What makes food "disagree" with you?

I have found that a close relative avoids certain foods–for example, chocolate, root beer, and “snickerdoodle” ice cream, because they seem to be disruptive to her body functions. Why should this be? What ingredient in foods would upset one’s “regularity” or similar functions?

In my particular case it’s because my immune system goes nuts and attacks innocuous molecules for no damn good reason. That is, I have allergies.

In the case of celiac/gluten intolerance there is a different immune malfunction.

Lactose intolerance comes about because one’s body has stopped producing lactase and can no longer digest lactose. This leads to problems like bloating, diarrhea, and farts of truly epic foulness.

There are medical conditions that can be aggravated by certain elements in the diet. For example, a lot of salt plus high blood pressure can be a bad combination.

There are genetic disorders where the body can’t properly deal with something, but they’re kind of rare.

Too much or too little fiber can affect how quickly food moves through the body, which can lead to constipation (too little) or diarrhea (too much).

It could also be that she happened to get bad batches of those foods a couple of times, and quickly concluded a pattern which doesn’t actually exist. We form such patterns very quickly with food, as an evolved protection against poisoning.

Well…she’s 86 years old…I suppose THAT can figure in it… [Shrug]

There are several things at play:
Your individual biochemistry and makeup really impacts the way that substances can be digested and absorbed into your body.
Your gut bacteria - we al have bacteria inside of our digestive system which helps us to digest food and can really play a vital role in digestion.
What you were exposed to as a child can play a role because your body may not be used to foreign substances and have a more difficult time digesting and breaking down the molecules in the food and turning them into molecules that your body can use.
And, as was mentioned by someone else, some medical conditions can influence your body’s ability to digest (celiac is a great example).

Granted, most of this information is coming from only one semester as a biology major, so take my suggestions with a grain of salt.

Well, I told my pizza that Bart Starr is a highly underrated quarterback, and he snapped back that the Packers dynasty was built on the Power Sweep, and then…

Well, how do you know that Bart Starr even likes pizza?

I don’t know about the other two, but chocolate can cause reactions because it contains a stimulant. This can increase motility. Other stimulants like caffeine may not have the same reaction if you’ve gotten used to them–though you’ll find a lot of people who do say that coffee helps their bowel movements, too.

As for the rest, I can just IMHO it.

Both root beer and snickerdoodle ice cream seem too specific to cause a problem. Though maybe the comination of dairy and less digestible stuff like peanuts explains the snickerdoodle. And I guess root beer is one of the more foamy sodas, and excess carbonation can react weirdly with gut bacteria.

That’s all correct as far as it goes, but something that seems to be little understood is that the intestine is basially a small, distributed brain; it is the second largest collection of neurons after the brain and brainstem, comprising what is now termed the enteric nervous system, and secretes its own hormones (including those from the pancreas) which act as neuromodulators and neurotransmitters. This, in combination with peptides produced by gut bacteria and (suspected although not conclusively proven) hormones absorbed through digestion which can influence the process of digestion, either enhancing or preventing it, depending on the state and composition of the material to be digested.

Refined sugar, which is not part of any natural human diet in any significant quantities, basically bypasses most of the hormonal regulation in the intestines and so is more rapidly absorbed than normal unprocessed organic matter. Ditto for alcohols and many other substances that are considered toxins, stimulants, relaxants, et cetera, so these can disrupt both enteric function and base metabolic and neural function. Consumption and growth of large amounts of unfamiliar flora, various fungi, and some families of viruses as well as imbalance in non-organic nutrients can all cause disruption of the gastrointestinal system.


Er… since when do snickerdoodles have peanuts? You must be using a very different recipe than I do. Or many manufacturers do (I’m an obsessive label reader).