Are We Born Craving a Balanced Diet?

Children choose healthy foods when left to their own devices, according to a classic experiment. Do those results still hold up?

By Bee Wilson|Thursday, January 21, 2016
RELATED TAGS: NUTRITION
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William Zuback

“He won’t eat anything but cornflakes,” complained the mother of a boy I used to know. Breakfast, lunch, dinner — always a bowl of cornflakes and milk. Even at other people’s houses, he made no concessions. To his mother, his extreme diet was a source of worry and exasperation. To the rest of us, he was a fascinating case study. Where did it come from, this bizarre cornflake fixation? It just seemed to be part of his personality, something no one could do anything about.

Whether you’re a child or a parent, the question of “likes and dislikes” is one of the great mysteries. Human tastes are astonishingly diverse and can be mulishly stubborn. Even within the same family, likes can vary dramatically from person to person. Some prefer the components of a meal served separate and unsullied, with nothing touching; others can fully enjoy them only when the flavors mingle in a pot.

Because our tastes are such an intimate part of our selves, it’s easy to make the leap to thinking they must be mostly genetic: something you just have to accept as your lot in life. Parents often tell children their particular passions place them on this or that side of the family — you got your fussiness from your grandfather! — as if you were destined from birth to eat a certain way.

The question remains to what extent we can override this genetic inheritance and learn new tastes. This riddle can seem impossible to unravel, given children don’t learn to eat under laboratory conditions. As we take our first bites, our parents supply us simultaneously with both nature (genes) and nurture (environment in its broadest sense, including everything from cuisine to family dynamics to religion to cutlery and table manners to the ethics of meat to views on whether it’s acceptable to eat food off the floor if it was there for only five seconds). The two are so intertwined, it’s hard to tell where one starts and the other stops.

In one remarkable experiment, however, a group of children did learn to eat under lab conditions. In the 1920s and ’30s, Clara Davis, a pediatrician from Chicago, spent six years trying to study what children’s appetites would look like if allowed to blossom without any preconceived ideas of what tasted good. Davis’ results have often been taken as a clear indication that likes and dislikes are fundamentally built-in and natural, though, as we’ll see, Davis herself drew a rather different conclusion.

The Eating Experiment Orphan

In 1926 at Mount Sinai Hospital in Cleveland, Davis started the most influential experiment ever conducted to address the question of human likes and dislikes. As a doctor, Davis saw many children with eating problems — mostly refusal to eat — whose appetites didn’t match their nutritional needs. She wondered what children’s appetites would look like, freed from the usual pressures of parents and doctors pushing them to eat nutritious foods such as cereal and milk, regardless of whether they liked it. Conventional medical wisdom at that time was that children’s particular likes should not be indulged, lest they became “faddy.” But Davis wasn’t so sure eating what you liked was automatically a bad thing.

She borrowed a number of infants — some orphans from institutions and some the children of teenage mothers and widows — and placed them on a special self-selection diet under her medical care. The children — age 6 months to 11 months, who had not tasted solid food yet — were offered a selection of whole, natural foods and given free rein to eat only what they wished.

From left: Copyright by Alumni Association of the University of Michigan. Reprinted with permission from April 1918 Michigan Alumnus; American Journal of Diseases of Children/Volume 36/Number 4/1928

At each meal, the infants could choose from around 10 foods off this list, all of them mashed, ground up or finely minced. Some, such as bone marrow, beef, peas and carrots, were offered both cooked and raw. The selection was laid out in bowls while nurses sat by, waiting to see what the children chose. As Davis described it:

“The nurse’s orders were to sit quietly by, spoon in hand, and make no motion. When, and only when, the infant reached for or pointed to a dish might she take up a spoonful and, if he opened his mouth for it, put it in. She might not comment on what he took or did not take, point to or in any way attract his attention to any food, or refuse him any for which he reached. He might eat with his fingers or in any way he could without comment or correction of his manners.”

Davis continued this experiment for six years, starting with three babies and building to 15. The results, which doctors have hotly discussed ever since, were dramatic. Without any preconceived notions about what foods were suitable for them, the babies showed enthusiasm for everything from bone marrow to turnips. They didn’t realize they weren’t supposed to like beets or organ meats. All of them tried all 34 foods, except for two who never attempted lettuce and one who shunned spinach.

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William Zubak
Within a few days, Davis noticed, “they began to reach eagerly for some and to neglect others, so that definite tastes grew under our eyes.” It soon became obvious to her that for the 15 children, there were 15 different patterns of taste. The children made some very odd selections, which looked like a “dietician’s nightmare,” she said. One day, they might gorge on liver or eat a meal of nothing but bananas, eggs and milk. A boy, Donald, showed a rare passion for oranges, cramming in nearly 2 pounds of them one day. In the process of trial and error of finding out what tasted nice, some of the children “chewed hopefully” from plates and spoons, while others grabbed handfuls of pure salt. On trying something new, Davis observed that their faces initially showed surprise, then indifference, pleasure or dislike.

However bizarre and unbalanced the children’s likes and dislikes look to our eyes, they served them well. In a 1928 article writing up her findings, Davis included a before and after photo of one child, Abraham G. At 8 months, upon arriving in her care, he looks a little pale. At 20 months, after a year on the diet, he is cherubic and plump.

