Attention breeders: If you want healthy grandchildren, better eat right during pregnancy. That's right. Grandchildren. A new study by local scientists shows that diet-induced changes in a pregnant mother's DNA may affect the well-being not only of her children, but of subsequent generations - as if a mother's guilt wasn't already enough. "We don't know how long this change persists, but we do know that it is in the germ line [the cells from which eggs and sperm are generated]," says lead researcher Dr. David Martin of the Children's Hospital Oakland Research Institute. "The germ line goes on and on and on for generations. So potentially [the effects] could go on for generations."
Lest you panic - since, as many a couple has discovered, a pregnant woman is often resigned to eating whatever she can keep down, which breeds resentment of the "best-odds diet" created by the authors of the popular prenatal tome What to Expect When You're Expecting - we should note that this study was done in mice. Then again, lab mice do a pretty good job of mimicking people.
The CHORI scientists, in collaboration with colleagues in Australia, used a special mouse called "viable yellow agouti." These critters have a mutant gene that links fur color (a yellow-to-brown range) with this strain's natural propensity to get fat and develop diabetes and cancer - the yellower mice are fatter and more susceptible, the browner ones less so.
In their study, some mama mice (the control group) got a standard lab diet based on common human foods. The test moms got the same thing spiked with nutritional supplements including folate, choline, betaine, vitamin B-12, zinc, and methionine. They ate this chow for one week mid-pregnancy, the equivalent of a human trimester. After the resulting mouse pups reached a certain age, the researchers recorded their fur color.
The females among the offspring were then mated to produce grandpups, only this time around all the expectant-mother mice got the standard lab diet. The researchers discovered that the babies whose maternal grandmothers had eaten the supplements (but whose mothers had not), had browner coats, and hence were destined for better health than the standard offspring. In short, you'd better hope your mama's mama ate her veggies while pregnant.
The study, to be published this month in the Proceedings of the National Academy of Sciences, is the first case in which the relationship between an animal's prepartum diet and the health of its grandchildren has been linked to specific genetic changes, Martin says.
In humans, similar effects have been observed on a population level. "In the Dutch famine, mothers who were starved while pregnant in first trimester ended up having children who were very obese," says CHORI assistant scientist Kenneth Beckman, who collaborated with Martin on the study. "But [researchers] didn't have any molecular knowledge about why this occurred. In this case, we have specific information about a specific gene."
So how exactly does diet affect DNA? The scientists can't say for sure. They have some hunches. For instance, Martin says, the supplements in question might recharge a donor molecule that's known to modify proteins and DNA. But that's just speculation, both admit.
It's certainly tempting to draw conclusions from their work, such as: Take your prenatal vitamins! But the researchers won't go there. "I think it's not a good idea to make any prescriptions based on this study," Martin says. "Taking vitamins is probably a good idea for most people, but it's not necessarily the case that the results of taking a supplement like the ones we used will have a beneficial effect."
Beckman summed it up like this: "I think the implication is that what you do when you're pregnant could not only affect your child, but also your grandchild. The direction of the change is less clear. What happens in pregnancy might not stop with the child. It might affect the grandchildren and beyond."
The scientists are currently testing whether environmental toxins, such as arsenic, can have similar, negative multigenerational effects. As far as the supplement study goes, Martin says, the next step is to determine how long, generationwise, the effects persist, and also to see whether they can be accentuated by giving supplements to mothers over multiple generations.
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