Diet before conception affects a baby’s genes. Paula Dominguez-Salas from the MRC International Nutrition Group reports from the field.
In recent years evidence has been accumulating that nutrition during pregnancy can have a profound effect on the offspring. Our group, the MRC International Nutrition Group, works in maternal and child nutrition and is particularly interested in this ‘fetal programming’ idea, because a child’s health (and possibly even its children) could be effected throughout its whole life – not just its early years.
However, more understanding is needed on the causal mechanisms. Our collaborator, Rob Waterland from the Baylor College of Medicine in Houston, US, showed in mice that supplementation with certain nutrients such as B-vitamins during pregnancy affected their offspring, switching their coat from brown to yellow, and their metabolism from being lean to fat.
These changes were the result of ‘epigenetic’ modifications to the DNA, specifically the tagging of a certain gene with chemical compounds (methyl groups), which resulted in silencing the genes. He also identified some candidate genes that may be susceptible to these types of effects in humans.
In the field
Our study population surrounds a field station in a rural area of The Gambia in West Africa where this MRC-funded project has had a presence for more than 60 years.
The research focuses on an interesting natural experiment which is characterized by strong climate seasonality, with marked rainy and dry seasons that affect agriculture production and thus women’s dietary intake and nutritional status. The rainy season is the most challenging season because the women typically lose weight due to lower food availability and an intense agricultural workload. Conversely, the dry season is when the crops are harvested and food is more plentiful.
In this context we followed women of reproductive age to identify those getting pregnant at the height of each season. For our experiment we needed to obtain a blood sample as close to conception as possible. Because pregnancy disclosure can be a sensitive matter, we took a blood sample when they reported not to have seen their menses over a month, and then after their second loss we did pregnancy testing for confirmation and estimation of the gestational age.
It was not so easy though, because not all the women would easily admit to being pregnant. Our fieldworkers became expert pregnancy detectors. Yet some heavily pregnant women still were reporting seeing their menses, which made us miss a few of them.
All women with an eligible pregnancy (according to the time of conception) were followed up, and we later collected DNA from their baby’s blood and hair. This was probably the hardest part of the study since blood is hard to get from small babies and they hated to have hair taken, so it was as painful for me to watch! But it was good that we did as we ended up getting some robust results.
Analysis and impact
This study formed part of my PhD at the London School of Hygiene & Tropical Medicine, following on from my Public Health Nutrition MSc. I spent most of the first two years in the field in The Gambia. For me the two great joys of this work were having a great field team and a friendly and welcoming population.
Both my fieldworkers and the participants hosting us took amazing care of me, probably because in their eyes I was fragile and clumsy, based on my poor style at pounding rice, and my tendency to pour all the rice on my lap while trying to eat hot sauce with my “untrained” hands.
Ultimately our published research has shown that infants conceived in the rainy season show consistently higher levels of methylation at the six genes studied. This appears be mediated – at least in part – by differences in maternal nutrition status with respect to the nutrients required for methylation, such as B-vitamins. This might be explained by better nutrition due to a more diverse diet.
We do not yet know the effect of these genes or any specific effects they might have on health. However this study, which was a collaboration between our group and others in North Carolina, Vancouver, Houston and Cambridge emphasizes the importance of a well-balanced diet, not only during pregnancy but also prior to conception.
About Paula Dominguez-Salas
Dr Paula Dominguez-Salas is a veterinarian and a human nutritionist. She has worked for five years in the MRC International Nutrition Group based at the London School of Hygiene & Tropical Medicine and the MRC Unit, The Gambia, studying the effect of maternal diet during pregnancy in the offspring. Presently, she works at the Royal Veterinary College investigating the links between livestock value chains with maternal and child nutrition.