When they arrived at the hospital, the infants were generally in poor health. Four were seriously underweight; five had rickets. Yet within a few months, all were pink-cheeked and optimally nourished. One of the rickets sufferers was offered cod liver oil, which he took the occasional glug of, but the other four managed to get enough vitamin D and calcium to cure their rickets through diet alone. When they suffered colds, they appeared to self-medicate, eating vast amounts of carrots, beets and raw beef. Even though they had no guidance on what their bodies needed, their ratio of calories averaged at protein 17 percent, fat 35 percent and carbohydrates 48 percent — much in line with contemporary nutritional science.

Davis' Lasting Legacy

Davis created an unprecedented body of information on childish appetites (though it was never fully analyzed, and after she died in 1959, all of the raw data were discarded). When Davis took a new job, the original setup in Cleveland moved to Chicago, where she established what amounted to “an eating-experiment orphanage.” In all, she logged around 36,000 meals, recording changes in height and weight, blood and urine, bowel movements and bone density.

It’s unlikely any scientist will collect 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 at least six months and up to four and a half years, during which they were always at the hospital. No friends visited, and those who were not orphans had little or no parental contact — their lives were subordinated to the needs of the experiment. But Davis evidently cared for the children very much, in her way. She adopted two, as a single mother: Abraham G, the plump cherub; and Donald, the passionate orange eater.

It was such an extraordinary, audacious, borderline-crazy thing: 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’ orphanage has been cited as evidence that appetite is mostly genetic and that the foods children like or dislike are a sure guide to what their bodies need. What this interpretation fails to consider is that Davis radically restructured the children’s food environment.

She was the first to point out that the real secret was her choice of the 34 foods — all unprocessed whole foods. With such foods preselected, it didn’t matter which ones the children were drawn to on any given day because, assuming they took food from several bowls each meal, they couldn’t help but eat a diet of an excellent standard of nutrition. Davis said her food choices were designed to mimic the conditions of “primitive peoples,” though the servings were surely more plentiful. The experiment proved that when your only food choices are good ones, preferences become unimportant. The 15 patterns of taste resulted in a single healthy whole-food diet because of the setup. There was no option to like unhealthy food and dislike healthy food.

Davis herself concluded her experiment showed the food selection for young children should be left “in the hands of their elders where everyone has always known it belongs.”

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William Zubak
It was obvious to her there was no “instinct” pointing blindly to the good and bad in food. The two most popular foods overall in her study were also the sweetest: milk and fruit. Had she offered a choice of sugar and white flour, staples of a 1930s diet, it’s unlikely the children would’ve ended up in such fine fettle. Self-selection, she concluded, would have little or no value if children selected from “inferior foods.”

The real test would be to offer newly weaned infants a choice between natural and processed foods. This would’ve been Davis’ next experiment, but the Depression dashed this prospect, as her funding ran out at the crucial moment. Nonetheless, 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 built-in and benign, without paying attention to the way Davis had changed the babies’ food environment.

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, pediatrician Benjamin Scheindlin noted Davis’ work contributed to a widespread change in attitudes in pediatric medicine from the 1930s onward. Whereas a previous generation lamented the pickiness of children’s changeable tastes, now doctors positively welcomed childish vagaries of appetite. Many child-rearing experts 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. As recently as 2007, a popular website about feeding children discussed Davis and concluded there was “a strong biological plausibility . . . that children will instinctively choose a balanced diet.”

Beyond the Orphanage

“The wisdom of the body” is an alluring theory. 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 kiwi!) The scientific evidence — both from humans and rats — shows the theory is flawed at best. For it to be true, omnivores would need specific appetites for the essential nutrients the body needed at any given time. This is a very unlikely proposition, given the nutrients omnivores need come in so many guises, depending on the environment we happen to live in. An innate appetite for the vitamin C in black currants would be no use if you lived where black currants don’t 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. Other trials have attempted to find out whether rats could self-select to correct certain vitamin deficiencies and concluded many of them couldn’t. 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 specific appetites that will correct certain imbalances — particularly a salt craving when lacking in sodium — but that’s a different matter.

Ninety years after Davis’ experiment, the view that food 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 non-identical twins, the chances are that there is a genetic cause. Twin studies suggest that many aspects of eating are indeed somewhat heritable. Body weight — measured as body mass index, or BMI — is 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. In one study of 214 same-sex twins, identical twins were more likely to enjoy the same protein foods, but when it came to fruit and vegetables, their likes were only marginally more similar than with the pairs of non-identical 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 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 that they like than couples do, suggesting that nurture — the people you eat with — is more powerful than nature in determining our food habits.

Whatever our innate dispositions, our experience with food can override them. Maybe you share your parents’ hatred of celery because you have seen them recoil from it at the dinner table. Researchers found 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.

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 we learn to eat in. Apart from changing the infants’ food environment, there was another bigger trick to Davis’ experiment, one she did not mention, perhaps because it is so obvious. She radically changed the children’s social experience when eating, removing extraneous social influence. 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 pick 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.

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Adapted excerpt from First Bite: How We Learn To Eat by Bee Wilson. Available from Basic Books, a member of The Perseus Books Group. Copyright © 2015.

(This article originally appeared in print as "Taste Test.")
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