A study at Harvard Medical School reported on results collected in Denmark, has shown that eating fish before birth, leads to infants with better physical and cognitive developments. Breast milk was also shown to improve development in infants, indicating that longer breastfeeding is beneficial to infants.
Pregnant women in the United States have been advised to eat less fish because of high mercury levels found in some fish. This study, published in the September 2008 issue of the American Journal of Clinical Nutrition, recommends the opposite, a minimum of three meals with fish per week for expectant mothers.
Fish with low levels of mercury should be chosen, such as cod, haddock, hake, herring, mackerel, plaice, salmon and sardine. The U.S. Food and Drug Administration have a list of mercury levels in commercial fish on their website.
The study also focussed on the effect on infants of breastfeeding. Each of these, higher fish consumption and longer time mothers breastfed their babies, improved the infants' mental and physical development.
Over 25,000 Danish women were asked about their diet before the birth, and if they were breastfeeding at six months. Their diet was followed from the time they were six months pregnant, especially the amount and type of fish eaten. The children's development was assessed at six and eighteen months age.
At six months, specific physical and cognitive abilities were tested, such as whether they could hold up their heads, sit with a straight back, sit unsupported, respond to sound or voices, imitate sounds, or crawl. At 18 months, they were tested to see whether they could climb stairs, remove their socks, drink from a cup, write or draw, use word-like sounds and put words together, and whether they could walk unassisted.
The results showed the children of mothers who ate least fish had the lowest scores at eighteen months. Compared with women who ate the least fish, women with the highest fish intake had children 25% more likely to have higher scores at 6 months, and almost 30% more likely to have higher scores at 18 months.
Children breastfed longer also showed better development, especially at 18 months. For children of mothers breastfeeding longer, there was no discernable difference if the mother had eaten fish or not. Breast milk contains omega-3 fatty acids, and so apparently compensates for the mother's diet in the cases the mother ate little fish during the last three months of pregnancy.
Mercury poisoning inhibits development, causing depression, ADHD, autism and a host of other problems. What this study shows is that eating fish with minimal mercury outweighs the harmful effect of mercury.
Now, on a less serious note:
That this is news, is news to me personally. I was taught by my mother half a century ago that fish was good for my cognitive development. My wife breastfed our children longer than was usual, as she believed that breast milk was good for the children's development. It was recommended in books published all those years ago.
Another interesting fact was illustrated in the press release for the study. Being an academic seemingly exposes one to cognitive occupational injury. In the press release, meant for the media, and general public, not an academic clique, it was stated, “mothers were interviewed about child development markers at 6 and 18 months postpartum.” Why use words and phrases such as “markers” or “percent units?” What is a “percent” if not a unit? The study asked mothers for breastfeeding history, “postpartum.” The rest of the sentence was in English, why the abrupt change to Latin. Also, is it possible to breastfeed “prepartum?” Surely cognitive development markers are difficult to measure “prepartum” at six months. At eighteen months “prepartum” both cognitive and physical “markers” are impossible to get.
The study was an important step in understanding mercury in the context of nutrition and poisons in our environment. Unfortunately, it is impossible to be 100% free of environmental toxins.