To eat or not to eat fish is a question that has long concerned pregnant women. Now, a new study shows that children whose mothers ate fish from one to three times a week during pregnancy were more likely to have a better metabolic profile as they grow — despite the risk of exposure to mercury — than children whose mothers ate fish rarely (less than once a week).

The findings appear today in JAMA Network Open.

“Fish is an important source of nutrients, and its consumption should not be avoided,” said Lida Chatzi, MD, PhD, associate professor of preventive medicine at the Keck School of Medicine at USC, and the senior investigator on the study. “But pregnant women should stick to one to three servings of fish a week as recommended, and not eat more, because of the potential contamination of fish by mercury and other persistent organic pollutants.”

Fish is a major source of omega-3 long-chain polyunsaturated fatty acids, which are important for the developing fetus. However, some types, such as swordfish, shark and mackerel, can contain high levels of mercury — a potent toxin that can cause permanent neurological damage. Mercury contamination is also found in soil, air, water and plants.

Researchers looked at 805 mother-and-child pairs from five European countries participating in a collaborative research project known as the HELIX study, which is following women and their children from pregnancy onward.

During their pregnancy, the women were asked about their weekly fish consumption and tested for mercury exposure. When the children were between 6 and 12 years old, they underwent a clinical examination with various measurements, including waist circumference, blood pressure, high-density lipoprotein cholesterol, triglyceride levels and insulin levels. These measures were combined to calculate a metabolic syndrome score.

More fish is not better

The children of women who ate fish from one to three times a week had lower metabolic syndrome scores than the children of women who ate fish less than once a week. (A lower score is better for health outcomes.) But the benefit declined if women ate fish more than three times a week.

“Fish can be a common route of exposure to certain chemical pollutants, which can exert adverse effects,“ said Nikos Stratakis, PhD, a USC postdoctoral scholar who was one of the study’s authors. “It is possible that when women eat fish more than three times a week, that pollutant exposure may counterbalance the beneficial effects of fish consumption seen at lower intake levels.”

The study found that higher mercury concentration in a woman’s blood was associated with a higher metabolic syndrome score in her child.

The study also examined how fish consumption by the mother affected the levels of cytokines and adipokines in her child. These biomarkers are related to inflammation, a contributor to metabolic syndrome. Compared with low fish intake, moderate and high fish consumption during pregnancy were associated with reduced levels of proinflammatory cytokines and adipokines in the children.

This is the first human study to show that reduction in these inflammation biomarkers could be the underlying mechanism explaining why maternal fish consumption is associated with improved child metabolic health.

Next, the researchers plan to look at the effects of consuming different types of fish with different nutrients and mercury levels. The goal is to follow up on these children until the age of 14-15 years.


Study contributors

In addition to Drs. Chatzi and Stratakis, the study’s additional authors are David Conti, PhD, Shohreh F. Farzan, PhD, and Rob McConnell, MD, from the department of preventive medicine at the Keck School; Eva Borras and Eduardo Sabido from the CRG/UPF Proteomics Unit, Barcelona, Spain; Xavier Basagana, Mariona Bustamante, Maribel Casas, Dr. Serena Fossati, Juan R. Gonzalez, Lea Maitre, Jose Urquiza and Martine Vrijheid from the ISGlobal Institute, Barcelona, Spain; Theano Roumeliotaki and Marina Vafeiadi from the Department of Social Medicine, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece; Eleni Papadopoulou, Anne-Lise Brantsaeter, and Helle-Margrete Meltzer from  the Department of Environmental Health, Norwegian Institute of Public Health, Oslo, Norway; Lydiane Agier from the Team of Environmental Epidemiology Applied to Reproduction and Respiratory Health, Inserm, CNRS, University Grenoble Alpes, Institute for Advanced Biosciences, U1209 Joint Research Center, La Tronche, Grenoble, France; Regina Grazuleviciene, the department of Environmental Sciences, Vytautas Magnus University, Kaunas, Lithuania;  Barbara Heude, from Centre of Research in Epidemiology and Statistics, Inserm, Institut National de la Recherche Agronomique, Universite de Paris, Paris, France; Rosemary R. C. McEachan,  Jane West and John Wright from the Bradford Institute for Health Research, Bradford Teaching Hospitals NHS Foundation Trust, Bradford, UK; and Ioannis Theologidis from the Foundation for Research and Technology, Institute of Molecular Biology and Biotechnology, Heraklion, Greece.

— Laura LeBlanc

This study was supported by the European Community Seventh Framework Program (Human Early Life Exposome Project, grant ID: 308333) and by the National Institute of Environmental Health Science (R01 ES029944, R21 ES029681, R21 ES028903, P30 ES007048-23, P01CA196569).