Potential carcinogen? Pyrrolizidine alkaloid levels in dried and deep-frozen spices and herbs too high, report concludes

21 May 2019 --- High levels of the potentially carcinogenic organic compound 1,2-unsaturated pyrrolizidine alkaloids (PA) have been detected in borage, as well as in some samples of commercially purchased deep-frozen and dried lovage, oregano and marjoram, according to a report by The German Federal Institute for Risk Assessment (BfR). The regulatory body points out that when assessing the possible health risk to consumers, all sources of 1,2-unsaturated PA have to be taken into consideration. Particularly, these include herbal teas, other teas and honey. As no safe uptake level can be defined for genotoxic-carcinogenic substances, the Institute recommends that overall exposure to PA from all foods be kept as low as possible, as even low uptake quantities may lead to an increased cancer risk, especially if consumed regularly.

The MOE concept is used in the EU for substances with a genotoxic-carcinogenic mode of action in order to determine the urgency of risk management measures. An MOE value below 10,000 is regarded, in principle, as being of little concern in the perspective of public health.

“The thing to bear in mind here is the cross contamination of food-grade products from plants that produce these compounds, such as borage,” a representative of the BfR tells FoodIngredientsFirst.

The BfR regularly deals with the contamination of food with 1,2-unsaturated PA, having already published opinions on the occurrence of the compound in herbal teas, honey, salad mixtures and food supplements. Although the consumption quantity of contaminated herbs is low in prepared foods, the BfR notes it can make a considerable contribution towards short- and long-term exposure.

The report cites the primary target organ of 1,2-unsaturated PA-induced adverse effects in humans and animals is the liver, but other organs can be affected as well, such as the lungs. The effects can occur within a short period of time if larger doses of the compound have been ingested and within a longer period of time with lower doses. 

Typical symptoms, especially if high doses of 1,2-unsaturated PA have been ingested, are closure of the central sublobular hepatic vein and liver damage, which can lead to liver necrosis. This effect was studied in animal experiments, which revealed the mutagenic and carcinogenic properties of the compound.

Preliminary assessment of 1,2-unsaturated PA health risk
The BfR made a preliminary assessment of the health risk posed by short as well as long-term uptake on the basis of the levels of 1,2-unsaturated PA, determined in the samples of deep-frozen and dried herbs and spices.

To estimate the risk of possibly non-carcinogenic (non-neoplastic) damage, an orientation value of 0.1 μg PA per kilogram body weight and day was used in a makeshift manner. This health-based guidance value was derived from a chronic study with animals. With a daily intake quantity of less than 0.1 μg 1,2-unsaturated PA per kilogram body weight and day, the occurrence of non-carcinogenic liver damage is not to be expected with short as well as long-term exposure. 

The exposure scenarios, which are based on model food dishes which, according to the recipe, are usually prepared with certain herbs, indicate that an exceedance of the orientation value through the consumption of individual dishes containing highly contaminated herbs is possible. As no reliable information is available on the dose-response relationship, it has not been possible up to now to define a sufficiently safety margin between the uptake of a quantity with which severe health effects occur and the safe uptake level.

The data provided to the BfR by the monitoring authorities of the federal states shows that the mean levels of 1,2-unsaturated PA in borage – an ingredient used in European cuisine – which produces PA by itself, are particularly high. High contents of 1,2-unsaturated PA were also detected in samples of lovage and samples from the “Oregano, Marjoram” group. Only very low levels of 1,2-unsaturated PA or none at all were found in fresh herbs such as parsley.

On the basis of consumption data from this study, the BfR calculated that consumption of highly contaminated herbs may lead to long-term exposure levels solely through this food category. 

The report, however, notes that a conclusive assessment of the possible health risk resulting from the consumption of herbs contaminated with 1,2-unsaturated PA is not possible at the moment as there is not enough data on the longer as well as the short-term consumption of various herbs.

Still, the BfR recommends that efforts should be continued to further reduce PA levels through the improvement of cultivation, harvesting and purification methods. The Institute describes a method on its website detailing how plant material can be examined to establish its levels of 1,2- unsaturated PA analytically.

By Benjamin Ferrer