Mark Schatzker

Mark Schatzker

25-04-2022

13:29

Four years ago, a scientist I'd never met approached me and said: "I think you are probably wrong." Instead of arguing, we collaborated on a study to see if humans possess "nutritional wisdom." What we learned will surprise you! 🧵

The story begins in July 2018, at the annual meeting of the Society for the Study of Ingestive Behavior, where I had been chosen to deliver a keynote talk about my book The Dorito Effect, which tells the story of food through the lens of flavor.

Very simply, whole foods are getting blander, thanks to a long crusade to maximize agricultural output. And processed foods are getting more flavorful, thanks to advances in flavor technology. We have shifted that incentive from whole foods to junk food.

And there is no better example than Doritos. The first ever Doritos were just salted tortilla chips. They didn't sell. Then Frito-Lay added flavorings to make “taco" Doritos and suddenly a snack no one wanted to eat became a snack people couldn't stop eating.

Why, I wondered, does flavor have such a hold over us? And why do so many scientists carry on as though nutrition starts from the neck down, that what truly matters in food is carbs, protein and fat, and flavor is just some meaningless and frivolous indulgence?

Our flavor sensing equipment—the nose and mouth—takes up more DNA than any other bodily system. Why is there so much DNA devoted to a sense we tend to think of as superfluous?

This led me to the work of Fred Provenza, a behavioral ecologist at Utah State who studied appetite and food selection in sheep and goats. Fred’s research showed that sheep possess “nutritional wisdom.” They are intuitively attracted to foods that meet their nutritional needs.

In one study, Fred made sheep deficient in phosphorus (an essential mineral) and then paired maple-flavored feed with phosphorus. Every time they ate the maple-flavored feed, there would be an infusion of phosphorus in the gut.

The sheep thus "learned" to associate the flavor of maple to the needed nutrient. When they started running low on phosphorus, they would “seek” the flavor of maple.

Do humans also possess nutritional wisdom? Does our desire and enjoyment of food bear some relation to the inner workings of the body? This brought me to the one of the most interesting studies in the history of nutrition.

Nearly a century ago, a Chicago pediatrician named Clara Davis put fifteen babies on a "self-selection" diet. They could what they wanted from a selection of thirty-three foodstuffs.

The prevailing scientific view at the time was that children were nutritional dunces. But Davis found those babies did a remarkable job of feeding themselves.

The very first infant Davis received, in fact, had a severe case of rickets—a deficiency of vitamin D—and with each meal was given a small glass of cod liver oil (which has mucho vitamin D).

Children’s dislike of cod liver is notorious, but this child consumed it “irregularly and in varying amounts”until he was better, then never touched another drop. These babies, it turned out, were master nutritionists! Humans do indeed possess nutritional wisdom!

Or do they? Because over in the human sciences, the view is quite different.

That view goes roughly as follows: It's calories that count. We find calories “reinforcing.” Vitamins and minerals have nothing to do with it. How do we balance our diets? Simple. By eating a “variety” of different foods, we get all the vitamins and minerals we need.

This point of view has a lot going for it. Why do we like pizza, ice cream, cheeseburgers and potato chips? Calories! Why do we pour an emulsion of fat and vinegar over lettuce? Calories! Why are so many people overweight or obese? Calories!

But there was so much it does not explain. For instance, if calories are all that matters, why does a great peach taste so much better than a mediocre cheeseburger or slice of microwave pizza?

Why do we sprinkle spices on food given that spices contain no calories? Why does a $1000 bottle of red wine cost 100 times more than a $10 bottle of red wine, even though the $10 might have more calories?

Is the secret to deliciousness really as egregiously simple as "salt, sugar and fat"? Take soft drinks as an example. The reason we drink them, we are told, is because of all that sugar. Really?

Do you find the prospect of a can of soda water with 9 teaspoons of sugar appealing? I don't. It's the *flavorings* that animate these beverages with life! Flavorings are why Sprite tastes like Sprite and Coke tastes like Coke.

And if flavor has something to do with how the brain gets its vitamins and minerals, then dumping flavors in soft drinks and potato chips and tortilla chips and leeching the flavor out of vegetables and whole grains and meat might be a VERY BAD IDEA.

So, there I was at the at the annual meeting of the Society for the Study of Ingestive Behavior, in a hall filled with very accomplished scientists who tended to think "nutritional wisdom" is outdated, Goop-worthy claptrap. I was among some serious heavyweights.

