An enteric capsule is built to survive the stomach’s acid and release its contents further down the digestive tract, which matters for a small group of actives that either break down in acid or work better delivered past the stomach. It is also a format where the line between a food ingredient and a medicine ingredient is stricter than for most other capsule types, because some acid-resistant coating materials are used in both.
This guide covers what makes a capsule acid-resistant, which coating materials are permitted as food in Japan, and which actives are the strongest candidates for an enteric capsule.
Health supplements are foods, not medicines, and are not a substitute for medical treatment.
💬 Considering an enteric capsule for a Japan-made product? We confirm the coating’s food-additive status before quotation. See Japan-made supplement OEM.
What makes a capsule acid-resistant
An enteric coating stays intact at stomach pH (around 1.5–3.5) and dissolves only at the higher pH found further down the digestive tract, so the capsule survives the stomach and opens later than a standard capsule.
This differs from a standard hard capsule or softgel, which is designed to start dissolving in the stomach. An enteric capsule can be built two ways: as a two-piece hard capsule shell manufactured to be inherently acid-resistant, or as a standard capsule that is coated afterwards with an acid-resistant film. Either way, the coating (or shell polymer) is the part of the specification that decides whether the capsule actually survives gastric conditions in practice, not just in theory.
Coating materials and their status
Shellac, zein and cellulose-derivative polymers such as HPMC-AS are the main acid-resistant coating options, and their status as a food ingredient versus a pharmaceutical excipient differs by material and by country.
| Coating material | Source | Status as food in Japan and the EU | Notes |
|---|---|---|---|
| Shellac | Resin secreted by the lac insect | EU: approved food additive E904, re-evaluated by EFSA in 2024 with an extended approved use in foods for special medical purposes as a tablet coating. Japan: long-standing use as a food glazing agent | One of the more established acid-resistant food coatings; also used as a confectionery glaze |
| Zein | Corn protein | US: GRAS-recognised. EU and Japan food-additive status for zein needs confirming for your exact use before you specify it | Plant-protein-based film former, sometimes used with shellac in combination coatings |
| HPMC (plain, unmodified) | Plant cellulose | Japan: designated food additive, with no specific use standard restricting what it may be used in. EU: permitted food additive (E464 methylcellulose/HPMC group) | The base cellulose polymer; not itself acid-resistant in its unmodified form |
| HPMC-AS / HPMC-P (acetate succinate or phthalate esters, “HPMC-AS”) | Modified cellulose, esterified for acid resistance | Well established as a pharmaceutical excipient in the Japanese, US and European pharmacopoeias for enteric coating. Confirm with the factory whether the specific grade is approved as a food ingredient, or only for pharmaceutical use, before specifying it for a food-labelled product | The acid-resistance comes from the acetate-succinate or phthalate modification, not from plain HPMC |
The practical takeaway is that a coating material’s use in a pharmaceutical enteric tablet does not automatically mean the same exact grade is approved for a food-labelled supplement — the food-additive status has to be checked for the specific grade and market, which is exactly the kind of check a factory quotation should include before production, not after.
💬 Specifying an enteric coating and unsure of its food-additive status in your target market? Send us the coating and market and we confirm it before quotation.
Which actives benefit from an enteric capsule
Actives that are unstable in stomach acid, that irritate the stomach lining, or whose absorption or activity improves when released further down the gut are the strongest candidates for an enteric capsule.
| Active type | Why an enteric capsule can help |
|---|---|
| Certain probiotic (lactic acid bacteria) strains | Some strains lose viability in stomach acid; an enteric capsule can improve the number of live organisms that survive to the intestine — strain-dependent, not a universal benefit |
| Lactoferrin | An iron-binding milk protein that can be degraded by stomach acid and pepsin; enteric delivery is one formulation approach used to protect it before it reaches the intestine |
| Certain enzyme or peptide actives | Proteins and peptides in general are vulnerable to acid and enzymatic breakdown in the stomach |
Whether an enteric capsule measurably improves the outcome for a given strain or active depends on the specific ingredient and its own stability data — not every probiotic strain needs enteric protection, since some are naturally acid-tolerant, so this is a decision to make with the ingredient supplier’s own data rather than by default. See our lactic acid bacteria guide and lactoferrin guide for more on each ingredient’s own formulation considerations.
The check that comes first
Every coating and shell material must be permitted in foods in Japan, or a Japanese factory cannot make the product as a food supplement.
Because some acid-resistant coatings sit closer to the food/medicine boundary than other excipients, an enteric capsule specification needs this check earlier than most: confirm the exact coating grade’s status as a food ingredient in Japan (and in your own market) before committing to a formula, not after a trial batch is made. See the Japan-made supplement OEM page, and compare with our hard capsule shell and softgel shell guides for the other capsule-material decisions in a formula like this.
Before you ask for a quotation
A factory can quote an enteric capsule accurately once the active, coating material and target markets are fixed.
- Active ingredient and any existing acid-stability or bioavailability data
- Preferred coating approach: inherently acid-resistant shell or post-coated capsule
- Coating material and grade, confirmed as food-approved in your markets
- Capsule size and fill type
- Countries you will sell in
💬 Ready to specify an enteric capsule made in Japan? Send us the active ingredient and target markets and we confirm the coating before quotation.
Frequently asked questions
1. Does every probiotic supplement need an enteric capsule?
No. Acid tolerance is strain-specific — some lactic acid bacteria strains survive stomach acid well without special protection, while others benefit from an enteric capsule. Check the strain’s own published stability data rather than assuming enteric delivery is required.
2. Is shellac vegetarian?
No. Shellac is secreted by an insect (the lac insect), so a shellac-coated capsule is not suitable for a strict vegetarian or vegan claim even though it is a widely approved food and pharmaceutical coating material.
3. Can a pharmaceutical-grade enteric coating always be used in a food supplement?
Not automatically. Some enteric coating polymers are well established as pharmaceutical excipients but need a separate check for food-additive approval in the specific grade and market before they can be used in a food-labelled product.
4. What pH does an enteric coating need to survive?
It needs to stay intact through stomach pH, roughly 1.5 to 3.5, and then dissolve at the higher pH found further along the digestive tract — the exact release point depends on the polymer chosen.
5. Does lactoferrin always need enteric protection?
Not always — it depends on the formulation goal and the product’s own stability data. Enteric delivery is one approach used to protect lactoferrin from stomach acid and pepsin, but it is a formulation decision to confirm against your specific product, not a default requirement.
Sources: EFSA Journal 2024, “Re-evaluation of shellac (E 904) as a food additive and a new application on the extension of use of shellac (E 904) in dietary foods for special medical purposes” (efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2024.8897; pmc.ncbi.nlm.nih.gov/articles/PMC11292212); shellac’s status as a US and EU approved food additive and listing in pharmacopoeias (sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/shellac, cross-checked against the EFSA re-evaluation above); Japan Food Sanitation Act Enforcement Regulation, Annex 1 (designated food additives, including hydroxypropyl methylcellulose) (laws.e-gov.go.jp); Consumer Affairs Agency, Specifications and Standards for Food Additives, Section F use standards, with no specific use standard for HPMC (caa.go.jp); HPMCP/HPMCAS pharmacopoeial (Japanese, US, European) status as an enteric coating excipient (setylose.com/en/products/healthcare/hpmcp; shinetsu.co.jp/en/products/functional-materials/hpmcp-2). Checked on 12 October 2026.