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The Carrot Cake Effect


An interesting thing about the cake is that people imagine it to be healthy. It contains a vegetable, therefore it must be healthy.

With the same reasoning potato-chips and potato salad must be healthy as well because it contains a vegetable. And pizza is healthy because it contains tomatoes and olives.

It appears that the mental model that supports this belief is the “additive nutrition model”. The belief that the body is able to utilize all the beneficial nutrients that is added to it, and it dispenses what it does not need.

A mental model is how a person believes how something works. It is a worldview or framework that we carry around in our minds that helps us interpret things. We all have a myriad of mental models that we use to interpret the world around us. They are never 100% correct, but some models have more utility than others. A mental model that can explain many phenomena with a high accuracy is more useful than one that explains a few things poorly.

We get our mental models from our own experiences and from other people. Mental models are often biased and prejudiced, and sometimes plain wrong.

We have all observed “that things fall to the ground”. Greek philosophers claimed that the falling to the ground was the nature of an object due to it’s gravitas. It was a naive explanation that was accepted for a lack of a better alternative and a deeper understanding. However Newton’s theory of gravity has more utility because in addition to explaining objects falling to the ground, it also can explain the motion of celestial bodies.

I find it fascinating to observe how my parents use computers. They manage a surprising array of tasks. But when they ask questions, it shows that they have a different mental model of the internet and computers than me (I am a full stack software developer). If something is slow they always suspect the ISP (Internet Service Provider).

A superficial mental model is often good enough. It is impossible to understand everything to a fundamental level. People should not need to know the internal workings of a combustion engine in order to drive a car. Those details are abstracted away in a modern car.

Back to the carrot cake and the mental model of additive nutrition. Although I have not heard this model explicitly stated, it appears to me that it is a widespread model. I base this observation on how some people talk about food, on how they choose what to eat and how they justify their food choices.

We face a jungle of nutritional advice. Many of them are contradictory. It is hard to make sense of it all.

Eat a big variety of foods The FDA food pyramid prescribes a base of vegetables, grains and fruits. In addition eggs, dairy and meat/fish. The vitamin and supplement industry has a pill for all problems. The more the better.

Those popular nutritional rules, combined with only superficial understanding of biology and chemistry, can contribute to people constructing a mental model of additive nutrition.

But most of us have also heard of the danger of sugar and fat, some of us even about the inflammatory effect of gluten. So I suspect that people deep down don’t really believe the carrot cake to be healthy, at least not in large quantities. Maybe it is just an expedient lie that we choose to tell ourselves? A way to justify a desire for something sweet.

In a few cases the mental model of additive nutrition may be useful. If the baseline is bad, then additive nutrition may raise the baseline. If a person suffers from a nutritional deficiency, then eating a food that contains a missing nutrient is indeed beneficial. For example a person who has scurvy, a nasty disease caused by lack of vitamin C, could benefit from eating potato chips which have some vitamin C. However he would be even better off eating fresh fruits and vegetables instead of the potato chips.

In the western world, nutritional deficiencies are rare. It can happen to people who eat an extremely limited variety of food. A few years ago there was a case in Norway where a student got scurvy (vitamin C deficiency) because he exclusively ate frozen pizza and he removed all the papricas.

For most of us we have the opposite problem. Rather than nutritional deficiencies we have overloads.

It is clear that “the carrot cake effect” - the mental model of additive nutrition, has some shortcomings, just like Aristotle's model of gravitas.

A more useful model when thinking of what to eat is via negativa - it is more important what you remove than what you add.

Salmon has an attractive fat profile and protein content, but farmed salmon are often high in antibiotics and heavy metal, so it is better to err on the safe side and apply via negativa. Be cautious about consuming farmed salmon.

The proponents of industrial farming (a.k.a. conventional farming), say that organic food does not contain more vitamins than their conventionally farmed produce. It may be correct, but they miss the point. With the perspective of via negativa we know to appreciate what organic food does not contain. Namely pesticides and herbicides (or at least smaller doses and less toxic variants).

Via negativa also applies to areas outside nutrition. For example it is more important for your happiness to remove a toxic relationship than to add more friends. It is more important for your health to cut the habit of smoking than to add the habit of exercise. It is more important for your economy to stop spending money on stupid things than to save on cheap groceries.

Berkshire Hathaway Vice-Chairman Charlie Munger put it, “It is remarkable how much long-term advantage people like us have gotten by trying to be consistently not stupid, instead of trying to be very intelligent.”

I say “it is remarkable how much long-term health people can get by consistently avoid bad foods, instead of trying to add a health-food”

Another useful mental model is hormesis - A small dose of something can have the opposite effect of a high dose. Hormesis graph

For example spending 10-30 minutes in the sun can be beneficial, but spending 8 hours in the sun will cause sunburn and melanoma. Exercising for 15-60 minutes will stress your body constructively, but lifting weights for 6 hours every day will destroy your muscles.

Stress yourself, but not too much.

The idea of hormesis has been around for a long time. The buddhists have the concept of golden mean.

... one day, Siddhartha heard an old musician on a passing boat, speaking to his pupil:
"If you tighten the string too much, it will snap, and if you leave it too slack, it won’t play".
Suddenly, Siddhartha realized that these simple words held the great truth, and that in all these years he had been following the wrong path. The path to the enlightenment is in the middle way. It is the line between two opposite extremes ...

I have experienced the hormesis firsthand. I have tried to eat healthy since my early 20s, and I have felt fine most of the time. Until one morning a few months ago when I got out of bed and suddenly everything went black. I fainted and fell to the ground. A case of postural bradycardia. The doctor could not tell me the exact reason, but low blood pressure and low heart rate are contributing factors. I did some research myself and scrutinized my eating habits. Was something missing from my diet? Too little or too much salt? Later the blood test came out normal, so there were no clear indicators or something missing. Perhaps it was something I ate too much of? After using the search engine for everything I could think of, the most likely candidate was that I ate too much spinach. One website stated a max allowance of 200 grams spinach per week. I estimate that I exceeded it fivefold for a period of a couple of months. Apparently a little dose of oxalic acid and nitrates is beneficial, but they have detrimental effects when dosage is too high. One website claims that the oxalic acid can interfere with absorption of calcium. A hormetic effect.

I was a victim of “carrot cake thinking”. I’ve heard experts recommend eating more leafy green vegetables, whatever “more” means, so I thought I could just dig in on spinach. Spinach is high in vitamins K, A and C, and minerals like magnesium. Great. I fell for the trap of “the more the better” because I was not informed about hormesis.

We must always consider the whole. Don’t only consider the virtues of a thing, but also look at the demerits. And when you have found something good, don’t overdo it. Take the middle way.

For instance, a charismatic politician is appealing to many voters. But getting blinded by the charisma is like believing a carrot cake is healthy due to its vegetable content. Instead we must look at the whole. Does the candidate possess a character of integrity? We should pay more attention to the flaws. It can turn out that they are more important than a superficial virtue.