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Desert island nutrition and black and white thinking about food


desertislandplatePsychologist Paul Rozin and his colleagues asked a fabulous question in a 1996 study investigating people’s attitudes about food:

“Assume you are alone on a desert island for one year.  You can have water, oranges that grow on the trees, and one other food.  Pick the food that you think would be best for your health (never mind what food you would like).  Which of these foods would you pick:

Corn…Alfalfa sprouts…Hot dogs…Spinach…Peaches…Bananas…Milk chocolate”

Desert island questions are always fun, but they usually focus on recreational items.  One CD.  One movie.  One book.

Here is a much more consequential question.  One food – from a rather small list of choices – that you’d have to eat every day (along with water and oranges) in the hopes that it would keep you alive for 12 months.

What would you pick?

If you were like 39% of the 124 students surveyed, you picked spinach.  Also popular were bananas (24%).

My preferred option, hot dogs, was selected by 17% of the respondents.

The authors of the study argued that only two of the foods stood a reasonable chance of keeping someone alive for 12 months – hot dogs and milk chocolate.  These are more complete foods than the others on the list – containing reasonable quantities of all 3 macronutrients (fats, carbohydrates, and protein) as well as a healthy supply of minerals.  In the case of hot dogs, in fact, there is very little nutritional requirements lacking other than vitamin A and vitamin C, which accounts for why the question specifies that oranges are also available.  (In a previous version of the survey, oranges were lacking, making survival unlikely with any option.  Still, you’d have lasted longest on the hot dogs or milk chocolate even then, although only 10% of respondents selected hot dogs or milk chocolate in the first version of the survey.)

Of course, hot dogs and milk chocolate are usually considered unhealthy foods, whereas peaches, spinach, sprouts, bananas, and corn are considered healthy foods.  The idea of eating an unhealthy food for 12 months was apparently unthinkable for 79% of the respondents (hot dogs + milk chocolate), even though these were the most complete foods, nutritionally.  When all you have is one food source, your best bet is to go with the more complete food source.

ronturkeyIn general, of course, fruits and vegetables are considered to be healthy foods, and the perception is that meats are unhealthy.  But we are animals – we need, for the most part, the same things that other animals need – and so by eating them, by eating meat, we have a better chance to consume all that we need in one sitting.  Even the chocolate, which I hadn’t considered a viable option, contains fats and proteins associated with milk, an animal product, and thus is the second-best option on the list.

None of this is to imply that eating a year’s worth of hot dogs is a great idea when other options exist, and even in the original question there is the necessity of oranges.  But the failure of most of the respondents to consider hot dogs or milk chocolate does speak to our black and white thinking about food.

salt-amountsThis was made plain in another part of Rozin’s questionnaire.  Here, he asked people to decide if a diet lacking salt is better than a diet containing a teaspoon of salt each day.  Fully 51% of the respondents agreed with this statement (and another 18% considered these equally healthy options).  For context (not provided to the respondents, of course), a teaspoon of salt is right around the recommended daily amount.  By contrast, going completely salt free will kill you in about a month, and you’ll feel truly miserable after a week.

A second parallel question asked about a no fat diet vs. a diet in which you consumed the equivalent of 1 teaspoon of butter a day.  Similarly to salt, 49% agreed that the fat free diet was healthier, and 18% said it was a wash.  This is probably even more surprising a result than the salt question, because although you won’t die as quickly from a lack of fat, a teaspoon of butter contains only 6% of the recommended daily fat intake, and only 10% of the recommended limit for saturated fat.  Furthermore, when asked to compare a no fat diet to a diet with the equivalent of 5 teaspoons of butter, which still doesn’t reach recommended levels, fully 79% said the fat free diet was healthier.

Again, salt and butter are seen as unhealthy foods.  But this categorization omits a very important detail:  foods are (for the most part) neither good nor bad; what matters is dose.  As I’ve written about before, sodium is an essential micronutrient that your body cannot make or store.  Since you lose sodium in sweat, urine, and feces, you simply have to replace it on a regular basis.  Life does not go on without it.  Furthermore, it is so critical to normal functioning that we have evolved mechanisms to regulate sodium levels (so-called hydromineral balance) so that we can tolerate excess sodium relatively easily.  It is not until levels get well above physiological norms that problems arise.

Fat is less well understood.  The primary reason to consume fats is for energy, but we can also get energy from other sources (carbohydrates and protein).  But fats also make up key structures in our bodies, including all cell membranes, and thus fats are broken down and reformed into structures that we need to grow and to maintain our tissues.  Fatty foods also contain fat-soluble vitamins, like vitamin E, that are necessary for life and which are difficult (impossible?) to obtain without consuming some fat.  The icing on the cake is that some people believe that fat never deserved its negative reputation at all – though I always tend to favor the notion of moderation until controversies are settled.

Whereas some foods have a sinful reputation – like fats, salt, sugar, and carbs – others have a “health halo” – they are seen as good in all contexts.  I was stunned to see that, in another part of the study, 21% of respondents agreed with the statement “A person cannot eat too many vitamins” and another 8% neither agreed nor disagreed.  Likewise, 19% agreed (and another 18% did not disagree) that “A diet cannot have too much protein in it”.  Some vitamins are quite dangerous in excess, and high protein consumption, though rare, can lead to kidney problems.  As with “bad” foods that can be fine or even necessary at low doses, “good” foods can be harmful or even deadly at high doses.

We see the same kind of thinking with non-food items, such as medication.  Recreational sports players will take Advil on a regular basis, before, during, and after pain, operating under the false belief that anything sold over the counter is always safe.  Students hand out their ADHD medication as a substitute for a cup of coffee, on the grounds that their doctor wouldn’t prescribe (and their mother wouldn’t let them take) anything that could be dangerous.  Activists exploit the success of marijuana in alleviating pain and nausea in cancer patients to drum up support for legalization of marijuana for recreational use, on the grounds that because it is helpful in one context, it is safe in all contexts.

It doesn’t help that we live in an environment saturated with a sensationalizing media.  When you hear reports that this or that is linked to cancer, or heart disease, or diabetes, you never – really very close to never – hear anything about the important information: how much?  How much of a certain food leads to how much of an increased risk?  They don’t tell us, and we don’t ask.  In a confusing and complicated environment in which we are bombarded with scary information at every turn, people fall back on black and white categories.  It’s a shame, because as the political scientist Aaron Wildavsky once wrote: “The richest, longest lived, best protected, most resourceful civilization, with the highest degree of insight into its own technology, is on its way to becoming the most frightened.”

Frightened even of sodium and fat, two things you would die without.  Frightened of hot dogs – even when they’re the only thing that can save you!


The Rozin article is:

Rozin, P; Ashmore, M, Markwith, M (1996).  Lay American conceptions of nutrition: Dose insensitivity, categorical thinking, contagion, and the monotonic mind.  Health Psychology, 15(6), 438-447.

The Wildavsky quote is in:

Wildavsky, A. (1979).  No risk is the highest risk of all.  American Scientist, 67, 32-37.




1 Comment

  1. SoundEagle says:

    It is very unfortunate that many people have quite simplistic views or understandings of various issues and matters. I would like to commend you on publishing such a fine post here, and to reward you with sumptuous food to be enjoyed at without any fear!

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