Why are my faeces black in colour the morning after I eat some Oreos?

Day 1 : Eat a handful of Oreos & the next morning your stool is black.
Day 3 : Eat a handful of cocoa flavored biscuits & the next morning your stool is normal.
Day 5 : Eat a handful of Chocolates & the next morning your stool is normal.

I'm aware of the beetroot digestion story, and how it doesn't happen to everyone. What is surprising in the case of Oreos is that it just takes a handful of Oreos to turn the stool black. But with any other biscuits or chocolates, my faeces are normal.

I don't have anything other than anecdotal evidence but a lot (NOT ALL) of my friends have had similar experience. Just Googling "Black stool after eating Oreos" & I see a lot of people (not all) having similar experience. Do note that to my knowledge it doesn't affect my body in any way.

Why is that the case? Why doesn't it happen to everybody? What ingredient in Oreos makes it happen? What is the physiological underpinning? Asking this question with curiosity than caution. Looking for biological/biochemical perspective.

  • 1
    $\begingroup$ Hi KharoBangdo! I appreciate your enthusiasm on this site. While this question surely probes deep into the recesses of medical science, it seems as though your data are not well-formed. Perhaps you could carry out a more robust study and then report on the results for the community to respond to. $\endgroup$
    – user891
    Jul 29, 2013 at 7:00
  • $\begingroup$ @jreut sorry, i didnt understand what you are trying to suggest. Are u offended by my little not-so-funny joke at the end. Should i rephrase the question. Was my question unclear? $\endgroup$ Jul 29, 2013 at 7:04
  • $\begingroup$ Before you put any more effort into rephrasing your question, just know that's not what I'm asking you to do. I'm saying that your assertion that 'a handful of Oreos' vs. 'excessive beet root' causes similar magnitudes of color change in your excrement is not well-formed or founded in evidence. You simply need to be more specific in the amounts of either food you've eaten and describe more concretely the effects. $\endgroup$
    – user891
    Jul 29, 2013 at 7:26
  • $\begingroup$ its based on the food coloring so the food coloring is black so then it caused by that and the choclate just don`t to much oreos $\endgroup$
    – Oreos
    May 23, 2017 at 0:52

2 Answers 2


This is a perfectly reasonable question based on a self-adminstered (human) trial. Morever, the proposer bases their observations not on one subject but several reports. The impromptu survey of friends etc. is also acceptable. By the way, self-reported intakes/output records are an accepted method in nutrition research.

My 2-year-old child exhibited the symptoms described above, after consuming two Oreo biscuits in the afternoon. That evenings soiled nappy (diaper) revealed a dark but otherwise well-textured stool. When my concerned partner brought this to my attention, it immediately reminded me of the use of carmine red and related food dyes for the measurement of gastrointestinal transit times. The principle here is that the dyes are not absorbed in the gut, so the time from consumption to excretion gives a measure of bowel function. Short transit time means no constipation and is considered a sign of great bowel function.

Based on the observations reported for Oreos, my educated guess would be that Oreo products contain miniscule amounts of non-absorbed colorants - something that is generally regarded as safe. Self-reported symptoms are generally considered valid by health professionals. I am still intrigued by the Oreo colouring puzzle, as this colourant must be natural.

  • $\begingroup$ Transgenics are also "generally regarded as safe", "because they contain DNA and our species has always eaten DNA". Just a comment. $\endgroup$
    – Rodrigo
    Mar 25, 2014 at 21:53
  • 4
    $\begingroup$ I agree the question is reasonable, but I don't think you've answered it in any meaningful way. You've provided more anecdotal evidence which OP already has, brought in the example of beetroot (also raised by OP). The answer essentially here is "non-absorbed colorants" which isn't specific enough for me! $\endgroup$
    – James
    May 23, 2016 at 5:04

According to this site there is something called black cocoa powder, a particularly dark product referred to as an ultra-Dutch processed cocoa powder. The site recommends this for anyone trying to reproduce the colour of Oreos, claiming that it acts more as a colouring agent than a flavouring agent.

The site also recommends two commercially-available products so now you should be able to do a real experiment by baking two batches of cookies that differ only in whether they contain this. Then you can report back here, but maybe this time with photographic evidence.


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