Walnut Consumption Alters the Gastrointestinal Microbiota, Microbially Derived Secondary Bile Acids, and Health Markers in Healthy Adults: A Randomized Controlled Trial

• Published in: The Journal of nutrition 2018-06, Vol.148 (6), p.861-867
• Main Authors: Holscher, Hannah D, Guetterman, Heather M, Swanson, Kelly S, An, Ruopeng, Matthan, Nirupa R, Lichtenstein, Alice H, Novotny, Janet A, Baer, David J
• Format: Article
• Language: English
• Subjects: Acids; Adult; Adults; Aged; Bacteria; Bacteria - classification; Bacteria - metabolism; Bifidobacterium; Bile acids; Bile Acids and Salts - chemistry; Bile Acids and Salts - metabolism; Biomarkers; blood sampling; blood serum; Body mass; Body mass index; Body size; campesterol; Cancer; cardiovascular health; Cholesterol; Clinical trials; Clostridium; Consumption; Control methods; Coronary artery disease; Cross-Over Studies; Crossovers; Deoxycholic acid; Dialister; Diet; Digestive system; Epidemiology; Evidence-based medicine; Faecalibacterium; Female; Gastrointestinal Microbiome; Health; health effects assessments; Heart; Heart diseases; Humans; Inflammation; intestinal microorganisms; Juglans; lithocholic acid; Low density lipoprotein; low density lipoprotein cholesterol; Male; Markers; men; microbiome; Microbiota; Middle Aged; mortality; neoplasms; Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions; Nuts; Oscillospira; Randomization; randomized clinical trials; Relative abundance; Roseburia; Ruminococcus; tree nuts; Walnuts; women
• ISSN: 0022-3166; 1541-6100; 1541-6100
• DOI: 10.1093/jn/nxy004

Epidemiologic data suggest that diets rich in nuts have beneficial health effects, including reducing total and cause-specific mortality from cancer and heart disease. Although there is accumulating preclinical evidence that walnuts beneficially affect the gastrointestinal microbiota and gut and metabolic health, these relations have not been investigated in humans. We aimed to assess the impact of walnut consumption on the human gastrointestinal microbiota and metabolic markers of health. A controlled-feeding, randomized crossover study was undertaken in healthy men and women [n = 18; mean age = 53.1 y; body mass index (kg/m2): 28.8]. Study participants received isocaloric diets containing 0 or 42 g walnuts/d for two 3-wk periods, with a 1-wk washout between diet periods. Fecal and blood samples were collected at baseline and at the end of each period to assess secondary outcomes of the study, including effects of walnut consumption on fecal microbiota and bile acids and metabolic markers of health. Compared with after the control period, walnut consumption resulted in a 49–160% higher relative abundance of Faecalibacterium, Clostridium, Dialister, and Roseburia and 16–38% lower relative abundances of Ruminococcus, Dorea, Oscillospira, and Bifidobacterium (P