Daily Fermented Whey Consumption Alters the Fecal Short-Chain Fatty Acid Profile in Healthy Adults

Abstract

Gut microbiota influences many aspects of host health including immune, metabolic, and gut health. We examined the effect of a fermented whey concentrate (FWC) drink rich in L-(+)-Lactic acid, consumed daily, in 18 healthy men (n = 5) and women (n = 13) in free-living conditions. Objective: The aims of this 6-weeks pilot trial were to (i) identify changes in the gut microbiota composition and fecal short chain fatty acid (SCFA) profile, and (ii) to monitor changes in glucose homeostasis. Results: Total fecal SCFA (mM) concentration remained constant throughout the intervention. Proportionally, there was a significant change in the composition of different SCFAs compared to baseline. Acetate levels were significantly reduced (-6.5%; p < 0.01), coupled to a significant increase in the relative amounts of propionate (+2.2%; p < 0.01) and butyrate (+4.2%; p < 0.01), respectively. No changes in the relative abundance of any specific bacteria were detected. No significant changes were observed in glucose homeostasis in response to an oral glucose tolerance test. Conclusion: Daily consumption of a fermented whey product led to significant changes in fecal SCFA metabolite profile, indicating some potential prebiotic activity. These changes did not result in any detectable differences in microbiota composition. Post-hoc analysis indicated that baseline microbiota composition might be indicative of participants likely to see changes in SCFA levels. However, due to the lack of a control group these findings would need to be verified in a rigorously controlled trial. Future work is also required to identify the biological mechanisms underlying the observed changes in microbiota activity and to explore if these processes can be harnessed to favorably impact host health. Clinical Trial Registration: www.clinicaltrials.gov, identifier NCT03615339; retrospectively registered on 03/08/2018.

Keywords: dietary supplementation; fermented whey concentrate; microbiota; postbiotic; short chain fatty acids.

Figure 1

Flow diagram of study participants. *1 participant excluded, as blood samples could not collected due to fainting. **6 participants data excluded as values below threshold of detection of kit. Adapted from (32).

Figure 2

Study Flow (6 weeks continuous intake), single arm intervention, with three separate study visits at the Human Nutrition Unit (referred to as t1, t3, and t6). FD, 3-days food diary; GI-Q, gastrointestinal questionnaire; OGTT, oral glucose tolerance test.

Figure 3

Oral Glucose tolerance test showing group plasma glucose profile in response to a 75 g bolus of glucose, at commencement of study (Baseline) and after 6-weeks of chronic fermented whey consumption (Fermented whey, n = 17).

Figure 4

Fasting insulin profiles pre- (t1) and post-intervention, t6 (n = 12). (A) Insulin concentration shown by individual volunteers, at baseline (t1) and after the intervention (t6). (B) Group average fasting insulin levels. There was a reduction of −0.9 mUI/L which failed to reach significance (p = 0.089).

Figure 5

Short chain fatty acid composition of fecal samples (n = 18). Values are proportions of total SCFA concentration. Boxplots whiskers represent min/max values. Acetate levels decreased significantly (by 6.48%, p < 0.01), while both propionate (p < 0.05) and butyrate (p < 0.001) levels increased. No lactate or succinate were detected. (* = P ≤ 0.05, ** = P ≤ 0.01, *** = P ≤ 0.001).

Figure 6

Microbiota alpha diversity metrics, analyzed by calculating the Shannon index comparing samples based on time point (t1—red, t3—green, t6—blue). Differences over time were not significant.

Figure 7

Taxonomic profile of individual volunteers at phylum level, grouped by time-point, t1, t3, and t6.

Figure 8

Principle component analysis plots based on Bray-Curtis Dissimilarity Index, comparing each sample from individual volunteers (n = 18).

Figure 9

Relative abundance of Coprococcus eutactus in volunteers with the highest (Responder, n = 5) and lowest (Non-responders, n = 5) changes in fecal butyrate concentration. Kruskal-Wallis test show non-significant changes in abundance across sample types in both responders (p = 0.38) and non-responders (p = 0.38).