I added fiber, made it noticeably worse, and only later worked out that I had added the bulk without adding the water.
So the question, as narrowly as I can put it: what the mechanism is, because if it is transit rather than water then fiber is the wrong lever.
Tell me what I have not thought of.
Short answer first, then the reasoning. 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.
kate.chem said:Fiber trials in this population are thin, and most of what gets quoted is extrapolated from idiopathic constipation in people eating normally.
Drug interaction alert relevant to constipation: if you take oral levothyroxine (Synthroid), GLP-1 agonists can reduce absorption due to delayed gastric emptying. My TSH drifted up after starting semaglutide.
Solution: take levothyroxine on an empty stomach, 60 minutes before any food, and have your TSH rechecked 6-8 weeks after starting or changing GLP-1 dose. My endo had to increase my Synthroid by 12.5mcg.
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View Resultsbbq_ray_KC said:I added fiber, made it noticeably worse, and only later worked out that I had added the bulk without adding the water.
Can confirm the pattern bbq_ray_KC describes. 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.
From the other side of the consultation, briefly.
Sulfur burps on constipation — the most underrated side effect nobody warned me about. 🤢 The smell is absolutely vile and comes on without warning.
What finally helped: Gas-X (simethicone) daily. Also, eating smaller portions and chewing thoroughly reduces the gas production.
If sulfur burps persist beyond 2-3 weeks, talk to your provider — it could indicate gastroparesis that needs medical attention.