Comparison of taste and texture of Metamucil®, Volcolon® and psylium orange generic (WC2016-037)


Starting date: 01/11/2016

Study design

It is a double blind, randomized study.   


There will be 100 volunteers recruited. Recruitment will primary be among medical students. Volunteers will receive 25 euro for participation of the study.   

Inclusion criteria

healthy volunteers, age 18-70 years, in good health, able to understand the instruction and give informed consent.  

Exclusion criteria

gastrointestinal problems, swallowing disorders, rheumatic related diseases, known hypersentivity to the study medication.  


All volunteers will try the 3 different formulas. After swallowing the first formula, the mouth will be rinsed with water. Then the second formula will be tried, after rinsing the mouth again the third formula will be tried. Every time after tasting a formula, the questionnaire is filled in, before starting with the next formula. The maximum intake is 3 x 25 ml (75 ml). This is 37,5% of one dosage advised quantity of fiber. The sequence in which the formulas are tasted is randomized.  

The results concerning taste and texture will be noted on a form with a Likert 5- point scale (two different questions): 1 = very poor taste / unpleasant 2 = poor taste / unpleasant 3 = neutral 4 = tasty / pleasant 5 = very tasty / very pleasant  

Arbitrarily, a difference of 0.4-0.5 will be considered clinical significant. Statistical analysis is able to demonstrate a difference of 0.4 on the likert scale   

Preparations and dosage:

Each sachet needs to be solved in a glass of water. This matches (approximately) 200 ml. During the study the volunteers will taste 3 x 25 ml of water. This matches 37,5% of one dosage. The average intake of psyllium fibers is 1-3 sachets a day.  

Dosage if the different products: 

- Volcolon sugar free (Dutch name: Volcolon suikervrij): 1 sachet contains 4g powder o 980mg/g psyllium fibers x 4g per sachet=3.92 g psyllium fibers/sachet o So 25 ml contains 0.490 g psyllium fibers - Metamucil Orange: 1 sachet contains 3.4 g psyllium fibers o So 25 ml contains 0.425 g psyllium fibers - Psyllium Orange: 1 sachet contains 3.25 g psyllium fibers o So 25 ml contains 0.406 g psyllium fibers  

These three products are the most used products for each brand (Metamucil orange, Volcolon and generic orange). This leads to the greatest coverage of the three brands in the Netherlands. The volunteers will swallow 25 ml of each product, three in total. This leads to an intake of 1.32 g (0.490 g + 0.425 g + 0.406= 1.32 g) psyllium fibers. According to the Dutch Board of Health (in Dutch: Gezondheidsraad) the average intake of fibers should be between 30 and 40 g a day. So, the volunteers will swallow approximately 4% (3.3 – 4.4%) of the advised intake of fibers. Therefore, we do not expect any problems when the volunteers swallow these products.     

Statistical analysis 

Randomization by a statistical program will be performed for the sequence in which the volunteers will taste the preparations. All results will be analyzed and testes with the Friedman test. Additionally a Wilcoxon test can be performed when necessary. Considering an α of 0.05 and β 80% at a sample size of 100 persons, a difference of 0.4 can be demonstrated with the effect size of 0,13 (small = 0.01; medium = 0.06; large = 0.14).