The use and availability of herbal preparations covered by food law is increasing in the Netherlands and in other European Member States. Correspondingly, safety concerns relating to herbal preparations are growing as well. The aim of the present PhD project was therefore to review the toxicity of selected herbal preparations, to investigate the presence and actual levels of selected naturally-occurring toxic substances and contaminants in herbal preparations on the Dutch market and to estimate the associated risks.
First, an overview is provided of the Dutch and European legal provisions for food commodities with botanical ingredients, the nature and mechanism of action of various toxic botanical ingredients specifically covered by these provisions, and the health concerns defined by risk assessors related to several botanicals for which no specific legal provisions exist. Secondly, data are presented on the actual occurrence in traditional herbal preparations (THPs) of a group of phytotoxins, i.e. aristolochic acids, which were banned by the Dutch Commodities Act Decree ‘Herbal preparations’. Aristolochic acids and derivatives are nephrotoxic, genotoxic and carcinogenic and are present in several plants from the Aristolochiaceae family. Aristolochic acids were found in 25 of 190 THPs used in Traditional Chinese Medicine (TCM) sampled on the Dutch market. This shows that testing for aristolochic acids of Chinese THPs at risk of contamination is essential in the framework of food safety.
Thirdly, the presence of selected toxic contaminants in herbal preparations on the Dutch market was investigated. Lead, mercury and arsenic levels were analyzed in THPs used in several Asian traditional medicine systems, such as Ayurveda, TCM, and Traditional Tibetan Medicine (TTM). These metals and metalloids were present in 186 (64%) of 292 THPs and use at recommended dose levels of 59 THPs (20%) would result in intakes of these contaminants significantly above established toxicological safety limits. It was concluded that the mercury, arsenic and lead contents of these Asian THPs are cause for concern. Because metals such as mercury can exist in various defined chemical species with different toxic properties, a study was performed using selective acid extraction procedures to determine the presence or absence of the relatively non-toxic elemental form of mercury in 19 Ayurvedic THPs, which were shown in the previous study to result in mercury intakes above the safety limit for inorganic mercury when used at the recommended daily dose level. It was concluded that in these THPs the main part of the mercury content is not present in the elemental form, that the mercury detected in Ayurvedic THPs is likely to be present in the inorganic form and that therefore the estimation of the related risks based on the safety limits for inorganic mercury is justified.
In the last study of this PhD thesis, polycyclic aromatic hydrocarbons (PAH) were determined in more than 1500 food supplements sampled on the Dutch market, many of which contained herbal ingredients. Herbal preparations can become contaminated with PAH through various processes including direct atmospheric deposition on plant surfaces and drying practices during manufacturing. Several PAH, such as benzo[a]pyrene are genotoxic and carcinogenic. Supplements containing herbal ingredients such as St. John’s wort and Ginkgo biloba, the phytochemical resveratrol and the bee product propolis showed the highest mean PAH levels. It was shown that individual food supplements can contribute significantly to PAH exposure, whereas on average PAH intake resulting from food supplement use will be at the lower end of the range of contributions of main food groups to PAH exposure.
From the work described in this thesis it can be concluded that for herbal preparations ‘natural’ does not equal ‘safe’. Given that uncertainty exists whether additional European legal measures will be taken in the near future to restrict or prohibit the use of specific toxic herbal substances in foods and the fact that several herbal preparations for which specific provisions are absent in Dutch food safety law raise toxicological concern, would suggest that it is prudent to keep the Dutch Decree ‘Herbal preparations’ and other national legislation up to date in order to protect consumers from serious risks resulting from use of botanicals in food products such as herbal preparations.