Does Align Probiotic Cause Constipation?

Align Probiotic, which contains the strain Bifidobacterium longum subsp. infantis 35624, is not known to cause constipation as a common side effect. Clinical trials have primarily evaluated Align for irritable bowel syndrome symptoms and have not flagged constipation as a frequent adverse event. That said, there is a plausible biological pathway through which this particular strain could slow gut transit in some individuals, and the story involves an unexpected gas: methane.

What Align’s Clinical Trials Actually Report

Align was developed and studied primarily as a treatment for IBS-related symptoms, especially abdominal pain and bloating. A systematic review of probiotic trials noted that in a randomized, double-blind trial of 362 women with IBS, the group taking Bifidobacterium longum subsp. infantis 35624 at a dose of one hundred million colony-forming units per day experienced a meaningful drop in abdominal pain scores compared to placebo after four weeks.¹ That trial and others like it focused on pain, bloating, and bowel habit satisfaction as primary outcomes. Constipation was not reported as a standout side effect.

This is important context because most people reaching for Align are dealing with IBS-type discomfort, not trying to speed up a sluggish gut. The clinical data suggests the product does what it advertises for pain and bloating. But it was not specifically designed or widely tested as a constipation remedy, which leaves a gap in what we know about how it affects transit time over weeks or months of daily use.

The Methane Connection

Here is where things get more interesting, and where a possible link to constipation emerges. A study examining the effects of Bifidobacterium infantis 35624 on breath test results found that methane levels rose significantly during probiotic use. Before taking the probiotic, three out of nineteen subjects showed a notable rise in methane on their breath test. After taking the probiotic, that number doubled to six.² The study was small, but the finding is worth paying attention to because of what methane does in the gut.

Methane is produced by a specific group of organisms in the gut called methanogens. When these organisms are especially active, the methane they release has a direct effect on how fast material moves through the colon. Research has established that excessive methane production slows colonic transit.³ People with constipation tend to harbor more methane-producing bacteria than people with normal bowel habits. The methane itself appears to inhibit the smooth-muscle contractions that push stool along.

So the chain of events could look like this: you start taking Align, the probiotic shifts your gut microbial environment in a way that favors methanogen activity, methane output goes up, and your gut slows down. This is not guaranteed to happen. It was observed in a small study, and the degree of methane increase varied among individuals. But it offers a biologically plausible explanation for why some people might feel more backed up after starting Align, even though the product was not designed to cause that effect.

How Gut Bacteria Influence the Speed of Digestion

Understanding why a probiotic could either help or hinder constipation requires a look at what gut bacteria actually do to keep things moving. One of the key players is a short-chain fatty acid called butyrate, which gut bacteria produce when they ferment dietary fiber. Butyrate promotes the production of serotonin in the gut lining, and serotonin in turn triggers the release of acetylcholine, a chemical that stimulates the muscular contractions of the intestinal wall. Animal research has shown that restoring butyrate production in a constipated gut led to shorter transit times and less fecal accumulation.⁴

Different probiotic strains interact with this pathway in different ways. A strain that boosts butyrate production and serotonin signaling is more likely to speed up transit. A strain that primarily shifts the microbial balance in other directions, for example by increasing methanogen populations, could have the opposite effect. This is why “probiotics help with constipation” is too simple a statement. The strain matters enormously, and even the same strain can behave differently depending on your existing gut flora, your diet, and what else is going on in your digestive system.

Why the First Few Weeks Can Feel Different

A common experience among people starting any probiotic, not just Align, is a temporary shift in bowel habits during the first one to two weeks. Some people notice increased gas and bloating. Others report looser stools. And yes, some feel more constipated. This adjustment period reflects the gut microbiome reorganizing itself in response to the new influx of live bacteria.

During this window, the balance of gas-producing organisms in the gut fluctuates. Your existing microbial residents are competing with the newcomer for resources. The types and amounts of gases produced, including hydrogen, carbon dioxide, and methane, can shift unpredictably. For most people, these changes settle down within a couple of weeks as the microbial community reaches a new equilibrium. If constipation appears during this phase and resolves on its own, it was likely a transient adjustment rather than a lasting side effect of the probiotic.

The distinction matters for practical decision-making. Stopping a probiotic after three days because you feel a bit blocked up may not give it a fair trial. On the other hand, if constipation is still present or worsening after three to four weeks, the product may genuinely not be a good fit for your gut.

Which Strains Have Stronger Evidence for Constipation

If your primary goal is to relieve constipation rather than manage IBS-related pain, Align may not be your best bet. The research literature on probiotics for chronic constipation points to other strains with more direct evidence. A review of human studies on probiotics and chronic constipation found that the most frequently studied strains for this purpose were various subspecies of Bifidobacterium lactis and Lactobacillus casei Shirota. Single-strain probiotic formulations appeared to have a stronger effect on stool frequency, stool consistency, and constipation-related symptoms compared to multi-strain blends.⁵

Lactobacillus casei Shirota, in particular, has been shown across several trials to reduce straining, improve the feeling of complete evacuation, decrease abdominal discomfort, and increase how often people have bowel movements.⁵ Bifidobacterium lactis strains like HN019 and DN-173010 have similarly been studied specifically for their ability to speed up sluggish colons.