The keynote prior to mine was delivered by Terry Robinson, the research partner of Kent Berridge, whom I believe to be one the greatest living scientists. (There is a whole chapter on Kent’s amazing research in my most recent book, The End of Craving.)

I stood at the podium and made my case. I re-examined some of the old science. I presented the work of Fred Provenza. I pointed out that among British sailors, the the first symptom of scurvy—a deficiency of vitamin C—was a *craving* for fruits and vegetables.

And I presented the research of Harry Klee, the world’s leading tomato expert, who found that liking for tomatoes is driven flavor compounds that the tomato synthesizes from essential nutrients—as though tomato flavor is shouting “this is nutritious!” to your brain.

After the talk, I was approached by a friendly man with an English accent who said, “Great talk. I think you are probably wrong. Would you like to test it?”

That man was @JeffBrunstrom, a professor of experimental psychology at the University of Bristol whose research "focuses on psychobiological controls of food choice and food intake, and on how underlying principles inform our understanding of human appetite and energy balancing."

My answer to Jeff: "I would love to test it." Roughly twice a month thereafter, Jeff and I met over Zoom to try and figure out how to scientifically test nutritional wisdom in humans. It is anything but simple!

You can test it in animals by making them deficient in a vitamin or mineral, then seeing what they eat. Performing such an experiment on humans, alas, is a no-no. Doing another Clara Davis-type experiment on babies was also out of the question, due to ethical considerations.

So how do you measure people's dietary preferences without measuring what they eat? We settled on pictures of food. There is a longstanding body of research showing that how people respond to food images corresponds to what they actually eat.

We started by showing subjects two pictures, each depicting a fruit or vegetable paired with another fruit or vegetable, then asked which pair they preferred. We asked them to do this 210 times!

From this set of data, we looked to see if some pattern appeared to be driving their choices. Were subjects just maxing out calories? Were they hunting for variety? Did the vitamin and mineral content of each depicted pairing bear some relation to what was chosen?

We found that the vitamin and mineral content had an effect on choice, and in more ways than one. Subjects not only chose food pairs that elevated the total amount of micronutrients, these desired pairings achieved better micronutrient "complementarity."

Translation: Instead of just piling on the micronutrients, the subjects seemed to be choosing food pairs that did a better job of meeting the need for the full "complement" of essential vitamins and minerals.

But there was a problem! What if subjects were just choosing foods they had been are "good for you." Time for another study! Different foods! Nearly twice as many subjects! And this time we asked if they thought each food was rich in vitamins and minerals.

Once again, vitamins and minerals influenced food choice independent of people beliefs about vitamins and minerals. This time, however, the tendency towards just cranking up total micronutrients faded, but the inclination towards "micronutrient complementarity" remained.

I was convinced! Jeff was not. Jeff, you see, is animated by a compulsion that seems like roiling self-doubt but is, in fact, a kind of unrelenting drive to challenge his interpretation of data. He seems to begin each day by asking, "How might I be wrong?"

So we ran a THIRD study. But this time, we measured choices based on meals that have *already* been eaten. How? By looking at the National Diet and Nutrition Survey, and enormous set of data that contains the food diaries of thousands of people.

Specifically, we examined more than 4 thousand "two component meals," which is to say occasions where two foods were paired together—fish *with* chips, eggs *with* ham, etc. Then we randomly swapped meal components and asked how the nutrition of random pairs stacked up.

This was a way asking if people just seek "variety"—different foods in combination. Or is there something more going on? It looks like the answer is: something more is going on.

Once again, people's food choices maximized "complementarity"—the spread of all the different vitamins and minerals we need. Even more interesting, people seem to choose against pairings that produce an unneeded excess of micronutrients. Nutritional wisdom seems wise indeed.

So, have we unequivocally proved that humans possess nutritional wisdom? Not so fat. But we believe we have found new and intriguing evidence regarding an important question with critical implications.

If humans do indeed possess nutritional wisdom, how does it work? And how is it manifesting itself in the modern food environment? Are added flavorings contributing to the epidemic of obeisty? Is this inmate ability working in ways we as yet do not understand?

For the first time in almost a century, we have found a new way to pose these and other important questions.

And for the first time in my life, I had the privilege to participate in scientific research, for which I am eternally grateful to @JeffBrunstrom It was an honour and it was a thrill. And this is just the beginning....



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