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Frequently Asked Questions on Pyrrolizidine alkaloids in food
BfR FAQ, 3 February 2012
Pyrrolizidine alkaloids are secondary metabolites that are produced by certain plants. Due to their potential detrimental health effects, they are unwanted in food and feed. In Germany, cases have occurred where PA-containing plants of the Senecio genus (ragwort, groundsel) were mixed into salads. Depending on their origin, certain honeys may have elevated PA contents. In the opinion of the BfR, efforts are needed to reduce this contamination. The consumption of honey does not pose an acute risk to consumers. As regards salad, the BfR recommends that special care is taken during harvesting and preparation in order to avoid contamination with groundsel and resulting potential health risks.
What follows below is a list of questions and answers compiled by the BfR.
- What are pyrrolizidine alkaloids (PA)?
- Are there known cases of acute poisoning with PA?
- What chronic effects can PA have?
- Why can PA be contained in food?
- Are there limit values for PA in food?
- Why are PA so difficult to detect?
- Is there a risk for consumers?
- What efforts are required on the part of the BfR in order to lower the contamination with pyrrolizidine alkaloids?
- What can consumers do in order to minimise PA contamination?
Pyrrolizidine alkaloids are secondary metabolites that are produced by some plants. Certain types of plants produce PA in order to protect themselves against predators. There are more than 500 different PA which are found in over 6,000 plant species. The PA-containing plants are mostly members of the daisy, forget-me-not or borage families as well as the legume family. PA-containing plants native to Germany include, for example, tansy ragwort, common groundsel and viper’s bugloss. Chemically speaking, pyrrolizidine alkaloids are esters composed of 1-hydroxymethylpyrrolizidin (necine base) and aliphatic mono or dicarbon acids (necine acids).
In high dosage, PA can lead to fatal liver failure. The clinical syndrome of PA poisoning is known in animals as seneciosis and is usually caused by groundsel found in pastures. For example, beef cattle that have eaten Alpine ragwort with hey and silage have increased rates of liver cirrhosis.
There are also known cases of humans becoming ill as a result of consuming PA in high doses. For example, people were taken ill in Pakistan, India and Afghanistan after eating wheat contaminated with seeds from Heliotropium or Crotalaria species. In Jamaica, cases of poisoning have occurred through so-called bush teas containing Crotalaria and parts of the ragwort plant.
There is consensus that animal experiments have conclusively shown the genotoxic and carcinogenic effects of certain unsaturated PA. These findings are seen as relevant for human risk assessment. However, no findings exist that confirm such an effect on humans. The embryotoxic effect of certain PA is also known from animal experiments. Nevertheless, the data are incomplete and nothing is known about the possible toxicity of PA to human development.
It is possible that pyrrolizidine alkaloids enter food via plant-based food components. PA have been detected, for example, in herbal teas, cereals, salads and honeys. Cases of elevated PA contamination in wheat are known to have occurred in Afghanistan. This contamination was caused by a strong proliferation of plants of the Heliotropium genus in wheat fields. In Germany, there have been incidents of contamination of salads with ragwort and groundsel containing PA.
Plants that can contribute to PA contamination of honey include Echium, Senecio and Borago species whose PA-containing pollen are used for honey production by the bees. Raw honeys from certain countries in Central and South America as well as Asia show higher PA-contents compared to raw honeys from some European countries. Humans could also ingest PA when such substances get into agricultural production animals along the food supply chain, i.e. from contaminated feed into production animals and from there into animal-based food such as milk, eggs and meat. Based on the current state of knowledge, there are no indications at present to suggest that such animal-based foods contain PA in concentrations that would pose a health risk to consumers.
In contrast to drugs, there are no legal limit values for PA in feed or food.On the basis of the available data, the Federal Institute for Risk Assessment (BfR) has conducted a provisional assessment of the health risk of pyrrolizidine alkaloids in foods and especially in honey. This assessment took into account both acute and chronic toxic effects. The BfR concludes that overall consumer exposure to genotoxic and carcinogenic pyrrolizidine alkaloids from various foods is to be kept as low as possible. A daily intake of 0.007 micrograms (μg) of unsaturated pyrrolizidine alkaloids per kg of body weight (BW) should, if possible, not be exceeded in case of chronic exposure. If average amounts of locally produced honeys are consumed, this daily intake is not reached.
Due to their structural diversity, their low concentrations, and the complex matrix of composite foods, pyrrolizidine alkaloids pose special challenges in terms of their analysis. Currently only a few pyrrolizidine alkaloids can be reliably determined in food and feed. The BfR therefore concludes that further research is needed in order to develop the relevant validated specific detection and screening methods for pyrrolizidine alkaloids. These methods can then be used in food and feed monitoring programmes of the federal states as well as the food and feed industry.
No acute health risk from PA poisoning is posed to consumers by eating honey. Normal users need not worry. As a general principle, measures to reduce PA should be taken in the production of honey in order to minimise to the greatest extent possible the potential health risks even for high long-term use of honey. As regards salad, the BfR recommends that special care is taken during harvesting and preparation in order to avoid contamination with groundsel and resulting potential health risks.
What efforts are required on the part of the BfR in order to lower the contamination with pyrrolizidine alkaloids?
In order to minimise the potential health risk for people consuming honey in high quantities and especially for children, efforts should be made to reduce the PA contents of contaminated honeys. A judicious selection of raw honeys which are used for the manufacture of mixed finished products can contribute to a reduction of PA contents in ready-to-eat honeys.
It is recommended that PA and PA-containing plants and / or parts of plants should be eliminated from the food supply chain to the greatest extent possible. In addition, consumption of pollen containing PA and / or products (e.g. food supplements) which are partially composed of PA-containing plants should be avoided.
Taking great care when cultivating and harvesting lettuces, vegetables and herbs can significantly enhance food safety. Due to their conspicuousness, common groundsel types that may contain PA are easy to spot in most cultures and can therefore be effectively controlled by suitable measures.
The BfR recommends that special care is taken when preparing salads, leafy vegetables and herbs. Consumers should clean and wash them thoroughly before use and take out all plant parts that cannot be assigned to any edible plants.
Raw honeys from certain countries in Central and South America as well as Asia show higher PA-contents compared to raw honeys from some European countries.
Consumers can ascertain where honey comes from (for example, the packaging will inform them whether the honey comes from non-EU or EU countries). In accordance with the honey regulation from 16 January 2004 (the current version thereof) the origin of the honey must be stated on the packaging. An elevated intake of PA via honey can be avoided by choosing the right products. Consumers who take pollen-based food supplements should be aware that such products can contain PA in higher concentrations. Based on the current state of knowledge, there are no indications at present to suggest that animal-based foods contain PA in concentrations that would pose a health risk to consumers.