In a recent study published in the Nutrients Journal, researchers reviewed the relationship between the gut microbiome and oat consumption. They discussed the health benefits of the metabolites produced by the gut microbiome, primarily short-chain fatty acids.
Study: Relationship between Oat Consumption, Gut Microbiota Modulation, and Short-Chain Fatty Acid Synthesis: An Integrative Review. Image Credit: Vladislav Noseek/Shutterstock.com
Background
Oats are a good source of soluble and insoluble fibers. Because of their phenolic compound, lipid, and fiber content, they are considered functional food and a good source of prebiotics.
The soluble fiber β-glucan has been extensively studied as a prebiotic and is believed to have cholesterol-lowering and hypoglycemic effects.
Furthermore, the fermentation of β-glucan by the gut microbiota is thought to produce acetate, butyrate, propionate., and short-chain fatty acids, as well as impact the composition of the gut microbiome.
Unique phenolic compounds, such as avenanthramides, avenacolysates, and avenacins, present in oats are believed to have anti-inflammatory and antioxidant properties. Thus they could protect against colon cancer, coronary heart disease, and dermatological problems.
Oats are also a source of proteins such as prolamins and globulins, and because of their lack of gluten, they can be consumed by individuals with celiac disease.
The gut microbiome plays a vital role in metabolism, nutrient digestion and uptake, and immunomodulatory and endocrine functions. Furthermore, the gut microbiome is also involved in maintaining the integrity of the mucus layer and improving intestinal permeability.
Dysbiosis of the gut microbiome has been linked to various diseases such as psoriasis, tuberculosis, Parkinson's disease, and even mental health and cognitive problems.
Diet has a significant impact on gut microbiome diversity and function, and foods containing fibers with prebiotic properties that can help modulate the gut microbiota have been of substantial research interest recently.
About the study
In the present study, the researchers conducted an integrative review of original articles comprising in vivo, in vitro, and clinical trials published between 2012 and 2023 that examined the use of oat products and supplements in modulating the gut microbiome function.
Publications were screened for relevance, and those not specific to oats that had examined a population with a particular disease or other reviews were eliminated. The final evaluation was based on 16 publications consisting of in vitro studies, in vivo using animal models, and clinical trials among humans.
Major findings
The findings suggested that oats are an excellent source of fiber and can help meet the adequate fiber intake requirements for adults of both sexes.
Furthermore, based on the protein, carbohydrate, unsaturated fatty acid, mineral, vitamin, and insoluble fiber composition of oats, as well as the presence of β-glucan, which has cholesterol-lowering properties, oats should be considered a functional food.
While the United States (U.S.) Food and Drug Administration (FDA) does not have a regulatory definition for the term 'functional food,' it has authorized the use of soluble fiber from oats for lowering the risk of coronary heart disease.
Major bioactive compounds in oats consist of flavonoids, vitamin E, phenolics, avenanthramides, and phytosterols. Vitamin E is known to have anti-inflammatory and antioxidant properties that are believed to lower the risk of cardiovascular disease and cancer.
Phenolic compounds such as caffeic, phytic, coumaric, and vanillic acids and over 25 avenanthramides found in oats are also thought to have potent antioxidant properties. Studies have also investigated the antiatherogenic, pro-apoptotic, anti-proliferative, and anti-inflammatory properties of avenanthramides.
Evidence from various studies indicates that the consumption of oats effectively lowers the low-density lipoprotein and total cholesterol levels in overweight or obese individuals, as well as type 2 diabetes patients.
A meta-analysis in the review reported that β-glucan consumption was linked to a significant reduction of total cholesterol. The researchers discussed various mechanisms through which β-glucan can lower cholesterol levels.
β-glucan is thought to increase the viscosity of the intestine's contents, limiting the reabsorption of bile acids to the terminal ileum, resulting in the excretion of bile through feces. Lowering bile acids triggers the de-novo synthesis of bile acids, which utilizes cholesterol.
β-glucan is also thought to modulate the gut microbiome composition and function, with the increase of bacteria such as Lactobacillus, Bacteroides, and Bifidobacterium with high bile salt hydrolase activity playing a major role in the deconjugation of bile acids and limiting their reabsorption.
Emerging data also suggests that the fermentation of fiber by the gut microbiome produces short-chain fatty acids, which inhibit the release of renin by activating receptors in the blood vessels and kidneys, lowering blood pressure.
Furthermore, while additional studies are required on the health benefits of short-chain fatty acids, early evidence indicates that β-glucan from oats encourages the growth of beneficial gut microbiota and exhibits prebiotic properties through fermentation and production of short-chain fatty acids.
Conclusions
Overall, the review provided a comprehensive view of the current research on the beneficial effects of oat consumption on gut microbiome function and the synthesis of short-chain fatty acids.
While evidence from various studies suggests that the soluble and insoluble fibers, as well as the phenolic compounds found in oats, provide a wide range of health benefits, including cholesterol-lowering, anti-inflammatory, and antioxidant properties, further research is required for conclusive evidence.
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