The three common shells

Gelatin

The traditional capsule material, and still the most common. Gelatin is a protein made by partially hydrolyzing collagen, sourced from animal hides and bones, and in practice almost always bovine or porcine.

It is what makes a two-piece capsule snap together and what makes a softgel a softgel. It dissolves reliably and has been used for well over a century, and manufacturers like it because it performs consistently.

The problem, for a large number of people, is the one the word "gelatin" does not answer: which animal.

HPMC (hypromellose)

Also written hydroxypropyl methylcellulose. A plant-derived cellulose material, permitted as a food additive at 21 CFR 172.874 as an emulsifier, film former, protective colloid, stabilizer, suspending agent or thickener.

This is the standard vegetarian and vegan alternative, and it is what "vegetable capsule" or "veggie cap" almost always means. It is made from plant cellulose, typically wood pulp or cotton.

HPMC capsules hold up better than gelatin in humid conditions and are less prone to becoming brittle when they contain hygroscopic ingredients. They are also more expensive, which is why they are not universal.

Pullulan

A polysaccharide produced by fermentation. FDA issued a "no questions" letter in response to a GRAS notice for pullulan in August 2002.

Pullulan capsules are plant-based and fermentation-derived, with very low oxygen permeability, which makes them attractive for ingredients that oxidize. They are the most expensive of the three and you will see them mainly on premium products.

The disclosure gap

Ingredients must be listed by their common or usual name. "Gelatin" is the common or usual name. No requirement was found, in the labeling regulations or in FDA's labeling guidance, that the animal source of gelatin be disclosed.

So a label reading "Other ingredients: gelatin, magnesium stearate, silicon dioxide" can be perfectly ordinary and still not tell you whether the gelatin came from cattle or pigs.

For someone avoiding pork specifically (and that is a great many people), the ingredient list cannot answer the question. Neither can "beef gelatin" be assumed from silence, and neither can "not pork."

What to do about it

Look for an explicit statement. Responsible manufacturers who know their customers care will often say "bovine gelatin" or "porcine gelatin" outright. When a label does say, believe it, because that is a labeled ingredient statement.

Look for a certification mark. A kosher certification (various agencies, various symbols) or a halal certification addresses the source directly, because that is what those certifications are for. This is the most reliable route if it matters to you religiously: the certifying body has looked at the supply chain.

Look for "vegetarian capsule," "vegetable capsule," "HPMC" or "pullulan." These sidestep the question entirely. If the shell is cellulose or pullulan, no animal is involved.

Ask. Every supplement label has to carry a domestic contact point. "What is the source of the gelatin in your capsules?" is a simple question with a simple answer, and a company that cannot answer it quickly has told you something about how well it knows its own supply chain.

Softgels are a separate case

A softgel, the squishy one-piece capsule used for fish oil, vitamin D, vitamin E and other oil-based ingredients, is usually gelatin with a plasticizer, most often glycerin.

Plant-based softgels exist, using modified starches or carrageenan-based systems, but they are less common and generally more expensive. If you avoid animal products and take an oil-based supplement, the softgel is the place to check most carefully, because the default is animal-derived and the alternatives are not universal.

The shell of a softgel may also carry colors and opacifiers. Titanium dioxide is commonly used to make a shell opaque, which protects a light-sensitive oil. Those appear in the Other ingredients list.

Allergens: what is and is not covered

Nine substances are major food allergens in the United States requiring declaration: milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat, soybeans, and sesame, which took effect January 1, 2023.

Gelatin is not on that list. Bovine or porcine gelatin is not a major food allergen and does not trigger allergen labeling. Gelatin allergy exists but is uncommon, and the labeling system does not treat it as a major allergen.

Fish-derived gelatin is a more complicated question: "fish" is a major allergen, and FDA has historically handled certain fish-derived ingredients through exemption petitions. If you have a fish allergy and are considering a product whose shell might be fish-derived, that is a question for the manufacturer and for your clinician rather than something to settle from an ingredient list.

Soy can appear in supplements as a carrier, an emulsifier or in a softgel formulation. It is a major allergen, so it must be declared. Scan the Other ingredients line.

Does the shell affect the product?

Mostly, no. It is a container that dissolves. But there are three places it makes a practical difference.

Moisture. Gelatin is more sensitive to humidity than HPMC. In a hot, humid environment (or a bathroom cabinet), gelatin capsules can soften, stick together or become brittle. If your capsules have ever fused into a clump, humidity and a gelatin shell are the likely explanation.

Oxidation. For oils, the shell's oxygen permeability matters. This is one reason pullulan and certain specialty shells are used for omega-3 products, where oxidation is a real quality issue.

Disintegration. A capsule has to open. This is not usually a problem, but it is one of the things a quality certification tests. USP's Verified program, for example, includes a standard that the product "will break down and release into the body within a specified amount of time." That is a real failure mode, and it is worth knowing that someone checks for it.

