A good gut feeling: the benefits of soya intake on gastrointestinal health

Aim

This review aimed to collate data from clinical trials, observational studies and animal trials relating to the impacts of soya bean and soya-based product consumption on a variety of gastrointestinal (GI) health outcomes.

Soya was selected as a legume of importance due to its high-quality nutritional quality and versatility as a plant-based protein source.

Method

An initial literature review encompassed publications that included information on gut health endpoints as well as soya consumption as a modulating mediator of these endpoints.

1024 pieces of research were identified and then sorted into two groups: 20 reviews and meta-analyses as well as 33 other relevant records.

Soya protein, and specific soya products were considered and their impact on microbial composition, microbial metabolites and GI diseases like colorectal cancer are reported.

Key findings

Anti-inflammatory potential and the gut microbiome

By restoring gut microbial balance, soya can improve several measures of inflammation and intestinal cellular damage.

Soya milk alternative has shown varying effects on the gut microbiome, with fermented soy milk alternatives potentially exerting probiotic effects by increasing the abundance of beneficial microbes like Bifidobacterium and Lactobacillus.

The review found that isoflavones, found abundantly in soya, may influence the gut microbiome, particularly in individuals who can metabolize equol.

Clinical trials have shown inconsistent results regarding the effects of isoflavones on microbial composition, suggesting the need for further investigation.

Clinical trials evaluating soy milk alternatives anti-inflammatory properties have shown mixed results, with some studies indicating potential benefits in inflammatory bowel disease models in patients with type-2 diabetes.

Studies are currently underway to assess if soya milk alternative consumption can improve ulcerative colitis symptoms, building on the beneficial impacts of soya observed on inflammation and cell wall damage in animal models. Unfermented soya milk alternative’s impact on microbial abundance is also inconsistent.

Soya proteins

Studies on soya proteins in particular have primarily been conducted in animal models and indicate that soya protein consumption may increase microbial diversity and alter the abundance of specific microbes, although results vary between studies.

Soya proteins have been associated with increased production of healthy short-chain fatty acids (SCFAs). Additionally, soya protein consumption may modulate bile acid metabolism, but evidence is limited and inconsistent.

These findings suggest that soya protein may be used by the microbiome to promote SCFA production, a benefit not observed with dairy protein consumption.

Colorectal cancer

Epidemiological evidence regarding soya food consumption and CRC risk suggest a modest inverse association, particularly in Asian populations.

This effect may be heightened by the addition of fermentable fibres to the diet. In vitro studies have indicated potential anticarcinogenic properties of soya isoflavones, but further research is needed to confirm these effects in colon cancer-derived cell lines.

Conclusion

In conclusion, soya and its components show promise in modulating gut health through a range of potential mechanisms.

An area of particular interest is soya’s role in potentially reducing CRC risk. Further clinical and mechanistic studies are warranted to better understand effects and mechanisms of action.

The type and quantity of product consumed is particularly important for further research to consider.

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