Improving constipation by stimulating fiber intake using personalized dietary advice

- Age *18 years and <55 years.
- BMI < 30 kg/m2
- Has constipation-related complaints. For our study, subjects has to fulfill
the following criterion: response <6 to the question *how satisfied are you
with your stool pattern*, which is rated on a visual analog scale (VAS) from
1-10, together with at least one of the following criteria:
1. Habitual stool form of Bristol stool type 1-4 or
2. *4 defecations per week
Note: these criteria are less stringent than the official *constipation*
definition [35], because we preferably want to include participants that do not
use laxatives (yet), and we assume that in this *mild constipation* group
increasing fiber intake can have the most beneficial effects. Moreover, we
chose not to use the Rome IV criteria as definition of constipation-related
complaints, due to the proven inability to distinguish functional constipation
from Irritable Bowel Syndrome [2]. If there are sufficient eligible
participants, the participants with the lowest stool frequency will be selected.
- Relatively low fiber intake, for females <26 grams and males <33 grams, as
assessed by a fiber screening questionnaire which was validated in the previous
study. When enough eligible participants are available, we will choose the
participants with the lowest dietary fiber intake.
- Living in the surroundings of Wageningen (max. 50 km). Subjects have to visit
the research facilities of Human Nutrition a few times for weighing and to
drop-off of fecal samples, therefore it is logistically not feasible if
subjects life far away. If recruitment is unsuccessful, subjects who live
further away will be included and samples will then be collected by researchers
or by a parcel service.
- In possession of computer (with Chrome browser available) for the PDA, and a
mobile phone with android *4.4 or iOS system *9 to use apps. In general, phones
which are bought *2013 are compatible with the apps. And independently able to
install applications on a phone and log-in on to a website, with the use of a
manual and video provided by the researchers.
- Signed informed consent.

- Subjects with a disease that may interfere with the personal dietary advice
or outcomes, such as a known autonomic disorder, inflammatory bowel disease,
coeliac disease, cancer, dialysis patients, chronic kidney failure, depression
or hypothyroidism.
- Currently following strict diet and unwilling or unable to change; for
example a gluten free diet or a *crash diet* using meal substitutes.
- Use of medication that can interfere with the study outcomes, including
diuretics, antidepressants, codeine, antibiotics or fiber supplements.
Preferably laxative use is excluded, but if recruitment is hurdled by this, we
at least exclude specific laxatives like resolor, relistor and constella. These
are laxatives who have a significant impact on bowel movements, and are only
available on prescription. Osmotic (over the counter available) laxatives will
be included if recruitment is difficult. Subjects will then be asked to keep
their laxative use stable or reduce, but not to increase usage from their
habitual pattern (unless necessary, but then report it to the researchers).
Moreover, additional questions regarding laxative usage will be included to
estimate the effect of laxatives on stool pattern.
- Female subjects: currently pregnant or breastfeeding, or intending to become
pregnant during the study, as this can affect stool patterns and wellbeing.
- Are simultaneously participating in another study.
- Unwilling or unable to fulfil the study criteria.