Every mother warns her children—eating right will make you healthy. And every pregnant mother’s doctor warns her—a good diet means healthier children. But this age-old adage may not always be true. A group of British scientists found that a poor maternal diet can actually boost her children’s resistance to disease.
Mike Boots of the University of Exeter and Katherine Roberts of the University of Leeds found that female Indian meal moths fed a sub-optimal diet had offspring that were better able to fend off viral infections. This finding was the reverse of what is usually expected—that a poor maternal diet would result in weaker children.‘
This effect is seen no matter how many resources the offspring themselves have,’ said Boots. ;’This is interesting because you expect mothers in poor environments to have fewer resources to give their offspring.’
Scientists have known that changes in a mother’s environment can be passed on to her children. When Kittiwake gull females endure poor nutrition, for example, higher levels of antibodies are passed on to their eggs. And, when Daphnia water fleas mature in crowded, low-resource conditions, their offspring are born less prone to bacterial infection. But it’s never been clear how these traits are passed on.
The new study asks; How does poor-diet disease resistance come about? Surely, recommending a poor maternal diet would be far from the minds of public health officials.
Boost and Roberts raised five different maternal populations of the Indian meal moth; each of the five groups received feed of decreasing quality. Offspring of these moths were then exposed to a virus and their ability to generate an immune response measured.
Surprisingly, offspring whose mothers had the poorest diet were best able to generate an immune response. No matter how good the offspring’s diet was, its ability to resist disease was mostly dictated by its mother’s diet.
Why did this happen? Boots suggests that it comes down to costs of resources. Every adaption is costly—putting more energy and resources into growth, for example, may be done at the expense of bolstering the immune system. “Under poor environments each offspring may be more valuable to the mother and she may invest more overall into each offspring.”
The researchers believe that their results show that poor environments make a mother’s offspring more valuable; therefore she will invest more in her offspring’s immunity. This is not a conscious process, but a genetic and physiological one. “High population densities often lead to poor individual resource levels, and may also be correlated with high individual disease risk” Boots and Roberts wrote. “We would expect natural selection to favor individuals that invest more where there is the greatest threat of disease.”
It’s not a sign for pregnant women to start eating badly. Instead , a mother’s own environmental changes has significant impacts on understanding how disease outbreaks occur. Looking at diet—including a mother’s diet before the outbreak—now occupies a more prominent position on that stage.
Source: Proceedings of the Royal Society
Boots, M., & Roberts, K. (2012). Maternal effects in disease resistance: poor maternal environment increases offspring resistance to an insect virus Proceedings of the Royal Society B: Biological Sciences, 279 (1744), 4009-4014 DOI: 10.1098/rspb.2012.1073