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New research raises quality issues of herbal supplements

(10 August 2022) A new, peer reviewed study published in Frontiers in Pharmacology(1), suggests that consumers should be cautious when buying unregulated supplements containing herbs, as some have been found to be prone to quality issues.

Herbal products containing the same ingredient and regulated under different categories can be of different quality. In this study, the quality of herbal medicines granted a Traditional Herbal Registration (THR) were compared with products categorised as food supplements in the UK. Both categories of herbal products contained the three most popular herbs, milk thistle, echinacea (coneflower) and black cohosh. The products were analysed using High-Performance Thin Layer Chromatography (HPTLC) fingerprints which can detect adulteration and other quality issues in herbal products.

Whilst 100 per cent of the THR herbal medicines contained exactly the herb and concentration displayed on their label, this was not the case with the food supplements where quality issues were found in 52 per cent of milk thistle products, 25 per cent of echinacea products, and 46 per cent of the black cohosh products.

Amongst the food supplement products tested, the research found quality issues that included: the absence of the herb declared on the label of the product, a lower concentration of the herb in the product than specified on the label, and the presence of undeclared herbs, incorrect species of herb and/or other adulterants.

UK pharmacies, health stores and supermarkets commonly stock herbal medicine products and food supplements but few consumers realise that there are two types. The first are regulated and assessed for quality and safety by the UK’s Medicines and Regulatory Healthcare Products Regulatory Agency (MHRA) and once approved for sale, display the Traditional Herbal Medicine (THR) symbol on the packaging. The second are unregulated food supplements that contain herbs and are sometimes combined with vitamins and minerals. These food supplements will comply with Good Manufacturing Process (GMP) if they are produced by companies that are member of a UK Trade Association (see below). However, for products that are produced by companies who are not members of specific trade associations, these food supplements may not be produced to GMP standards and may not contain what is specified on the label, as this latest research shows.

Dr Chris Etheridge, Chair of the British Herbal Medicine Association, medical herbalist and co-author of the research says: “The results show that THR herbal medicines regulated by the government’s MHRA provide a reliable, herbal medicinal product for the consumer to buy. However, whilst there are many responsible manufacturers of unregulated food supplements containing herbs, this is not the case across the board.”

Under the current regulatory system, when buying a herbal medicine for a specific self-limiting condition, such as for joint pain, menopausal symptoms or for cough and cold symptoms, Dr Etheridge advises that “consumers should always look for the THR symbol which is displayed on each pack. This symbol provides assurance that the product is of high quality, regulated by the MHRA and contains exactly what it should. These herbal medicinal products have been assessed for safety and quality and carry an approved medicinal claim on their pack explaining precisely what symptoms they relieve such as hot flushes or joint pain. Inside each pack there is always a Patient Information Leaflet (PiL) that provides important information about its use, and any warnings or contraindications with other medicines.”

Some of the herbs that can be bought in the UK as approved THRs include:

Agnus Castus

Arnica Flowers


Black Cohosh

Blue Flag

Burdock Root

Celery Seed

Clivers Herb

Comfrey Root (external use only)


Devil’s Claw


Eucalyptus Essential Oil



Ginkgo Biloba


Horse Chestnut

Ivy Herb


Lemon Balm


Milk Thistle

Nettle Leaf

Norway Spruce

Passion Flower


Poplar Bark

Prickly Ash, Southern Bark





St John’s Wort

Tea Tree Essential Oil




Wild Lettuce

Witch Hazel

Yarrow Herb

Consumers can find brands that provide approved, regulated THR herbal medicines from the British Herbal Medicine Association /

However, some herbs are not yet available as THR herbal medicines. Consumers who wish to buy these herbs for their health will only be able to find them in the food supplement category which should be bought from credible brands registered with one of the following UK Trade Associations:

• The Health Food Manufacturers Association /

• The Proprietary Association of Great Britain /

• The Council for Responsible Nutrition /

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