Folic acid fortification may have
lowered stroke deaths
March 6 Fortifying enriched grain products with
folic acid in the 1990s appears to have been followed by a decline in
stroke and ischemic heart disease deaths, government researchers
reported yesterday at the American Heart Associations 44th
annual Conference on Cardiovascular Disease Epidemiology and Prevention.
We found evidence of a three-fold acceleration in
the decline of stroke-associated mortality that is temporally related to
fortification of flour with folic acid, said study investigator Lorenzo
D. Botto, M.D., a medical epidemiologist with the Centers for Disease
Control and Preventions National Center on Birth Defects and
Developmental Disabilities in Atlanta. If folic acid fortification is
responsible for the improvement in stroke-associated mortality, the
public health benefits are substantial.
The research team, led by Dr. Quanhe Yang,
estimated that 31,000 stroke-associated deaths and 17,000 deaths related
to ischemic heart disease may have been prevented each year since
fortification was implemented.
In 1996, the United States Food and Drug
Administration required enriched grain products be fortified with folic
acid to reduce the risk of neural tube defects in newborns. The
researchers hypothesized that fortification might offer a secondary
benefit of reducing serum homocysteine concentrations in the population
as a whole, which might lead to a decline in death rates due to
cardiovascular disease and stroke.
Many studies have shown that folic acid can lower
serum homocysteine levels, and that people with higher-than-average
homocysteine levels are at higher risk for stroke and heart disease,
Botto said. We think high homocysteine somehow causes an insult on the
vascular wall, weakening the vessel and making it more prone to damage.
The researchers analyzed national death certificate
data to assess mortality rates for cardiovascular disease and stroke in
the United States among people 40 or older, from 1990 to 2001. They
then looked for changes in mortality trends.
The study showed that fortification of flour with
folic acid was shortly followed by a doubling of the average serum
folate concentration, from 6.6 ng/mL to 15 ng/mL, and an average 14
percent reduction of the serum homocysteine concentration, from 9.6
μmol/L to 8.3 μmol/L.
As hypothesized, the reduction in homocysteine
levels was associated with declining mortality rates due to stroke and
cardiovascular disease, Botto said.
Overall, stroke-associated mortality was 10 to 15
percent lower in the three years after fortification (1999-2001),
compared with the three years before fortification (1994-96), he said.
Before 1997, overall stroke mortality rates declined by about 1 percent
per year, compared with 4.5 percent per year after 1997.
Importantly, the decline in mortality associated
with stroke showed a consistent pattern that ran across all genders and
racial groups, with improvements for both men and women, whites and
blacks, Botto said.
For example, among black men ages 40-59, death
rates due to stroke declined by 1.2 percent per year before 1997,
compared with 7.4 percent per year after 1997. Among black women 40-59
years, stroke-related mortality declined about 0.7 percent per year
before 1997, compared with 3.9 percent per year after 1997.
Among whites of all age groups, the estimated
annual percent decline in mortality rates was less than 1 percent before
food fortification, but 3 percent or more after food fortification.
Researchers observed an improvement in mortality rates due to ischemic
heart disease over the same period.
The accelerating improvement in death rates due to
stroke and ischemic heart disease could not be explained by changes in
other major risk factors, such as cigarette smoking, hypertension,
diabetes and total serum cholesterol levels, many of which did not
improve or worsen during the period studied, Botto said.
Co-authors include Quanhe Yang, Ph.D. and Jan M.
Friedman.
