For early humans, the entire world was a supermarket stocked with seasonal fare. Each forest crawled with potential edibles, each thicket offered a buffet. But alas, this open-air store was void of nutritional labels and the protection of the FDA.
People could only rely on instinct and harsh experience to guide them. Ripe fruit was safe and also packed with vitamins, and so our ancestors developed a preference for sweet foods over the years. At the same time, they evolved an aversion to bitterness, since natural poisons are bitter. Those who avoided such flavors were less likely to eat something toxic and die.
The legacy of the ancient food environment survives to this day. Babies are still born with a love of sugary foods like cookies and a dislike of bitter substances such as coffee. Most people crave fatty fare, which was scarce in the old days (and all too prevalent now). But beyond such general patterns, there are surprisingly few universals when it comes to the human diet. Some of us love tomatoes, or hot peppers, or stinky cheese, while others cannot abide them. When it comes to eating, "the larger problem of accounting for preferences is an area of considerable ignorance," says Paul Rozin, a psychologist at the University of Pennsylvania. But researchers are now beginning to understand the complicated stew of genes and environment that helps determine our favorite—and least favorite—foods.
1: Picky Palates
Three decades ago, when Marla Lopez was out to dinner with the man who is now her husband, she announced her order: two dinner rolls, two orders of toast, an English muffin, and a croissant. Lopez told the incredulous waitress that she was on the "bread diet." Soon after, the other waitresses in the restaurant descended on slender Lopez's table, wanting to know all about this intriguing plan.
But Lopez, a 51-year-old Realtor in Idaho, wasn't cutting calories. She is an extremely picky eater. She doesn't like steak ("It's like biting the sole of a shoe," she says), or chicken, or any kind of meat—with the exception of very crisp bacon. She doesn't like fruit or vegetables, either. Breakfast is plain Cheerios or cornflakes with just a touch of milk. Lunch is often French fries and dinner might be a plain tortilla, a dinner roll, and a big glass of milk. "You can put pizza, a hamburger, a hot dog, escargot, and dog poop on a plate and I'd have a hard time picking which one I'd rather eat," she says. "To me, they're all gross."
Picky eating is common in children, who naturally exhibit food neophobia, or a reluctance to try new meals. "In the course of things, with repeated exposure, most picky eating in childhood remits," says Marsha Marcus, a psychiatrist at the University of Pittsburgh who is working to register adult picky eaters into a national database for research purposes.
Many of the members of PickyEatingAdults.com, an online support group, report the same aversions as Lopez—fruits, vegetables, and meats. And yet, they almost universally embrace grains and other carbohydrates. "Picky eaters usually dislike bitter and sour, and carbs aren't bitter or sour," explains Elizabeth Capaldi, a psychologist at Arizona State University.
More than flavor, what really seems to bother picky eaters is texture. Although texture is rarely cited as a reason for liking a food, often it is enough to make someone despise it. Many picky eaters are also opinionated about how food is combined and prepared. They might like both peas and rice but refuse to eat the two mixed together.
Where does this behavior come from? Lopez says she has been this way all her life and even gagged on all sorts of common baby foods. "I don't believe it to be a choice," she says. Indeed, a 2007 study of European twins found that food neophobia was strongly heritable.
In fact, a combination of genetic tendencies could be at work. Certain aspects of picky eating resemble known disorders—the concern with texture could be a sign of a sensory processing disorder, for instance, while a distaste for foods that mix or touch could be a manifestation of an anxious or obsessive streak. Picky eaters do score higher than others on tests of anxiety.
The behavior could also be linked to natural human variation in the taste system. Among a group of caucasians studied in the U.S., about 30 percent qualified as nontasters, who are unable to detect bitter compounds. Among the remaining 70 percent, a small subset had a mutation that makes them extremely sensitive to such tastes. These so-called "supertasters" may find the bitterness present in vegetables—and other compounds, such as cheeses and coffee—to be so extreme that they just can't stomach them.
Family environment may also play a role—or at least make picky eating worse. "Forcing children to eat something, or having them eat it in order to get dessert, or making them sit at the table until they eat something they don't like, will make them dislike the food in question even more," Capaldi says. Repeated exposure to new foods doesn't seem to help extremely picky adult eaters, Marcus says. Perhaps they're ultrasensitive, requiring more exposures than most of us. Or perhaps their visceral responses are so strong that they can't even get new foods in their mouths.
By age 30, Lopez (who is currently still slender and without health problems) had managed to add a few things—cheese and mashed potatoes—to her diet. But it's been a lifelong struggle. "When I was in sixth grade," she recalled, "my dad said, 'You eat six new foods and I'll buy you a horse.' I tried hot dogs, orange juice, and that was it. I couldn't get to three, four, five, and six."
