Salmon, often eaten
with bagels, contains a healthful omega-3 fatty
acid known as DHA, short for docosahexaenoic acid. |
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Secrets of Fish Oil Compound
Probed
By
Marcia Wood
December 3, 2007
A compound found in oil-rich fish such as salmon
reshaped the blood lipid profiles of volunteers in an
Agricultural
Research Service-led study.
Research chemist
Darshan S. Kelley of the
ARS Western Human Nutrition Research Center in
Davis, Calif., and federal and university
co-investigators conducted the study of DHA, or
docosahexaenoic acid, a polyunsaturated fatty acid
thought to improve cardiovascular health.
The research, reported earlier this year in the
American Journal of
Clinical Nutrition, is likely the first to
analyze—in high-triglyceride males—DHA's effects on
both fasting and post-meal triglycerides, and on
quantities and sizes of HDL, LDL and VLDL cholesterol
particles. High triglycerides, high cholesterol and a
high number of small particles of LDL cholesterol in
the blood increase risk of cardiovascular disease, the
nation's leading cause of death, according to Kelley.
The study is also one of only about a dozen, in
humans, to probe the effects of DHA alone, rather than
in tandem with another natural oil, EPA, or
eicosapentanoic acid. EPA occurs with DHA in fish oil.
Half of the study’s 34 volunteers, age 39 to 66,
consumed about one-half teaspoon of DHA daily, in
addition to regular meals, for 90 days. The other half
received olive oil in place of DHA oil.
Blood samples taken after fasting, and within eight
hours after meals, showed that DHA reduced by 22
percent the number of small LDL (low-density
lipoprotein) particles. LDL’s small particles are the
size most harmful to the cardiovascular system. DHA
increased the number of large LDL particles by 127
percent. Since large LDL particles are less harmful
than small ones, some researchers believe large LDL
particles do not harm the arteries.
DHA also lowered triglycerides by 24 percent in
both the fasting and post-meal samples. The after-meal
effect, shown in only a few other studies, may be of
particular interest to medical professionals looking
for alternatives to conventional triglyceride-lowering
therapies, according to Kelley.
ARS is the U.S.
Department of Agriculture's chief scientific
research agency.
