Summary:
Almonds are known to be extremely nutrient dense due to their high content of fiber, polyphenols and healthy fats however research surrounding the benefits of foods are usually focused on isolated nutrients as opposed to examples of whole foods. Understanding the role of particular foods in the gut microbiota and overall human health is directly relatable and translatable for the wider public to implement. The purpose of this randomized controlled trial was to examine the impact of both whole and ground almonds (almond flour) on the composition of the gut microbiota and whether the fiber and other nutrients from almonds can positively benefit the digestive tract and transit time. The participants received whole almonds, ground almonds or a placebo in the form of muffins for four weeks. The diversity and composition of the participants bacterial environment was monitored at the start and end of the four weeks, as well as transit time and any gut symptoms.The results showed that almonds increase butyrate concentration in adults, which is an important short-chain fatty acid that is known to be anti-inflammatory and helps prevent colon cancer. Almonds also showed to positively impact other microbiota functionality, without contributing to any common gut symptoms.
Abstract:
Background: Almonds contain lipid, fiber and polyphenols and possess physicochemical properties that impact nutrient bioaccessibility, which are hypothesized to impact gut physiology and microbiota. Objectives: Investigate the impact of whole almonds and ground almonds (almond flour) on fecal bifidobacteria (primary outcome), gut microbiota composition and transit time. Design: Healthy adults (n = 87) participated in a parallel, 3-arm randomized controlled trial. Participants received whole almonds (56 g/d), ground almonds (56 g/d) or an isocaloric control muffin in place of habitual snacks for 4 weeks. Gut microbiota composition and diversity (16S rRNA gene sequencing), short-chain fatty acids (gas-chromatography), volatile organic compounds (gas-chromatography mass-spectrometry), gut transit time (wireless motility capsule), stool output and gut symptoms (7-day diary) were measured at baseline and endpoint. The impact of almond form on particle size distribution (PSD) and predicted lipid release was measured in a subgroup (n = 31). Results: Modified intention-to-treat analysis was performed on 79 participants. There were no significant differences in abundance of fecal bifidobacteria following consumption of whole almonds (8.7%, SD 7.7%), ground almonds (7.8%, SD 6.9%) or control (13.0%, SD 10.2%; q = 0.613). Consumption of almonds (whole and ground pooled) resulted in higher butyrate (24.1 μmol/g, SD 15.0 μmol/g) in comparison to control (18.2 μmol/g, SD 9.1 μmol/g; p = 0.046). There was no effect of almonds on gut microbiota at the phylum level or diversity, gut transit time, stool consistency or gut symptoms. Almond form (whole versus ground) had no effect on study outcomes. Ground almonds resulted in significantly smaller PSD and higher predicted lipid release (10.4%, SD 1.8%) in comparison to whole almonds (9.3%, SD 2.0%; p = 0.017). Conclusions: Almond consumption has limited impact on gut microbiota composition but increases butyrate concentrations in adults, suggesting positive alterations to microbiota functionality. Almonds can be incorporated into the diet to increase fiber consumption without triggering gut symptoms. Clinical trial registry: ClinicalTrials.gov identifier – NCT03581812.
Article Publication Date: 20/09/2022
DOI: 10.1093/ajcn/nqac265
