I like a piping hot mug of mint tea as much as the next
person but I wouldn’t say I ride the herbal medicine bandwagon. That’s not to
say I don’t think natural medicines can be beneficial, I simply wouldn’t know
where to start. If you are the type to put flaxseed in your smoothies or take
krill oil before bed here’s something you might want to know.
The ginseng tea you have been sipping to reduce stress
may actually be half alfalfa sprouts. Researchers in Ontario, Canada performed genetic
analysis on 44 commercially available herbal supplements from 12 companies in North
America and found that most contained something other than what was on the
label.
The scientists used a process they call “DNA barcoding” which
allows them to compare DNA they found in the supplements to a huge database of DNA
sequences and the plant species they belong to. DNA barcoding is a relatively
young procedure for comparing plant DNA, but the authors of this paper make
exciting headway. The procedure relies on comparisons between the sequences of
a common gene among plants. The tricky part is finding a gene that all plants
have but whose sequence varies enough between species to differentiate them.
The winner? A gene called rbcL that codes for an enzyme
nicknamed RuBisCo. RuBisCo is arguably the most important enzyme a plant has
because it starts the plant’s metabolic cycle. The sequence of a plant’s RuBisCo
gene turns out to be highly conserved within species, but significantly varied
between species. This made it an excellent candidate for the DNA barcoding the
scientists used in this study.
The scientists, just like we consumers, expected that
bottles labeled “Ginkgo” would contain only Ginkgo DNA. However they found that
one Ginkgo product was contaminated with walnut DNA and a product labeled St.
John’s Wort contained Senna alexandrina
which can cause chronic diarrhea. The authors found scores of contaminants and
fillers in most of the products they tested, some with nasty sounding
side-effects and others that were obviously just used to skimp on production
costs. Nine percent of the products tested were actually just ground up rice or
wheat to be sold as this, that or the other.
Even though some of the contaminants and fillers sound
harmless—people eat walnuts and rice all the time—you can imagine that someone
with a nut or gluten allergy would probably be worried about them! The point is
not that everyone should avoid herbal supplements at all costs. The misrepresentation
of product labels and the lack of industry standards for what constitutes a “pure”
supplement are obviously out of whack. Even with the study’s small sample size,
the degree of deception is surprising, emphasizing the vigilance we all need to
have with regard to what we consume. And we should all be concerned enough
about what we put into our bodies to take note of this study.
Sources and further reading
Newmaster, S.G; Grguric, M; Shanmughanandhan, D;
Ramalingam, S; Ragupathy, S. (2013) DNA barcoding detects contamination and
substitution in North American herbal products. BMC Medicine, 11:222.
Accessed here: http://www.biomedcentral.com/content/pdf/1741-7015-11-222.pdf
Newmaster, S.G; Fazekas, A.J; Ragupathy, S. DNA barcoding
in land plants: evaluation of rbcL in a multigene tiered approach. (2006) Can. J. Bot. 84, pp 335-341. Accessed here: http://www.nrcresearchpress.com/doi/pdf/10.1139/b06-047
New York Times article: http://www.nytimes.com/2013/11/05/science/herbal-supplements-are-often-not-what-they-seem.html?ref=science
Also check out what a Hendrix college alum,
pharma-blogger Derek Lowe had to say about it: http://pipeline.corante.com/archives/2013/11/04/the_herbal_supplement_industry_is_not_a_very_funny_joke.php
Background photo credit: http://www.lmitchellacupuncture.com/services.html
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