Effects of oats on gastrointestinal health as assessed by in vitro, animal, and human studies

Abstract

Oats are uniquely nutritious, owing to their composition of bioactive compounds, lipids, and β-glucan. Scientific research has established that oats can improve diet quality, reduce cholesterol, regulate satiety, and protect against carcinogenesis in the colon; however, determining the effects of oats on gastrointestinal health and the gut microbiome is a newer, evolving area of research. To better understand the effects of oats on gastrointestinal health in humans, a literature review with predefined search criteria was conducted using the PubMed database and keywords for common gastrointestinal health outcomes. Moreover, to examine the gastrointestinal effects of oats across the scientific spectrum, a similar search strategy was executed to identify animal studies. In vitro studies were identified from the reference lists of human and animal studies. A total of 8 human studies, 19 animal studies, and 5 in vitro studies met the inclusion criteria for this review. The evidence in humans shows beneficial effects of oats on gastrointestinal health, with supportive evidence provided by in vitro and animal studies. The effective dose of oats varies by type, although an amount providing 2.5 to 2.9 g of β-glucan per day was shown to decrease fecal pH and alter fecal bacteria. For oat bran, 40 to 100 g/d was shown to increase fecal bacterial mass and short-chain fatty acids in humans. Differences in study design, methodology, and type of oats tested make valid comparisons difficult. The identification of best practices for the design of oat studies should be a priority in future research, as the findings will be useful for determining how oats influence specific indices of gastrointestinal health, including the composition of the human gut microbiome.

Health benefits of whole grain: effects on dietary carbohydrate quality, the gut microbiome, and consequences of processing

“…Dietary fibers elicit different gastrointestinal responses largely due to their solubility and fermentability affecting transit time and stool weight. These effects vary between intact cereal fibers, and dietary fiber from fruits and vegetables (de Vries et al., 2016), and between cereal types (de Vries et al., 2015; Korczak & Slavin, 2020; Korczak et al., 2019). The impact of dietary fiber on health outcomes is indisputable and has been the subject of numerous reviews (see, e.g., Koç et al., 2020; Veronese et al., 2018) but the relative importance of cereal fiber compared with dietary fiber from fruits and vegetables is less certain (Cui et al., 2019), and while most food‐based dietary guidelines stress the importance of whole grains as sources of dietary fiber, the emphasis in most guidelines remains on fruits and vegetables as primary sources of dietary fiber.…”

Effect of Oat β-Glucan on Affective and Physical Feeling States in Healthy Adults: Evidence for Reduced Headache, Fatigue, Anxiety and Limb/Joint Pains

“…However, the association between GI and non-GI symptoms could have a physiological basis via the gut-brain axis. There is abundant evidence from studies in vitro and in animal models that oats and OBG influence SCFA production and the colonic microbiome [ 14 ], although the results are inconsistent and there are few studies in humans. OBG-enriched oat bran containing 20 g/d dietary fiber and 10 g/d OBG did not increase fecal SCFA after 4 weeks but did so at 8 and 12 weeks in healthy subjects [ 28 ].…”

“…Oats and oat bran appear to increase stool weight per gram of dietary fiber to a similar extent as other sources of fiber [ 13 ]. Oats also decrease fecal pH (a marker of increased short-chain fatty acid (SCFA) production) and increase the growth of beneficial gut microbiota [ 14 ]. Plausible mechanisms have been proposed whereby the stimulation of SCFA production and alteration of the colonic microbiome can influence systemic oxidative stress and inflammation and thereby influence both physical and mental functioning [ 15 , 16 , 17 ].…”

Gluten‐free and prebiotic oat bread: Optimization formulation by transglutaminase improvement dough structure

“…β-glucan plays a critical role in improving the intestinal environment by promoting beneficial microorganisms growth and reducing harmful metabolites in the intestinal tract (Shen et al, 2012). An oat-based diet had a positive effect on intestinal Lactobacillus abundance in pigs (Cardinal et al, 2020), which can also increase Bifidobacterium in colon, producing butyrate in cecal, and reducing fecal ammonia emissions (Korczak et al, 2020). The rats were administered an oatmeal diet the number of Bifidobacterium in colon, and Lactobacillus in cecum, colon, and feces were higher than those of the control (p < .05) (Fu et al, 2020).…”

“…Scientific evidence from in vitro studies suggests that oats or oat ingredients were good for gastrointestinal health (Korczak et al, 2020). Intake of oats also produced short-chain fatty acids, making the intestinal environment acidic, thus promoting beneficial intestinal flora growth and improving intestinal flora imbalance (Guo et al, 2020).…”