The body of evidence about nuts and gut health continues to grow, with new local and international research papers regularly published.

Body of evidence

Walnuts and vegetable oils containing oleic acid differentially affect the gut microbiota and associations with cardiovascular risk factors: Follow-up of a randomized, controlled, feeding trial in adults at risk for cardiovascular disease. (2019).
Similarities between enrichment of SCFA-producing bacteria, including Roseburia and Eubacterium, following the walnut diet (WD) and walnut fatty acid matched diet (WFMD) illustrate the effect that the high unsaturated fat content, including ALA, may have on gut bacteria. The unique enrichment of Gordonibacter following the WD suggests that walnut-derived bioactive compounds and fibre modulate gut microbiota. The associations between Lachnospiraceae and improved cardiovascular risk factors suggest that the gastrointestinal microbiota may contribute to the underlying mechanisms of the beneficial health effects of walnut consumption.

Walnut consumption alters the gastrointestinal microbiota, microbially derived secondary bile acids, and health markers in healthy adults: A randomized controlled trial. (2018).
Walnut consumption affected the gastrointestinal microbiota and microbially derived secondary bile acids and reduced serum total and LDL cholesterol in healthy adults. These results suggest that the gastrointestinal microbiota may contribute to the underlying mechanisms of the beneficial health effects of walnut consumption, including cardiometabolic and gastrointestinal health.

The effects of ‘activating’ almonds on consumer acceptance and gastrointestinal tolerance. (2018).
According to a study published in the European Journal of Nutrition, soaking (or activating) almonds did not reduce phytates, nor did it improve GI tolerance when compared to unsoaked nuts.

Prebiotic nut compounds and human microbiota. (2017).
Nuts contain non-bio-accessible material (mainly polysaccharides and polymerised polyphenols) and emerging evidence suggests that they appear to have a prebiotic effect, which may help to explain their many health benefits. However, data are very limited and more research is required, particularly from human intervention studies, as well as research on different types of nuts, doses, and over a sufficiently long period of time.

Health benefits of walnut polyphenols: An exploration beyond their lipid profile. (2017).
The main polyphenol in walnuts is pedunculagin, an ellagitannin. After consumption, ellagitannins are hydrolysed to release ellagic acid, which is converted by gut microflora to urolithin A and other derivatives such as urolithins B, C, and D. Ellagitannins possess well known antioxidant and anti-inflammatory bioactivity, and several studies have assessed the potential role of ellagitannins against disease initiation and progression, including cancer, cardiovascular, and neurodegenerative diseases.

Dietary pattern and colonic diverticulosis. (2017).
High-fibre diet does not prevent diverticulosis occurrence, and results about prevention/treatment of diverticular disease and acute diverticulitis are still conflicting. No association was seen between nut, corn or popcorn consumption and occurrence of diverticulosis, diverticular disease and acute diverticulitis.

Diverticular disease: reconsidering conventional wisdom. (2013).
Nuts and seeds do not increase the risk of diverticulitis or diverticular bleeding.

Lifestyle factors and the course of diverticular disease. (2012).
Contrary to a long-standing belief, a large prospective study found that nuts and corn did not increase the risk of diverticulitis or diverticular bleeding.

Low-residue diet in diverticular disease: putting an end to a myth. (2011)
Historically, low-residue diets have been recommended for diverticulosis because of a concern that indigestible nuts, seeds, corn, and popcorn could enter, block, or irritate a diverticulum and result in diverticulitis and possibly increase the risk of perforation. To date, there is no evidence supporting such a practice. In contrast, dietary fibre supplementation has been advocated to prevent diverticula formation and recurrence of symptomatic diverticulosis, although this is based mostly on low-quality observational studies.

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