Folate Deficiency and Plasma Homocysteine during Increased Oxidative Stress

To the Editor: Several reports have indicated that elevated plasma levels of the amino acid homocysteine are associated with, or are a primary risk factor for, coronary and vascular disease and Alzheimer's disease. However, a number of additional studies do not show such a correlation. 1 This discrepancy may arise because there are multiple metabolic fates for homocysteine, depending on the nature and extent of cellular oxidative stress. Most homocysteine is converted to methionine through folate-dependent and vitamin B 12 –dependent reactions. Compromise of this conversion as a consequence of folate deficiency can lead to increased export of homocysteine from cells, . . .