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What are the gastrointestinal advantages of consuming soybean?

What are the gastrointestinal advantages of consuming soybean?

In a recent review published within the journal Nutrients, researchers at Australia’s CSIRO reviewed existing literature on the dietary implications of soy intake in regards to the intestinal microbiome.

Soybean, an economically essential legume worldwide, is enriched in dietary plant-based protein, comprising several ingredients that make suitable meat substitutes. Soy protein may modulate gut health and significantly mitigate the chance of colorectal cancer (CRC) by influencing the gut microbial structure and activities.

Soy and Gastrointestinal Health: A Review. Image Credit: nnattalli / Shutterstock

In regards to the review

In the current review, researchers presented the gastrointestinal (GI) advantages of soy consumption.

Literature search and soybean content

The PubMed database was searched in June 2021 to discover human and animal observational studies, meta-analyses, clinical trials, and reviews on the impact of soy intake on intestinal health. Initially, 1,024 records were identified, following which 20 records, including meta-analyses and reviews, and 33 records, including other forms of study designs, underwent full-text screening and were considered for the ultimate evaluation. Nearly all of the included records focussed on the advantages of consuming soy milk on gastrointestinal health.

No other plant-based protein apart from soy protein comprises all nine essential forms of amino acid substances in sufficient quantity to fulfill the physiological needs of humans. As well as, soy proteins comprise almost double the quantity of protein in often consumed legumes and beans and a greater amount of polyunsaturated fatty acids resembling omega-6 fatty acids, linoleic acid, and α-linolenic acid than other legumes.

As well as, soy accommodates an equivalent amount of leucine to eggs and fish. Concerning GI health, the important thing dietary constituents of soybeans include phytoestrogens, isoflavones, oligosaccharides (resembling stachyose and raffinose), and soy proteins. Soy phytochemicals resembling phytates, phytosterols, protease inhibitors, phenolic acids, and saponins have anti-carcinogenic properties. Genistein, an isoflavone in soy, may very well be used to administer tumors since genistein can induce apoptosis and cellular differentiation and inhibit angiogenesis and cellular proliferation.

Along with the content of dietary fibers, mainly oligosaccharides, soybeans comprise non-starch-type polysaccharides resembling cellulose, pectin, hemicellulose, xyloglucan, and pectic polysaccharides, that promote gut fermentation. Soybeans are also a terrific source of micronutrients resembling zinc, iron, and calcium, often in limited quantities in plant-sourced foods. As well as, the high content of calcium in soybeans makes them suitable dairy substitutes.

Effects of soybean intake on gut health

Various dietary constituents of soy milk, soybeans, and textured soy proteins escape digestion within the upper gastrointestinal tract and turn into substrates for microbial organisms that reside within the colon. Studies have reported either an inverse or no relationship between soy (particularly isoflavone) consumption and the chance of CRC. Fermented soy milk, as an alternative of normal soy milk, has shown more consistent fecal microbiome alterations, probably as a result of probiotic effects, especially amongst equol-metabolizing individuals.

The oligosaccharides in soy products increase fecal and caecal short-chain fatty acid (SCFA) content, which supply energy to colonocytes, regulate regulatory T lymphocyte counts, and exert protective physiological effects on various organs of the human body. Nonetheless, a high-level intake of soy proteins (above 25.0% weight) can induce genotoxic and cytotoxic damage to the intestine, which could be lowered by adding fermentable fibres to soy-based diets.

Fermented soy products, resembling tofu, contain microbes resembling Streptococcus, Bifidobacteria, and Enterococcus. Soy consumption, particularly fermented soy milk, can increase the abundance of Lactobacilli, Fusobacterium prausnitzii, Coprococcus, Faecalibacterium, Roseburia, Parabacteroides, and Faecalibacterium prausnitzii.

Quite the opposite, soy intake reduces the abundance of Bacteroidaceae, Porphyromonadaceae, Ruminococus, and Lachnospiraceae. Nonetheless, lowered Lactobacillus abundance has also been reported, followed by soy intake, in just a few studies. Replacing dietary casein with soy-containing milk can reverse microbial imbalances by elevating the Firmicutes to Bacteroidetes ratio within the fecal microbiome.

By restoring gut microbial balance, soy can improve several measures of inflammation and intestinal cellular damage. Further, soy protein can modulate the metabolism of bile acids within the intestines by elevating the ratio of secondary to primary bile acids and expanding the taxa that may very well be involved in bile acid transformation.

A murine model-based study reported that combining raffinose and soy proteins considerably increased immunoglobulin A (IgA) antibody titers within the caecum, an effect not observed within the raffinose and casein group. This increase in IgA titers is taken into account a positive response to stop pathogenic microbes from invading the colon.


Overall, the review findings showed that soy foods could improve GI health by increasing the abundance of useful microbes and reducing that of pathogenic microbes, reducing gut inflammation and associated cell damage. The GI-protective effects against cancer and intestinal diseases are pronounced by means of fermented soy milk (somewhat than unfermented) and amongst individuals with equol-metabolizing potential.

Nonetheless, existing data has emphasized using soy milk, which has a low protein content. Subsequently, further research, including large-scale randomized controlled trials (RCTs), is required to evaluate the advantages of consuming other soy-based products, including those comprising textured soy proteins in high amounts, to guide dietary decision-making and policy formulation.


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