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Still Incriminated in Heart Disease
By Rosalie Marion
May 16, 2002
Mounting evidence indicates that the
amino acid homocysteine, when found circulating at high levels in the
bloodstream, increases risk of heart attack and stroke. Because some studies
contradict those findings, researchers funded by the
Agricultural Research Service looked for
a link among data collected from the most recent National Health and Nutrition
Examination Survey (NHANES III). The survey is a six-year collection of data on
health and diet taken from a sample of the American population.
To get the homocysteine data that underlies the study, researchers with the
Jean Mayer USDA Human Nutrition Research
Center on Aging at Tufts University in Boston, Mass., proposed testing
blood samples taken from the last three years--or Phase 2--of the NHANES III.
Jacob Selhub, chief of the centers
Metabolism Laboratory, tested 8,585 samples taken from males and females
aged 12 and above.
Men and women aged 40 and older who had blood homocysteine levels of more
than 12 micromoles per liter were more than twice as likely to have experienced
a heart attack or stroke. According to Tufts nutritional epidemiologist
Martha Morris, who analyzed the data, the new finding shows blood homocysteine
concentrations were not related to heart attack or stroke in women prior to
menopause, although the relationship was strong in men of the same age group.
Conversely, the relationship faded among older men and surfaced among
The implication is that earlier studies found no across-the-board
association between mixed groups elevated homocysteine levels and heart
disease precisely because the association is age- and gender-dependent.
According to Morris, the findings support the idea that women may be protected
from heart attack and stroke by their high estrogen status.
Read more about effects of elevated homocysteine levels in the
issue of Agricultural Research magazine.
ARS is the chief scientific research agency in the
U.S. Department of Agriculture.