May 2014

Most readers know me as a photographer, but I happen to be a biochemist by training.  There are several food-related articles on this site, and hopefully more to follow.

Right now I'd like to talk about something most of us have experienced at one time or another:  acid reflux.  Commonly known as "acid indigestion" or GERD, this happens to many people when they eat something that "doesn't agree with them".

Lately I've been noticing that proton pump inhibitors (PPI's) are being pushed like candy.

The lower part of your digestive tract-- everything past the stomach-- is set up to handle a certain extent of pre-digestion by the stomach acid.  Now, let's say you turned off that pre-digestion.  Let's say that now your digestive tract is receiving foods that are not broken down as much.   This could have serious long-term consequences.  There are some peptides, for example, that are bio-active.  Not necessarily a good kind of bio-active, either.  And maybe they weren't meant to get past the stomach.  (A "peptide" is an amino acid sequence that's not long enough to be a "protein".) 

Oh, and how about this.  You have bacteria in your intestines, and those bacteria have a lot to do with your overall health.  In the science, we call these the "intestinal flora".  Well, when you take PPI's, your undigested food gives the intestinal flora something different than they're normally fed.  This can and probably does cause unwanted natural selection.  Result?  Now you've got different intestinal bacteria, or ones with different proportions or numbers, than you should have.  This, again, could lead to serious, serious long-term health problems.  I know someone who once had a "C. diff" overgrowth (Clostridium difficile), and she's messed up pretty much permanently from it.  Probiotics helped enormously, but she has to keep eating them regularly even years after the fact.  (You see, it just so happens that L. acidophilus doesn't survive well in the human digestive tract unless you keep re-colonizing it by taking the supplements.  Not many people realize that, it seems.)

Taking PPI's every day, constantly keeping the stomach above pH 4, and the next thing you know there's an overgrowth of some harmful bacteria in your stomach itself:  a place where it never should have been in the first place. 

Do we even know what happens when we hamper the stomach's ability to digest food?   If the answer is "not really", then it would kind of make sense not to mess with it.  Unfortunately, once you start taking proton pump inhibitors, you're basically forced to stay on them forever, because then it becomes unsafe to stop taking them.  The body tries to maintain homeostasis.  Suppressing acid formation is going to have a bad outcome:  the stomach will respond by having more acid-generating cells to make up for it!

Some people may get relief from proton pump inhibitors, but I stay well clear of them. 

That brings us to a discussion of one of my favorite beverages. 

The ACV Drink

Someone I know had acid reflux (GERD) so badly that she was practically on the floor.  This was not your average GERD episode.  Well, she made this beverage and the symptoms went away.  (Disclaimer).   And I know other people who have had similar results.

What's the beverage?  It's just two teaspoons of organic, unfiltered apple cider vinegar (ACV) in an eight-ounce glass of water, with some honey stirred in.

Oh, I know.  Several "official" sources will warn you of the horrible, dreadful dangers of "too much acidity" from apple cider vinegar. 

Can apple cider vinegar cause "too much acidity" in your stomach?  Let's try to find out.

The stomach, before it even has food in it, has a pH of around 4.5.  That's moderately acidic.  Now, when you eat food, the stomach pH can drop down to 1 or 2.  That's rather strongly acidic.

Vinegar has a pH of maybe 2.7 to 2.8.  And so, only if you drank it neat (i.e., straight) on an empty stomach would you be able to have "too much acidity".  But wait, there's more.  Vinegar is a very dilute solution of acetic acid.  Informally, the shorthand for acetic acid is "HOAc" (I'm not going to explain why, because you don't need to know it right now.)

Now, acetic acid is a very weak acid.  What's an "acid"?  In scientific terms, it's something that ionizes to release hydrogen ions (protons) into solution.  (Technically it creates a hydronium ion, H3O+, but you don't need to know that right now.) 

Very strong acids ionize completely, meaning they make a lot of hydrogen ions. 
Weak acids do not ionize that much, so there are not that many hydrogen ions.

