Health Supplements Checked by DNA Barcoding

Did you know that after the New York State attorney’s office ordered four major retailers of herbal supplements to pull store-branded supplements from their shelves, they are now demanding ingredient and quality control information from the manufacturers of these products?

The tests for these products used DNA sequencing technology, but first some background is in order.

The Consortium for the Barcode of Life is an international initiative established in 2004 for global standardization for species identification. Analogous to a supermarket barcode, a short sequence of DNA is chosen that is evolutionarily conserved, but has enough sequence variation to differentiate species.

Taxonomy historically depended upon human judgment which involves an evaluation of morphology. A taxonomist would look at the shape, size and color of different body parts of an invertebrate or mammal and make the appropriate assignment. Recently, non-specialists can obtain precise species identification using very small amounts of tissue (instead of the entire organism) with Sanger sequencing equipment. The highly conserved mitochondrial gene cytochrome c oxidase 1 CO1 is effective in identifying diverse standard Sanger sequencing equipment. The original proposal for animal species was a highly conserved mitochondrial cytochrome c oxidase 1 gene CO1, and at about 600 bases is very effective at identifying species as diverse as butterflies, salmon or monkeys.

However in plants, the mitochondrial genome has a much lower substitution rate, so alternative genes in plastids have been chosen; the Consortium recommended two loci rbcL+matK and published this work in 2009.  A few months later an improved locus (a nuclear ribosomal DNA spacer regions) ITS2 could potentially be used for finer discrimination for plant species.

In 2013 a group at the Center for Biodiversity Genomics at the University of Guelph (Guelph Ontario, Canada) published work establishing Standard Reference Material (SRM) for 100 herbal species of known provenance, using both the rbcL and ITS2 regions. They also blind-tested 44 herbal supplements found at retail outlets in North America.

They found that of these 44 herbal products, 59% had DNA barcodes from plant species not on the label; in 68% of the supplements product substitution occurred. The authors were led to conclude: “Most of the herbal products tested were of poor quality, including considerable product substitution, contamination and use of fillers.”

The $6 billion herbal health supplements industry (2013 estimate by the American Botanical Council) is currently under close scrutiny by the State of New York, joined recently by prosecutors from Connecticut, Indiana and Puerto Rico. The Office of the Inspector General (US Department of Health and Human Services) issued a report in 2012 raising concerns to the FDA about dietary supplements, and this 2012 commentary in the Journal of the American Medical Association Internal Medicine reviews the dangers of adulterated health supplements. In North America the challenge of checking each product is a formidable one .

The New York State Attorney’s Office has taken the lead in working to remove questionable herbal supplements off the shelves of major retailers. Their testing showed only five out of 24 supplements tested had DNA evidence of containing the supplement as labeled. The supplements industry has criticized the testing methodology used by the State of New York, arguing that extraction and purification methods that may be used to manufacture these supplements destroys the DNA that is available for testing, and that other methods such as Mass Spectrometry and High Performance Liquid Chromatography should be used.

Do you agree with the state attorney general’s action, or do you think that the supplements industry is justified in asking for additional types of testing? Leave a comment below.