Is high homocysteine bad for my heart?

High levels of homocysteine in the blood are strongly associated with a greater risk of cardiovascular disease. This link has been found in dozens of clinical and epidemiological studies involving more than 10,000 patients. The risk rises gradually as homocysteine levels increase, with no clear threshold value. That makes it a striking measurement to track, but there is an important caveat.

Whether high homocysteine itself damages the cardiovascular system, or is simply a signal that something else is wrong, is not yet certain. The most compelling evidence on this point comes from large clinical trials: B vitamins reliably lower homocysteine by around 25%, yet in those trials this does not translate into fewer cases of heart disease or stroke. If homocysteine were the true culprit, you would have expected to see that effect. This makes it plausible that homocysteine functions more as a warning light than as a direct cause.

If you also have other risk factors such as smoking, the concerns are somewhat more concrete. There are indications that high homocysteine amplifies the effect of those factors, although the exact size of this combined risk remains uncertain.

Folic acid and other B vitamins are the most studied way to lower homocysteine, and they do work well for that purpose. However, as described above, they have not been proven to reduce your chance of a heart attack. If your homocysteine is considerably elevated, discuss it with your doctor, because sometimes there is an underlying cause (such as a vitamin B12 deficiency) that deserves attention for reasons unrelated to your heart.