A report prepared for the European Parliament, co-authored by Harvard Chan School’s Philippe Grandjean, adjunct professor of environmental health, outlines the health benefits of eating organic food and practicing organic agriculture.

Why did the European Parliament commission this report and what was its most important takeaway?

The European Parliament is concerned about food safety and human health. They asked a group of experts from several countries to review the possible health advantages of organic food and organic farming. Our report reviews existing scientific evidence regarding the impact of organic food on human health, including in vitro and animal studies, epidemiological studies, and food crop analyses.

The most important information in this report is about pesticides in food. In conventional food, there are pesticide residues that remain in the food even after it’s washed. Organic foods are produced virtually without pesticides.

Authorities in both the European Union and the United States insist that current limits on the amount of pesticides in conventional produce are adequate to ensure that it’s perfectly safe. But those limits are based on animal studies, looking at the effect of one pesticide at a time. The human brain is so much more complex than the rat brain, and our brain development is much more vulnerable because there are so many processes that have to happen at the right time and in the right sequence—you can’t go back and do them over.

Three long-term birth cohort studies in the U.S. suggest that pesticides are harming children’s brains. In these studies, researchers found that women’s exposure to pesticides during pregnancy, measured through urine samples, was associated with negative impacts on their children’s IQ and neurobehavioral development, as well as with ADHD [attention deficit hyperactivity disorder] diagnoses. Also, one of the studies looked at structural brain growth using magnetic resonance imaging and found that the gray matter was thinner in children the higher their mothers’ exposure to organophosphates, which are used widely in pesticides. I think that’s quite scary.

My strong advice, based on our review of the evidence, is that pregnant and breastfeeding women, and women planning to become pregnant, should eat organic rather than conventional food. If there are times when you can’t get organic food, buy foods that have to be peeled—baking potatoes or pineapples, for example—but stay away from produce like leafy vegetables. A good resource for learning about the pesticide content of various foods is the Environmental Working Group, which maintains lists of produce with the highest pesticide levels as well as those with the lowest levels.