Most women obsess over their diets during pregnancy to ensure the healthiest outcomes for their babies, but a new study has found that some of food's most significant influences on a child’s development can occur even before conception.

Researchers studying the diets of women in the Gambia have found that the function of their babies’ genes changed depending on the nutrients they consumed before they became pregnant, according to the new paper, published in the journal .

"Our results represent the first demonstration in humans that a mother's nutritional well-being at the time of conception can change how her child's genes will be interpreted, with a life-long impact,” said senior author Branwen Hennig in a press release.

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How Does a Mother's Diet Affect Her Baby's Genes?

The key is epigenetics, which affects how genes are expressed. Some epigenetic traits are passed down directly from parent to child.

This study focused on the epigenetic process of DNA methylation, in which a chemical compound called a methyl group is added to strands of DNA. Certain key nutrients, including folate and vitamins B2, B6, and B12, make this process possible. When gene regions are tagged with methyl groups, gene silencing occurs, meaning that some of the genes aren’t expressed in the body.

As arbitrary as it might seem, seasonal variations in the diets of the women studied greatly influenced their infants’ genetic makeup because some of these important nutrients were only available during certain times of year.

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Researchers from the MRC International Nutrition Group, based at the London School of Hygiene & Tropical Medicine, separated the pregnant Gambian women they studied into two groups, one comprised of women who had conceived at the peak of the rainy season, and one of women who had conceived at the peak of the dry season.

The researchers tested the women's blood for the presence and concentration of vital nutrients. After birth, their two- to-eight-month-old infants also had their blood and hair follicles tested. The babies conceived during the rainy season were shown to have higher levels of DNA methylation as a result of their mothers’ higher nutrient levels. 

Amounts of the compounds cysteine and homocysteine in the women’s bloodstreams were also found to influence gene expression, along with their body mass index (BMI), which are a measure of body fat.

What Does This Mean for You?

Women clamoring for the meaning of a dry-versus-rainy season diet—and how it applies to their own lives—will have to wait for additional research. Currently, the research only shows that differences in pre-pregnancy diets can affect children’s genes, but not what these epigenetic changes mean for offspring in the long-term.

“Even though we studied this population in [the] Gambia, our overall goal was to test for an inference of maternal nutrition on this type of epigenetic mechanism,” said Robert A. Waterland, PhD, an associate professor of molecular and human genetics at Baylor College of Medicine in Houston. “We know that there are many more regions of the human genome that behave this way.” 

He hopes to catalogue all the regions in the human genome that respond similarly to maternal nutrition, and also to serious maternal illnesses. “The whole reason we’re doing this is we’re interested in the developmental origins of health and disease,” he said.

This study doesn’t reveal the secret to an ideal pregnancy diet, but there are certain things all expectant mothers can do to improve their health and the health of their babies. Maintaining a healthy BMI is critical, along with eating well-balanced meals, getting regular exercise, and taking all of the prenatal vitamins recommended by your doctor. 

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