Optimizing Bioavailability in Delivery Technology

Finished product manufacturers strive to provide consumers with dietary supplements that offer optimum health and value. In order to achieve these goals, the appropriate delivery system must be selected. When determining whether to formulate in a tablet, capsule or softgel, ingredient consideration, pill size and dosing compliance are important issues to consider. The chosen delivery system will have a significant impact on bioavailability, as supplement efficacy is highly dependent on how the nutrients are delivered to the body.

Bioavailability indicates the rate and extent to which a bioactive ingredient is absorbed intact from the gastrointestinal (GI) tract into the bloodstream to become available for use or storage in the body. Absorption into the circulatory system is an important part of delivery. Bioavailability depends on how rapidly a particular form releases the nutrient into the biological fluids, or how rapidly the nutrient may enter a cell. Low bioavailability is most common with oral dosage forms of poorly water-soluble, slowly absorbed nutrients. Not surprisingly, absorption is most rapid from liquid solutions and decreases in this order: solutions, suspensions, capsules, compressed tablets and coated tablets.

Many different factors can affect bio availability; one key factor is disintegration time. The U.S. Pharmacopeia (USP) has time limit standards set for disintegration, which refers to a supplement’s ability to break apart and fragment into small particles. Most products should disintegrate within 30 minutes to one hour, except for time-release products. Disintegration time can be affected by variables such as part iclesize, crystalline form, disintegrators and/or lubricants used, compression force used to press tablets, etc. Reputable manufacturing companies will comply with USP standards for disintegration and/or dissolution.

Dissolution is the ability of a supplement to dissolve in solution, usually expressed as a percentage or rate. A prerequisite to absorption is dissolution, which determines the availability of the nutrient for absorption. Nutrients are absorbed in a specific region of the GI tract once in solution. Absorption can be controlled by manipulating the formulation. For example, reducing particle size increases the nutrient’s surface area, thus increasing the rate and extent of absorption.

Another consideration is the use of excipients, the inactive ingredients added to a formula to give the desired consistency and form, and assist in manufacturing. Although excipients don’t contribute significant health benefits, their inclusion is essential, and their presence can influence absorpt ion.

Excipients can be classified according to their function and some serve multiple functions—binders, disintegrators, fillers (diluents), colorants, flavors, sweeteners, preservatives, lubricants, gliders (flow enhancers), coating agents and emulsifying agents. Many herbs and other ingredients clump together and don’t mix well unless excipients are added. Reputable companies only include excipients necessary for efficient manufacturing support the delivery system. These manufacturers also fully disclose all ingredients used in a formula.

Nutrient form, i.e. the biochemical makeup of the compound, can also affect bioavailability. Minerals, in particular, come in different chemical forms (chelated, colloidal, etc.). Certain forms are better absorbed than others, and nutrients are more bioavailable when necessary co-factors are present in the formula. Various ingredients have differing characteristics such as solubility in lipids or water, small or large particle size, and form—granular or crystalline, for example. Different delivery systems such as tablets, two-piece hard shell capsules, and soft gel capsules have characteristics that lend themselves to optimizing the delivery and absorption of various ingredients.

There are other variables to consider as well. Bioavailability varies from person to person. Everyone has a unique biochemical makeup, which will affect how nutrients get absorbed. It depends on the individual’s nutritional needs, the time of day a supplement is taken, the presence of drugs that could have potential interactions, whether disintegration occurs in the body, duration in the GI tract, and efficacy of absorption both in the GI tract and at the cellular level. These factors are outside of manufacturers’ control, although education about proper ways to take supplements is crucial.

Bioavailability plays a critical role in ensuring the proper utilization of supplements. With these factors in mind, finished product manufacturers can work with a product development team to determine the best delivery system for a particular ingredient or formula. Ultimately, the function of a delivery system would be to improve bioavailability and enhance absorption. 

Ron Udell has been involved in the nutritional supplement industry for over 20 years. He is currently the president of Soft Gel Technologies Inc. (SGTI) as well as executive vice president of OptiPure Brand Chemco Industries. Udell currently serves on the Natural Products Association Compli Committee and is a member of the American Herbal Products Association (AHPA) and the Drug, Chemical and Associated Technologies (DCAT) association.