AUDIE CORNISH, HOST:
Picky eaters may drive their parents up the wall, and for most, it's just a phase. But a study in the journal "Pediatrics" finds that occasionally, it's a sign of deeper problems. In extreme cases, it's linked to social anxiety and depression. NPR's Richard Harris wondered why picky eating occurs in the first place.
RICHARD HARRIS, BYLINE: It turns out that picky eating is about more than children and their taste buds. It involves all the senses and the social setting as well.
KATHLEEN KARA FITZPATRICK: Our notions of what is typical eating have changed radically over the last hundred years.
HARRIS: Kathleen Kara Fitzpatrick treats children with eating disorders at the Stanford University Medical School. She says modern parents typically introduce foods to children at an older age, so the American palate takes longer to mature.
FITZPATRICK: And that's why most kids' menus in restaurants look exactly the same.
HARRIS: Research suggests that about 20 percent of kids age 2 to 6 years old fall into the category of moderate to severe pickiness. At the extreme, it can be debilitating.
FITZPATRICK: I had a patient that I worked with who was a bit older who actually only ate pizza and drank Coke every single meal. It wasn't any pizza. It had to be Domino's pizza, and it had to be pepperoni.
HARRIS: This is clearly a behavioral issue, but it's tied closely to sensory experience. Fitzpatrick says she wanted to get a deeper insight into that sensory process, so she tried an experiment on herself by eating the exact same thing for six straight weeks.
FITZPATRICK: What really surprised me was that after about a month and sort of toward the end of my experiment, I could taste incredibly subtle differences in the food that I was eating. Even though it was exactly the same thing, if I put more cheese or more tomato just kind of accidentally, it would significantly change the taste of the food to me.
HARRIS: Fitzpatrick was experiencing something that psychologists have noticed about picky eaters. They have heightened sensitivities. That's not a bad thing, and neither is the basic impulse to be selective.
FITZPATRICK: You don't want your kid picking up and eating everything 'cause then they're going to eat dirt and hair and cat poop. And so (laughter)...
BEVERLY TEPPER: To some extent, it's a natural biological response.
HARRIS: Beverly Tepper is a professor of food science at Rutgers University. This evolutionary adaptation to avoid poisonous foods involves all the senses, not just taste. In fact, picky eaters make their first judgment based on how food looks.
TEPPER: Once we get past the how-it-looks stage and we smell it, and it has an attractive odor, we might be interested in consuming it or tasting it.
HARRIS: Once it's in the mouth, texture comes to bear and finally, the flavor. No surprise bitterness plays a critical role, which explains a lot about kids and broccoli.
TEPPER: We are very sensitive to bitter taste. Individuals differ in their sensitivity to bitter taste. This is a genetically driven trait.
HARRIS: What's remarkable is not that children often reject bitter foods, but why anyone develops a taste for a sensation that can be a warning sign. Tepper has been contemplating why that might be to our advantage.
TEPPER: Not only is variety the spice of life, but healthier diets tend to be higher in variety. So this may be a mechanism that ensures greater variety in the diet.
HARRIS: And building variety into a diet takes times. Adults may only try new foods once or twice before they decide whether they like them or not. Fitzpatrick says most children need about eight tries.
FITZPATRICK: Extreme picky eaters can require 52 or more presentations of a food before it's no longer considered novel.
HARRIS: When picky eating persists to the point where it's that much of a challenge, conquering it won't be easy. So Nancy Zucker at Duke University says don't try to add new foods to a child's diet during meals where a conflict can disrupt important family time.
NANCY ZUCKER: What I suggest parents do is if there's going to be food adventures, that it happens during snack.
HARRIS: And remember, children will usually grow out of it. Richard Harris, NPR News.
NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.