Oats as a Safe Alternative to Triticeae Cereals for People Suffering from Celiac Disease? A Review

Relationship between Oat Consumption, Gut Microbiota Modulation, and Short-Chain Fatty Acid Synthesis: An Integrative Review

The gut microbiota consists of a set of microorganisms that colonizes the intestine and ferment fibers, among other nutrients, from the host's diet. A healthy gut microbiota, colonized mainly by beneficial microorganisms, has a positive effect on digestion and plays a role in disease prevention. However, dysregulation of the gut microbiota can contribute to various diseases. The nutrition of the host plays an important role in determining the composition of the gut microbiota. A healthy diet, rich in fiber, can beneficially modulate the gut microbiota. In this sense, oats are a source of both soluble and insoluble fiber. Oats are considered a functional ingredient with prebiotic potential and contain plant proteins, unsaturated fats, and antioxidant compounds. The impact of oat consumption on the gut microbiota is still emerging. Associations between oat consumption and the abundance of Akkermansia muciniphila, Roseburia, Lactobacillus, Bifidobacterium, and Faecalibacterium prausnitzii have already been observed. Therefore, this integrative review summarizes the findings from studies on the relationship between oat consumption, the gut microbiota, and the metabolites, mainly short-chain fatty acids, it produces.

Analysis of oat seed transcriptome with regards to proteins involved in celiac disease

Oat (Avena sativa L.) is considered to be a healthy food. In contrast to other grain crops, oat is high in protein, lipids, dietary fiber, antioxidants, and uniquely in avenanthramides. The question of whether it can also be consumed by people suffering from celiac disease is still unresolved. The main aim of this study was to extract and sequence genes for potentially harmful avenins, globulins, and α-amylase/trypsin inhibitors in six oat varieties and to establish their variability using PacBio sequencing technology of enriched libraries. The results were compared with sequences of the genes already present in databases. In total, 21 avenin, 75 globulin, and 25 α-amylase/trypsin inhibitor genes were identified and mapped in the hexaploid oat chromosomes. In all of the three gene families, only marginal sequence differences were found between the oat varieties within the individual genes. Avenin epitopes were found in all four types of avenin genes occurring in all oat varieties tested within this study. However, the number of avenin genes was nearly four times lower than of globulin genes and, on the protein level, formed only 10% of storage proteins. Therefore, the question of whether oat is safe to celiac disease people is a question of boundary values.

Specific Avenin Cross-Reactivity with G12 Antibody in a Wide Range of Current Oat Cultivars

Current clinical studies confirm that the consumption of oats for people suffering from celiac disease is safe. Some studies have confirmed different levels of immunoreactive gluten epitopes of oats in different cultivars, while others explain these differences due to contamination with gluten-rich species or as random cross-reactivity ELISA of homologous oat epitopes with anti-wheat gliadin antibodies. The aim of our two-year study was therefore to map cross-reactive oat epitopes in a set of 132 oat cultivars using a G12-based ELISA kit. The results were focused on the varietal and annual level of cross-reactivity (interference) of avenin epitopes with the G12 antibody on the identification of potential cultivars with significantly different interferences and assessing the degree of risk of possible false-contamination with external gluten. Although repeated evaluations confirmed high year-to-year variability (RSD ≥ 30%) in approximately 2/3 of the cultivars, the content of interfering avenin epitopes with G12 did not exceed the considered safe limit (20 mg·kg−1) for celiacs. At the same time, not only annual but, above all, significant cultivar dependences in the interference of avenins to the G12 antibody were demonstrated. Genetic dependence was further confirmed in connection with the proven avenin polymorphism as well as immunoblotting with the identification of interfering peptides with the G12 antibody in the 25 and 30 kDa regions. It was the occurrence of two bands around 30 kDa that predominantly occurred in oat cultivars with a relatively higher content of cross-reactive avenins (12–16 mg·kg−1). Due to the fact that the contents of interfering avenins ranged in several cultivars even over 16 mg·kg−1, the choice of a suitable oat cultivar may be crucial for gluten-free food producers, as it reduces the risk of a possible false-response of the commercial ELISA kits when checking the real-gluten contamination.

A Review of Health-Beneficial Properties of Oats

Oat is among the food crops and ancient grains cultivated and consumed worldwide. It is gaining in popularity owing to its nutritional composition and multifunctional benefits of select bioactive compounds. Beta-glucan is an important component of dietary fiber found in oat grains. It is the major active compound in oats with proven cholesterol-lowering and antidiabetic effects. Oats also provide substantial levels of other bioactive compounds such as phenolic acids, tocols, sterols, avenacosides, and avenanthramides. The consumption of oats has been determined to be beneficial for human health by promoting immunomodulation and improving gut microbiota. In addition, oat consumption assists in preventing diseases such as atherosclerosis, dermatitis, and some forms of cancer. While much has been published in relation to oat nutrients and oat fibers and their impact on major diseases, the oat industries and consumers may benefit from greater knowledge and understanding of clinical effects, range of occurrence, distribution, therapeutic doses and food functional attributes of other oat bioactives such as avenanthramides and saponins as well as other anti-inflammatory agents found in the cereal. This review focuses on the various studies relevant to the contribution of the consumption of oats and oat-based products in preventing human diseases and promoting human health.

