[Fennel tea: risk assessment of the phytogenic monosubstance estragole in comparison to the natural multicomponent mixture].

For centuries, fennel fruits have been used as traditional herbal medicine in Europe and China. For the treatment of infants and sucklings suffering from dyspeptic disorders, fennel tea is the drug of first choice. Its administration as a carminativum is practiced in infant care in private homes and in maternity clinics as well where it is highly appreciated for its mild flavor and good tolerance. The long standing positive experience is astonishingly contrasted by a recent statement of the German 'Bundesinstitut für gesundheitlichen Verbraucherschutz und Veterinärmedizin' (BgVV, May 11, 2001), where consumers are advised to reduce their intake of foods containing estragole and methyleugenol, e.g. tarragon, basil, anis, star anis, jamaica pepper, nutmeg, lemon grass as well as bitter and sweet fennel fruits for reasons of health. These warnings are based on experiments with rats and mice where estragole, a natural ingredient of fennel fruits, proved to be carcinogenic. Meanwhile, criticism arose amongst experts concerning the interpretation of these studies. The crucial points of criticism concern the transfer of data obtained in animal models to the human situation as well as the high doses of the applied monosubstance, which do not at all represent the amounts humans are exposed to as consumers of estragole-containing foods and phytopharmaceuticals. Furthermore, studies on estragole metabolism revealed at least quantitative differences between the estragole metabolism of mice and men. In addition, it has been shown that an agent when administered in its isolated form may have significantly different effects and side effects than the same agent applied as a constituent in naturally occurring multicomponent mixtures. Thus, a multicomponent mixture such as fennel tea contains various antioxidants known to be protective against cancer. These differences were not considered in the risk assessment. A well done risk assessment should be based on appropriate data collected in humans. Considering the long traditional use of fennel tea and the total lack of epidemiological and clinical studies indicating a well founded cancerogenic potential, the probability of a serious risk connected with the consumption of fennel tea seems to be negligibly small.