Align’s strain, Bifidobacterium longum subsp. infantis 35624, was developed with a different focus. Its strengths lie in modulating the immune response in the gut lining and reducing the visceral hypersensitivity that drives IBS pain. That is a genuinely useful function, but it is a different function than stimulating motility. Choosing a probiotic based on the symptom you most need to address, rather than brand recognition alone, will generally give you better results.

The Role of Methanogens in Constipation

The methane story deserves a closer look because it connects to a broader pattern in constipation research. Scientists have found that the prevalence of methane-producing organisms is consistently higher in people with slow-transit constipation than in healthy controls. One proposed mechanism for how probiotics can help constipation is by reducing the proliferation of these methanogens, thereby lowering methane output and allowing normal motility to resume.⁶

This creates an interesting paradox for Align specifically. If the small study showing increased methane during Align use holds up, it would suggest that this particular strain might, in some people, inadvertently feed or create favorable conditions for methanogens rather than suppress them. That is the opposite of what you would want if constipation is your problem. The evidence here is thin, based on fewer than twenty subjects, so it would be wrong to declare this a settled finding. But it does give biological context for anecdotal reports of constipation during Align use, and it highlights why probiotic effects are so strain-dependent.

Not everyone’s gut harbors the same baseline population of methanogens. People who already produce relatively high levels of methane might be more susceptible to this effect than people whose guts are dominated by hydrogen-producing bacteria. There is no simple consumer test for this, though a lactulose breath test ordered by a gastroenterologist can measure your methane output if the question becomes clinically relevant.

Safety in Older Adults

Constipation becomes more common with age, and older adults are a large part of the probiotic market. A systematic review and meta-analysis of probiotics for constipation in geriatric patients found that adverse reactions were rare and mild across the trials examined. In the pooled data, only one adverse event occurred in the probiotic groups compared to six in placebo groups, and the difference was not statistically significant. The reported adverse events were primarily diarrhea, abdominal pain, and bloating, not constipation.⁷ No severe adverse reactions linked to probiotic use were found in any of the studies reviewed.

This is reassuring for safety, though it is worth noting that the trials included in that review used various probiotic strains, not exclusively Align. The general picture is that probiotics as a category are well tolerated by older adults, even those already dealing with constipation. If an older adult starts Align and notices worsening constipation, the more likely culprits are medications (opioids, calcium channel blockers, iron supplements, and anticholinergic drugs are common offenders), reduced physical activity, or inadequate fluid and fiber intake.

Practical Steps If You Suspect Align Is Slowing You Down

If you have been taking Align and feel more constipated than before, a reasonable approach is to give it two to three weeks to see if the issue resolves on its own. During that time, make sure the basics are in order: adequate water intake, sufficient dietary fiber from vegetables, fruit, and whole grains, and regular physical movement. These factors influence gut transit independently of any probiotic and can mask or amplify whatever the supplement is doing.

If constipation persists beyond three to four weeks, stopping the probiotic for a similar period and observing what happens is a straightforward way to test whether Align is contributing. A clear improvement after stopping and a return of symptoms after restarting would be a strong personal signal, even if it would not qualify as clinical proof.

For people whose main complaint is constipation rather than IBS-type pain or bloating, switching to a strain with more direct evidence for motility is worth considering. Look for products containing Bifidobacterium lactis (particularly HN019 or DN-173010) or Lactobacillus casei Shirota, and check that the colony-forming unit count matches what was used in the relevant trials. Probiotic doses that worked in studies are not always what ends up on store shelves.

When Constipation Needs More Than a Probiotic

It is easy to reach for a supplement when bowel habits change, and for mild or intermittent constipation, that can be a reasonable first step. But certain patterns warrant a conversation with a doctor rather than another trip to the supplement aisle. New-onset constipation that comes on suddenly in someone over fifty, constipation alternating with diarrhea, unintended weight loss, blood in the stool, or constipation that does not respond to any dietary or supplemental intervention should all prompt medical evaluation. These scenarios can point to conditions ranging from thyroid dysfunction to structural problems in the colon that no probiotic will address.

Chronic constipation that has been present for months or years also benefits from a proper workup. A gastroenterologist can assess whether the issue is slow transit through the colon, a problem with the muscles involved in defecation, or something else entirely. Probiotics can be part of a management plan for functional constipation, but they work best when you know what you are managing. Using Align or any other probiotic as a long-term workaround for unexplained constipation can delay a diagnosis that might lead to more effective treatment.