Citrus Beverages and Gastrointestinal Function

The Effect of Citrus Beverages on Gastrointestinal Function in Healthy Adults: a Randomized, Double-blind, Controlled Clinical Trial

The purpose of this study is to evaluate the effect of daily intake of orange pomace on gastrointestinal function as measured by stool frequency. Additional outcomes will include aspects of digestive health, diet quality, and fasting blood glucose and lipid concentrations. Possible explanations for the mechanism of the pomace will be explored in microbial ecology analyses.

In this randomized, double-blind, controlled trial, healthy adults will be asked to consume daily servings of orange juice containing either 0 g (n=120; control) or 180 g (i.e. 10 g fiber; n=120) of orange pomace for 3 weeks to assess the effect of the pomace on stool frequency. Blood samples will be obtained to assess the effect of the pomace on metabolic markers. Stool samples will be collected for analyses of the effect of the pomace on fecal bacteria known to be associated with health benefits (e.g., bifidobacteria). For exploratory analyses, additional groups will be asked to consume orange juice containing 90 g of pomace (i.e. 5 g fiber; n=40) or orange-flavored, calorie-matched water (n=40); outcomes from the water group will be compared to those of the 0 g pomace juice group to assess any effects of the juice alone, and outcomes from the 90 g pomace group will be compared to those of the 180 g and 0 g groups in microbiota analyses.

Inclusion Criteria:

• Healthy adults 18-60 years of age
• Willing and able to consume 16 oz. of a citrus beverage daily for the 3-week study intervention
• Willing and able to avoid consumption of any orange, grapefruit, tomato or V-8 juice and whole oranges or grapefruits during the two weeks leading up to the study and during the study, not including the study beverage
• Willing and able to complete daily questionnaires online regarding dietary intake and general health and well-being, including gastrointestinal habits Note: we will recruit participants who will have Internet access for the duration of the protocol, but understand that, once enrolled, situations may change. If this is the case, paper copies of the online forms will be provided
• Willing to discontinue any prebiotic, probiotic, and fiber supplements after consenting
• Willing to provide blood via finger prick and a stool sample twice each, once at the beginning and once at the end of the study

Exclusion Criteria:

• Women who are lactating, know that they are pregnant, or are attempting to get pregnant
• Currently being treated for any physician-diagnosed diseases or conditions
• Vegetarians/vegans