First Bite: How We Learn to Eat (4 page)

Davis created an unprecedented body of information on childish appetites (though it was never fully analyzed; and, after her death in 1959, all the boxes of raw data were discarded). When she took up a new job, the original setup in Cleveland was moved to Chicago, where she established what amounted to “an eating-experiment orphanage.” In all, she logged around 36,000 meals as well as recording changes in height
and weight, blood and urine, bowel movements and bone density. It is unlikely that any other scientist will ever get such detailed data again, given the dubious ethics of keeping children locked up in an experimental nursery for so long. The babies stayed on the diet for a minimum of six months and a maximum of four and a half years, during which time they were always at the hospital.

No friends visited, and those who were not orphans had little or no contact with their parents. While in the hospital nursery, their lives were subordinated to the needs of the experiment. Such an arrangement would never be allowed now, though Davis evidently cared for the children very much, in her way. She adopted two of them, as a single mother: Abraham G (the plump cherub) and Donald, the passionate orange eater. Many years later, after Donald was dead, his widow recalled that he and Abraham had always been “easy to cook for” and “happy to try all kinds of foods”—they remained omnivores all their lives.

It was such an extraordinary, audacious, borderline-crazy project that Davis attempted: to get to the heart of where children’s food passions come from. It’s just a shame that her experiment proved so easy to misread. Time and again, Davis’s orphanage has been held up as evidence that appetite is mostly genetic, and, as a consequence, that the foods children like or dislike are a sure guide to what their bodies need. Davis’s food orphanage has been taken as proof that in their natural state, likes and dislikes are genetic and highly individual, like fingerprints: our tastes are a matter of nature, not nurture. What this interpretation fails to take into account is that the biggest thing Davis did was to radically restructure the food environment of the children.

There was a “trick” to the way the experiment was set up, as Clara Davis was the first to point out. The real secret was in her choice of the thirty-four items on her list, which were all unprocessed whole foods. With such foods preselected for them, it didn’t matter which ones the children were drawn to on any given day, because, assuming they took food from several of the bowls at each meal, they could not help but eat a diet of an excellent standard of nutrition. Davis said that her choice of foods was designed to mimic the conditions of “primitive peoples,” though the heaping bowlfuls were surely more plentiful than any hunter-gatherer re
gime. The experiment proved that when your only food choices are good ones, preferences become unimportant. The “fifteen patterns of taste” resulted in a single healthy whole-food diet, because of the setup. Not one of the children was totally omnivorous, but nor were their likes and dislikes a problem, as they so often are in normal family life. There was no option to like unhealthy food and dislike healthy food.

Davis herself concluded that her experiment showed that the selection of food for young children should be left “in the hands of their elders where everyone has always known it belongs.” Instead of the “wisdom of the body,” Davis spoke of the “glaring fallibility of appetite.” It was obvious to her that there was no “instinct” pointing blindly to the “good” and the “bad” in food. The two most popular foods overall in her study were also the sweetest: milk and fruit. Had she offered the children a free choice of “sugar and white flour,” those staples of a 1930s diet, it is unlikely they would have ended up in such fine fettle. Self-selection, she concluded, would have little or no value if the children were selecting from “inferior foods.”

The real test, Davis recognized, would be to offer newly weaned infants a choice between natural and processed foods. This was to be have been her next experiment, but the Depression dashed this prospect, as her funding ran out at the crucial moment. Davis never got the chance to test the effects on appetite of the “pastries, preserves, gravies, white bread, sugar and canned food” that had in her lifetime become so popular. Her experiment left a powerful legacy that took no account of the trick at the heart of it. Doctors, particularly in America, interpreted her experiment to mean that children’s appetites are inbuilt and benign, without paying attention to the way in which Davis had changed the food environment in which the babies ate. Her work was seized on as proof that our individual appetites are messages encoded with exactly the nutrients that our particular body needs. If we need protein, we will crave chicken. If we have rickets, we will naturally gorge on vitamin D until we are cured. All we have to do to eat well is listen to our cravings. Mother Nature knows best. Davis herself gave license to such a view, commenting that the children’s successful “juggling and balancing” of more than thirty essential nutrients
suggested “the existence of some innate, automatic mechanism
 . . .
of which appetite is a part.”

