The polyphenol quercetin strongly increases homocysteine production in a human hepatoma (Hep G2) cell line.

Hultberg, M., Isaksson, A., Andersson, A., & Hultberg, B. (2006). Clinical biochemistry, 39(2), 160–163.

2006 Feb

DOI: 10.1016/j.clinbiochem.2005.11.002

Since elevated plasma tHcy is associated with premature vascular disease, high long-lasting dietary intake of polyphenols might be harmful.