Ask the Expert: What's the least toxic diet to eat during pregnancy?

The choice of organic over conventionally grown fruits can contribute to lower exposures of pesticides

Q: I'VE just found out I'm pregnant – what's the safest, least toxic diet for me and my baby?

A: Dr Lida Chatzi, an associate professor of preventive medicine at the University of Southern California, has just co-authored a study into diet and levels of environmental contaminants in mothers and children. She says: "During gestation and early development, the foetus and the child, respectively, are vulnerable to the effects of environmental chemicals. A balanced diet during these periods is also critical for optimal nutritional status, but what to eat, and how much, are critical questions.

"We conducted the largest study to date examining the association between diet and levels of 33 environmental contaminants in mothers and their children. The study was conducted within the Human Early-Life Exposome (HELIX) project, a study including 1,000 pregnant women and their children who were followed up to the age of six-to-10 years across six European countries: France, Greece, Lithuania, Norway, Spain and the United Kingdom.

"We found that the higher the fish consumption, the higher the levels of toxic persistent chemicals in the blood for both pregnant women and their children. The chemicals included polychlorinated biphenyls (PCBs), perfluoroalkyl substances (PFAS) and the toxic metals arsenic and mercury.

"We also assessed the effect of dietary recommendations for fish on maternal and child levels of environmental chemicals: specifically, up to three servings of fish per week for pregnant women and up to two servings per week for children. We found that, if the recommendation was followed, it resulted in lower levels of PFAS, arsenic and mercury than if they were exceeding the dietary recommendations.

"In general, women should eat a variety of types of fish each week and avoid consumption of raw fish and large predatory fish, such as king mackerel, swordfish, shark, and tilefish. Given that there's variation of levels of pollutants potentially contained within fish, women should be aware of dietary recommendations, and adhere to guidelines.

"We also showed fruit consumption was associated with increased levels of four organophosphate pesticides metabolites, measured in urine samples for both pregnant women and children. On the other hand, children who ate organic food more than once per week had lower levels of pesticides metabolites in their urine, compared to children who reported not eating organic food.

"The choice of organic over conventionally grown fruits can contribute to lower exposures of pesticides and other environmental pollutants, while retaining the health benefits of fruit and vegetable consumption. We believe the results carry important public health messages related to the avoidance of excess exposure to environmental contaminants with toxic effects on humans."

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