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The same vitamins and supplements that mothers-to-be take to protect their kids from birth defects could predispose children and even grandchildren to asthma.

If mice studies are confirmed by studies in humans, expectant mums may need to strike a balance between amounts of supplements such as folate, which reduces the risk of spina bifida, and those that bring on asthma, says John Hollingsworth, a doctor who specialises in diseases of the respiratory system – pulmonology – at Duke University Medical Center in Durham, North Carolina. “A little could be helpful and a lot could be harmful,” he says.

He and his colleagues fed pregnant mice supplements including folate, vitamin B12 and zinc in doses roughly equivalent to those recommended for pregnant women. These chemicals turn down the expression of certain genes and mark the DNA of a developing embryo so that the effect is passed from generation to generation, a process known as epigenetics.


Mice who ate the supplement-rich diet delivered pups with some signs of asthma. Their lungs contained high levels of immune cells and proteins that predict asthma in humans compared with mice that ate a supplement-poor diet.

To future generations

When Hollingsworth’s team bred these pups on a normal diet, their offspring still showed some signs of asthma – an indication of epigenetics in action.

Indeed in a genome-wide search for genes epigenetically marked for lowered expression in the first generation of mice pups, the researchers turned up several genes important for harnessing the immune system. Mice completely lacking one such gene, called Runx3, develop spontaneous asthma, and the researchers suspect epigenetically reduced expression of the gene could have the same effect.

“It’s a nice mouse model, but it’s a mouse model,” says Rachel Miller, an allergist and pulmonologist at New York Presbyterian Hospital. She says that to prove that maternal supplements could predispose kids to asthma, researchers would need to closely track the diets of expectant mothers, as well as any asthma that develops in their children.

“I think it needs to be tied back with human disease,” agrees Hollingsworth. But if confirmed by such human studies, the link between dietary supplements and asthma might explain the mysterious rise of the disease in developed countries, where pregnant women are advised to take folate supplements.

However foods such as leafy greens, broccoli and nuts, also contain folate and can silence genes. Cigarette smoke makes the same epigenetic changes, and one retrospective study found that grandmothers who smoked while pregnant are more likely to have asthmatic grandchildren than non-smoking grannies.

“You are what you eat – or you are what your grandma eats,” Hollingsworth says.

Journal reference: Journal of Clinical Investigation, DOI: 10.1172/JCI134378 (in press)

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