Summary: Consuming a hand full of almonds each day increases butyrate production, improves bacterial metabolism, and positively influences health.
Source: King’s College London
A team of researchers from King’s investigated the impact of whole and ground almonds on the composition of gut microbes.
The study, published today in the American Journal of Clinical Nutrition, is funded by the Almond Board of California.
The gut microbiome consists of thousands of micro-organisms living in the gut. These play a vital role in digesting nutrients and can have a positive or negative influence on our health, including our digestive and immune systems.
The mechanisms of how the gut microbiomes have an impact on human health is still being investigated, but evidence suggests eating specific types of food can positively influence the types of bacteria in our gut or what they do in our gut.
Researchers recruited 87 healthy adults who were already eating less than the recommended amount of dietary fibre and who snacked on typical unhealthy snacks (e.g. chocolate, crisps).
Participants were split into three groups: one group changed their snacks for 56 g of whole almonds a day, another for 56 g of ground almonds a day, and the control group ate energy-matched muffins as a control. The trial lasted four weeks.
“Part of the way in which the gut microbiota impact human health is through the production of short-chain fatty acids, such as butyrate. These molecules act as a fuel source for cells in the colon, they regulate absorption of other nutrients in the gut, and help balance the immune system,” said lead author Professor Kevin Whelan, Head of Department of Nutritional Sciences
Researchers found that butyrate was significantly higher among almond eaters compared to those who consumed the muffin. Butyrate is a short-chain fatty acid that is the main source of fuel for the cells lining the colon.
When these cells function effectively, it provides an ideal condition for gut microbes to flourish, for the gut wall to be strong and not leaky or inflamed and for nutrients to be absorbed.
No significant difference was observed in gut transit time – the time it takes for food to move all the way through the gut – however whole-almond eaters had an additional 1.5 bowel movements per week compared to the other groups. These findings suggest eating almonds could also benefit those with constipation.
Testing showed that eating whole and ground almond improved peoples’ diets, having higher intakes of monosaturated fatty acids, fibre, potassium and other important nutrients compared to the control group.
Professor Whelan added: “We think these findings suggest almond consumption may benefit bacterial metabolism in a way that has the potential to influence human health.”
Almonds contain lipid, fiber and polyphenols and possess physicochemical properties that impact nutrient bioaccessibility, which are hypothesized to impact gut physiology and microbiota.
Investigate the impact of whole almonds and ground almonds (almond flour) on fecal bifidobacteria (primary outcome), gut microbiota composition and transit time.
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).
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).
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.