Research in the Gambia has found that different diets, coinciding with rainy and dry seasons, influence a baby's gene expression.
The findings provide the first evidence in humans that a mother's nutritional status around the time of conception can result in epigenetic changes.
'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 Dr Branwen Hennig, at the London School of Hygiene and Tropical Medicine.
The team obtained blood samples from 167 women around the time of conception to determine levels of different nutrients in their blood and then analysed samples of their children's hair follicles and white blood cells when they were two to eight-months-old. Half of the women conceived during the peak of the rainy season, and half during the peak of the dry season. Seasonal changes in the Gambia mean that rural diets vary considerably over the year, allowing the researchers to compare the possible effects of nutrition on the children's gene expression.
The results, published in Nature Communications, showed that a mother's diet before conception had an effect on certain aspects of the children's DNA. The way genes inherited from the mother are expressed is partly determined by the presence of methyl groups that are able to silence genes, affecting the way they function. Babies born in the rainy season were found to have higher rates of methyl groups in their DNA that were linked to their mother's nutrients in the blood.
'Our results have shown that maternal nutrition pre-conception and in early pregnancy is important and may have implications for health outcomes of the next generation', Dr Hennig told the BBC. The consequences of these epigenetic changes for the child were unknown, however.
The team also looked at specific regions in the genome called metastable epialleles that are turned on or off very early on in the development of the embryo and remain stable throughout development. This enabled the researchers to identify the period when a maternal diet has affected the methylation process. Andrew Prentice, professor of international nutrition at the London School of Hygiene and Tropical Medicine, explained to The Scientist that the relevant period is 'either occurring in the mother's ovary some two weeks prior to conception or within the first two days or so of conception'.
Similar effects have already been found in mice. In these animals, research has shown that maternal diet can have permanent effects on offspring's fur colour through epigenetic influences, but so far this effect has not been shown to occur in humans.
Dr Hennig told the BBC that 'Women should have a well-balanced food diet prior to conception and during pregnancy'.
Commenting on the findings, Dr Karin van Veldhoven from the UCL Institute of Child Health, who was not involved in the study, said: 'As factors such as diet are modifiable, they are potentially of great importance. However, the consequences of these changes in DNA methylation for children's health need to be further investigated'.