Modern medicine has made some stunning advances like eradicating small pox and mapping the human genome, but it still hasn’t answered a basic question: when to start feeding babies solid foods.

In fact, the matter is a fairly burning issue right now.

For years, the prevailing wisdom was that introducing solids before 6 months of age – and certain allergenic foods before a year – can contribute to food sensitivities and allergies. But now, the theory is emerging that waiting actually causes the immune system to think these food are invaders when later introduced.

Local doctors interviewed about the debate described the science around it as “waffling” and “conflicting.”

With so much uncertainty, what’s a parent to do? With a collective shrug, most experts say do what feels right.

Food allergies

The incidence of food allergies in the U.S. population has been steadily rising. Centers for Disease Control and Prevention statistics show a 20 percent increase in reported food allergies among children since 1997, when national data first became available.

The primary culprits of food allergies are milk, eggs, peanuts, wheat and tree nuts.

Dr. W. Donald Cooke, a local allergy specialist, said there is evidence to suggest that this has something to do with how we, in developed countries, raise our kids.

The term “hygiene hypothesis” is being applied to the theory that we are rearing children in an overly sterile environment that deprives them of exposure to the good bacteria necessary to develop a strong immune system.

Local pediatrician Pakhi Chaudhuri said another possible contributor is genetically modified organisms. She acknowledged this premise is getting more attention in the lay world than in mainstream medicine. Nonetheless, she said the concurrent surge in GMO foods on store shelves and rise in food allergies is highly suspect.

In fact, there’s so much that has changed in our diet and environment in such a short time, it could be some time before researchers untangle the web of causality.

“I don’t know that we have a good grasp on what’s going on,” she said.

Parents’ predicament

I remember as a new mother waking up to the realization that my son wasn’t going to be able to survive on breastmilk alone forever. Of course, this is obvious, but in the fog of endless sleepless nights, you tend to lose sight of everything but the next diaper change and how much you would like a shower.

As I began to plan for this transition, I asked a trusted friend for advice. She referred me to a book called Super Baby Food, which was first printed in 1996 (a time when said friend and I were much more concerned about keeping ourselves well fed and in passably good wine than about baby food).

I was more than a little daunted when I discovered the book topped 600 pages. Still, I religiously followed its rigid dictates – rice cereal at 6 months, egg yolks but not whites after 7 months and no cow’s milk before a year. But eventually, the demands of regular life foiled my best intentions. Chocolate ice cream isn’t listed anywhere in the Super Baby Food diet, but it was introduced nonetheless. By the time the second child arrived, it was pretty much open season. Foods were introduced willy-nilly and – gasp – sometimes in unison.

Any residual guilt I may have felt for my lack of dietary rigor was eased when I read “The Peanut Puzzle,” an article that appeared in The New Yorker in February 2011. Some pre-eminent specialists, it turns out, had done a 180-degree turn, coming to believe that early exposure was beneficial.

The pediatrician who headed up the American Association of Pediatrics committee on nutrition for children told The New Yorker, “We in medicine are making a lot of decisions and recommendation based on not a lot of solid evidence.”

The American Academy of Allergy, Asthma & Immunology came out in November 2012 and said that no evidence exists to show that delaying the introduction of solid foods before 4 to 6 months prevents food allergies and that delaying the introduction of solid food, “especially the highly allergenic foods, may increase the risk of food allergy or eczema.”

Picking a path

Chaudhuri, the local pediatrician, said she lays out the current state of the research for parents then talks about how ancient cultures have handled food introduction (usually waiting until about 6 months). Her family comes from India, where a whole ceremony is conducted around babies’ first meal, at around 6 months. She tells parents to introduce new foods one at a time and wait a couple of days for a reaction.

Local mother Cheryl DeMarco Mellor said she did a lot of reading before starting her baby, Mya, now 10 months, on solid foods. She herself has food allergies, so she admits to being cautious, carefully documenting what Mya has eaten and how she reacted. She goes “back and forth” on whether to start egg whites and peanut butter.

“It’s a lot to sort through and a lot of decision making – and huge decisions because you have a life in your hands,” she said.

Louvelle Zinser, whose son just turned 2, said she is gluten intolerant, but she and her husband decided to give their son foods with gluten. So far, he has not shown any signs of food allergies or sensitivities. She said every parent has to decide what approach is right for them.

“The first thing is trust your own instincts,” she said.