Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2017 Oct;48:94-102.
doi: 10.1016/j.jnutbio.2017.07.001. Epub 2017 Jul 9.

Changes in the Gut Microbial Communities Following Addition of Walnuts to the Diet

Affiliations
Free PMC article

Changes in the Gut Microbial Communities Following Addition of Walnuts to the Diet

Lauri O Byerley et al. J Nutr Biochem. .
Free PMC article

Abstract

Walnuts are rich in omega-3 fatty acids, phytochemicals and antioxidants making them unique compared to other foods. Consuming walnuts has been associated with health benefits including a reduced risk of heart disease and cancer. Dysbiosis of the gut microbiome has been linked to several chronic diseases. One potential mechanism by which walnuts may exert their health benefit is through modifying the gut microbiome. This study identified the changes in the gut microbial communities that occur following the inclusion of walnuts in the diet. Male Fischer 344 rats (n=20) were randomly assigned to one of two diets for as long as 10 weeks: (1) walnut (W), and (2) replacement (R) in which the fat, fiber, and protein in walnuts were matched with corn oil, protein casein, and a cellulose fiber source. Intestinal samples were collected from the descending colon, the DNA isolated, and the V3-V4 hypervariable region of 16S rRNA gene deep sequenced on an Illumina MiSeq for characterization of the gut microbiota. Body weight and food intake did not differ significantly between the two diet groups. The diet groups had distinct microbial communities with animals consuming walnuts displaying significantly greater species diversity. Walnuts increased the abundance of Firmicutes and reduced the abundance of Bacteriodetes. Walnuts enriched the microbiota for probiotic-type bacteria including Lactobacillus, Ruminococcaceae, and Roseburia while significantly reducing Bacteroides and Anaerotruncus. The class Alphaproteobacteria was also reduced. Walnut consumption altered the gut microbial community suggesting a new mechanism by which walnuts may confer their beneficial health effects.

Keywords: Bacterial diversity; Diet; Gut microbiome; Prebiotics; Probiotics; Walnut.

Conflict of interest statement

Conflicts of interests

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Body weight (1A) and daily food intake (1B) for the two diet groups. Body weight and food intake did not differ significantly between the two groups.
Fig. 2
Fig. 2
Alpha diversity (within a community) of the gut microbiome shown using Shannon analysis. The addition of walnuts significantly increased (P=.018) the diversity evenness of the gut microbial community.
Fig. 3
Fig. 3
Beta diversity (between communities) of the gut microbial communities. The principle coordinate analysis (PCoA) plot based on unweighted (shown in the figure) UniFrac distances showed two distinct gut microbial communities (replacement diet red circles, walnut diet blue circles) (Fig. 3A). Although Fig. 3A suggests one outlier from the walnut group in the replacement group, rotating the axis shows clearly three outliers (Fig. 3B) – two from the walnut diet and one from the replacement diet.
Fig. 4
Fig. 4
Relative abundance of the bacterial phyla between the walnut and replacement diet. Relative abundance was calculated from the relative abundance of 16S rRNA gene sequences assigned to each bacterial community using the Greengenes database. Fig. 4A shows the changes at the phyla level for the walnut diet and Fig. 4B shows the phyla changes for the replacement diet. Only Firmicutes and Bacteriodetes were significantly changed, and the ratio of Firmicutes to Bacteriodetes is shown in Fig. 4C.
Fig. 5
Fig. 5
The top 25 most abundant bacteria in genus. The two columns on the left graphically represent the data shown in the table. The taxa in the boxes are shown in the same descending order as the table.
Fig. 6
Fig. 6
Inferred functional capacity of the microbial communities associated with walnut and replacement diet determined by linear discriminative analysis (LDA) effect size (LEfSe) analysis of KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways. Positive LDA scores are enriched in animals eating the walnut diet (green bars) while negative LDA scores are enriched in those animals eating the replacement diet (red bars).

Similar articles

See all similar articles

Cited by 20 articles

See all "Cited by" articles

References

    1. Bao Y, Han J, Hu FB, Giovannucci EL, Stampfer MJ, Willett WC, et al. Association of nut consumption with total and cause-specific mortality. N Engl J Med. 2013;369:2001–11. - PMC - PubMed
    1. Ellsworth JL, Kushi LH, Folsom AR. Frequent nut intake and risk of death from coronary heart disease and all causes in postmenopausal women: the Iowa Women’s health study. Nutr Metab Cardiovasc Dis. 2001;11:372–7. - PubMed
    1. van den Brandt PA. The impact of a Mediterranean diet and healthy lifestyle on premature mortality in men and women. Am J Clin Nutr. 2011;94:913–20. - PubMed
    1. Kris-Etherton PM. Walnuts decrease risk of cardiovascular disease: a summary of efficacy and biologic mechanisms. J Nutr. 2014;144:547s–54s. - PubMed
    1. Akinsete JA, Ion G, Witte TR, Hardman WE. Consumption of high omega-3 fatty acid diet suppressed prostate tumorigenesis in C3(1) tag mice. Carcinogenesis. 2012;33:140–8. - PMC - PubMed

Publication types

LinkOut - more resources

Feedback