Obstetricians and fertility specialists often give this advice to improve chances of conception, but new research suggests that a mother’s diet can have a permanent effect on their baby’s DNA as well.
A Natural Experiment in Rural Gambia
Studying the effects of maternal nutrition in humans is difficult, due to the ethical implications of experimenting with women’s nutrition during conception and pregnancy. Women in rural Gambia, though, rely on self-produced food, and the region’s strong fluctuation between rainy and dry seasons imposes a seasonal variation in their nutritional intake – with the rainy season being nutritionally poor compared to the dry harvest season.
A team of researchers from the London School of Hygiene and Tropical Medicine (LSHTM) used this natural variance to study the effect of altered diet around the time of conception.
Methlyation: A Chemical Tag Added to DNA
We know that environmental factors such as diet can chemically modify DNA. The most important modification of DNA is methylation. DNA methylation normally turns genes off, and the degree of methylation naturally varies between cell types, and between individuals.
Like DNA itself, DNA methylation can be passed on from one generation to another, at least in animals. Experiments in mice found that changing the diet of females (in a way that encouraged DNA methylation) changed the coat colour of their offspring. The question is, can similar dietary changes also cause heritable changes in humans?
Metabolite Levels in the Bloodstream Vary with the Season
The LSHTM research team followed a group of Gambian women and analysed blood samples from those who conceived during the study period. They measured seasonal variations in certain metabolites that are required for DNA methylation, including folate, vitamins B2, B6 and B12, choline and methionine. The team found significant differences in blood concentrations of eight of the 13 metabolites between samples from women who conceived at the peak of the rainy season and those who conceived at the peak of the dry season.
Mother’s Diet Alters Babies’ DNA
After the babies were born, the researchers found a correlation between the season of conception and the level of methylation in the babies’ DNA. Babies that were conceived in the rainy season had significantly higher levels of methylation in all 6 genes the researchers looked at.
So, it seems that the mothers’ diet at the time of conception had a permanent genetic effect on their children’s DNA. The women’s BMI (body mass index) also had an effect on DNA methylation: A higher BMI was correlated with decreased methylation.
This correlation is expected, as during the nutritionally rich dry season (associated with decreased methylation in babies), women’s BMIs will be highest.
This result is similar to a study from 2008, which examined a group of people who were conceived around the time of the 1944-1945 “Dutch Hunger Winter” famine. People whose mothers had been exposed to the famine in early pregnancy had reduced methylation in a gene called IGF2. This difference in DNA methylation had persisted for sixty years; the age of the individuals when their DNA was analysed.
Pre-/early Pregnancy Dietary Supplements?
Folate is already recommended as a supplement in pre- and early pregnancy to prevent neural tube defects, and the LSHTM team suggest their research could eventually identify the optimal diet for mothers at the time of conception.
This may be some way off, however. The life-long consequences of altering the 6 genes they looked at is not yet known. Even more challenging will be gauging the amount and effect of altering methylation patterns across the entire human genome, which contains over 20,000 genes.
Such facts will need to be established before researchers can develop peri-pregnancy supplements designed to change DNA methylation.