Influenced by Davis, the dominant view on appetite among pediatricians became “the wisdom of the body,” which went along with the vogue for “child-centered” learning. In 2005, Benjamin Scheindin, MD, a pediatrician, noted that Davis’s work had contributed to a widespread change in attitudes in pediatric medicine from the 1930s onward. Where a previous generation lamented the pickiness of children’s changeable tastes, now doctors positively welcomed childish vagaries of appetite. Dr. Benjamin Spock, author of the best-selling
Baby and Child-Care
, first published in 1946, devoted ten pages to the Davis experiment. A mother, in Spock’s opinion, “can trust an unspoiled child’s appetite to choose a wholesome diet if she serves him a reasonable variety and balance.” It didn’t matter if a child developed a temporary dislike of a vegetable, because his or her cravings would naturally provide everything the child needed in the way of nutrition.

Many experts in child-rearing still think like this, operating on the assumption that children are born with special appetites for exactly the nutrients they most need and that it will all balance out, if only they are given free rein to eat what they like. A book on solving children’s eating problems that went through several reprints in the 1980s and 1990s argued that Davis’s work showed that children should be given total control over food selection: let them eat cornflakes! As recently as 2007, a popular website about feeding children discussed Davis and concluded that there was “a strong biological plausibility
 . . .
that children will instinctively choose a balanced diet.”

The “wisdom of the body” is an alluring thought (like maternal instinct and other biological myths). Eating would be such a simple business, if only we had little memos inside our bodies telling us what we needed to eat at each precise moment (your vitamin C levels are dropping—quick, eat a kiwifruit!). If only we liked just the stuff that was good for us and disliked anything superfluous or bad. We can certainly learn to get better at reading the body’s cues for food, but this tends to come with age and experience, as you notice little things like how pasta for lunch makes you sleepy, or that a handful of nuts and a
cup of Greek yogurt keep you full longer than white toast and jam. But children’s omnivorous bodies—after the milk stage, when breastfed infants do self-regulate—are not so wise.

Many children habitually seek out precisely the foods that are least suitable for them. They crave sugar and shun green vegetables. They neglect to drink enough water. Nutritious meals are rejected, while junk is revered. Can we really believe that a preschooler demanding a packet of the latest sugary kid’s breakfast cereal, having seen it on TV, is responding to the body’s need for certain vitamins and carbohydrate?

The scientific evidence—both from humans and rats—shows that the theory of the “wisdom of the body” is flawed at best. For the theory to be true, omnivores would need to have specific appetites for the essential nutrients the body needed at any given time. This is a very unlikely proposition, given that the list of nutrients needed by omnivores comes in so many guises, depending on the environment in which we happen to live. An innate appetite for the vitamin C in black currants would be of no use if you lived somewhere that black currants did not grow.

In lab conditions, rats—our fellow omnivores—have shown a very erratic ability to self-select the diet that would do them the most nutritional good. In one study, rats were given a choice between a bad-tasting but protein-rich diet and a good-tasting but low-protein diet. Over the course of a week, fourteen out of eighteen rats failed to develop a preference for the food that would have done them the most good, and they lost weight. Other trials have attempted to find out whether rats could “self-select” to correct certain vitamin deficiencies, and concluded that many of them could not. With thiamine-deprived rats, the process of learning to like a thiamine-rich diet took a week or more, and the rats that did not adapt quickly enough to the correct food died. As for human subjects, there is, notes one specialist in the field, no data to suggest innate appetites for specific foods. It does seem possible for humans to learn over time specific appetites that will correct certain imbalances—particularly a craving for salt when lacking in sodium—but that is a different matter.

