Why We Eat Spicy Food

Imagine you are some kind of small mammal, like a rodent. You are minding your own business when you notice a snake sneaking up on you. What do you do? Run? Hide? Fight back? These are all are fine choices. Now imagine that you are some kind of plant. Lacking any ability to detect the presence of animals trying to eat you, you are completely unaware of the cow sneaking up on you. And even if you were aware, what could you do about it? With no ability to locomote, you cannot run, hide or fight back. Now, some plants can hide by being inconspicuous or by blending into their surroundings, but this is not the norm. Some plants can fight back with thorns or spines or hairs, but not all plants do this, either. The third option is to produce chemicals that lower the digestibility of the plant, make the plant taste bad, or are harmful to animals. These three strategies (hiding, fighting and chemical warfare) are all very cool, but it is the third option that I will be talking about today.

Those plants couldn’t run away from the water buffalo. Image from wikimedia.org

Plants actually produce chemical defenses for two reasons: The first is to prevent being eaten by herbivores, and the second is to prevent infection. Plants do not have an immune system in the same way that animals do, so these chemicals are very important in repelling pathogens.
But what does all of this have to do with us? Plants suffer from the same type of parasites that we do — viruses, bacteria, worms, fungi, and protozoa. Before the advent of the pharmaceutical industry, people had to rely on plants for medicine. The compounds that plants produce to keep themselves safe from infection can be harnessed by humans for the same purposes.
Which brings me to the point of this: spices.
Cultures across the world vary in how much spice they use in their food, particularly with meat. Consider the types of cuisine that are the spiciest — e.g. Mexican, Thai and Indian. It’s no coincidence that these countries are in the tropics. Research has shown that spices are used most in areas of the world where there is the highest burden of infectious disease: both in numbers and intensity.

The birds-eye pepper is high in capsaicin, which has antimicrobial properties. Image from wikimedia.org

The most common spices in the world — such as garlic, thyme and cloves — have been shown to be powerful antimicrobial agents. Adding these to food can prevent food spoilage and food-borne illnesses. (Please don’t rely on this as your only method of keeping your food safe.) Infectious disease is a big problem for people in the world today, and has been a big problem throughout human evolution. Food-born illnesses that are a problem for people today include typhoid fever, hepatitis B, Salmonella, Escherichia coli, Listeria, cholera, and Norovirus. Cooking with spices will not eliminate these diseases, but they can reduce the likelihood that you will catch them. Spices don’t just taste good — they can save your life.

Here’s simple experiment you can do at home to test the antimicrobial effects of spices:

I’ve made a simple bread recipe and separated the dough into two equal portions. Store-bought dough will usually contain preservatives (which prevent the growth of bacteria and mold), so you’ll have to make your own if you want this to work.

I’ve kneaded in 1.5 teaspoons of red chile powder to one half of the dough and the same amount of flour to the other, just so both conditions are as similar as I can make them. I used chile powder because I like to cook with it, but you could do this with any spice or herb you wanted:

The dough has been made, and the spice measured out.


The spice and extra flour has been kneaded into the dough.

I pressed them into flat, round loaves, baked them and sliced each one in half:


The bread has been baked and is ready to grow mold.

I put all four pieces into a big ziplock bag with a a couple of pieces of moldy cornbread. Mold would grow fine on its own, but seeding it with some already-mature mold helps things move along more quickly. I put a few drops of water in the bag, too, so it stays moist:


The bread will stay in the bag for the remainder of the experiment. The fresh bread has been seeded with a piece of moldy old cornbread.

After about a week, the plain bread is covered in mold. The spiced bread has a little bit of mold on it, but is mostly mold-free:

At the end of the experiment, the spiced bread is almost entirely free of mold.

At the end of the experiment, the spiced bread is almost entirely free of mold.

The plain bread is covered in mold.

At the end of the experiment, the plain bread is covered in mold.

The chile powder didn’t completely prevent mold growth, but there is certainly a lot less mold on the spiced bread than on the plain bread. Depending on where you are in the world, even a little bit less spoilage could mean the difference between life and death. Try this out on your own and let me know how it worked out.


Have a topic that you want me to cover? Let me know in the comments section.
Follow me on twitter @CGEppig


About Christopher Eppig, Ph.D.

I have a Ph.D. in biology and a passion for sharing my knowledge and understanding of the natural world with anyone who will listen. At a time where science is permeating public life more than ever, it is especially important that the public understand what science is, and how its findings intersect with their own lives. In addition to the more practical benefits of scientific literacy, I believe strongly that understanding the natural world enriches peoples lives. The man behind the curtain is not me — it is the real world, which we can discover through science, and it is beautiful. Let me show it to you.  Follow me on twitter @CGEppig. View all posts by Christopher Eppig, Ph.D.

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