Effects of Daily Strawberry Intake (4 weeks) on Plasma Bile Acid Composition in Humans: A Randomized, Placebo-Controlled, Crossover Trial

Abstract

Abstract Objectives Bile acids (BA) are liver derived compounds that undergo host and microbial metabolism. BA metabolites have multiple physiological roles including maintaining intestinal immune homeostasis. Dietary components influence BA metabolism/excretion through several mechanisms. This study aimed to evaluate the effects of daily strawberry intake (4 weeks) on bile acid metabolism in humans. Methods Thirty overweight/obese adults (age: 53 ± 7 years, BMI: 31 ± 4 kg/m,2) were recruited for this randomized, double-blind, placebo-controlled, crossover trial. Participants were randomized to 1 of 2 study sequences in a 1:1 ratio with 4 weeks washout period between two treatments. Participants consumed a strawberry beverage containing 25 g freeze-dried strawberry powder (∼1.75 servings of fresh strawberries) or energy-matched control beverage in random order twice a day for 4 weeks. Fasting blood samples were collected at weeks 0, 4, 8, and 12. Plasma samples (500 μL) were extracted using solid-phase C18 cartridges. An ultra-high performance liquid chromatography tandem mass spectrometry method was developed to quantitate bile acids and their metabolites (sulfates, glucuronides) in plasma. The method was validated in terms of linearity, sensitivity, recovery, and matrix effect. The data were analyzed using a paired student t-test with statistical significance set at P < 0.05. Results Twenty-nine glucuronidated and sulfated BAs were identified in plasma samples. Concentrations of primary BAs were not affected between the study treatments, whereas a significant decrease (P < 0.05) was observed in total secondary BAs (52 compounds) after 4 weeks of strawberry intake (11.2 ± 1.1 µmol/L) compared to placebo (18.3 ± 3.2 µmol/L). Individual secondary BAs including lithocholic acid (LCA), sulfo-glycolithocholic acid, and C24 oxidized LCA were significantly decreased after 4-week strawberry intake compared to placebo (P < 0.05). Conclusions Our results indicate that regular strawberry intake could lower pro-inflammatory LCA and other secondary BAs, suggesting a potential role of strawberry in ameliorating colonic inflammation and promoting gut health. Funding Sources This work was funded by the California Strawberry Commission and various donor funds to the Center for Nutrition Research, IIT.