Photo by Cyril Saulnier on Unsplash
I love coffee. I do. I’m not afraid to say it. I didn’t start drinking it until medical school, so I was late to the party, but I made up for it with my 4-5 cup per day addiction in residency. These days, I settle for one cup a day- perhaps a large cup, a gran lungo in one of my many, many thermoses, and I’ll vary between black as my soul or sweet as my smile, but that one cup gets me going. But I don’t usually drink more than one, because coffee can worsen anal fissures. And this is why.
Drinking coffee can have a mild diuretic effect, increasing urine output and reducing total body water if not compensated by extra fluids. Harder, drier stools increase strain during defecation → more micro-trauma to the fissure site.
Coffee stimulates the gastrocolic reflex (both caffeinated and decaffeinated coffee can do this), which tends to increase colonic motility and may cause urgency or more frequent bowel movements or wiping. More frequent wiping or irritation of the anoderm delays healing.
There is direct evidence that caffeine ingestion increases anal sphincter resting and squeeze pressure in healthy subjects: in one study, 3.5 mg/kg caffeine increased basal anal sphincter pressure and maximum squeeze pressure. (PubMed)
Higher sphincter tone → increased compressive pressure on the anoderm → reduced micro-circulatory perfusion at the fissure site.
Chronic fissures are best understood as ischemic ulcers of the anoderm:
The posterior midline of the anal canal has the lowest perfusion of all quadrants. (NCBI)
Elevated internal anal sphincter tone correlates with lower anodermal blood flow (i.e., higher pressure → lower perfusion). (SICCR)
When coffee/caffeine further increases sphincter tone and/or reduces blood flow (see next point), fissure healing may be delayed or fissure pain/spasm may be worsened.
Caffeine acts as an antagonist of adenosine receptors (especially A₁, A₂A, A₂B) on vascular smooth muscle, which normally mediate vasodilation. Blocking these leads to vasoconstriction in multiple vascular beds (brain, myocardium, splanchnic). (PMC)
Specifically:
In preterm neonates, an IV caffeine dose reduced peak systolic velocity in the superior mesenteric artery and coeliac axis for up to 6 hours. (PMC)
In older adults, caffeine given with a meal did not reduce splanchnic blood pooling compared to placebo, but the underlying mechanism invoked is blockade of adenosine-mediated vasodilation. (PubMed)
The takeaway: caffeine can reduce splanchnic/pelvic perfusion (or at least shift hemodynamics) in ways that potentially reduce blood flow to the hemorrhoidal/anal canal region. In the context of a fissure (especially at the posterior midline with compromised micro-circulation), this further ischemic effect may delay healing.
Caffeine also elevates blood pressure (via vasoconstriction), catecholamine release, and shifts blood flow toward skeletal muscle/heart and away from splanchnic circulation. (SpringerLink)
This “fight or flight” effect reduces perfusion in less priority vascular beds (including possibly the rectal/anorectal mucosa and internal anal sphincter region) which again may exacerbate ischemic conditions in the fissure site.
Coffee’s acidic nature plus possible softening of stool or increased urgency/wiping leads to more exposure of the damaged anoderm to irritants and friction, thus more pain and slower healing.
People drinking coffee may skip adequate water intake or pair it with low-fiber breakfasts, thus compounding dehydration + harder stools + straining. The combined effect intensifies the fissure cycle.
If coffee is consumed: ensure adequate hydration (add one glass of water per cup).
Switch to lower-acid coffee (cold brew, low-acid roast) if tolerated.
Avoid drinking coffee on an empty stomach — eat a fiber-rich breakfast before/with coffee.
Emphasize stool softening: fiber supplementation, hydration, avoid straining.
Recommend warm baths and topical therapies (e.g., nitrates, diltiazem) that increase anodermal perfusion and reduce sphincter tone. (Recall the ischemic nature of fissures). (PMC)
Monitor fissure healing: if refractory, ensure other causes (IBD, Crohn’s, etc) are considered.
Did I forget to introduce you to hemorrhoids and fissures? Oh, my.
