In vitro fermentation of nuts results in the formation of butyrate and c9,t11 conjugated linoleic acid as chemopreventive metabolites.
OBJECTIVE
The consumption of foods rich in dietary fiber and polyunsaturated fatty acids such as nuts can contribute to a healthy diet. Therefore, the formation of fermentation end-products which might exert chemopreventive effects regarding colon cancer was investigated after an in vitro simulated digestion and fermentation of nuts using human fecal microbiota.


METHODS
Fermentation supernatants (FS) and pellets (FP) were obtained after an in vitro fermentation of hazelnuts, almonds, macadamia, pistachios and walnuts. Short-chain fatty acids (SCFA) and bile acids (BA) in FS as well as fatty acids in FP were analyzed via gas chromatography. Malondialdehyde (MDA) levels in FS were determined photometrically.


RESULTS
Fermentation of nuts resulted in 1.9- to 2.8-fold higher concentrations of SCFA compared to the control and a shift of molar ratios toward butyrate production. In vitro fermentation resulted in the formation of vaccenic acid (C18:1t11, 32.1 ± 3.2 % FAME; fatty acid methyl ester) and conjugated linoleic acid (c9,t11 CLA, 2.4 ± 0.7 % FAME) exclusively in fermented walnut samples. Concentrations of secondary BA deoxycholic-/iso-deoxycholic acid (6.8-24.1-fold/4.9-10.9-fold, respectively) and levels of MDA (1.3-fold) were significantly reduced in fermented nut samples compared to the control.


CONCLUSIONS
This is the first study that demonstrates the ability of the human fecal microbiota to convert polyunsaturated fatty acids from walnuts to c9,t11 CLA as a potential chemopreventive metabolite. In addition, the production of butyrate and reduction in potential carcinogens such as secondary BA and lipid peroxidation products might contribute to the protective effects of nuts regarding colon cancer development.
Department of Nutritional Toxicology, Institute of Nutrition, Friedrich Schiller University Jena, Dornburger Straße 24, 07743, Jena, Germany. wiebke.schloermann@uni-jena.de.
W
W
Schlörmann
Department of Nutritional, Food and Consumer Studies, University of Applied Sciences, Leipziger Straße 123, 36037, Fulda, Germany.
M
M
Birringer
Department of Nutritional Physiology, Institute of Nutrition, Friedrich Schiller University Jena, Dornburger Straße 24, 07743, Jena, Germany.
A
A
Lochner
Department of Nutritional Biochemistry and Physiology, Institute of Nutrition, Friedrich Schiller University Jena, Dornburger Straße 25, 07743, Jena, Germany.|Competence Cluster for Nutrition and Cardiovascular Health (nutriCARD), Halle-Jena-Leipzig, 07743 Jena, Germany.
S
S
Lorkowski
Department of Nutritional, Food and Consumer Studies, University of Applied Sciences, Leipziger Straße 123, 36037, Fulda, Germany.
I
I
Richter
Department of Nutritional Physiology, Institute of Nutrition, Friedrich Schiller University Jena, Dornburger Straße 24, 07743, Jena, Germany.|Competence Cluster for Nutrition and Cardiovascular Health (nutriCARD), Halle-Jena-Leipzig, 07743 Jena, Germany.
C
C
Rohrer
Department of Nutritional Toxicology, Institute of Nutrition, Friedrich Schiller University Jena, Dornburger Straße 24, 07743, Jena, Germany.|Competence Cluster for Nutrition and Cardiovascular Health (nutriCARD), Halle-Jena-Leipzig, 07743 Jena, Germany.
M
M
Glei
D001647:Bile Acids and Salts / Q000378:metabolism; D002087:Butyrates / Q000737:chemistry*; D003110:Colonic Neoplasms / Q000517:prevention & control; D031211:Corylus / Q000737:chemistry; D005231:Fatty Acids, Unsaturated / Q000737:chemistry; D005243:Feces / Q000382:microbiology; D005285:Fermentation; D000069196:Gastrointestinal Microbiome; D006801:Humans; D006863:Hydrogen-Ion Concentration; D031324:Juglans / Q000737:chemistry; D044243:Linoleic Acids, Conjugated / Q000737:chemistry*; D039106:Macadamia / Q000737:chemistry; D008315:Malondialdehyde / Q000737:chemistry; D009754:Nuts / Q000737:chemistry*; D009829:Oleic Acids / Q000737:chemistry; D027927:Pistacia / Q000737:chemistry; D000068181:Prunus dulcis / Q000737:chemistry; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis
D001647:Bile Acids and Salts; D002087:Butyrates; D005231:Fatty Acids, Unsaturated; D044243:Linoleic Acids, Conjugated; D009829:Oleic Acids; D017392:Thiobarbituric Acid Reactive Substances; D008315:Malondialdehyde; C050413:11-octadecenoic acid
Colon cancer; Conjugated fatty acids; Dietary fiber; In vitro fermentation; Nuts; trans fatty acids