Impact of colonic fermentation on sterols after the intake of a plant sterol-enriched beverage: A randomized, double-blind crossover trial.

BACKGROUND: Cholesterol microbial transformation has been widely studied using in vitro fermentation assays, but less information is available on the biotransformation of plant sterols (PS). The excretion percentage of animal sterols (AS) (67-73%) is considerably greater than that of PS (27-33%) in feces from healthy humans following a Western diet. However, a lower content of AS in feces from subjects following a vegetarian, vegan or low-fat animal diet has been seen when compared to omnivorous subjects. Although only one human study has reported fecal sterol excretion after the consumption of PS-enriched food (8.6 g PS/day), it was found that the target group showed an increase in the excretion of cholesterol and a 57% decrease in its metabolites compared to the control group. OBJECTIVE: Evaluation of the impact of a PS-enriched milk based fruit beverage intake on fecal sterol excretion and the microbial conversion of sterols in postmenopausal women with mild hypercholesterolemia. METHODS: Forty postmenopausal women participated in a randomized, double-blind, crossover study with two beverages, with a PS-enriched (2 g PS/day) or without. The women were divided in two groups: 20 women consumed the PS-enriched beverage and the other 20 women consumed a placebo (without PS) beverage for 6 weeks. After a four-week washout period, the type of beverage was exchanged and consumed for another 6 weeks. Feces were collected at the start (0 and 10 weeks) and end of each intervention period (6 and 16 weeks), and fecal sterols were determined by capillary gas chromatography with mass spectrometry. RESULTS: The intake of the PS-enriched beverage modified the fecal sterol excretion profile. A significant increase mainly in PS and their metabolites versus the placebo intervention period was observed. Although the same effect was not observed in the case of AS, a tendency towards increased cholesterol and decreased coprostanol (the main metabolite of cholesterol) was recorded after PS-enriched beverage intake versus placebo. Furthermore, the PS-enriched beverage also modified the microbial conversion of sterols. In this context, an important decrease in the conversion percentage of cholesterol in 16 women (between 11% and 50%) and of sitosterol in 24 women (between 15% and 61%) was observed. CONCLUSIONS: The results obtained suggest that the microbiota could preferably use PS as a substrate, when present in a greater proportion compared with cholesterol. Besides, a lower sitosterol and cholesterol conversion trend would mean that intake of the PS-enriched beverage could modulate the metabolic activity of the gut microbiota. Therefore, further studies on the impact of PS-enriched foods upon gut microbiota modulation are needed. Clinical Trial Registry Number: NCT02065024 listed on the NIH website: ClinicalTrials.gov. Clinical Trial Registry Name: Food Matrix and Genetic Variability as Determinants of Bioavailability and Biological Effects of Beta-cryptoxanthin and Phytosterols (foodmagenpol). The full trial protocol is available upon request to the corresponding author.

Determination of Fecal Sterols Following a Diet with and without Plant Sterols.

The aim of this study was to develop a method for neutral fecal sterols determination in subjects receiving a normal diet with or without a plant sterols-enriched beverage using gas chromatography-mass spectrometry (GC/MS). Sample preparation conditions (homogenization of lyophilized feces with water) were evaluated. Sterol determination required direct hot saponification, unsaponifiable extraction with hexane, and the formation of trimethylsilyl (TMS) ether derivatives. The method allows the quantification of cholesterol, plant sterols and their metabolites (coprostanol, coprostanone, cholestanol, cholestanone, methylcoprostanol, methylcoprostanone, ethylcoprostenol, stigmastenol, ethylcoprostanol and ethylcoprostanone). Good linearity was obtained (r > 0.96) and interference was only observed for coprostanone, where the standard addition method proved necessary for quantification. The limits of detection (LOD) ranged from 0.10 to 3.88 µg/g dry feces and the limits of quantitation (LOQ) from 0.34 to 12.94 µg/g dry feces. Intra- and inter-assay precision (RSD %) were 0.9-9.2 and 2.1-11.3, respectively. Accuracy, expressed as percentage recovery (80-119%) was obtained for all determined sterols.