BOSTON, MASSACHUSETTS. Fetal life and early infancy are recognized as critical periods for brain development and growing evidence suggests that early nutrition plays a role in neurodevelopment. Furthermore, the long-chain omega-3 fatty acid docosahexaenoic acid (DHA) is an essential structural component of the brain. Humans must get DHA from food (or the health food store) and the primary dietary source is fish and other seafood. DHA is present in breast milk but only recently has it been added to infant formulas. This is a particularly important issue since a dislike of fish is not uncommon nor are fears of fish consumption due to the presence of mercury and other contaminants. Furthermore, the culture of mainstream medicine works against the physician suggesting supplementation, although folic acid supplementation is an exception due to its success in reducing a common birth defect. A recent study has addressed this issue by examining the association between maternal fish or omega-3 fatty acid DHA intake during pregnancy and the duration of infant breastfeeding with the attainment of so-called child development milestones.
Dr. Emily Oken and colleagues at the Harvard Medical School studied over 25,000 children of mothers participating in the Danish National Birth Cohort, a prospective population-based study that enrolled pregnant women between 1997 and 2002. Data was collected on maternal fish intake, the duration of breastfeeding and measures of child development milestones. The primary outcome was total development at 18 months ascertained by an interview. Mothers were questioned about whether the child could climb stairs, remove socks and shoes, drink from a cup, be occupied for 15 minutes with adult participation, fetch an object when requested, write or draw, orient a book correctly, use word-like sounds, and put two words together. Ages at which the child could first sit unsupported and could walk unassisted and the total number of words the child could correctly say was recorded. Data was also collected at 6 months with an appropriate set of questions. From this data scales were constructed and scores derived. Other data collected included birth weight and evidence of early or late delivery (gestational age), maternal smoking and alcohol use and other information which allowed correcting for confounding. It was found that higher maternal fish intake during pregnancy and the duration of breastfeeding were associated with higher child development scores at 18 months. For example, 5.7% of children with a mother in the lowest quintile of fish intake had the lowest total development score at 18 months whereas only 3.5% of children with their mother in the highest quintile of fish intake had the lowest total development score. Women in the lowest quintile consumed < 1 fish serving/week whereas in the highest quintile it was about 3.5 servings/week. Fish most frequently consumed were cod, plaice, salmon, herring and mackerel. Species with high mercury content are not commonly consumed in Denmark.
Longer duration of breastfeeding was associated with better development at 18 months. After adjusting for maternal fish intake, longer breast-feeding remained associated with a greater achievement of developmental milestones with a 28% increase when = 10 months was compared with = 1 month. This pattern of association with fish intake and duration of breastfeeding was a robust result which persisted after a number of different corrections for potential confounding.
The authors comment that in the U.S. and Europe, expert panels have advised that pregnant women consume a minimum of 200 mg/day of DHA. They point out that most women do not consume this much DHA from fish or other dietary sources, and thus supplements may offer a reasonable alternative. They cite studies which found improved development in children of women randomly assigned to take supplemental DHA although doses were much higher (1-2 g/day) than the experts recommended. The authors cite evidence that in the case of the long-chain polyunsaturated fatty acids, supplementation with a single acid may be less desirable than providing a more natural balance of these nutrients. Fish oil, for example contains both DHA and EPA.
Oken E, et al. Associations of maternal fish intake during pregnancy and breastfeeding duration with attainment of developmental milestones in early childhood: a study from the Danish National Birth Cohort. Am J Clin Nutr 2008 September;88(3):789-96