Why Your Grandma May Recommend Brown Apples for Diarrhea

Sam Westreich, PhD

The FDA says it’s out, but they may be missing the microbial payoff

A diarrhea remedy, or just an old wives’ tale?Photo byPhoto by Louis Hansel on UnsplashonUnsplash

Table of Contents

· What is pectin, anyway?
· Does pectin help with diarrhea?
· So apples are useless for treating diarrhea?
· In summary, anti-diarrheal apples are probably a myth
Are there any other food-related myths you’ve heard about?

Apples are delicious and decently healthy for us if eaten as a whole fruit (not just the juice), although, as a doctor, I have to say that they don’t do anything to keep me away, even if consumed daily.

We’ve been eating apples for a long time, and there are plenty of myths and legends about them. One interesting health-related tale I heard recently was a recommendation for how to consume apples to help with cases of diarrhea.

The recommendation, which comes from a “naturopathy” site (strike one against it being factual) suggests:

A well-known home remedy to treat uncomplicated diarrhoea (especially in children) is to grate an apple, skin included, mix with a little honey and leave to go brown. The pectin provides soluble fibre to bulk stools up, and the honey helps restores minerals and electrolytes lost via diarrhoea.

Why let the apple go brown? It’s not stated on this site, but other sites claim that this is supposed to help increase the pectin content.

Does this work? Should apples be stocked in the pharmacy alongside other anti-diarrheal medications?

Let’s take a look at what the science says about apples, pectin, and loose bowel movements.

What is pectin, anyway?

Before we tackle whether pectin is good for the gut, let’s just clarify what it is — and whether grating an apple gets you any more of it.

Pectin is a carbohydrate; in nature, it’s part of the glue that helps hold cell walls together in plants. (Unlike blobby water-balloon animal cells, plant cells have a rigid wall around each cell, providing structure and rigidity.) At the molecular level, a pectin is a chain of sugars, linked together. Each sugar is a ring of carbons, and the pectin is a long string of those sugars, linked together in a chain.

We find pectin occurring naturally in a lot of different fruits; apples, pears, guavas, plums, citrus, and quince all contain high levels of pectin, and it’s present at a lower level in other fruits like grapes, cherries, and strawberries.

If you really wanted to get the most, richest pectin, you’d want to eat citrus peels. Barring that, apples are a pretty decent source of pectin, too.

When we mix pectin with acid and sugar, we get a gel-like structure that forms. This is the basis behind natural jams and jellies; the pectin in the fruit, combined with acid and sugar, creates a stable gel-like matrix.

There’s more pectin in just-barely-ripe fruit than in overripe fruit — but what about in oxidized fruit?

Unfortunately, the claim seems to fall short there. When apples are exposed to the air, they oxidize — this is why they turn brown. And a 1993 study looking at apple pulp showed that oxidation reduced the amount of soluble pectin, rather than increasing it.


In summary, now we know that pectin is a carbohydrate in many fruits, commonly used in jams and jellies. Apples are rich in pectin, but oxidized (browned) apples don’t have more free pectin than their just-cut counterparts.

Does pectin help with diarrhea?

Now, on to the meat of the claim: the pectin is supposed to help reduce diarrhea, supposedly at least in part by bulking up the stools. And it sort of sounds right when you first hear it, like mixing more flour into a batter that is too watery.

And, for a while, pectin was given as an anti-diarrheal medicine, approved by the FDA. It was sold under the label Kaopectate, which contained a mixture of kaolinite (a type of clay) and extracted pectin.

However, in 2003, the FDA issued an updated ruling, banning the sale of Kaopectate for the treatment of diarrhea. You can find the full text of the ruling online, but the gist is that, when the FDA looked at studies for giving kaolinite or pectin to diarrhea sufferers, either alone or in combination, the medications:

[…]did not provide sufficient statistical evidence that kaolin and pectin as a “fixed” combination is superior to kaolin in terms of improving stool consistency on day 2 of treatment. There was no statistical evidence that pectin is effective in improving stool consistency.


[…]study 303 provides reasonable statistical evidence that kaolin as a single ingredient is likely to improve stool consistency in subjects with acute nonspecific diarrhea in 24 to 48 hours. Data from this and other studies have shown that pectin has no effect.

In response to these findings, the makers of Kaopectate updated their recipe to instead use bismuth subsalicylate, the same active ingredient in Pepto-Bismol. Pectin was dropped as an active ingredient.

Kaopectate, still containing pectin, is still sometimes sold over-the-counter for treating diarrhea in cats and dogs. The FDA hasn’t issued any ruling on that, which basically means “we aren’t saying whether it works or not, use at your own risk”.

In summary, using pectin as an anti-diarrheal medicine is probably not going to work; the FDA has banned the sale of pectin as a specific treatment for diarrhea, after studies failed to show it had any effect.

So apples are useless for treating diarrhea?

Not so fast! Just because pectin is out, doesn’t mean that an apple is a bad choice if you’re suffering from loose stools.

Specifically, pectin may still provide some relief to individuals with irritable bowel syndrome with diarrhea (IBS-D). For these individuals, diarrhea isn’t a one-time occurrence; it happens repeatedly, with semi-regular flare-ups.

In one study, researchers gave IBS-D sufferers pectin supplements while also monitoring their gut microbiome, the collection of many different types of bacteria living in their small and large intestine.

The researchers observed that the individuals who received the pectin supplements (versus those who just received a “sugar pill” placebo) showed improvements in their Bristol stool scores, a measurement of how loose their poops were. They also reported greater quality of life improvements over the placebo group.

But why? Did the pectin help “firm up” their stools?

It doesn’t appear to be the case. Rather, it looks like pectin served as a delicious prebiotic food source to bacteria in the genus Bifidobacterium, a type of bacteria that has been associated with a healthier gut. The microbiomes of the pectin-consumers also showed a decrease in Clostridium species, a group linked with several negative gut health outcomes.

This was a fairly small study, on only 87 individuals. Just as there are different types of IBS (IBS-C, characterized by chronic constipation, versus IBS-D, characterized by chronic diarrhea), there are likely different microbiome/bacterial imbalances responsible for different sub-types of IBS.

Pectin may not work for all types of IBS, but this study does offer some hope that it, along with other types of fiber, may be a prebiotic solution to IBS by encouraging the growth of a better microbiome that is less likely to agitate our own immune system.

In summary, some limited evidence suggests pectin may pay off for chronic IBS sufferers by encouraging the growth of healthier gut bacteria, although more evidence is needed.

In summary, anti-diarrheal apples are probably a myth

A nice grated apple to help settle the stomach… it’s probably pretty easy for someone to eat on an upset stomach, but studies disprove the supposed benefit.

Our myth falls apart in two different ways:

  1. Letting apples oxidize by grating them and leaving them to turn brown reduces the available pectin, not increases it;
  2. Apple pectin doesn’t help acute cases of diarrhea.

There is a little bit of silver lining in the fact that pectin may help cultivate a healthier gut microbiome, especially in sufferers of irritable bowel syndrome with diarrhea (IBS-D), but this doesn’t seem related to the main proposed treatment for diarrhea.

Overall, apples are totally fine to eat, and pectin is just one of the reasons why it’s healthier to eat the whole fruit — not just the juice! Just don’t expect that apple to cure your diarrhea.

Are there any other food-related myths you’ve heard about?


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A microbiome scientist working at a tech startup in Silicon Valley, Sam Westreich provides insights into science and technology, exploring the strangest areas of biology, science, and biotechnology.

Mountain View, CA

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