Almond consumption and processing affects the composition of the gastrointestinal microbiota of healthy adult men and women: a randomized controlled trial

Authors: HOLSCHER, HANNAH - University Of Illinois; TAYLOR, ANDREW - University Of Illinois; SWANSON, KELLY - University Of Illinois; Novotny, Janet; Baer, David

Submitted to: Nutrients
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2018
Publication Date: 1/26/2018
Citation: Holscher, H.D., Taylor, A.M., Swanson, K.S., Novotny, J., Baer, D.J. 2018. Almond consumption and processing affects the composition of the gastrointestinal microbiota of healthy adult men and women: a randomized controlled trial. Nutrients. 10. https://doi.org/10.3390/nu10020126.
DOI: https://doi.org/10.3390/nu10020126

Interpretive Summary: Almonds are a nutrient-dense food that are consumed whole as well as processed, including roasting, chopping and grinding. Processing has been shown to differentially impact metabolizable energy by changing the availability of energy. Roasting, chopping and grinding might also effect the human gastrointestinal microbiota. However, the effect of food processing on human gastrointestinal microbiota has not been well studied. In this research project, we aimed to assess the interrelationship of almond consumption and processing on the gastrointestinal microbiota in healthy adults. A controlled-feeding study was conducted was conducted in healthy adults who consumed 1) a control diet (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 roasted, chopped almonds, and 5) 1.5 servings/day of almond butter. Fecal samples were collected at the end of each diet period and the composition of the fecal microbiota was determined. Almond consumption decreased the relative abundances of Bifidobacterium, Parabacteroides, and Clostridium, and increased the relative abundances of Lachnospira and Roseburia. Comparisons between control and each of the four almond treatments revealed that chopped almonds increased the relative abundances of Oscillospira, Roseburia, and Lachnospira. These results 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. These results are likely due to differences in the particle size and nutrient availability. While there is much to learn about how these changes in food processing and fecal microbiota effect human health, this research provides data suggesting that there are measurable changes.

Technical Abstract: Almond processing has been shown to differentially impact metabolizable energy; however, the effect of food form on the gastrointestinal microbiota is under-investigated. We aimed to assess the interrelationship of almond consumption and processing on the gastrointestinal microbiota. A controlled-feeding, randomized, five-period, crossover study with washouts between diet periods was conducted in healthy adults (n = 18). Treatments included: (1) zero servings/day of almonds (control); (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 roasted, chopped almonds; and (5) 1.5 servings/day of almond butter. Fecal samples were collected at the end of each three-week diet period. Almond consumption increased the relative abundances of Lachnospira, Roseburia, and Dialister (p = 0.05). Comparisons between control and the four almond treatments revealed that chopped almonds increased Lachnospira, Roseburia, and Oscillospira compared to control (p < 0.05), while whole almonds increased Dialister compared to control (p = 0.007). There were no differences between almond butter and control. These results reveal that almond consumption induced changes in the microbial community composition of the human gastrointestinal microbiota. Furthermore, the degree of almond processing (e.g., roasting, chopping, and grinding into butter) differentially impacted the relative abundances of bacterial genera.