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Levels of pyrrolizidine alkaloids in herbal teas and teas are too high

18/2013, 15.07.2013

The first non-representative results of a BfR research project show that efforts are required to minimise levels

The BfR is currently conducting a research project on “Determination of Pyrrolizidine Alkaloids in Food and Feed”. Initially, various samples of off-the-shelf tea, herbal tea and medicinal tea were examined. As the first results of the non-representative tests, a total concentrations of 0 to 3.4 milligrams of pyrrolizidine alkaloids per kilogram of analyzed sample were found. “We measured unexpectedly high levels of pyrrolizidine alkaloids in some of the tea and herbal tea samples,” says BfR President Professor Dr. Dr. Andreas Hensel. “As data from animal experiments uncovered the detected pyrrolizidine alkaloids as genotoxic carcinogens, the levels are too high and should possibly be reduced” These include analysis of tea and herbal tea batches prior to marketing but also causal research by the economic operators. Despite the unexpectedly high levels in some of the samples, acute health damage to adults and children is unlikely if consumed over short periods. If, however, higher than average consumption of products currently measured with medium and high levels of pyrrolizidine alkaloids is maintained over longer periods, a risk to health could result, especially for children, pregnant women and nursing mothers if the current data is validated. Because there are considerable fluctuations in the concentrations of individual samples, however, even with teas of the same variety, it is currently impossible to make a definite statement regarding the health risk resulting from continous intake of contaminated tea infusions. Our initial recommendation is therefore that parents do not exclusively give their children tea and herbal tea. Expectant and nursing mothers should also consume tea and herbal tea alternately with other beverages. The first data collected in the research project have to be be verified by Food monitoring authorities.

Pyrrolizidine alkaloids are secondary plant substances produced by a large number of plant varieties all over the world as protection against predators. The occurrence of pyrrolizidine alkaloids in plants varies strongly, depending on the plant variety and part, and is also influenced by other factors (e.g. climate, soil properties). Due to their health-damaging potential, 1,2-unsaturated pyrrolizidine alkaloids (PA) in particular are not desired in foods and feeds as they can lead to acute liver damage when consumed in high doses. Some PA have proven to be genotoxic carcinogens in animal experiments.

Within the scope of a research project at the Federal Institute for Risk Assessment (BfR), an analysis method for determining pyrrolizidine alkaloids in tea and herbal tea samples was developed and tested for its applicability. In the course of the project, 221 different off-the-shelf tea, herbal tea and medicinal tea samples from German retailers were analyzed for their content of 1,2-unsaturated pyrrolizidine alkaloids. The samples were not obtained by means of a representative random sample of the corresponding products available on the German market.

The following herbal tea varieties were included in the estimation of exposure: baby fennel tea, fennel tea, chamomile tea, herbal tea, peppermint tea, nettle tea and melissa tea. Other tea varieties which were also tested but not included in the estimation of exposure due to the low total of samples were green tea, rooibos and black tea.

The BfR used the MOE (Margin of Exposure) method, which is an internationally approach to estimate the potential risk of substances with genotoxic and carcinogenic effects, as the basis for assessing the possible health risks of long-term intake. The margin of exposure is calculated as the ratio of human exposure (extent of contact) to a substance and the effective dose established or calculated in animal tests for a given tumour incidence (normally BMDL10 = benchmark dose; tumorigenic with 10 % of the animals tested). It is assumed here that a MOE of 10000 or higher for genotoxic would be of low concern from a public health point of view.

If tea and herbal tea contaminated with PA is consumed frequently in larger quantities, however, the MOE value for the intake of PA is well below 10000 for adults and children. This means that a health impairment is possible if large quantities of these tea or herbal tea with increased PA levels are consumed regularly.

If the data from the non-representative study prove to be typical for the PA levels in herbal teas and teas, the BfR is of the opinion that efforts are required to lower PA levels in teas and herbal teas to the greatest possible extent due to the genotoxic and carcinogenic effects of PA. This is also necessary because the possibility of additional PA exposure exists through other foods such as honey. The BfR considers adequate checks of the PA levels of tea and herbal tea batches prior to marketing and research by economic operators into the cause of the high PA levels in the corresponding products to be necessary. Food control  should make checks with regard to the potential PA levels of tea and herbal tea samples.

As a general rule, the BfR advises alternation and variety when selecting foods in order to prevent unbalanced burden with various potentially health-damaging substances, the isolated occurrence of which in foods has to be expected.

About the BfR

The Federal Institute for Risk Assessment (BfR) is a scientific institution within the portfolio of the Federal Ministry of Food, Agriculture and Consumer Protection (BMELV). It advises the Federal Government and Federal Laender on questions of food, chemical and product safety. The BfR conducts its own research on topics that are closely linked to its assessment tasks.



Date Title Size
BfR Opinion No. 018/2013
Pyrrolizidine alkaloids in herbal teas and teas 313.6 KB



Date Title Size
Updated BfR FAQ
Questions and Answers on Pyrrolizidine Alkaloids in Food 77.2 KB


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