You might have heard the phrase "order of magnitude".  I've lost count of how many times I've heard that phrase used incorrectly.  An order of magnitude is actually a ten-fold difference.  So, if something is one order of magnitude greater, it's ten times greater.  And if something is three orders of magnitude greater, it's 1,000 times greater. 

Hydrochloric acid is eleven or twelve orders of magnitude stronger than acetic acid.

That's 10 to the 12th power, or 1 trillion times.  I know that's hard to believe.  But if you look at the pKa values (which are an expression of proton affinity, pretty much), hydrochloric acid has a pKa of something like minus 8.   Meanwhile, acetic acid has a pKa of about 4.7.  That's a difference of more than twelve orders of magnitude, because each whole-integer difference in pKa equals one order of magnitude. 

What does all this mean?  Simple.  A stronger acid will protonate a weaker one.  What does that mean?  Basically, (no pun intended), it means the weaker acid actually acts like a base, not an acid.  (Technically it's not an acid that's doing this, but the conjugate base or counter-ion to the proton... again, you don't need to know that.) 

So if you have hydrochloric acid and acetic acid in solution, here's what happens.  The acetic acid (technically, acetate ion) acts as a proton acceptor.  Know what that means?

It means that when you have stomach acid present (and there's always some), vinegar actually becomes an antacid.  I should note that the primary effect is one of dilution, though.  That's because acetic acid doesn't ionize that much in the first place, so there isn't much acetate ion to take up protons.  Remember the orders of magnitude:  a trillion-to-one, or something like that. 

You cannot make a strong acid any stronger by adding a weaker acid.  Instead, you will make the solution less acidic.   When people tell you ACV helps with GERD because it remedies "low acid", I think they're probably incorrect.   ACV actually ties up some of the acid in your stomach.  Certainly it dilutes it.

The thing is, apple cider vinegar may work by some mechanism we can't even imagine.  It could be some signaling pathway.  Or it could be some enzyme from the unpasteurized vinegar, or it could be something else.  But if you want to make the beverage as it's traditionally made, you should use organic, unfiltered, unpasteurized ACV. 

Use Hard Water!

One more thing about the acid-base chemistry.  If you have hard water, that's a solution of calcium bicarbonate.  The moment you dissolve some acetic acid in that, you're creating an acetate buffer.  Two teaspoons of cider vinegar in 8 oz of hard water is going to produce a weakly acidic result;  you'll have a mixture of calcium acetate and acetic acid.  To calculate the resulting pH would involve some tedious calculations (which I could do if you really like), but it's easier just to measure the pH of the final product. 

Here's what I measured with some inexpensive pH paper.  (For more accuracy, get one of these.)

Starting with 8 oz. (240 ml) of water and adding 2 tsp of Bragg ACV:

Distilled, de-gassed water 
Hard water with 100 mg Ca++ / ml
Without vinegarpH 6 to 7pH 8
With vinegarpH 3 to 4
pH 5 to 6

The distilled water is a bit lower than pH 7 because I didn't bother to get all the carbon dioxide out of it (carbonic acid is, well... an acid).

So anyway, you can see that a glass of this drink is not going to make "too much acidity" as is commonly claimed.  Don't drink the vinegar neat (straight) and you'll be fine.  The main caution is that your esophagus could be irritated by even a mild acid, since it doesn't have the specialized environment of your stomach.  If that's the case, you may well find that orange juice, salad dressing, and tomato sauce are problem foods.  Again, though, if you make the ACV drink at a moderate pH of 5 or 6, it's not even going to be that acidic.  Carrots and potatoes are somewhere around pH 5;  oats, salmon, and brown rice are around pH 6. 

About 4.5 is the native pH of your stomach when it's not cranking out hydrochloric acid to digest a meal.   If you make this honey-ACV drink in the typical hard water, it won't even lower that pH.  ACV probably has other benefits that go beyond straight chemistry.

