# Homocysteine

Homocysteine is a sulfur-containing amino acid your body makes while processing methionine. It is cleared in two ways: remethylation or transsulfuration. Both depend on folate, vitamin B12, and vitamin B6. High blood homocysteine signals that your one-carbon metabolism is struggling. It is tied to blood-vessel lining dysfunction, atherosclerosis, and stroke. Cognitive decline and dementia are linked too. But whether homocysteine causes them is uncertain. Here is the catch. Big randomized trials of B-vitamin lowering have not reliably cut cardiovascular events overall. (Those trials include HOPE-2, NORVIT, VISP, SEARCH, and VITATOPS.) Some meta-analyses do suggest a small drop in stroke risk. So homocysteine is best read as a risk and metabolic-health marker, not a proven lever.

## Sources

- Wald DS, Law M, Morris JK. (2002). Homocysteine and cardiovascular disease: evidence on causality from a meta-analysis. BMJ. https://doi.org/10.1136/bmj.325.7374.1202
- Wald DS, Kasturiratne A, Simmonds M. (2011). Serum homocysteine and dementia: meta-analysis of eight cohort studies including 8669 participants. Alzheimer's & Dementia. https://doi.org/10.1016/j.jalz.2010.08.234
- Smith AD, Refsum H, Bottiglieri T, Fenech M, Hooshmand B, McCaddon A, et al.. (2018). Homocysteine and dementia: an international consensus statement. Journal of Alzheimer's Disease. https://doi.org/10.3233/JAD-171042

---

_Canonical: https://longevity-switzerland.com/en/glossary/homocysteine · Part of Longevity Cities · Updated 2026-06-22_