Randomized Trial: B Vitamins
Of Stroke and Cardiac Events
Publisher's abstract: Stroke.
A combination of B vitamins
can help reduce the risk of a second stroke, cardiac events and
death, according to study published in the journal Stroke.
The combination of folate, B12 and B6 is already known to lower
levels of homocysteine in the blood, a risk factor linked to cardiovascular
disease. However, firm evidence that lowering homocysteine levels
corresponds with reduced risk for stroke has been awaiting completion
of randomized controlled studies.
One of the first studies published was the Vitamin Intervention
for Stroke Prevention (VISP) trial. The VISP study group reported
that while the B vitamins therapy had lowered homocysteine levels
modestly in patients with nondisabling stroke, the combination
did not reduce the risk of a recurrent vascular event. However,
a second group of doctors re-analyzed the VISP trial data and
an entirely different conclusion emerged.
When Dr. David J. Spence and scientists from the Stroke Prevention
and Atherosclerosis Research Center in Ontario, Canada conducted
their efficacy analysis of the VISP data, it turns out that the
trial included patients who were not likely to respond to the
Spence and colleagues analyzed the results for a subgroup of subjects
that excluded individuals with very low or very high levels of
B12 (representing the 25th and 95th percentiles). Among the 2155
patients remaining, there was a 21% reduction of stroke, death
or coronary events.
"It is too early to conclude that vitamin therapy to lower
total homocysteine is ineffective in the prevention of cardiovascular
events," said Spence in a Reuter’s report.
When the researchers subdivided the patients by their initial
level of B12, the difference between the treatment groups widened
further. Participants who fared the best were those with higher
baseline B12 levels who received the high-dose vitamin combination
(25 mg of B6, 0.4 mg of B12, and 2.5 mg of folate); those who
did the worst came to the trial with lower levels of B12 and received
a low dose (0.2 mg of B6, 0.006 mg of B12, and 0.02 mg of folate).
In the era of folate-fortified foods, vitamin B12 status may now
be the key variable in lowering homocysteine to safe levels. Higher
doses of B12, plus other therapies, may be required to lower homocysteine
and thus reduce the risk of stroke, death, and heart attack.
Media reports and Spence JD, et al. Vitamin Intervention For Stroke Prevention trial: an efficacy analysis. Stroke. 2005 Nov;36(11):2404-9.
- Additional studies are forthcoming that will further
demonstrate whether folate intake has a direct, causal role
in reducing the risk for stroke, heart attack, or other cardiac
- Intake of more than 1000 mcg/day of folate can
hide symptoms of B12 deficiency. A blood test can measure
serum B12, or see if methylmalonic acid is elevated as a
proxy for functional B12 shortage. Oral supplementation
with 1000 mcg/day of B12 corrects or protects against most
cases of deficiency (except those due to metabolic or serious
malabsorption issues). If untreated, B12 deficiency can
result in nerve damage.
- This article is not intended to replace the
advice or attention of your doctor or other health care
professional. Do not stop taking medications or start taking
any nutrition supplement without first speaking to a qualified
health care professional.