The well-known Dr. Chris van Tulleken recently joined forces with Professor Michael Heinrich and Dr. Anthony Booker from the University College London School of Pharmacy to test a range of herbal products on sale in the UK. They bought over 70 herbal products from various high street stores and internet retailers. Some of the products were ‘THR’ (traditional herbal registration) herbal medicines, and some were marketed as food supplements. They then analyzed their chemistry to see whether each one really contained what the label says. The three popular herbal remedies we tested were:-
- Milk thistle (Silybum marianum),
- Ginkgo (Ginkgo biloba),
- Evening primrose (Oenothera).
The team at UCL used two different methods of analysis to verify the identity of these herbal products and extracts. High-performance thin-layer chromatography (HPTLC) is a sophisticated technique for the analysis of herbal products and is one of the most commonly used methods in the industry. HPTLC analysis creates a chemical fingerprint of the product which the researchers can then compare to an accepted reference standard for the herb. They look for a broad spectrum of ‘marker compounds’ these are the pharmacologically active and/or chemical constituents within a plant that can be used to verify its potency or identity. For complex samples or where additional confirmation is required, researchers often turn to ¹H nuclear magnetic resonance spectroscopy (¹H-NMR) which allows individual samples to be compared in detail against other samples or to the whole group.
In every THR product tested, the product contained what was claimed on the label. However, the food supplements showed a wide range of quality.
- Of the food supplement products labeled as Ginkgo, 8 out of 30 (27%) contained little or no ginkgo extract.
- 36% of the food supplement milk thistle products contained no detectable milk thistle. Although this is quite a small sample size it is still a startling result. Furthermore, in one case of milk thistle, unidentified adulterants suspected to be synthetic compounds were present in place of milk thistle.
- All of the evening primrose food products we tested did contain what the packet claimed.
The researchers concluded that their investigation shows that a regulatory system for herbal products, like the THR scheme, ensures that people have access to safe herbal medicine products. So, if you are considering buying herbal products then do look out for the THR mark– otherwise, you might not just be wasting your money, you might be consuming other, potentially dangerous, ingredients.
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This is an interesting investigation. The researchers should be commended for it! However, I disagree with some of their conclusions. Here is why:
- The investigation merely tested the quality of the products and NOT THEIR SAFETY! To claim that the THR ensures access to safe herbal medicines is incorrect. A product might be of adequate quality but can still be unsafe. The THR only implies safety because the herbal has been used for years without problems being noted. This is not the same as ensuring that it is safe. A direct test of safety is usually not available.
- The recommendation to buy a product with a THR mark is also somewhat misleading. It implies that these products are effective. I fail to see convincing evidence that either MILK THISTLE, GINKGO, or EVENING PRIMROSE are effective for any disease or condition. Thus the responsible recommendation should, in my view, be to NOT buy them regardless of whether they are of good quality or not.
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