Some nuts, such as almonds and walnuts, contain a type of polyphenol called ellagitannins. These are converted into ellagic acid in the stomach and small intestine, as well as by gut microbiota. Then, the microbiota in the colon further metabolizes ellagic acid to produce urolithins.
Ellagitannins have been shown to have the following properties:
- Antioxidant and radical scavenging, meaning that they can remove harmful free-radicals
- Anti-tumor promoting, this is, they can prevent a tumor from progressing into cáncer
- Immunomodulatory, which means that they can modulate or regulate the immune system
Urolithins seem to have both pro-estrogenic and anti-estrogenic effects, depending on the physiological context.