Maternal Fish Intake and Cognitive Testing in Children at Age 3 Years
Oken E et al. American Journal of Epidemiology. Epub (ahead of print 2008).
Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, Boston, MA.
The present study evaluated (in 341 mother-child pairs in Massachusetts) the association between the second – trimester fish intake of the mothers as well as their blood levels of mercury and measures of cognitive performance in their children at age 3 years. The cognitive testings included the children’s scores on the Peabody Picture Vocabulary Test (PPVT) and Wide Range Assessment of Visual Motor Abilities (WRAVMA) . The latter encompassed three domains of visual motor development: visual- motor (drawing test), visual-spatial (matching test), and fine-motor skills (pegboard test). In the case of women consuming more than two servings of fish/week (avg. intake of DHA plus EPA of 301 mg/day) relative to those essentially never consuming fish (avg. DHA/EPA of only 22 mg/day), the children from the former group exhibited higher relative overall PPVT scores ( by 2.2 %) and higher WRAVMA drawing scores (by 6.4 %) after adjusted for other variables including mercury levels in the red blood cells. However, the children of mothers who did not consume more than two servings of fish weekly and whose mothers had the highest decile (top 10 %) of blood mercury exhibited lower WRAVMA scores whereas higher WRAVMA scores were shown with more than two fish servings/week even if the mercury levels were in the top decile. The overall results suggest that the benefits of fish intake during pregnancy would be greater if mercury contamination were not present. The authors also propose that advice on fish intake during pregnancy for nutritional-health benefits for the child should consider the potential harm from concomitant mercury exposure.
It is noteworthy that the average fish consumption in North American women during pregnancy is much below the greater than 2 fish servings/week (and 301 mg or more of DHA/EPA daily) wherein the apparent cognitive benefits to the child appeared to emerge in the present study . North American intakes average approximately one fish serving every 7-10 days which contributes an average daily intake of DHA/EPA (sum) of 120- 150 mg. Future advisories on fish intakes may need to become much more detailed during pregnancy by balancing the known DHA/EPA contents per serving of specific fish/seafood with the levels of mercury to maximize the health benefit:risk ratio.