Some Biochemistry

Now let's talk biochemistry.  Apple cider vinegar has been found to have some remarkable effects.  I've read papers that suggest acetate is actually an important signaling molecule.  Furthermore, acetic acid (vinegar) in the diet has been shown numerous times to decrease blood glucose and increase sensitivity to insulin in healthy people.  Some researchers [1] found that cider vinegar significantly lowered LDL and raised HDL cholesterol.  The p-value they obtained was p<0.005, which means their findings were highly significant.  Some other researchers [2] found similar results, noting that cholesterol and triacylglycerols ("triglycerides") were lowered.  Also there was increased bile acid excretion.  This is an important way the body gets rid of excess cholesterol.  (Cholesterol "per se" is not bad, but oxidized LDL is bad stuff). 

Now, what about ACV and stomach acidity?  What about digestion?

Here are some ways it might work...

- By introducing acetate and malate, which can enter certain metabolic cycles (TCA / Krebs, etc) and may do other things.

- By introducing other components that were in the apples and possibly modified by fermentation.

- By introducing live Acetobacter

We've already seen that acetic acid actually decreases the number of hydrogen ions in a solution of hydrochloric acid.  

It does this because acetate is protonated by the free H+, creating undissociated HOAc.  This is simple acid-base chemistry.  I want to clarify here, though, because I don't think I had mentioned that dilution is probably much more important.  Hydrochloric acid ionizes more readily than acetic, by a factor of something like a trillion.  So, the amount of free acetate that sequesters H+ is not going to be as important as the dilution effect.  Simply put, ACV doesn't bring enough acidity to make your stomach more acid than it is, unless you drank it straight on an empty stomach where the pH was 4.5 and now it might decrease a bit from that.

Pretty much any food does that already, because the stomach will lower the pH when you eat something.

It might be that acetate has some biochemical signaling properties which cause the stomach to produce more HCl or less HCl. 

Many people have spoken of good results taking ACV capsules.  If it's true, then ACV's mode of action cannot really be the acetic acid.  A dry capsule does not contain acetic acid, because acetic acid is always a liquid at room temperature.  What it could contain, though, is malic acid, citric acid, and tartaric acid.  (All these would have that slight "conditional antacid" effect I talked about, because of their higher pKa than hydrochloric acid.)  A dry capsule could also contain viable Acetobacter, as well as various other solids from the ACV.  No one really knows what all they do!  Still, these pills would not be as effective as real, unpasteurized ACV.  For one, any beneficial compounds are more likely to remain intact in the liquid.  Drying has a tendency to oxidize a lot of stuff, sometimes to the point of destroying it.  (Same reason why fresh herbs are usually better than dried.) 

What's remarkable is that acetobacter have been found to survive in very limited oxygen environments.  I say "remarkable" because acetobacter are considered strict aerobes, meaning they always need oxygen.  Acetobacter xylinum also produce their own cellulose (fiber) from glucose (Brown et al.: Proc. Natl. Acad. Sci. USA, 73(12):4565-4569).  In fact, US Patent 6808703 seeks to employ these bacteria to treat or prevent obesity and diabetes mellitus.  Apparently the bacteria use the cellulose to form a matrix that helps them get near the surface and find oxygen.  Can you imagine??  A. xylinum happen to occur in apple cider vinegar.  It seems almost science-fiction to think of bacteria that can manufacture fiber in your digestive tract, but apparently it's plausible.  It also makes me wonder if perhaps raw ACV might contain soluble fiber, which is a good thing.  Apples certainly have fiber already.

By the way, all this talk of "low potassium caused by ACV" seems to originate from ONE anecdote of ONE person who drank an 8-ounce glass of it (neat) every day for several years.  What else might have been off in his diet?  Maybe he wasn't getting enough vegetables.  Maybe he was sweating a lot.  Maybe he was shoveling snow, sweating a lot, and not getting enough vegetables.  We just don't know.  We can't assume that ACV caused the low potassium there.

