Eating Fish One to Three Times a Week During Pregnancy Tied to Better Metabolic Health in Kids

By Lisa Rapaport

March 23, 2020

(Reuters Health) - Children whose pregnant mothers ate fish one to three times weekly, as current guidelines recommend, have better metabolic health profiles compared to those whose mothers rarely ate fish during pregnancy, a new analysis suggests.

Eating fish more often during pregnancy, however, didn't further impact kids' metabolic health. And women who were exposed to higher levels of mercury had children with worse metabolic health outcomes.

"Fish is an important source of nutrients for the developing fetus, and its consumption should not be avoided," said senior author Dr. Lida Chatzi of the Keck School of Medicine at the University of Southern California in Los Angeles.

"However, due to potential contamination of fish with mercury, pregnant women should adhere to current health recommendations and consume moderate amounts, no more than 3 times per week," Chatzi said by email.

The population-based prospective birth cohort study used data from studies in five European countries (France, Greece, Norway, Spain, and the UK) between April 1, 2003 and February 26, 2016, as part of the Human Early Life Exposome (HELIX) project. Mothers and their singleton offspring were followed until the children were aged 6 to 12 years.

Researchers used food frequency questionnaires to assess fish consumption during pregnancy. They assessed mercury exposure by testing maternal blood and cord blood samples.

When the children were between ages 6 and 12, researchers calculated aggregate metabolic syndrome scores using the z scores of waist circumference, systolic and diastolic blood pressures, and levels of triglycerides, HDL cholesterol, and insulin. A higher metabolic syndrome score (score range, −4.9 to 7.5) indicated a poorer metabolic profile.

In addition, three protein panels were used to measure several cytokines and adipokines in children’s plasma.

Fish intake consistent with health recommendations (1 to 3 times per week) during pregnancy was associated with a 1-U decrease in metabolic syndrome score in children (Beta = −0.96; 95% CI, −1.49 to −0.42) compared with low fish consumption (<1 time per week) after adjusting for maternal mercury levels and other covariates.

No further benefit was observed with fish intake of more than 3 times per week.

A higher maternal mercury concentration was independently associated with an increase in the metabolic syndrome score of the offspring (Beta per 2-fold increase in mercury concentration = 0.18; 95% CI, 0.01-0.34).

Compared with low fish intake, moderate and high fish intake during pregnancy were associated with reduced levels of proinflammatory cytokines and adipokines in children. An integrated analysis identified a cluster of children with increased susceptibility to metabolic disease, which was characterized by low fish consumption during pregnancy, high maternal mercury levels, decreased levels of adiponectin in children, and increased levels of leptin, tumor necrosis factor alpha, and the cytokines interleukin 6 and interleukin 1-beta in children.

Certain fish are better than others for pregnant women, Chatzi said.

"Among fish species, there is considerable variation in the content of both beneficial nutrients and mercury," Chatzi said.

"For instance, oily fish is higher in the beneficial omega-3 fatty acids compared to lean fish. Moreover, small or short-lived species (e.g., salmon, sardine, trout) have lower concentrations of mercury compared to larger, longer-lived predators (e.g., swordfish, mackerel, tuna)."

The researchers lacked data on the type of fish women consumed during pregnancy, the researchers point out.

An advantage of the analysis is that it looked both at fish servings and mercury exposure, providing a more complete picture of the potential benefits of fish consumption during pregnancy, said Dr. Emily Oken, a researcher at Harvard Medical School and the Harvard Pilgrim Health Care Institute in Boston, who wasn't involved in the study.

"You can see from these results that if they had only studied mercury, they might have come out with a different message, i.e. that higher mercury levels are associated with poorer metabolic health; and since fish is the main source of mercury, that could be interpreted to mean that pregnant women should eat as little fish as possible," Oken, who wasn't involved in the study, said by email.

"But looking at the larger picture, we can see that the women whose children had the best outcomes were those women who did eat fish - namely, consumption of 1-3 servings per week, which is exactly what guidelines tell us to do," Oken said.

SOURCE: JAMA Network Open, online March 16, 2020.