Impact of Almond Consumption on the Composition of the Gastrointestinal Microbiota of Healthy Adult Men and Women
Authors: Taylor Andrew M. , Swanson Kelly S. , Novotny Janet A , Baer David J , Holscher Hannah D 
Published: June 2021

Background

Dietary fiber has been shown to diversify and support growth of beneficial bacteria in the human gastrointestinal tract. Almonds contain fiber as well as phytonutrients that may impact the microbiome. Diets rich in nuts, including almonds, have beneficial effects on cardiovascular disease risk factors including blood lipids and inflammation. Much of this research has been conducted using whole almonds. Emerging data also suggests the gastrointestinal microbiome may play a role in mediating cardiovascular disease risk factors. The interrelationship of almond consumption, the gastrointestinal microbiome, and cardiometabolic health of humans remains to be investigated. An important first step is characterizing the impact of dietary consumption of almonds and almond processing on the human gastrointestinal microbiota.

Objective

We aimed to assess the interrelationship of almond consumption and processing on the gastrointestinal microbiota in healthy adult men and women.

Methods

A controlled‐feeding, randomized, crossover design study consisting of five 3‐week treatment periods with washouts between treatment periods was conducted in healthy adult men and women (n=18). The 5 treatments were: 1) 0 servings/day of almonds, 2) 1.5 servings (42 g)/day of whole almonds, 3) 1.5 servings/day of whole roasted almonds, 4) 1.5 servings/day of diced almonds, and 5) 1.5 servings/day of almond butter. Urine, fecal, and blood samples were collected at the beginning and end of each period for metabolic, immunologic, and microbial analyses. Following fecal DNA isolation, a Fluidigm Access Array was utilized to generate barcoded amplicon pools of archaeal, bacterial, and fungal sequences. High‐throughput sequencing was conducted on a MiSeq. Sequence data were analyzed using QIIME 1.8.0 and SAS 9.4.

Results

Principal coordinates analysis (PCoA) of UniFrac distances between samples based on their 97% OTU composition and abundances indicated that bacterial communities were impacted (p=0.05) by treatment. Furthermore, the composition of the microbiota of participants consuming whole almonds (whole raw and whole roasted) was different (p=0.01) than when participants did not consume whole almonds (almond pieces, almond butter, and control). At the phyla level, almond consumption decreased the relative abundance of Actinobacteria compared to control, 3.9% vs. 5.5%, respectively (p=0.03). Shifts in bacterial genera following almond consumption included a decrease in the relative abundances of Bifidobacterium (p=0.03), Parabacteroides (p=0.02), and Clostridium (p=0.04), and increases in the relative abundances of Lachnospira (p=0.01) and Roseburia (p=0.03). Comparisons between control and each of the four almond treatments revealed that chopped almonds increased the relative abundances of Oscillospira (p=0.02), Roseburia (p=0.02), and Lachnospira (p=0.04).

Conclusions

Our data reveal that almond consumption induced changes in the microbial community composition of the human gastrointestinal microbiota. Furthermore, the degree of almond processing differentially impacted bacterial genera with chopped almonds having the largest effect compared to control. Additional study is ongoing to determine if connections exist between the changes in microbial taxa and metabolic improvements.

Support or Funding Information

Funding provided by USDA and Almond Board of California.