Anyone who's sought solace in pizza or a pint of ice cream knows that food can be comforting. But experts still don't know exactly why we gravitate toward fatty or sugary foods when we're feeling down, or how those foods affect our emotions.
Taste and the pleasant memories associated with junk foods surely play a role, but that may be only part of the story. According to a small new study, hormones in our stomachs appear to communicate directly with our brains, independent of any feelings we have about a particular food.
Most research on food and emotion has looked at the overall experience of eating -- the tastes, smells, and textures, in addition to nutrients. In this study, however, the researchers took that subjective experience off the table by "feeding" the volunteers through an unmarked stomach tube.
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Even in this artificial environment, saturated fat appeared to fend off negative emotions. The study volunteers were more upbeat after listening to sad music and seeing sad faces if their bellies were full of saturated fat versus a simple saline solution, which suggests that emotional eating operates on a biological as well as psychological level, researchers say.
The study is among the first to show that the effect of food on mood is "really independent of pleasant stimuli," says Giovanni Cizza, M.D., an obesity and neuroendocrinology researcher at the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), in Bethesda, Md., who was not involved in the study. "It is even more rooted in our biology."
The biological mechanism at work is still unclear, but the findings suggest that the stomach may influence the brain by releasing hormones, says Lukas Van Oudenhove, M.D., one of the study authors and a postdoctoral fellow at the University of Leuven, in Belgium.
The deep-seated connection between our stomachs and our brains helped keep humans alive when food was scarce (as it was during most of human history), but it may have outlived its usefulness and may be contributing to modern health problems such as obesity, Van Oudenhove adds.
"Evolution has made every aspect of feeding as rewarding as possible," he says. "These days it may not be a good thing anymore. When food is available anywhere, then it may be a bad thing, leading to obesity or eating disorders in some people."
The study drives home just how difficult it can be to eat healthy and resist so-called emotional eating in our stressful world, says Susan Albers, Psy.D., a psychologist at the Cleveland Clinic and the author of "50 Ways to Soothe Yourself Without Food."
"Given the strong soothing effect of food on a biological level, we have to work even harder to find ways to soothe and comfort ourselves without calories," Albers says. "This is important in the long run for managing your weight, improving your self-esteem, and protecting your overall health."
The study, which appears in the August issue of the Journal of Clinical Investigation, included 12 healthy, normal-weight volunteers. Van Oudenhove and his colleagues infused one of two "meals" into the stomachs of the volunteers: a solution of saturated fatty acids, or a saline control solution. (The researchers used a fat-based solution because comfort foods are often fatty, and because they were familiar with the brain's response to the solution from earlier research.)
After the feeding, the researchers induced feelings of sadness in the volunteers by playing sad classical music and showing them images of faces with sad expressions -- techniques that have proven to be downers in previous experiments.
Brief mood surveys administered throughout the experiment revealed that the participants found the sad music considerably more depressing after receiving the saline solution than after the fat solution.
Functional MRI brain scans taken during the experiment echoed these findings: Compared to the saline solution, the fatty solution appeared to dampen activity in parts of the brain that are involved in sadness and that responded to the gloomy music.
The fleeting feelings of sadness experienced by the study volunteers pale in comparison to some of the emotions that people try to address with food in real life, Albers says. "Think about how this compares to some real-world problems people face, like illness, loss of a job, or a divorce," she says. "We are often under a constant state of stress."
Therapy or other treatments that "teach people how to deal with strong emotions would likely ... help people improve their eating habits," she says.
In an editorial accompanying the study, Cizza and a colleague at the NIDDK say that the "most important" question raised by the study is whether obese people respond to fatty foods in the same way as the normal-weight volunteers. For instance, he says, the brains of obese people may resist soothing signals from the gut more strongly than the brains of leaner people.
But there's nothing wrong with occasionally eating unhealthy comfort food, Cizza adds.
"Evolution has provided us with, if you wish, an over-the-counter anti-anxiety or anti-sadness product," he says. "Maybe if you're sad and you feel like that chocolate could help you, go for it. Don't feel too guilty, but try to limit what you eat and maybe later cut down on something else."