“Homocysteine is a sulfur-containing amino acid produced during the metabolism of methionine, an essential amino acid found in dietary protein. Normally, homocysteine is converted into other substances with the help of B vitamins—folate (B9), B6, and B12.  Epidemiological studies have consistently shown that higher homocysteine levels correlate with increased risk of coronary artery disease and stroke.”

Cleveland Clinic (Homocysteine: Function, Levels & Health Effects)