The alleged toxicity of fennel seeds

In 2011, a study published by INRAN (National Institute for Food and Nutrition Research) raised concerns about the use of fennel-based herbal teas, stating that they could be harmful, even potentially carcinogenic, due to a minor component found in the seeds: estragole.

The study examined three types of fennel-based products (loose seeds, soluble teas, and sachets). From the obtained data, researchers argued that the levels of estragole were too high to be considered safe for health.

These findings created significant alarm and confusion, especially since fennel teas have always been recommended to alleviate colic in infants and promote breastfeeding.

As we know, sensational news spreads rapidly and often undergoes unfortunate “adjustments” for communicative reasons.

Following the widespread information that fennel seeds could be carcinogenic, the Integrative Medicine Center of Careggi (Florence) documented, with literature data and targeted research, that not only are fennel seeds not considered carcinogenic or harmful to health, but the study also demonstrates the presence of several substances inside them that have anticancer effects, in greater quantities than estragole.

In particular, among the polyphenols, a molecule was identified (epigallocatechin gallate, EGCG for short), known to be the main anticancer agent in green tea. Besides inhibiting carcinogenesis, it promotes apoptosis (programmed cell death of tumor cells). Moreover, this substance inhibits a class of enzymes (sulfotransferases) that are responsible for activating estragole, thus preventing the presumed oncogenic processes within our body.

Therefore, we can affirm that fennel seeds contain anticancer substances. Still, it cannot be claimed that fennel tea might have antitumor effects, as the concentration of these active principles in the herbal tea is too low for clinical purposes.

It’s essential to note that estragole, a substance found in traces within fennel seeds, is also present in other plant species traditionally used for food or therapeutic purposes, such as basil, anise, tarragon, cloves, and cinnamon. None of these plants have ever been attributed with any toxicity causing alarm or specific precautions in use.

Furthermore, for estragole to be toxic, it must be taken pure and directly into the bloodstream. However, the inside of fennel seeds is mixed with other substances that are part of the phyto-complex, particularly flavonoids, which, as demonstrated, prevent its toxic activation.

In conclusion, herbal teas or capsules based on fennel extracts pose no risk to health.

It all comes down to common sense and staying within the intake limits specified by regulations, which should always be indicated on the label.

The risk for all supplements, medications, and foods is indeed always related to the dosage and the method of intake.