Fiber Study
Logo Image
"The purpose of this study is to determine if dietary fiber increases overall gut health"
Age: 18-45
Healthy Volunteers: Yes
Keywords: dietary fiber, healthy volunteers, healthy diet, gut microbiome, gut health, nutrition, cholesterol, HDL
Type: Dietary Intervention Clinical Trial
20 Participants
The purpose of this study is to investigate whether consuming a packet of fiber powder per day changes the composition and/or function of the gut microbiota and high density lipoproteins (HDL) or good cholesterol.

If you take part in this research, you will be responsible to keep your normal diet with low fiber content, defined as less than approximately 15g/day, or equivalent to approximately 4 servings of fruit, vegetable, legume, or whole grain combined per day.

You also need to attend all the visits until the endpoint of the study and provide all the questionnaires and biological samples as instructed under your consent.
This study requires
  • Study Visit: The study will be carried out at the Ragle Human Nutrition Research Center on the UC Davis campus. The address is 1283 Academic Surge, University of California, Davis, in Davis CA 95616. If you decide to participate in this study and are found to be eligible, you will first be asked to schedule a consent visit. We will explain the study to you and answer any questions you have.

  • 12-hour overnight fast: On your clinic visit, you will be asked to arrive at the Ragle Human Nutrition Research Center between 7:00-9:00 am after a 12-hour overnight fast (no food or beverage, except water) from 7:00-9:00 pm the night before.

  • Blood Draw: You will have a blood draw of about 3.5 tablespoons (50.5 mL/month). Blood draw will be conducted 4 times throughout the study.

  • Stool Sample Collection: You will be given stool collection kits to be used throughout the course of the study. Stool collection kits are used to collect samples of bowel movements at the beginning and end of each study arm for microbiome analysis. Stool samples need to be collected 7 times throughout the study.

  • Dietary Fiber/Placebo Consumption: The Dietary Fiber and/or Placebo (no fiber) will be consumed in powder form and includes mostly dietary fiber (resistant starch, fructo-oligosaccharide, sugarcane fiber, and inulin), rice flour, xanthan gum, and fruit powders. The Dietary Fiber and/or Placebo packet will contain a total of 12 g/serving of powder, which you will be asked to consume mixed in a beverage of your choice (one packet per day).

  • Diet Record: You will be given a 3-day food diary to record your food and beverage intake on 3 separate days 7 times throughout the study period along with tips on how to keep a consistent and accurate food record.

  • Questionnaires: Bristol stool scale and bowel movement questionnaire, health questionnaire

  • Anthropometric Measurements: Height/weight/blood pressure measurement

Who can participate

Inclusion Criteria:

  • Healthy male and female adults 18-45 years old

  • BMI: 23.0-32.0 kg/m2 (slightly “overweight”)

  • Current diet includes low quantity of fiber, defined as less than approximately 15g/day, or equivalent to approximately 4 servings of fruit, vegetable, legume, or whole grain combined per day, and determined using diet recall.

  • Willingness to consume dietary fiber drink daily for 4 weeks, and a placebo drink for 4 weeks, as well as a 4-week washout period with no intervention.

  • Willingness to provide diet records, blood samples (4 total collections) and stool samples (self-collected) biweekly for the duration of the study (7 total collections).

  • Willingness to adhere to “diet control period” biweekly (eating the same, self-selected foods and abstaining from alcohol each day for 3 days prior to each stool collection/blood draw).

  • General bowel movement frequency of at least once every three days and maximum of two times per day.

Exclusion Criteria:

  • A plan to or desire to lose weight

  • Smoker

  • Anemia and difficulty with blood draws

  • Currently, within previous 6 weeks of the study, or during the study taken probiotic or prebiotic formulations (food products considered to have these properties in their natural or unadulterated forms are acceptable).

  • Antibiotic use during the study or within 6 months prior to study commencement.

  • Medication: statins, blood pressure medications, other prescription medications

  • Pregnant, planning to be pregnant or breastfeeding at any point during the study or study enrollment.

  • Start or change in use of hormonal birth control in the last 6 months or plans to change or start use of hormonal birth control during the study period

  • Allergies to any prebiotic or placebo ingredients – Prebiotic ingredients: Resistant Tapioca Starch, Fructooligosaccharide, Sugarcane Fiber, Agave Inulin, Gum Arabic, Xanthan Gum, Apple Powder, Raspberry Powder, Blueberry Powder / Placebo Blend: Rice Flour, Xanthan Gum, Grape Powder, Plum Powder

  • Illness (flu/cold in the last two weeks)

  • Documented chronic diseases including diabetes, thyroid disease, metabolic syndrome, hypertension, cancer, or previous cardiovascular events

  • Irritable bowel syndrome, celiac disease, or any inflammatory bowel disease (including Crohn’s Disease, and/or Ulcerative colitis)

  • Any immunosuppression symptoms at any point during the study or study enrollment

  • Consumption of >1 alcoholic drink/day or frequent binge drinking (>3 alcoholic drinks in one episode) > 1 day per month

  • Plans to change or recent significant changes in lifestyle (e.g. diet or exercise routine, major travel, etc)

  • Recent weight fluctuations (greater than 10% in the last six months)

  • Regular use of over-the-counter pain medications (>1/week)

  • Taking prescription lipid medications (e.g. statins) or other supplements known to alter lipoprotein metabolism such as isoflavones

  • Recent medical procedure such as surgery within the last 6 months

  • Any changes in the above during the course of the study

Benefits and risks of participating
We cannot promise any benefits to you as a result of taking part in this research study.

Study personnel will discuss the risks associated with taking part in this research study. Potential risks include the possibility of discomfort or bruising during a standard blood draw, and the possibility of bloating or other temporary gut discomfort.
If you agree to take part in this research study, we will compensate you $200 in gift cards for your time and effort.
PDF Docs
Study duration and period
We expect that you will be in this research study for up to 13 weeks total. This includes the study procedures which last for 12 weeks, and a week beforehand during which you will complete a consent, enrollment, and questionnaires.
Recruitment period
From April 1, 2019 to Sept. 9, 2019
Jea Woo Kang
(415) 889-9540 (530) 752-3973

Have any questions or want to learn more? Leave your contact details below and the research team will reach out to you.


Send SMS with Study Info:

SMS Sent!

Share Study Info via Email:

E-mail Preview