I am a PhD student on the Wellcome Trust-funded EDESIA programme in Dr Paul Kroon’s research group. My work focuses on the gut microbe-driven metabolism of L-carnitine into trimethylamine (TMA), which is subsequently converted in the liver into the proatherogenic compound trimethylamine N-oxide (TMAO). Specifically, I am investigating the inhibitory effects of pomegranate polyphenols on the metabolism of L-carnitine into TMA and TMAO.

As part of my project, I am the PI of the TESSA study, which investigates the effects of a pomegranate extract on TMAO production in healthy individuals.

Prior to my PhD position at the Quadram Institute, I have obtained both my BSc and MSc in Nutrition and Health at Wageningen University in the Netherlands. During this time, I completed six months of taught modules at the University of California, Los Angeles (UCLA) and spent ten months as a Visiting Graduate Researcher at their Neuroscience department. I also did a six month research internship in the Microbiomics, Nutrition & Health group at NIZO Food Research in the Netherlands.

Key Publications

Haarhuis J, Day-Walsh P, Shehata E, Nemeckova B, Saha S, Kroon P. A pomegranate extract inhibits the conversion of dietary L-carnitine to prothrombotic trimethylamine (TMA) by the gut microbiota. Proceedings of the Nutrition Society. 2023;82(OCE5):E343. doi:10.1017/S0029665123004421

Haarhuis, J. E., Kardinaal, A., & Kortman, G. A. M. (2022). Probiotics, prebiotics and postbiotics for better sleep quality: a narrative review. Beneficial Microbes, 13(3), 169-182. DOI: 10.3920/bm2021.0122