Why Do People Get Religious About Nutrition?

If you have ever decided that a particular food is unhealthy, no matter how rational or evidenced based your decision, it is possible that your opinion has triggered disgust, which is a very primal emotion that can lead to some powerfully irrational impulses.

I think disgust helps to explain much of the obsessive compulsive, quasi religious, polarized, and just plain dumb nature of some of the commentary on nutrition that we see on the internet (and even in academic journals). Read on for information on how disgust makes us dumb.

Disgust defined

Disgust is an aversive reaction to potential toxins. It is experienced by almost all organisms, even very primitive ones, and evolved to provide protection against ingesting potentially harmful substances. As such, it is considered part of the “behavioral immune system” - a way to avoid pathogens instead of battling them inside the body.

The expression of disgust involves a strong sense of visceral revulsion and a characteristic facial expression (gag me with a spoon!)


Different human societies are disgusted by different things. But although disgust can be learned and modified by culture, some things seem to be universally disgusting, which are:

  • bodily fluids (e.g. blood, spit, feces, urine, vomit)
  • spoiled meats (dead animals)
  • live organisms that are common carriers of disease (cockroaches, fleas, rats);
  • visible signs of infection.

Did you notice what all these disgusting substances have in common? The essential quality of an inherently disgusting object seems to be that it is a potential carrier of microscopic pathogens.

Germs have some very particular characteristics that are relevant to understanding the nature of disgust. First is that they are too small to see. Second is that contact with even the tiniest amount of a pathogen can cause a deadly disease, because they can multiply exponentially.

Thus, in order to effectively promote safe behavior in the presence of potential pathogens, disgust should encourage an animal to COMPLETELY and totally avoid contact with potential carriers, even without strong confirming evidence that they are actually contaminated. It’s not good enough to just limit your contact, or eat some of it. Even the smallest morsel of contaminated meat can be as bad as a whole steak. So you need to be an extremist when it comes to germs, and that is what a sense of disgust will encourage you to be.

Here’s a fun passage from the excellent book The Blank Slate by Steven Pinker, where he describes how disgust can be powerfully antirational:

People won’t eat soup if it is served in a brand-new bedpan or if it has been stirred with a new comb or flyswatter. You can’t pay most people to eat fudge baked in the shape of dog feces or to hold rubber vomit from a novelty store between their lips. One’s own saliva is not disgusting as long as it is in one’s own mouth, but most people won’t eat from a bowl of soup into which they have spat.

Are you starting to see how the experience of disgust might discourage moderate stances in a debate about nutritional toxins?


A staple of solid nutritional advice is “everything in moderation.” While this is rather simplistic and does not rise to the level of universal truth, there is some logic here. Many nutrients that are good for you in moderation are actually deadly at large doses. And some toxins that are deadly at moderate doses are actually beneficial in very small doses.

For example, water is very beneficial if you are dehydrated, but adds very little additional value after that, and can actually kill you if you drink too much. On the other hand, excessive exposure to X-rays can cause cancer, but small amounts seem to prevent it, probably by upregulating anticancer processes (hormesis). Many experts believe that veggies are good for you precisely because their toxins cause a hormetic effect. So the dose makes the cure, and the dose makes the poison. It is therefore often a mistake to completely avoid a food you think may be toxic. But that is exactly what a sense of disgust will encourage you to do.

Many vegetarians or vegans will go to great lengths to avoid consuming even the tiniest quantities of meat. I recall a vegan friend almost puking after eating a meal she later discovered was made with beef bullion as a flavor base. Paleo dieters will sometimes get OCD worrying about whether a food is "primal." At the Whole Foods where I shop, the organic and nonorganic bulk spices have separate scooping spoons! As if one grain of inorganic turmeric will somehow spoil my curry. (I’m surprised they don’t make the purchasers of the inorganic foods use a different bathroom.)

And in recent news of irrational disgust, the residents of a town near Portland Oregon elected to have their entire eight million gallon reservoir of drinking water drained, at the cost of $50,000, after discovering video of a man peeing in the lake. (Even though urine is sterile, and birds are basically pooping in the lake all the time.)

I could go on and on about this - there are as many irrational avoidances as there are people. Fat, carbs, sugar, HFCS, GMOs, squats with the knees past the toes, Crossfit, stretching, running, these are all alleged toxins that many people will try to limit completely, even though there is no rational reason to do so.

The evolution of disgust

Because disgust is such a primal and basic emotion that emerged so early in our evolution, the neural structures which create it became a building block for many other more sophisticated emotions and thought patterns that have an aversive nature.

For example, moral disgust is a revulsion to associating with individuals who violate group norms. Sexual disgust discourages mating with a biologically costly partner. In fact, artistically sensitive people experience the same basic reaction to bad art as a dog would to rotting meat. No surprise to me. I once saw part of the Jersey Shore.


Jonathan Haidt thinks that disgust is the foundation for religious ideas about purity, sacredness, sin, and defilement. Many religions such as Judaism, Islam, and Hinduism have extensive rules for keeping classically disgusting objects such as bodily fluids and meats separate from sacred objects and practices.

Research has discovered some interesting connections between the sense of disgust and seemingly unrelated emotions or behaviors. People with a stronger sense of disgust to food are more likely to have obsessive or anxiety disorders such as OCD, anorexia, and certain phobias like fear of spiders and needles. They are also more likely to be fear people outside their cultural group, and to have negative attitudes towards obese people. Deciding that a particular food is unhealthy often leads to moralizing about consumption of the food - others who consume it are deemed to be morally inferior.

I think this research sheds light on many irrational behaviors we see in regard to food - the idea that it has spiritual significance, the polarization between different nutritional camps, and problems like anorexia and orthorexia. Is it any wonder that intelligent rational debate is difficult?

What do you think? (If you find yourself in violent disagreement with any of the ideas in this post, consider the possibility that you simply find them disgusting.)