In vitro fermentation of nuts results in the formation of butyrate and c9,t11 conjugated linoleic acid as chemopreventive metabolites

• Published in: European journal of nutrition Vol. 55; no. 6; pp. 2063 - 2073
• Main Authors: Schlörmann, W., Birringer, M., Lochner, A., Lorkowski, S., Richter, I., Rohrer, C., Glei, M.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-09-2016; Springer Nature B.V
• Subjects: Bile Acids and Salts - metabolism; Butyrates - chemistry; Chemistry; Chemistry and Materials Science; Colonic Neoplasms - prevention & control; Corylus; Corylus - chemistry; Fatty Acids, Unsaturated - chemistry; Feces - microbiology; Fermentation; Gastrointestinal Microbiome; Humans; Hydrogen-Ion Concentration; Juglans; Juglans - chemistry; Linoleic Acids, Conjugated - chemistry; Macadamia; Macadamia - chemistry; Malondialdehyde - chemistry; Nutrition; Nuts - chemistry; Oleic Acids - chemistry; Original Contribution; Pistacia - chemistry; Prunus dulcis; Prunus dulcis - chemistry; Thiobarbituric Acid Reactive Substances - analysis; Conjugated fatty acids; Colon cancer; Nuts; In vitro fermentation; fatty acids; Dietary fiber; trans fatty acids
• ISSN: 1436-6207; 1436-6215
• DOI: 10.1007/s00394-015-1020-0

Purpose
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 (C18:1
t
11, 32.1 ± 3.2 % FAME; fatty acid methyl ester) and conjugated linoleic acid (
c
9,
t
11 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.
Conclusion
This is the first study that demonstrates the ability of the human fecal microbiota to convert polyunsaturated fatty acids from walnuts to
c
9,
t
11 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.