Why do we eat spicy food?

There are many festivals in Chicago this summer and fall, and many of them will involve food. A Taste of Latin America and The Chicago Hot Dog Fest just passed, and Chicago’s New Orleans Festival and festival de la  Villita are coming up soon. The food at some of these festivals will be very spicy, and the food at other festivals will not be spicy.

Why is it that food from some parts of the world is very spicy but not in other places? Some would attribute this to people’s preference, and people’s preference certainly factors in to some degree. But something else is going on, too. Bear with me while I put this into context.

Imagine that 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 fine choices. Now imagine that you are some kind of plant. Lacking any ability to see, hear or feel, 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 move, you cannot run, hide or fight back.

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

Herbivores aren’t the only type of thing trying to eat plants. Plants are subject to infection by the same types of pathogens that humans are – viruses, bacteria, worms, fungi, and protozoa. With the exception of viruses, these parasites get all the energy they need by eating the plant they infect. Animals are able to fight off these parasites by producing white blood cells and antibodies that attack invading organisms. Plants do not have an immune system in this sense. While it may seem that plants are getting the short end of everything, they have a surprise up their metaphorical sleeve. Plants can produce a wide range of chemicals that make them taste bad, make them hard to digest, or are harmful to organisms trying to eat them.

Infectious diseases are a big problem for most organisms, and humans are no exception. Even in modern times, food-borne illnesses are common throughout the world, including typhoid fever, hepatitis B, Salmonella, Escherichia coli, Listeria, cholera, and Norovirus.

What we call herbs and spices are certain plants (or certain parts of certain plants) which contain chemical compounds that have a particular smell or taste to them that some people enjoy. And most of them, including thyme, garlic and cloves, also have powerful abilities to prevent or slow the growth of potential infectious agents that cause spoilage. Consider this: when you want to eat spicy food, what type of cuisine do you pick? Indian? Mexican? Thai? It’s no coincidence that these parts of the world are all in tropical or sub-tropical regions. The parts of the world that use the most herbs and spices in their traditional cooking are the same parts of the world that have the most human pathogens.

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

Adding herbs and spices to food can slow the rate at which harmful microorganisms grow in your food. Harmful microorganisms are a bigger problem in certain parts of the world, and the people in those parts traditionally add more herbs and spices to their food to combat these pathogens. Before the advent of the pharmaceutical industry, people harnessed these plant chemicals to fight off deadly pathogens. Spices don’t just taste good, they can save your life.

Don’t let spices be your only way of keeping your food safe, though. Modern technological innovations like high-pressure pathogen removal can keep packaged food safer for longer. Monitoring programs can stop disease outbreaks before they start, as well as help control them when they do. C2ST’s program “I.F.S.H. – Is This Food Safe to Eat?” which took place this past March, covered modern innovations in food safety in greater detail.

Here is a 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 dough 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 use chile powder because I like to cook with it, but you could try 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, then 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 couple of pieces of moldy cornbread. Mold would grow just fine on its own, but seeding it with some already-mature mold helps things move along more quickly. I also put a few drops of water into the bag so the bread 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 plain bread is covered in mold.

This experiment was a big success: the chile powder didn’t completely prevent mold growth, but there is 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.

Chris Eppig is the Director of Programming for C2ST. This article was originally posted at http://christophereppig.wordpress.com/2014/03/28/why-we-eat-spicy-food/ and was published in a shorter form in the C2ST Fall 2014 newsletter. Chris blogs about science at christophereppig.wordpress.com