Classic gelatin capsules are made from collagen, which must be sourced from the skin, bones, and connective tissues of an animal. Typically, collagen products are sourced from beef-industry cattle, though it is possible to obtain collagen from other animal sources. While this practice is standard and fine for the average customer, individuals following vegan or vegetarian diets, people with gelatin allergies, or people that do not consume animal products for religious purposes may all avoid products that utilize gelatin. In the past decade, many manufacturers of gelatin capsules have updated their supply chain to make their capsules both Kosher and Halal friendly, a critical move for companies that wish to compete in the global market.
Vegetable capsules are made from hydroxypropyl methylcellulose, a material derived from cellulose from the walls of plant cells. Common plant sources for vegetable capsules include soy, pine, and fermented tapioca, so most vegetable capsules will be gluten free. Vegetable capsules are suitable for a wide range of people with dietary restrictions, only limited if a customer has a specific allergy to one of the ingredients, which is rare. Vegetable-based capsules have become more readily available in recent years, due to their appeal to a wider customer base and versatility in application.
Gelatin capsules come in two forms, hard and soft. Hard gelatin capsules are the traditional two-piece capsules that usually come to mind when imagining a pill. These capsules are good for dry substances but cannot hold liquids. Soft gelatin capsules are one-piece capsules that are designed to hold medications suspended in oil. Both kinds of gelatin capsules dissolve quickly in the stomach and thus are poorly suited for medications that require controlled release. Neither is suitable for compounds that need to be suspended in liquids other than oils.
Vegetable capsules have the potential to be more versatile than gelatin capsules, depending on the grade of hydroxypropyl methylcellulose used in manufacturing. “Vegetable capsules can be designed to withstand stomach acid for controlled release in different parts of the digestive tract or designed to dissolve slowly for extended release of medication over a longer period of time,” according to CapsuleDirect. Even basic grades of vegetable capsules are suitable for a range of dry, semi-solid, and gel-based contents. Vegetable capsules can be two-piece, like traditional hard gelatin capsules, or more complex for specialized release.
For either material, two-piece hard gelatin and vegetable capsules can be purchased empty and filled with any contents that will not dissolve the capsule, while one-piece soft gelatin capsules and controlled release vegetable capsules must be filled at the time of manufacture in most cases. Both types of capsules are widely available in a variety of formulations.