Posting this because the summary going around does not say what the paper says, and the difference matters for how people here are using it.
The mechanism is slowed transit plus reduced intake, and that combination determines which interventions work. Less food means less bulk, slower motility means more water reabsorbed, and the result is a smaller, drier, slower stool. Insoluble fiber adds bulk to a system that is already moving slowly, which is why it frequently makes things worse. Soluble fiber holds water and is the better first choice, and an osmotic agent works with the mechanism rather than against it.
Where I think it is weakest: the comparator does most of the work in how this gets reported, and it is not the comparator most people think they are citing.
The narrow version of the question is what the mechanism is, because if it is transit rather than water then fiber is the wrong lever. Numbers rather than impressions, if you have them.
Figures above are from the primary publication rather than the press summary. If a number here disagrees with one you have, post yours and we will work out which of us is reading a secondary source.
RetaRick_CA said:The mechanism is slowed transit plus reduced intake, and that combination determines which interventions work.
RetaRick_CA has the substance of this right. The condition it depends on is worth stating. The escalation order that reflects the mechanism: water and salt first, then soluble fiber, then magnesium or an osmotic agent, then a stimulant only briefly and only if the osmotic has failed. Stimulants first is the commonest error and the one most likely to end in a cycle of dependence.
RetaRick_CA said:The mechanism is slowed transit plus reduced intake, and that combination determines which interventions work.
Worth saying plainly that not all of this is benign. Severe constipation on delayed gastric emptying has produced obstruction and ileus cases, rarely but genuinely. Pain with vomiting and no bowel movement is not a fiber conversation.
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View ResultsAnswering the narrow version, because the broad one does not have a single answer. Fiber trials in this population are thin, and most of what gets quoted is extrapolated from idiopathic constipation in people eating normally. The extrapolation is not unreasonable but it is an extrapolation, and it fails specifically for insoluble fiber at low intake — the case that comes up here most often.
LarryQC_SD said:The escalation order that reflects the mechanism: water and salt first, then soluble fiber, then magnesium or an osmotic agent, then a stimulant only…
This is my experience too, for whatever a second data point is worth. Nothing to add that would improve it.