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

The antioxidative agent Quer strongly increased the extracellular concentration of homocysteine in hepatoma cell cultures probably due to increased cellular methylation. In the human body, the same phenomenon might lead to increased plasma tHcy. Since elevated plasma tHcy is associated with premature vascular disease, high long-lasting dietary intake of polyphenols might be harmful. The interaction between Quer and homocysteine turnover may therefore warrant a re-evaluation of polyphenols as relatively harmless antioxidative food supplements or therapeutic antioxidative agents.