… are secondary plant metabolites containing several phenol groups. Polyphenols occur in vegetables, fruits and cereals but also in tea, coffee and wine. Polyphenols can reduce the effects of oxidative stress and protect against the development of certain diseases (several types of cancer, cardiovascular diseases, diabetes etc.) (Imam et al., 2017) but they can also inhibit non-haem iron absorption (Anderson & Frazer, 2017).

Polyphenols also exhibit "prebiotic-like" effects as they can modulate the intestinal microbiome by affecting the growth and metabolism of microorganisms. Thereby, polyphenols increase growth of beneficial bacteria like Bifidobacteria and Lactobacillii, while hampering the growth of pathogens like C. perfringens (Filosa et al., 2018).