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I'm very curious to hear what the biologists think about this result.

In a related vein, the post reminds me of the movie "The Informant" about Mark Whitacre, an ADM executive, who was caught up in a price fixing scandal involving lysine and citric acid. It seems like a quiet, stable corner of the food business, but maybe we should be paying more attention.

https://www.imdb.com/title/tt1130080/plotsummary

Our son was sensitive to citric acid in his foodstuffs as a toddler. So much rash - until we figured out what it was. I'm glad this is getting some light shone upon.
I am allergic/sensitive to natural or not. I have only met two other people with the same affliction.
I'm also intolerant to citric acid. It's good to see it come up here as it's hard to find 'paper' on it and this community cross-references into interesting fields, which are absent most of the places I've been able to find any information about it.
If I understand this correctly, the potential problem lies not with the citric acid itself, but with the fungus we use to produce it, traces of which can make it into the end product and might cause allergic reactions.

I'm surprised, I thought citric acid was created synthetically. Does anyone know how much more expensive would it be to synthesize it without involving an organism?

Interesting. The fungal production process for making citric acid leaves traces of fungal allergen in the product. Some people are sensitive enough that they suffer a reaction when consuming citric acid made this way.

Depending on how common the reactions are, it sounds like there needs to be a warning on food packaging (like for peanuts) or assays developed for the allergens plus further purification of citric acid destined for human consumption.

Maybe someone from the medical research community can comment, but the evidence here seems pretty weak. 4 cases, all self reported, where the patient is the one that identified the food additive when looking for such things. The chance for a placebo effect is strong. Also not sure how to interpret having multiple vegetarians in such a small sample. None of this of course invalidates the hypothesis, but the evidence appears super flimsy.
I'm not sure how you could be so skeptical after reading case report 4. Sure low sample size blah blah blah, but case report 4 had isolated her issues to MCA so precisely, that it seems to validate the hypothesis.

- 43 years old, raw food diet, never/rarely consumed MCA.

- Started to drink water w/ vitamin c powder and had bad reactions for 2 years.

- Stopped drinking the vitamin c mixture she was drinking, and her symptoms went away

- Tried ANOTHER vitamin c mixture without MCA, and she has NO symptoms.

Paragraph 1 of the Conclusion:

> We recognize the limitations of the level of evidence from our four case reports. We cannot conclusively affirm that MCA is the causative factor in the subjects’ inflammatory symptoms. However, our findings demonstrate a significant likelihood that MCA may be the culprit and are suggestive of valid concerns which warrant proper double blind studies to determine presence or absence of harm.

Self isolated and self reported improvements. Where did these studies come from? Relying on self reported anecdotes seems pretty far from science. Maybe it’s normal as a starting point - but it strikes me as the sort of bias science aims to weed out.

Compelling well written anecdotes are still anecdotes.

You're being overly critical of a scientific article that is very aware of its statistical limitations.

I would also venture to guess that you've never suffered from or attempted to self diagnose a chronic health issue. The people in this article had been suffering for years (case 1 was possible 10+ years) and each went through a pretty scientific process of food elimination. To suggest that this might be a placebo effect is ridiculous.

Cases 1, 2 and 3 all mention a reocurrence of symptoms after consuming MCA - unlikely that these people are dealing with repeated placebo effect that happens to occur after eating MCA.

Again self reported. There are no statistical limits on a story which may or may not be true and has no control over outside factors. This simply isn’t science - it’s a reasonable place to start for a hypothesis, but it’s not science. This is how we end up with chiropractors and acupuncture.
MCA (manufactured citric acid) is on my list of ingredients to avoid, as it seems to cause sores on the inside of my mouth. I don't get the same reaction from lemons/limes, so I figured it's the fungus contaminants.

Juices are commonly contaminated with MCA. I refer to MCA as a 'cosmetic food ingredient', which are added to change mouthfeel of a manufactured food and do not provide nutrition. Gums are the other common cosmetic food ingredient - they are added to change the mouthfeel or storage properties. Most gums are safe; I avoid all foods with carageenan, as this one supposedly has inflammatory properties.

The fine article says that Italy used to make citric acid from lemons, but that this got too expensive. I didn't realize fungus-derived citric acid has been in use since 1919.

If you're avoiding it, it may be helpful to know (if you didn't already; in that case, for anyone else reading) that, at least in the US, manufactured citric acid is a frequent additive not stated in ingredient lists ("natural flavors", among other things), as well as a reactive agent in some non-perishables eg. soaps and detergents. I was bit by that last one several times before researching the chemistry of soapmaking and learning about it with tired aggravation.
This is interesting, I hadn't seen this paper before.

I've had a citric acid allergy (both natural and mold-produced) most of my adult life, but it really seemed to kick into high gear after I spent an extended period of time living somewhere with severe mold problems. Since some people in this thread seem to be unaware of the black mold/citric acid relationship entirely, I'll further clarify that aspergillus niger, the citric-acid-producing "black mold" on rotting fruit, is not the "black mold" associated with wet drywall. (The place I was staying had both...)

Since it's only a single anecdote, and I'm not an immunologist, I've had no way to reason about whether these could be connected. Good to see at least someone is studying it in some cursory way.