Will Apple Cider Vinegar Nuke Your Stomach?

By Josh Bloom — Jun 02, 2023
One of the (many) overhyped "miracle cures" we're seeing constantly is apple cider vinegar. Sure sounds nice, right? Of the dozens of health claims about the stuff perhaps the claim that it treats heartburn and acid reflux makes the least sense since vinegar is acidic enough to dissolve steel wool. What's the deal?

It's time for a rant, and apple cider vinegar (ACV) – one of today's supplement darlings gets the spotlight.

If you believe all the claims, then you'll need to accept that the stuff is useful for:

  • Diabetes
  • Weight loss
  • Allergies
  • Inflammation
  • Reducing serum cholesterol
  • Ulcerative colitis
  • Eczema and psoriasis 

Of course, this is a bunch of baloney, which I'll be writing about soon. In reality, the stuff will likely join the list of dietary supplements that are either useless, dangerous, or both. But for now, let's focus on what it might do for your stomach because of crazy s### like this: [Emphasis and snotty comments mine]

Apple cider vinegar (ACV) is an acetic acid [No, there is precisely one acetic acid. It is called "acetic acid."] with other substances, such as lactic, citric, and malic acids, as well as bacteria. People add it to their diets because some believe that not enough acid can signal your brain to relax the lower esophagus sphincter (LES) valve. [Some also believe that gasoline puts out fires.]

Source: The Verywell health site  (or is it the Very(un)wellhealth site?) (1)

And for a (mis)information check, there is no shortage of sites to go to. Just for laughs, let's try Dr. Axe, who runs the Ancient Nutrition website. Perhaps Hemiglossectomy.com or bloodletting.org were unavailable.

"Meet apple cider vinegar with a superfood twist. This unstoppable blend brings you the time-honored genius of apple cider vinegar, plus a regenerative blend of antioxidant-filled superfood ingredients."

Source: Ancient nutrition, which (not surprisingly) sells ACV:


Gotta hand it to him. Axe never runs out of BS buzzwords: superfood, unstoppable blend, time-honored genius (WTF?), regenerative blend, antioxidant, and all in two sentences!

ACV is quite acidic

Anyone with even a modestly functioning brain knows that putting more acid into your stomach when you have GERD or heartburn isn't such a hot idea, despite the many unsubstantiated claims that apple cider vinegar can be used to actually treat heartburn.

(Not convinced? Watch this YouTube video to see what vinegar does to steel wool.)

If vinegar is acidic enough to dissolve steel wool, there's a pretty good chance that if you've got excess stomach acid, it's probably something to avoid.

A chemistry experiment

Let's take a look at what vinegar might do to your stomach using the concept of pH, something that is taught in first-year chemistry. Does your tummy become more acidic, less acidic, or stay the same? To address this question, we need to make certain assumptions:

  • Values for the pH of the stomach range from 1.0-3.5. Let's pick 2.0. 
  • The volume of hydrochloric acid in the stomach ranges from 20-100 mL. Let's pick 60 mL. 
  • The pH of vinegar (or apple cider vinegar) is in the 2-3 range.
  • The "recommended" dose of apple cider vinegar is 10-20 mL. Let's pick 10 mL.

There are simple calculations that I somehow managed to do 85 years ago when I was in freshman chem (but wouldn't even attempt now) that can answer the question: "What happens in your stomach when you consume 10 mL of ACV?" Given all the variables involved, this question is pretty much impossible to answer, so I've tried to simulate (this will be approximate at best) what happens in the stomach by using a simple acid-base experiment that might be done in a chemistry lab. This is what ChatPCT came up with:

"What is the resulting pH of a solution of 60 mL of pH 2 HCl when 10 mL of 5% vinegar is added?"

ChatPCT: "Therefore, when 10 mL of 5% vinegar is added to a solution containing 60 mL of pH 2 HCl, the resulting pH is approximately 1.797, slightly more acidic, but probably not significantly so. (2).

In other words, there isn't much difference in the stomach when you drink a little ACV. I will spare my long-suffering readers by only giving a summary of ChatPCT answer. I included the answer in its entirety in Note #2 below for those who have a strong stomach.

