Seafood ChoiCeS

Seafood Choices: Balancing Benefits and Risks
http://www.nap.edu/catalog/11762.html
SEAFOOD ChOICES
mercury level at delivery of 0.55 ppm (range 0.02–2.38; 10 percent had
levels >1.2 ppm). At 6 months of age, infants’ scores on a visual recognition
memory task were positively associated with maternal fish intake
during the second trimester (4 points for each additional weekly serving),
but inversely associated with maternal hair mercury level (7.5 points per
ppm). Performance was best among infants whose mother consumed more
than two servings of fish per week but whose hair mercury level was less
than 1.2 ppm. This study was designed as a study of nutrition rather than
of methylmercury intake, however, so women were asked about their fish
intake using categories (canned tuna, shellfish, “dark meat” fish, other fish)
that relate more directly to omega-3 fatty acid levels than to MeHg levels
(see Box 3-1).
Data germane to the balance between the benefits and risks associated
with consumption of fish and development in children were also reported
from the Avon Longitudinal Study of Parents and Children (ALSPAC),
a large ongoing birth cohort study in the UK (Daniels et al., 2004). In a
subsample of 1054 of 10,092 eligible children, associations were evaluated
between maternal fish consumption during week 32 of gestation, reported
on a food frequency questionnaire, and maternal reports of children’s language
development at 15 months and general development at 18 months.
The categories used in collecting data on the types of fish consumed were
“white fish” (cod, haddock, plaice, fish sticks, etc.) and “oily fish” (pilchards,
sardines, mackerel, tuna, herring, kippers, trout, salmon, etc.). Most
women (88 percent) reported eating fish during pregnancy. Of these, 65
percent reported eating fish from both categories. Unfortunately, this way
of classifying fish results in groupings that differ from those that would
result if classification were based on mercury levels. Overall, children’s
developmental abilities, as reported by mothers, increased modestly with
increased maternal fish intake during pregnancy. Most of the benefit appeared
to be associated with any fish consumption, compared to none, as
maternal consumption of fish more than one to three times per week did not
seem to confer additional benefits, at least with regard to the child development
outcomes assessed. Higher mercury concentration in umbilical tissue,
for which the median was 0.01 µg/g wet weight, was not associated with
adverse developmental outcomes in children, although cord tissue mercury
is not a well-established biomarker of exposure. Cord mercury level did
increase across strata of maternal fish intake, although the greatest increase
was between the “none” and “1 per 2 weeks” strata, with little increase
evident in the two strata representing greater fish intake (“1–3 per week”
and “4+ per week”) (see Box 3-1).
Jensen et al. (2005) reported that the usual substantial neuropsychological
benefits associated with breastfeeding were not evident among the children
in the Faroe Islands cohort. The authors speculated that contaminants pres-
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