Weighing the Benefits, Limitations of Soft Gels

Weighing the Benefits, Limitations of Soft Gels

by Arup Mukherjee

Maximum Absorption, Easy to swallow, Shelf stable, Hermeticallysealed, Pilfer-proof ... These are just some of the claims being toutedby purveyors of nutritional supplements. The importance of optimum deliverysystems for nutrients and botanicals has been realized by the dietarysupplement industry. This has led to increased demand for reformulation ofexisting products into a soft gel dosage form. But as with all dosage forms,soft gelatin capsules have certain benefits and limitations.

Exploring the Advantages

Perhaps the most widely recognized benefit of soft gel technology is itspotential to enhance nutrient bioavailability. Productefficacy/performance is directly dependent on the amount of nutrient actuallyabsorbed through the gut into the bloodstream. Soft gel formulation optionsprovide the means to enhance the bioavailability of poorly absorbed nutrients byutilizing various stabilization and/or micronization techniques. It is in thecontext of poorly soluble nutrients such as coenzyme Q10 (CoQ10), variousherbal extracts or carotenoids that soft gel technology offers the potentialto play a key role in enhancing product effectiveness.

The enhanced bioavailability is part and parcel of the soft gel productionprocess. Soft gels are composed of two main partsan outer coating or shell,and the inner materials containing the active ingredient, known as the fill.Soft gel technology requires the fill be in the form of a suspension, liquid orpaste. This enables product formulators to utilize a variety of creativeformulation techniques in order to enhance a nutrients bioavailability.

For example, a formulator may treat a hydrophobic nutrient with asolubilizing or emulsifying agent (e.g., lecithin, phosphatidylcholine) toincrease its solubility, and thereby improve its bioavailability. Many of thesetechniques are not possible when working with solid dosage forms. Because ofthis, soft gels as a dosage form are uniquely effective in encapsulatinglipid-based molecules and enhancing the bioavailability of substances with poordissolution rates.

Also, the gelatin shell, which encapsulates the active ingredients, is aprotein that is easily digested by enzymes in the stomach. Hence, the physicalbreakdown of soft gels in the body is guaranteed. It is only then that the morecomplicated issues of bioavailability, discussed above, come into the picture.

Soft gels are the only existing form of encapsulation that is hermeticallysealed. This characteristic offers a variety of benefits. First, theingredients sealed within the soft gel are protected from oxygen. This isparticularly important for substances such as fish oil and flaxseed oil, whichhave a tendency to become rancid. The air-tight nature further offers productformulators the option of developing fill compositions that help increase thestability of the active ingredients. Moreover, the gelatin shell often containsagents that make it opaque, protecting the contents from light.

Because the fill is completely encapsulated, creating a hermetically sealedunit package, soft gelatin capsules are inherently tamper-evident. Anypuncture on the surface of the capsule would permanently damage the capsule,making the tampering clearly evident.

Unlike powder-filled capsules and tablets in which a lack of homogeneity inthe physical mixture can result in inconsistent amounts of the activeingredients from pill to pill, soft gel formulations ensure contentuniformity. Fill weights are precisely measured, and for those ingredientsthat need to be suspended in the fill, a suspending agent is added. This createsa homogenous blend, which translates into uniform distribution of activeingredients.

Finally, soft gel encapsulation may enhance product marketability.Tailored appearance (shape, color, size, etc.) of the soft gel to reflect theproduct or target an audience offers special product differentiation. Productidentification is also available by branding logos or designs directly on thecapsules. Laser etching is also available, which eliminates the need forunnecessary dyes and coloring agents. Lastly, the visual appeal of the finishedsoft gel capsule offers a sense of safety, stability and elegance to consumers.

Market research has also shown consumers perceive soft gel capsules as moreeffective. Certainly, the smooth surface and texture of soft gelatin capsulesmakes them easier to swallow. And the unpleasant tastes and odors inherent inmany ingredients (e.g., fish oil) can be effectively masked using a variety offlavoring agents.

Considering the Limitations

The major component of the capsule shell is gelatin, which is obtained bypartial hydrolysis of collagen derived from animals. This raises bioenvironmentalconcerns and may negatively affect consumer sensibility. When consideringthe increasing number of vegetarians, consumers adhering to kosher or halalrequirements, andperhaps most pressingthe growing concern over diseasestransmitted through animals such as bovine spongiform encephalopathy (BSE or madcow disease), the use of gelatin to encapsulate nutritional supplements seemsto be a significant drawback.

To address these concerns, efforts are being made in the industry to developvegetarian alternatives. These include starch, cellulose (from wood pulp) andcarageenan (extracted from seaweed). At this point in time, however, thealternatives are more costly than traditional soft gel encapsulation. Researchand development continues on this front.

Next, soft gel manufacturing is a semi-automatic process requiring constantoversight. End product quality relies heavily on skilled, welltrained andknowledgeable machine operators. Processing of the correct formulation ofspecified shell and fill compositions is more a craft than an automatic process.

The complex, sophisticated and sensitive nature of this production process,where there is little room for error, results in high installation andmaintenance costs for the manufacturer. Furthermore, the relatively slow rate ofproduction makes errors much costlier.

Additionally, the sensitivity of gelatin demands the strictest of controlsover temperature and humidity settings. The capsule shell is composed ofgelatin, water and a plasticizer such as glycerin. From manufacturing topackaging to storage, this requirement has to be met for the product to remainstable and meet quality standards. Therefore, soft gels are not the ideal dosageform to be produced in extreme climates. The gelatin shell may physicallydecompose in hot and humid climates; in freezing temperatures, the crystals mayenlarge, leading to decreased bioavailability.

The characteristics of the gelatin shell limit the kinds of fill formulationsit can encapsulate. Any ingredient that could dissolve the gelatin shell cannotbe used. For example, highly acidic or water-containing molecules cannot beencapsulated within a gelatin shell. Furthermore, fill formulations are limitedto only those therapeutic ingredients and solvents or suspensions that arecompatible with each other. And because this method of production deliversactive ingredients in the form of suspension, solution or paste, this excludespowder formulations from this method of encapsulation.

Arup Mukherjee is a project administrator for Westbury, N.Y.-based TishconCorp. (www.tishcon.com), a producer of softgels and supplier of coenzyme Q10 (CoQ10).