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Omega-3 fat DHA is accumulated in fetal tissues, particularly the
central nervous system. However, because animal cells cannot form
omega-3 fatty acids, a fetus must obtain all of its omega-3 fatty
acids from its mother’s diet. A mother’s dietary intake
and plasma concentrations of DHA directly influence the DHA status
of the developing fetus.
Studies have found that reduced brain and retinal DHA results in
decreased visual function and altered learning, behavior and neurotransmitter
metabolism. Further, newborns with higher levels of DHA display
more mature electroencephalography patterns.
DHA can be formed in the liver from acid -linolenic acid (ALA),
a dietary essential fatty acid. However, studies show that less
than one to four percent of dietary ALA is converted to DHA, indicating
the potential importance of dietary DHA in humans.
Moreover, when provided as ALA, the amount of ALA required for
fetal-tissue DHA accretion could be 25-fold higher than the requirement
if provided by DHA, and studies have shown that higher intakes of
ALA do not increase the concentrations of DHA in the blood lipids
of infants or adults.
The effect of dietary trends, such as the decline of saturated
fat intakes from 18 to 20 percent of total energy to 11 percent
of total energy over the past three to four decades, and the decrease
in meat consumption in North America, on the intakes of omega-3
fatty acids is not known. However, concentrations of DHA in breast
milk have decreased by 50 percent in Canada and Australia over the
past 15 years, according to studies.
Further, one study found that the intakes of DHA among some Canadian
women during the third trimester of pregnancy appear to be below
possible needs for fetal and maternal tissue DHA accretion. Researchers
say that this raises the need for studies combining functional outcome
measures of infant neural development, dietary fat intake, and DHA.
American
Journal Clinical Nutrition February 2003;77(2):473-8
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