A Balanced Risk–Benefit Analysis to Determine Human Risks Associated with Pyrrolizidine Alkaloids (PA)—The Case of Tea and Herbal Infusions

Abstract

Humans are exposed to pyrrolizidine alkaloids (PA) through different sources, mainly from contaminated foodstuff. Teas and herbal infusions (T&HI) can be contaminated by PA producing weed. PA can possess toxic, mutagenic, genotoxic, and carcinogenic properties. Thus, possible health risks for the general population are under debate. There is a strong safety record for T&HI and additionally epidemiological evidence for the preventive effects of regular tea consumption on cardiovascular events and certain types of cancer. There is no epidemiological evidence, however, for human risks of regular low dose PA exposure. Recommended regulatory PA-threshold values are based on experimental data only, accepting big uncertainties. If a general risk exists through PA contaminated T&HI, it must be small compared to other frequently accepted risks of daily living and the proven health effects of T&HI. Decision making should be based on a balanced riskbenefit analysis. Based on analyses of the scientific data currently available, it is concluded that the benefits of drinking T&HI clearly outweigh the negligible health risk of possible PA contamination. At the same time, manufacturers must continue their efforts to secure good product quality and to be transparent on their measures of quality control and risk communication.

Pyrrolizidine Alkaloids: Chemistry, Pharmacology, Toxicology and Food Safety

“…For example, the PA-induced tumourigenicity previously reported for animals has not, to this day, been demonstrated in humans. Anyway, it is still an open question whether the differences between species should exclude the results in animals for quantitative risk assessment in humans [ 91 ].…”

“…For this reason, quality control of foodstuffs is pivotal and can be important for establishing legally binding limits. The first step should be the choice of an appropriate and universal analytical method for PA, as it was requested by EMA to the European Pharmacopeia [ 91 ]. As far as we could determine, this is being undertaken at the moment [ 92 ].…”

A Balanced Risk-Benefit Analysis to Determine Human Risks Associated with Pyrrolizidine Alkaloids (PA)—The Case of Herbal Medicinal Products Containing St. John’s Wort Extracts (SJW)

“…Therapy with SJW should follow a medical rational [ 4 ], should be administered as a monotherapy, and is not suitable for polypharmacy. SJW products are not sufficiently investigated to be recommended for combination therapy with psychotropic drugs or medications for other indications.…”

“…Generally, there are four ways of how PA can enter the human food chain ( Figure 1 ): Contamination with PA-synthesizing weed in agricultural cultivations [ 1 , 2 ]: PA contamination of tea and herbal infusions is frequent and attributed to contamination of the raw materials that are harvested along with PA-forming weeds [ 4 ]. Contamination of pollen of plants and resulting bee products such as honey: The PA content of honey has been shown to be directly proportional to the amount of PA pollen in honey, and the transfer of PA from pollen to honey occurs rather quickly [ 31 ].…”

“…Pyrrolizidine alkaloids (PA) that exist ubiquitously in our environment possess mutagenic and genotoxic properties and can induce acute and subchronic toxic effects [ 1 ]. More than 6000 plants (about 3% of the world’s flowering plants) are known to synthesize more than 660 different PA [ 1 , 2 , 3 , 4 ]. Thus, PA can contaminate many biological products, such as foodstuff, beverages (milk, teas, and herbal infusions), and herbal remedies [ 4 , 5 , 6 ].…”