http://www.prevention.com/mind-body/natural-remedies/herb-supplement-tests
The NY State Attorney General’s office hired James A. Schulte II, PhD, associate professor, biology, of Clarkson University in Potsdam, NY, who used DNA testing to determine the supplements’ purity. But, according to experts we’ve consulted, DNA technology is not an accurate method of testing herbal supplements. That’s because many supplements contain herb extracts that are processed in ways that destroy the plant’s DNA. The absence of DNA, though, has no impact on the effectiveness of the supplement.
“These results do not ring true to me,” says Pieter Cohen, MD, assistant professor of medicine at Harvard Medical School. “The FDA spot checks hundreds of companies, and most mainstream companies check that they put the correct plant substance into their products. So it’s unbelievable that almost 8 in 10 products tested by the attorney general would not even contain the correct plant. On the surface, something is terribly wrong with these results.”