Ancient and Modern Cereals as Ingredients of the Gluten-Free Diet: Are They Safe Enough for Celiac Consumers?

Celiac disease is an autoimmune disorder that occurs in genetically predisposed individuals after consuming prolamins from some cereals. Although the products available for celiac subjects have increased significantly in quality and quantity over the last few decades, research still focuses on identifying new ingredients to improve the nutritional, sensorial and functional qualities of gluten-free products. In terms of toxicity for people with celiac disease, there is a wide variability between ancient and modern grains. The most contradictory results are related to the role of oats in the gluten-free diet. In order to clarify the role of minor cereals (such as oat) and ancient grains in the diets of celiac patients, this review discusses recent in vitro and in vivo studies performed on those cereals for which the toxicity for celiac subjects is still controversial. According to in vivo studies, selected oat varieties could be tolerated by celiac patients. On the other hands, although some wheat-ancient grains (Triticum monococcum, Triticum aestivum ssp. spelta and Kamut^®) showed a reduced in vitro toxicity, to date, these grains are still considered toxic for celiac patients. Contradictory results underline the importance of studying the safety of "unusual" cereals in more detail.

Impact of in vitro gastrointestinal digestion on peptide profile and bioactivity of cooked and non-cooked oat protein concentrates

Oat (Avena sativa) is one of the most cultivated and consumed cereals worldwide. Recognized among cereals for its high protein content (12%-24%), it makes it an excellent source of bioactive peptides, which could be modified during processes such as heating and gastrointestinal digestion (GID). This work aims to evaluate the impact of heat treatment on the proteolysis of oat proteins and on the evolution of antioxidant peptide released during in vitro static GID, in terms of comparative analysis between cooked oat protein concentrate (COPC) and non-heated oat protein concentrate (OPC) samples. The protein extraction method and cooking procedure used showed no detrimental effects on protein quality. After GID, the proportion of free amino acids/dipeptides (<0.2 ​kDa) reached >40% for both samples (OPC and COPC), thus producing peptides with low molecular weight and enhanced bioactivity. Furthermore, during GID, the amino acid profile showed an increase in essential, positively-charged, hydrophobic and aromatic amino acids. At the end of GID, the reducing power of OPC and COPC increased >0.3 and 8-fold, respectively, in comparison to the non-digested samples; while ABTS•+ and DPPH• showed a >20-fold increase. Fe2+ chelating capacity of OPC and COPC was enhanced >4 times; similarly, Cu2+ chelation showed a >19-fold enhancement for OPC and >10 for COPC. β-carotene bleaching activity was improved 0.8 times in OPC and >9 times in COPC; the oxygen radical antioxidant capacity assay increased 2 times in OPC and >4.7 times in COPC, respectively. This study suggests that OPC after cooking and GID positively influenced the nutritional and bioactive properties of oat peptides. Thus, COPC could be used as a functional food ingredient with health-promoting effects, as hydrothermal treatment is frequently used for this type of cereals.

Analysis of the genetic diversity of Russian common oat varieties using alleles of avenin-coding loci

Alleles of avenin-coding loci were identified in 24 varieties of common oat origin from 6 different breeding centers of the Russian Federation. It was found that 33% of the studied varieties are homogeneous. Heterogeneous varieties contain from 2 to 10 biotypes. The analysis revealed 67 different genotypes, ten of which are found in the spectra of several varieties at once. Despite the presence of matching genotypes, all the studied varieties differ in the genetic formulas of avenin, the number and frequency of occurrence of biotypes. This makes it possible to effectively identify and distinguish oat varieties sown by Russian breeding using the method of prolamin electrophoresis. The analyzed groups of varieties are characterized by high values of genetic (0.54-0.79) and intra-population diversity, which indicates the stability of populations. The exception is varieties originating from the Irkutsk region, low values of genetic and intra-population diversity in the population of which may indicate the process of genetic erosion. Analysis of the frequency distribution of alleles of avenin-coding loci does not allow to determine whether oat varieties belong to certain breeding centers, which is associated with the introduction of the same genotypes into the breeding programs of different regions.

Biliaderis C. Fermented Cereal-based Products: Nutritional Aspects, Possible Impact on Gut Microbiota and Health Implications

Fermentation, as a process to increase the security of food supply, represents an integral part of food culture development worldwide. Nowadays, in the evolving functional food era where new sophisticated technological tools are leading to significant transformations in the field of nutritional sciences and science-driven approaches for new product design, fermentation technology is brought to the forefront again since it provides a solid foundation for the development of safe food products with unique nutritional and functional attributes. Therefore, the objective of the present review is to summarize the most recent advances in the field of fermentation processes related to cereal-based products. More specifically, this paper addresses issues that are relevant to nutritional and health aspects, including their interrelation with intestinal (gut) microbiome diversity and function, although clinical trials and/or in vitro studies testing for cereal-based fermented products are still scarce.