New research shows that a person's health could be affected by the diet and lifestyle of their grandfathers during childhood. The studies, carried out at the University of Bristol in the UK and Umea University in Sweden, suggest that some environmental factors can affect the genetic information passed on to subsequent generations. The authors, who published their findings in the European Journal of Human Genetics, say such 'transgenerational' effects could have evolved as a short-term response to threats such as famine.
The scientists focused on the effects of smoking and food supply on the health of children and grandchildren. The first part of the study looked at 160 fathers who said they had started smoking before the age of 11. The families were all participants in the Avon Longitudinal Study of Parents and Children (ALSPAC), also known as the 'Children of the 90s' project, which is based at the University of Bristol. The researchers found that the sons of men who took up smoking at an early age are significantly larger than other children. However, the link is not present between early smokers and their daughters, which suggested that such effects could be 'sex-specific'.
The other part of the research used historical records from Overkalix, an isolated community in Sweden. A previous study looked at records of harvests and food prices dating back to the 19th century to identify times of famine, and periods when food was plentiful. The researchers looked at the health of three generations of 300 families living in the area, and found that the health and lifespan of the grandchildren was linked to their grandfather's access to food - in particular, between the ages of 9 and 12. 'Children tended to live longer if their grandfather had endured food scarcity during this particular time of life', said study author Professor Marcus Pembrey, head of genetics at ALSPAC.
When they reexamined the Swedish data in the light of their findings on early smoking, the scientists again found a sex-specific effect: the paternal grandfather's food supply was linked to the lifespan of grandsons, while the paternal grandmother's diet was linked to the lifespan of her granddaughters. In the grandfathers, the most crucial time appeared to be the 'slow growth' period just before puberty. This period is when sperm production is about to begin, which lead the team to propose that the effects are part of a system that allows a father's experiences to be somehow 'captured' by his sperm - allowing subsequent generations to respond to threats experienced by their parents or grandparents. The data on grandmothers from Overkalix backs up this theory - the crucial period for food supply affecting granddaughters is during the grandmother's fetal development and infancy, when eggs are being produced.
The researchers think the system could be down to 'epigenetic genes' changes that switch genes on and off, rather than changing the genes themselves. It was already known that such changes can affect a fetus growing in the womb, but the new study is the first to show that a father's experiences can also affect their children's genes.
According to a news report in the journal Science, some scientists remain unconvinced by the findings. At a recent meeting on environmental genomics and disease susceptibility, geneticist Bruce Richardson and others suggested that the results could be caused by statistical flukes. But Professor Pembrey thinks not, because the critical periods highlighted by the studies of smoking and food supply correspond to the periods when eggs are maturing in girls, and sperm production is about to begin in boys. He adds that the results have important implications for public health, and could have 'a big impact on the way we view our responsibilities towards future generations'.