Sunday, March 12, 2006

Has the homocysteine hypothesis been debunked?

No! But you can bet that’s what the media will say about two studies just released ahead of print by NEJM. One, the NORVIT trial, we already knew about. It was presented at the European Society of Cardiology months ago and I blogged my perspective here. The other, HOPE 2, had findings consistent with NORVIT: non-selective use of folic acid, vitamin B6 and vitamin B12 is ineffective for secondary prevention of vascular events.

Why don’t these results debunk the homocysteine hypothesis? Because the studies didn’t ask that question. These vitamins were tested on patients irrespective of their homocysteine levels. Baseline levels in the study populations were around 12 or 13---hardly what we would consider elevated, and not in the range that has been found to be associated with clear evidence of hypercoagulability in previous studies. What this work does confirm is a) if there is an optimal homocysteine target for cardiovascular health that target is unknown---previous targets of 9-10 were unnecessarily low and b) the popular practice of routine supplementation with B vitamins to prevent vascular events is not warranted. There still may be a role for measurement of homocysteine in selected patients, with consideration for treatment if it’s clearly elevated.

For a good perspective on these studies read the accompanying editorial. Don’t bother with the media reports.

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