Align Probiotic contains a single bacterial strain, Bifidobacterium longum 35624, along with several inactive ingredients that stabilize the capsule and keep the bacteria alive on the shelf. Each capsule is manufactured with 1 billion colony-forming units (CFUs) of live bacteria, though that number gradually decreases to about 10 million CFUs by the expiration date.
The Active Ingredient
The core of Align is one specific probiotic strain: Bifidobacterium longum subsp. longum 35624, sometimes marketed under the brand name Bifantis. Unlike many probiotic supplements that pack in multiple strains, Align uses only this one. It was originally isolated from the human digestive tract, which is part of the reasoning behind its selection for a gut-health supplement.
Each capsule contains 4 mg of this bacterium by weight. What matters more than weight, though, is the number of live organisms. At the time of manufacturing, each capsule holds about 1 billion live bacteria. By the time you take it (assuming it hasn’t passed its “best by” date), that number may have dropped to around 10 million, which the manufacturer considers an effective dose.
How the Strain Works in the Gut
Bifidobacterium longum 35624 produces a sugar-based coating on its surface called an exopolysaccharide. This coating is central to how the strain interacts with your immune system. Research published in Applied and Environmental Microbiology found that this surface layer helps dampen inflammatory responses in the gut. When researchers removed the coating from the bacteria in lab experiments, immune cells reacted much more aggressively, producing higher levels of several inflammatory signals. With the coating intact, the bacteria essentially fly under the immune system’s radar and help keep inflammatory activity in check.
The strain also interacts with specific receptors on immune cells, including those on dendritic cells, which act as sentinels in the gut lining. These interactions promote a more tolerant immune response rather than an aggressive one, which is why the strain has been studied primarily in the context of digestive discomfort and irritable bowel symptoms.
Inactive Ingredients
Beyond the probiotic itself, the capsule contains several supporting ingredients:
- Microcrystalline cellulose: A plant-based fiber used as a filler to give the capsule bulk.
- Hypromellose: The material that forms the capsule shell itself.
- Sucrose: A small amount of sugar that helps protect the bacteria during the freeze-drying process.
- Magnesium stearate: A common flow agent that prevents ingredients from clumping during manufacturing.
- Sodium caseinate: A milk protein used as a stabilizer. This is the reason Align carries a “contains milk” allergen warning.
- Titanium dioxide: A white pigment that gives the capsule its opaque color.
- Trisodium citrate dihydrate: A buffering agent that helps maintain a stable environment inside the capsule.
- Propyl gallate: An antioxidant preservative that prevents fats in the formulation from going rancid.
Allergens and Dietary Concerns
The most notable allergen in Align is milk. Sodium caseinate is a protein derived from milk, and the product may contain small amounts of lactose as a result. If you have a milk allergy or are highly sensitive to lactose, this is worth knowing before you take it. The amounts of lactose are small, so many people with mild lactose intolerance won’t notice any effect, but those with a true milk protein allergy should avoid it.
Align does not list gluten or soy among its ingredients.
Shelf Stability and Storage
One reason Align uses the specific inactive ingredients it does is shelf stability. The bacteria are freeze-dried during manufacturing, which puts them in a dormant state that doesn’t require refrigeration. The manufacturer has tested the formulation to confirm the bacteria remain viable for up to 24 months at room temperature.
That said, the packaging matters. The bottle is designed to protect the bacteria from moisture and environmental exposure, so keeping the capsules in the original container rather than transferring them to a pill organizer helps preserve potency. Heat and humidity will accelerate the decline in live bacteria counts, so storing the bottle in a cool, dry place (not a bathroom medicine cabinet) is ideal.
Common Side Effects
The most frequently reported side effects are bloating and gas, particularly during the first few days of use. These symptoms typically settle as your gut adjusts to the new bacteria. Allergic reactions are rare but possible, and would show up as hives, swelling, or difficulty breathing. Signs of infection, such as fever, chills, or unusual fatigue, are another reason to stop taking it and check in with a healthcare provider, though these reports are uncommon.