Speaking of evidence, I'm satisfied that a bit of ACV helps me with mild indigestion.  (I never get severe reflux anymore in the first place, because the bleached flour has gone into the garbage can where it belongs.) 


I like apple cider vinegar.  There are some very plausible reasons why it should and probably does work.   As we've seen, a couple teaspoons of ACV in a glass of water cannot directly lower stomach pH.  If you're using hard water, the resulting pH is a pretty-high 5 to 6, which also happens to be buffered somewhat (because that's not far away from the pKa of acetic acid...).  Just to put things in perspective, orange juice has a pH of about 3.5. 

So, when some official source tells you to stay away from ACV because of dangers of "too much acidity", I'd take that with a grain of NaCl. 

Should you drink an eight-ounce glass of neat cider vinegar every day?  Probably not, even if only because of tooth erosion.  I'm sure it's possible to drink "too much" vinegar.  Remember again the pH of an empty stomach.

However, as long as you're not allergic, and as long as you're not on some medication that's incompatible with it, then chances are that it wouldn't hurt to drink a couple teaspoons dissolved in a glass of water with some honey.  That's exactly what I like to do in the evening sometimes.  When it feels like there's a little bit of indigestion-y feeling there, I find this drink helps me.  A lot.  The thing is, though, I generally don't even get "acid reflux" anymore, since I stopped eating bleached flour products.  I also started eating a lot of probiotics.  That's all it took for me.  No purple or blue pills necessary.  I don't chew antacids, either.  (There is enough calcium carbonate / bicarbonate from the hard water, thank you very much).   

I'm not allowed to tell you to take apple cider vinegar to treat, prevent, diagnose, or cure any medical condition.  (Read that disclaimer again.) All I'm going to say is that I, personally, like to make an ACV-honey drink when there's a mild feeling of acid indigestion.  As for what I think you should do... I'll just say "Talk to your health professional."  If you look around you can find one who's tuned into this sort of thing.  Our friends in Europe have it a little better in this regard, because in Europe they started approving quite a few natural remedies.  They had to save money on healthcare costs for the public, so they looked for natural, cheap things that worked.  In a USA hospital, meanwhile, they'll charge you fifty bucks for an aspirin tablet.  Something ain't right, there.  

ACV can be a tasty ingredient for various forms of cooking, and for some reason the organic, unpasteurized kind tastes really good with honey in a glass of water.  So it's a delicious drink that's got some "kick", and you might want to try it on that basis.

I could recommend any old brand of ACV, but I prefer one that's (A.) organic and (B.) hasn't had the Acetobacter wiped out by heat.  Also I prefer to see it stored in a glass bottle.  That's because long-term treatment of plastics with something like ACV could begin to leach stuff.  These selection criteria bring us to a handful of different brands, so far:

Spectrum Naturals
Dynamic Health
Eden Organic

The Eden Organic brand has the added advantage of using amber glass, which prevents photochemical degradation of the contents.  (Amber blocks the blue-spectrum light that carries the most energy.)  Just on that basis I might give them a try. 

I could have used this page to review something expensive, but I chose to review a $5 or $10 food product, because I like to help people.  You can really help me out by purchasing any of your stuff through the Amazon or links on this site.  Cookware, blenders (use one to make your ACV drink), or just about anything else.  Thanks!


[1]  Shishehbor F, Mansoori A, Sarkaki AR, Jalali MT, Latifi SM.  "Apple cider vinegar attenuates lipid profile in normal and diabetic rats".  Pak J Biol Sci. 11(23):2634-8 (2008 Dec. 1).

[2]  Fushimi T, Suruga K, Oshima Y, Fukiharu M, Tsukamoto Y, Goda T. "Dietary acetic acid reduces serum cholesterol and triacylglycerols in rats fed a cholesterol-rich diet".  Br J Nutr. 95(5):916-24 (2006 May).

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