30 clinical trials of St. John's wort that demonstrates its benefits for mild-to-moderate depression, but what is not clear is whether that benefit comes from hyperforin, hypericin or flavonoids or a combination of all three," Cardellina added.

What to Do: To learn more about how to choose an herbal product, visit The Herb Research Foundation. To learn more about St. John's wort, check the National Center for Complementary and Alternative Medicine.

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