So, why is vinegar bad for heartburn? Here's one theory.

The normal pH for the esophagus is close to 7.0. Esophageal pH monitoring looks for lower readings (such as below 4.0) over the course of 30 seconds, indicating higher acidity. High acidity in the esophagus means a surge of stomach acid.

Source: Johns Hopkins 

Unlike the stomach, which has built-in mechanisms for protecting the cells that line it, the esophagus does not.

The esophagus, unlike the stomach and duodenum, has a very limited surface buffer zone...The reasons for this are that the esophagus lacks a mucus layer and its surface cells do not secrete bicarbonate ions.

Source:  Scand J Gastroenterol Suppl. 1988;155:23-8. doi: 10.3109/00365528809096277

So, if you've got heartburn, which involves excess acid in both the stomach and the esophagus, perhaps you might want to reconsider swallowing something that dissolves steel wool. Or maybe I'm just funny that way.

Let's close with a quote.

"But being an acid itself, it is not logical to assume that it will help in reducing acid related reflux symptoms. Being acetic acid, apple cider vinegar can lead to caustic injury to the esophageal mucous lining if the concentration exceeds 20%. As the consumer market in this segment is poorly regulated, taking vinegar for the control of reflux symptoms can be counterproductive and prove to be dangerous"

 Kiran Peddi, MD, a gastroenterologist writing on The health site

Bottom line

At some point, ACV will (like most fad supplements) probably be shown to be worthless, in which case it will simply be one more thing for people with stomach issues to avoid. 

Where'd those Rolaids go?


(1) To its credit, Verywell health does warn: "Even diluted ACV can cause: throat irritation, including the urge to cough or clear the throat, tissue burning in the mouth, esophagus, or stomach, and tooth enamel erosion, which can promote cavities."

(2) Don't say I didn't warn you. This is the full ChatGPT answer.

To determine the resulting pH when 10 mL of 5% vinegar is added to a solution containing 60 mL of pH 2 HCl, we need to consider the reaction between acetic acid (CH3COOH) in vinegar and HCl.

First, let's consider the initial solution, which contains 60 mL of pH 2 HCl. A pH of 2 indicates a concentration of 0.01 M for HCl.

Now, let's calculate the moles of acetic acid and HCl involved in the reaction:

Moles of acetic acid = (0.05 g acetic acid / 60.05 g/mol) * (0.01 L) = 0.000083 moles

Moles of HCl in the initial solution = 0.01 mol/L * 0.06 L = 0.0006 moles

The reaction between acetic acid and HCl is as follows:

CH3COOH + HCl -> CH3COO- + H3O+

Since HCl is a strong acid and acetic acid is a weak acid, the reaction will proceed almost completely to the right. This means that most of the acetic acid will be converted into acetate ions (CH3COO-) and hydronium ions (H3O+).

The moles of acetic acid that react with HCl are limited by the smaller number of moles between the two. In this case, 0.000083 moles of acetic acid will react with 0.000083 moles of HCl, leaving 0.0006 - 0.000083 = 0.000517 moles of HCl unreacted.

Next, let's calculate the total moles of HCl in the final solution:

Moles of HCl in the final solution = moles of HCl initially + moles of unreacted HCl

Moles of HCl in the final solution = 0.0006 moles + 0.000517 moles = 0.001117 moles

To determine the final concentration of HCl in the solution, we divide the moles of HCl by the final volume of the solution, which is 60 mL + 10 mL:

Final concentration of HCl = Moles of HCl / Final volume

Final concentration of HCl = 0.001117 moles / 0.07 L ≈ 0.01596 M

Finally, we can calculate the resulting pH using the formula:

pH = -log[H+]

pH = -log(0.01596) ≈ 1.797

Therefore, when 10 mL of 5% vinegar is added to a solution containing 60 mL of pH 2 HCl, the resulting pH is approximately 1.797.

Happy now?


Josh Bloom

Director of Chemical and Pharmaceutical Science

Dr. Josh Bloom, the Director of Chemical and Pharmaceutical Science, comes from the world of drug discovery, where he did research for more than 20 years. He holds a Ph.D. in chemistry.

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