Managing High Homocysteine with MTHFR Variants and the Role of Vitamin C in Brain Aging: Registered dietitian nutritionist Leyla Muedin discusses MTHFR genetic variants (C677T and A1298C), their links to impaired methylation, homocysteine, SAMe, mood issues, migraines, vitamin deficiencies, and pregnancy complications, noting many people are asymptomatic and some feel worse on methylated B vitamins and do better on standard formulations. Responding to a listener with C677T, high homocysteine, and borderline methylmalonic acid, she reviews optimal homocysteine targets and outlines other causes of elevated homocysteine such as hypothyroidism/subclinical hypothyroidism, kidney failure, obesity, hypertension, diabetes, smoking, inactivity, and medications (atorvastatin, methotrexate, fenofibrate). She suggests checking these factors, considering absorption issues (intrinsic factor) for B12, and trialing SAMe and more trimethylglycine, with possible pharmacologic folate if needed. She then summarizes an observational Japanese study (n=2,044 adults >64) linking lower plasma vitamin C to reduced gray matter and weaker default mode network connectivity, and notes diet and blood sugar can affect vitamin C status.