If you want to avoid the question entirely

Capsules are not the only delivery form, and some of the alternatives sidestep the shell question altogether.

Tablets have no shell. They are compressed powder, held together by binders, and they contain no gelatin unless something else in the formula does. For anyone avoiding animal products, a tablet is often the simplest answer, though it comes with a longer list of other mechanical ingredients, and some people find tablets harder to swallow.

Powders have no shell either. You are buying the ingredient and mixing it yourself, which also means you can see and smell what you are taking. The trade-offs are taste, measuring, and the flavoring system that usually comes with palatability.

Liquids and tinctures likewise. Check the carrier (alcohol, glycerin, oil) and note that glycerin can be animal- or plant-derived.

Gummies are usually gelatin-based, though pectin-based versions are common and are plant-derived. If you avoid gelatin, pectin gummies exist and are labeled as such.

So "I keep kosher and this product only comes in a gelatin capsule" is a smaller problem than it looks. The same ingredient is often available in a form that never raised the question.

Why vegetarian capsules cost more

It is a fair question, and the answer is not margin.

Gelatin is an inexpensive byproduct of the meat industry, produced in enormous volume with a century of process refinement behind it. HPMC is manufactured from purified plant cellulose through a multi-step chemical process, and pullulan is produced by fermentation, which means feeding an organism, running a culture and purifying the output.

The result is a real cost difference at the raw material stage, which is why gelatin remains the default and why plant-based shells cluster on products aimed at buyers who specifically want them.

There are also technical trade-offs in both directions. HPMC handles humidity better and is less prone to becoming brittle with hygroscopic fills. Gelatin has a longer track record and dissolves very predictably. Neither is simply superior. They are different materials with different strengths, and a manufacturer choosing gelatin is not necessarily cutting a corner.

A word on kosher and halal marks

If the shell matters to you religiously, the certification mark is the reliable route, but it helps to know roughly what these marks involve, because they are not all the same.

Kosher certification is issued by a number of independent agencies, each with its own symbol. The agency examines ingredients and, typically, the production facility. For gelatin specifically, the requirements are strict and the source is exactly what is being examined.

Halal certification works similarly, with several certifying bodies and a specific focus on animal-derived ingredients and their source.

Two practical notes. First, these marks are product-specific, not brand-wide: a company with one certified product has not certified the range. Second, as with any certification, the mark is only as good as the body behind it. The major agencies publish their certified-product listings, and a mark you can look up is worth more than one you cannot.

Other things people avoid, and where they show up

Carrageenan. A seaweed-derived thickener, permitted at 21 CFR 172.620. Some people prefer to avoid it. If it is present, it appears in the ingredient list by name, because the regulation requires it be declared as "carrageenan."

Titanium dioxide. Used to make shells opaque. As of September 2026 it remains permitted in the United States under 21 CFR 73.575, limited to one percent by weight, while being under active FDA review with a petition pending to revoke the listing. Covered in more detail in the article on other ingredients.

Glycerin. Used as a plasticizer in softgels. It can be animal- or plant-derived, and like gelatin, the source is not something the ingredient name tells you.

Magnesium stearate. Can be sourced from animal or vegetable fat. Most commercial supply is vegetable-derived, but again, the label will not usually say. If it matters to you, ask.

Several common supplement ingredients can be either animal- or plant-derived, and the ingredient name does not distinguish. Gelatin, glycerin, stearates, and some vitamin D3 sources all fall into this category. For anyone with a dietary or religious restriction, the certification mark and the manufacturer's answer are the two reliable routes, and the ingredient list alone is not.

A note on vitamin D3, since it comes up constantly

Vitamin D3 (cholecalciferol) is commonly described as being produced from lanolin, which comes from sheep's wool. Where that is the source, it makes the D3 unsuitable for vegans, though it is generally acceptable to vegetarians since no animal is killed. As with gelatin, the ingredient name does not tell you the source, so this is a question for the manufacturer.

A plant-based D3 derived from lichen exists and is used in vegan products. Vitamin D2, ergocalciferol, is derived from yeast or fungi and is plant-based.

Products intended for vegans will normally say so explicitly, because the manufacturer knows it is the reason someone is reading the label.

What to check, in order

1. Read the Other ingredients line. Look for "gelatin," "hypromellose," "HPMC," "pullulan," "vegetable capsule" or "vegetarian capsule."
2. If it says gelatin and the source matters to you, do not assume. Look for an explicit bovine or porcine statement, or a kosher or halal mark.
3. If it is a softgel, check harder. The default is animal-derived.
4. Scan the whole line for allergens, especially soy and fish.
5. Ask the company if the label does not resolve it. The contact information is there by law.
6. For a religious restriction, prefer a certification over a manufacturer's assurance, because certification means someone independent examined the supply chain.