Ninety years after Davis’s experiment, the view that likes are predominantly innate—or genetic—looks shaky. When trying to get to the bottom of where tastes come from, scientists have often turned to twins. If
identical twins share more food likes than nonidentical twins, the chances are that there is a genetic cause. Twin studies suggest that many aspects of eating are indeed somewhat heritable. Body composition—measured as body mass index, or BMI—appears to be highly heritable in both boys and girls. So is dietary “restraint,” or the mysterious urge to resist eating the thing you want to eat. But studies that look at likes and dislikes are much less conclusive. Several twin studies have suggested that identical twins are more likely to enjoy the same protein foods than nonidentical twins, but when it came to snacks, dairy, and starchy foods, their likes were only marginally more similar than those of the nonidentical twins. Overall, the evidence for tastes being heritable is very modest, accounting for only around 20 percent—at most—of the variation in foods eaten.

Genes are only ever part of the explanation for what we choose to eat. As one senior doctor working with obese children put it to me, you could be cursed with all the genes that make a person susceptible to heart disease and obesity and still grow up healthy, by establishing balanced food habits. “
All of it is reversible
,” he said. Parents and children resemble each other no more in the foods they like than couples do, suggesting that nurture—whom you eat with—is more powerful than nature in determining food habits. Whatever our innate dispositions, our experience with food can override them. Maybe the reason you share your parent’s hatred of celery is that you have seen them recoil from it at the dinner table. Researchers found that when they gave three groups of preschool children different varieties of tofu—one group had plain tofu, one ate it with sugar, and one with salt—they quickly came to prefer whichever one they had been exposed to, regardless of their genes. It turns out that, so far from being born with genetically predetermined tastes, our responses to food are remarkably open to influence, and remain so throughout our lives.

If you want to know what foods a person does and does not like, the single most important question you can ask is not “What are your genes?” but rather “Where are you from?” Had he lived in a part of the world where cornflakes are hard to come by, the cornflake boy would have had to find another way to annoy his parents. To a large extent, children eat—and therefore like—what’s in front of them, particularly in conditions of scarcity. “If you want your children to be less fussy about what
they eat,” a friend who had fallen on hard times during the recession advised me, “I can recommend poverty.” It’s not really an option to be picky about the staple food of rice if you live in rural China.

Genes do make a difference—to the foods we like, the way we taste them, and even how much we enjoy eating—but they turn out to be much less significant than the environment in which we learn to eat those foods. Contrary to our deepest beliefs about ourselves and our children, our likes and dislikes—the important ones, anyway, such as whether we eat enough vegetables or how much variety and balance we have in our diets—are much more about nurture than nature. Apart from changing the infants’ food environment, there was another, bigger trick to Davis’s experiment that she did not mention, perhaps because it is so obvious. She radically changed the children’s social experience when eating, removing all extraneous social influence. In place of the hubbub of the family dinner table, the babies had only expressionless nurses who “might not comment” in any way on their choices. The thought of being served in this silent, impassive way is creepy, particularly for the oldest children, who must have been as old as five by the time they left the orphanage. They ate without anyone caring what they ate, without any siblings fighting them for the last slice of pineapple, without any surrounding ideas about cuisine.

Davis was mistaken if she thought this was the way to discover the true nature of children’s appetites. Though the nutritional outcomes were excellent, it was a not-quite-human way to eat, and one that no child in a real situation will ever replicate. We cannot arrive at the truth about appetite by removing all social influences. Appetite is a profoundly social impulse. To a large extent, our likes and dislikes are a response to the environment we eat in. From our first toothless tastes, we are picking up cues about which foods are desirable, and which are disgusting, which, sadly, are so often the very ones the grown-ups most want us to eat.

The public discussion of eating habits is focused on temptation
and the idea of resisting desirable foods. But if we look at eating through the eyes of a child, we see that disgust may be even more powerful than desire in forming our tastes. Our urge to avoid eating something
that
makes us feel sick is often at the root of disordered eating, as we swerve away from whole categories of foods that we imagine would make us feel queasy. The most common reason for disgust is nausea: anything eaten just before a bout of stomach bug may be hated for life. Psychologist Paul Rozin, the world’s leading expert on disgust, has argued that a central feature of disgust is “contagion: when a disgusting food touches otherwise acceptable foods, it renders them permanently inedible.” And yet most of the foods that we happen to find disgusting are not toxins but perfectly edible and wholesome foods. Brussels sprouts, for example.