Delayed-Release Capsules: Do They Really Survive Stomach Acid?

What the stomach actually does to a capsule

Gastric fluid sits at roughly pH 1.5 to 3.5 in a fasted stomach. An ordinary gelatin capsule shell is designed to fall apart there in minutes — that is the point of it. Anything sensitive to acid that goes in an ordinary capsule meets the acid almost immediately.

That matters differently depending on the payload. Live bacteria are famously vulnerable: the reason probiotic manufacturing obsesses over delivery is that gastric acid and bile kill a large proportion of most strains. Soluble fibre, by contrast, does not care much — pectin and beta-glucan pass through acid essentially intact and would reach the colon in a plain capsule too. Which is why the delivery claim is much more load-bearing for a probiotic than for a fibre product.

How a delayed-release shell works

The trick is a pH-responsive polymer. Coatings in this family — methacrylic acid copolymers, cellulose acetate phthalate, hypromellose phthalate and similar — carry acidic groups that stay un-ionised and insoluble at low pH, then ionise and dissolve once the pH rises. Different grades are engineered to open at different thresholds, commonly somewhere between pH 5.5 and 7, which maps roughly onto the duodenum, the ileum or the proximal colon.

There are also non-pH approaches: time-dependent coatings that swell and rupture after a set interval, and colon-targeted systems that rely on bacterial enzymes to digest a polysaccharide shell. All of them are legitimate; all of them are also fiddly, because gastric emptying time and intestinal pH vary a lot between people, with food, and with medication.

A delayed-release claim is a statement about a coating's design. Whether that coating performed in a given product is a separate question, and it has an actual test.

The test that would settle it

Pharmacopoeial disintegration and dissolution methods for delayed-release solid dosage forms follow a standard shape: hold the product in simulated gastric fluid for a fixed period — two hours is the usual figure — and confirm that it has not disintegrated or released its contents. Then move it to a buffer at the target pH and confirm that it does release, within a specified window.

That is the sentence you are looking for on a label or a technical sheet: a statement that the finished capsule was tested to a recognised method and met the criteria. A phrase like “in internal testing the formula was observed to release in the colon within hours” is not that sentence. It may well be true. It is simply not verifiable from the outside, and a reader is entitled to notice the difference.

Reading a delivery claim in ninety seconds

What the label says	How much weight to give it
“Enteric coated, tested to USP disintegration for delayed-release”	Strong. A named method with pass criteria.
“Delayed-release capsule” with no method	Moderate. Real technology, unverified execution.
“Survives stomach acid” with no mechanism named	Weak. A benefit statement, not a specification.
“Patented delivery” with no patent number	Weak until you can look the number up.

Where FloraNew sits

FloraNew describes a delayed-release capsule built to pass through the stomach intact and open lower down, and cites internal testing rather than a published method. That puts it in the middle row of the table: the mechanism it describes is real and widely used, and there is no external evidence about this specific capsule.

The good news for a buyer is that the payload FloraNew's own ingredient sheets document — soluble fibres like oat bran and apple pectin — is the payload least dependent on the coating working perfectly. Fibre reaches the colon regardless. If the formula genuinely contained live probiotic strains, as the brand's FAQ claims, the delivery question would matter enormously and the absence of a strain name, a CFU count or a disintegration statement would be a much bigger problem. For more on that distinction, see prebiotic fibre versus probiotics.

Two practical questions follow from any delivery claim. The first is when you swallow the thing, because an empty stomach and a full one present a coating with very different conditions — the best time of day to take a probiotic works through that trade-off. The second is how to weigh delivery against everything else on a label, which is what our buyer's guide to judging strains, CFU, delivery and price is built to do.

Frequently asked questions