Add a Splash of Vinegar: Why Do We Eat Acids?

Written by: Joseph Flores Edited by: Kevin Nhan

A splash of acetic acid, or a squirt of sulfuric acid — which sounds better for lunch?  It might seem like a tough choice, especially if your idea of acid comes from cartoons or games.  Acids appear to be dangerous stuff: liquids that eat through metal, the burning spit of alien creatures, or a deadly trap of bubbling green ooze.  But did you know that we come across many acids every day?  In fact, we eat them constantly!  Lemons, yogurt, and other tangy foods all contain plenty of natural acids.

So, are acids really that dangerous?  Here, we’re going to use chemistry, the study of matter, to answer your burning questions: What are acids? Are acids dangerous? And if acids are harmful, why do we eat them?

What are acids?   To understand what acids are, let’s dive into the chemical world: at the microscopic level, all matter is made up of tiny pieces called atoms.  There are many different types of atoms, which we call elements.  The simplest and most common atom is the element of hydrogen.  Hydrogen atoms, along with other elemental atoms, interact with each other through chemical bonds.  When they come together, they form the molecules that make up our world.

Like us, molecules want to be in a relaxed and happy state.  For you, this might mean getting cozy in bed at home.  For molecules, we call this stability.  If a molecule is unstable, it will try to fix that.  This usually means changing atoms and chemical bonds.  Molecules will break apart, join together, or make other changes to gain stability.  If a molecule likes to break off hydrogen, we call it an acid.  

Think of it like a game of catch: an acid molecule likes throwing around hydrogen atoms, or protons (that’s what we call hydrogens in this game).  Other molecules like to catch protons; we call this a base.  Many molecules don’t have a strong preference and can play as both an acid and base.  In the chemical world, molecules are constantly playing this game: throwing and catching protons with each other to gain stability. 

Are acids dangerous?  Well... it depends!  Acids are always trying to become stable by throwing, or donating, protons.  If another substance is able, they help by catching or accepting it.  This may seem fun, but a strong acid can force almost anything to take its proton.  Worse, this can change the other substance, and in some cases, even cause it to break apart.  Ouch!

For us, this is especially bad.  We’re made up of molecules called proteins, which use tons of chemical bonds with hydrogen to make your skin and organs.  These bonds are disrupted by strong acids, which cause proteins to fall apart and create painful chemical burns.

Even though acids can be dangerous, they aren't necessarily bad. Strong acids are important for manufacturing products like batteries, plastics, and medicine.  And while strong acids can cause a lot of damage, not all acids are that strong.  So don’t be too quick to judge!

Why do we eat acids? By now, you might realize that the acids we consume are weak acids that won’t really harm us.  That’s true, but why eat them at all?  Wouldn’t it be safer to avoid them entirely?

Consider that practically all fruits and vegetables contain natural acids.  Even the chemicals that make up your own body include many acids.  Not all of them are weak: stomach acid is quite powerful and helps us digest our food.  Strong or weak, they’re everywhere!

Because of this, we’ve evolved to sense acids through taste: we call this sour.  While sour can be overwhelming, it can be pleasant in small doses.

Think about it: have you enjoyed the taste of lemonade, green apples, or sour candy?  But there's more than just flavor: acids break down proteins, which can make food soft and tender.  They can also kill harmful bacteria, helping with food safety.  Humans particularly enjoy citric acid, found in citrus fruits like lemons, limes, and oranges; acetic acid, the main component of vinegar; and lactic acid, found in fermented foods like yogurt and cheese.  These are the main theories as to why we love acids and might explain why most cultures use acids in cooking.

That means... acids are substances that can donate protons. While they can be dangerous, they have practical uses for humans.  In cooking, they provide a sour sensation and help with flavoring, tenderizing and fermenting food.  So, go ahead and add that splash of vinegar to your salad.  Just skip the sulfuric acid.

References:

“The types of acidity.” Culinary Crush. https://www.culinarycrush.biz/all/the-types-of-acidity.  Accessed 18 March 2025.

Tess Joosse. “Pucker up: Why humans evolved to taste sour foods.”  Science, 22 February 2022, https://www.science.org/content/article/pucker-why-humans-evolved-taste-sour-foods. Accessed 18 March 2025.