Tuesday, November 5, 2013

St. John's What? An herbal supplement analysis

photo: PatSullivan/Associated Press
A new scientific study that tested the authenticity and integrity of herbal medicine products by analyzing the DNA of their contents found that many herbal supplements are “little more than powdered rice and weeds.”

The Canadian researchers found that pills of 44 popular medicinal herbal products, from 12 companies in Canada and the U.S., were not what they claimed to be. Some used plants other than the advertised species, and others diluted or replaced the advertised herbs with cheap fillers, such as rice or soybean. Still others contained wheat or nuts, making them potentially harmful for people with celiac (coeliac) disease or nut allergies.

If you take herbal supplements (or not), this will be informative!

DNA-tested authenticity of herbal supplements. The bars represent the 12 companies in the test,
with the percentages of ingredients in their respective products that were and were not authentic.
image: The New York Times Company

For example, sample bottles of echinacea supplements, which millions use to prevent and treat colds, contained Parthenium hysterophorus, an invasive weedy plant that can cause dermatitis and breathing problems in people and livestock. So you might prevent a cold, but end up with a bad rash?

The two samples of St. John's wort, used most commonly to treat depression and related anxiety, contained no St. John's wort at all. One contained only rice, and the other contained an Egyptian shrub called Alexandrian senna, which happens to be a laxative with bad long-term side effects. Now that is depressing.

Gingko biloba supplements, taken to enhance memory, were found to contain fillers, as well as black walnut DNA, which could potentially trigger nut allergy symptoms.

Echinacea purpurea
photo: Jacob Rus, Wikimedia
St. John't wort (Hypericum perforatum)
photo: Anne Burgess, Wikimedia
Ginkgo biloba
photo: Crusier, Wikimedia

The supplements were supposedly single-ingredient products, so the researchers expected to find the genetic code of just one plant species in each.

While 48% of the products they tested did contain the key ingredient, about 1/3 of these, and 59% of all 44 tested products, contained other plant species that were not listed on the label. Oops. These would be fillers or contaminants.

Products from just 2 of the 12 companies were the genuine article - no substitutions, contaminants, fillers, or mislabeling - while the products of 3 companies completely lacked the main ingredient on the label.

So how did the scientists determine all this?

The research team asked: (1) whether the herb on the product label was, in fact, found in the bottle; (2) whether that herb was the main ingredient (or did something else make up the bulk of the sample); and (3) whether "filler" ingredients (e.g. rice) were used but not on the label.

They blind tested the herbal products with a technique called DNA barcoding, which uses a very short genetic section from a standard portion of the genome of an animal or plant to identify the species of its owner. (FYI only: Here's one of my early posts relating genes to natural selection and biological fitness.)

an Arctic warbler, from the outside
photo: Alnus, Wikimedia Commons
Genetic barcoding works in the same way a supermarket scanner distinguishes products using the black and white stripes of the UPC barcode of your purchases.

Two items may look very similar, but may have subtle distinctions that are reflected in their genetic makeup, so their respective barcodes would be distinct.

As an example, the genetic sequence of the barcode for the Arctic warbler (a northern European bird that wisely migrates to SE Asia in the winter) looks like this:


and its matching barcode image looks like this:

the Arctic warbler, from the inside   image: International Barcode of Life

Scientists use a particular gene region called CO1 to barcode almost all animal groups because each species has a different sequence of the 4 components of DNA. For plants, they use 2 different gene regions, but for the same reason.

To create a barcode for a sample, researchers must first get their hands on a specimen of biological material, usually blood, tissue, or leaves (for plants) from places like museums, zoos, aquaria, or seed banks. In the laboratory, they can produce a small genetic sequence from the specimen (in this case, the specimens were the herbal supplement capsules).

They then compare the sequence to a database of sequences of known animals or plants and find the closest matching record in the database.

plant barcode sequences
image: New York Botanical Garden
Here are the DNA barcodes for an orchid species and a magnolia species - they are quite different!

DNA barcoding is also being used to help uncover fraud in food labeling (when the snapper you ordered is really tilapia or Vietnamese catfish) and monitor the trade in wildlife and plant products. More to come on those topics.

For now, it's important for the millions of people worldwide that use natural remedies to maintain their health to remember that more than half of the herbal products tested in this study were guilty of product substitution, contamination, and/or use of filler material.

Aside from potentially harming consumers from nut or other contaminant material, by diluting the effectiveness of supplements that might otherwise be helpful, these activities may lower the value of other herbal products because they destroy consumer confidence in them.

On a good note, it IS possible to correctly produce each of these supplements: at least one company produced an authentic product for nearly all the herb species in the study.

The regulation of herbal remedies has been called "the Wild West," and purchasing herbal supplements requires no prescription or advice from a health-care professional, so consumers should review their products carefully and, as much as possible, verify their authenticity.

Here's the published paper for this study:

  • Newmaster, S., et al. 2013. DNA barcoding detects contamination and substitution in North American herbal products. BMC Medicine 2013, 11:222  doi:10.1186/1741-7015-11-222.


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