A "new" cause of asthma?

Asthma is one of those 1st world diseases that seems to become more, not less, prevalent with modernization, bucking the trend of most diseases. There's been several theories as to why this is so. Smoking and air pollution contribute to asthma rates, but perhaps less obviously, some studies hint that so do C-sections, antibiotic use, even chlorine in pools. The originally oddball theory, which has gained some real respect following a number of studies, is that we're too clean -- asthma may develop when our childrens' immature immune systems are never exposed to normal levels of bacteria, causing them to overreact to normal airborne pollutants.

This article from ScienceDaily summarizes a study, published in the Journal of Clinical Investigation, which suggests another possible cause. To summarize the summary, pregnant mice who ate diets rich in methyl-donors had offspring with higher rates of asthma and asthma-related symptoms. (The thought of an asthmatic mouse probably shouldn't strike me as so funny, but it does.) Among other methyl-donors is folic acid, now commonly recommended as a supplement for pregnant women, as well as added to most flour (and found in most breads) by law in the US and several other (mostly developed) countries. This is because too little folic acid during pregnancy can cause a specific type of birth defect. Can too much cause asthma? One study in mice only hints that it does, but also provides yet another hint that we may be better off leaving our nutrients in the foods they come in, and getting them from the source. (Folic acid occurs naturally in leafy greens, beans and peas, and some other fruits and vegetables, all of which are rich in other important nutrients, as well.)