Ear infections make fatty food sound good

PHILADELPHIA — Childhood ear infections may not just put hearing at risk. Kids who get them may develop a strong affinity for fatty foods and could be predisposed to obesity, surveys now suggest. Researchers suspect that infections of the middle ear may alter the sense of taste by damaging a nerve that carries sensations from the tongue to the brain.

A childhood history of frequent, serious ear infections (defined as those requiring antibiotics) doubles the risk of becoming obese later in life, psychologist Linda Bartoshuk of the University of Florida in Gainesville reported on August 20 in Philadelphia during a meeting of the American Chemical Society. Those with ear infection histories also have a stronger preference for fatty foods, she said.

Three out of four children experience at least one episode of middle ear infection by their third birthday, and one out of three experiences at least three episodes, according to the National Institute on Deafness and Other Communication Disorders, or NIDCD.

Bartoshuk says frequent ear infections may permanently damage the chorda tympani nerve, which picks up taste sensations from the front of the tongue and then runs through the middle ear — the hollow located between the eardrum and the cochlea — to the brain.

The study originated from informal questionnaires that Bartoshuk and UF colleagues Valerie Duffy and Derek Snyder started handing out at scientific meetings in 1993. The team collected thousands of questionnaires, which aimed to measure how demographic factors relate to the sense of taste. Snyder first noticed how the data suggested a correlation between ear infections and obesity .

Later, with the help of Howard Hoffman and Barry Davis of the NIDCD, the team looked at data from other, more formal surveys, including the National Health and Nutrition Examination Survey of the Centers for Disease Control and Prevention. The correlation was there, too.

Damage to the chorda tympani nerve appears to prime people for liking fatty foods, which are especially energy-rich, Bartoshuk says. Paradoxically, that’s not because the nerve damage increases taste sensation — in fact, it decreases it, she says. The link she proposes is more subtle.

In previous research, Bartoshuk and her collaborators showed how chorda tympani damage heightens the sensation of the texture of fatty foods, a sensation the brain associates with energy-density, she says. “Damage to taste makes oral touch feel more intense.” People who’ve had ear infections would then just receive more intense sensations from creamy, slippery foods.

In principle, heightened sensations might cut both ways, Bartoshuk admits. One effect could be that of increased pleasure. But another might be that it would take less fattiness to fool the brain into thinking it has secured enough energy. However, she says her surveys show that people with ear infections actually like fatty foods better, so that they may want to eat more of them.

Bartoshuk speculates that the link between chorda tympani damage and increased touch sensations may be an evolutionary accident. Tasting food tells the brain that food is coming, she notes. The brain ignores tactile sensations it might otherwise take as warnings — sensations that would, for example, trigger a reflex to cough.

The brain also ignores sensations of pain that may come from uncooperative food — for example, live prey that’s trying not to be swallowed. So the brain responds to the tongue’s taste by ignoring its touch. “It’s a beautiful system that’s built to make sure you eat,” Bartoshuk says.

Removing the taste sensations from the chorda tympani allows the touch sensation to be felt more strongly than usual. Thus fatty foods “feel” even fattier.

The chorda tympani is not the only nerve carrying taste sensations from the tongue, and people with a history of ear infection don’t usually report altered taste sensations, Bartoshuk adds.

Her colleague Hoffman also found a correlation between tonsillectomy and weight gain, Bartoshuk says, adding that tonsillectomy can damage a separate taste nerve.

Bartoshuk and her collaborators have presented parts of their results at scientific meetings in the past, but they only plan to publish them now, after the evidence has become more solid, Bartoshuk says. “We did not want to go public with this because it’s the sort of thing that frightens people.”

Julie Mennella, a biopsychologist at the MonellChemicalSensesCenter in Philadelphia, says her own surveys of children aged 7 to 11 are corroborating the team’s findings. “What Linda has found in adults, we’re already seeing in children, too,” she says.