Diet, Perceived Intestinal Well-Being and Compositions of Fecal Microbiota and Short Chain Fatty Acids in Oat-Using Subjects with Celiac Disease or Gluten Sensitivity  
[PERSON]  
1 Food Chemistry and Food Development, Department of Biochemistry, University of Turku, 20520 Turku, Finland; [EMAIL_ADDRESS] (L.N.); [EMAIL_ADDRESS] (S.H.); [EMAIL_ADDRESS] (B.Y.)  
[PERSON]  
1 Food Chemistry and Food Development, Department of Biochemistry, University of Turku, 20520 Turku, Finland; [EMAIL_ADDRESS] (L.N.); [EMAIL_ADDRESS] (S.H.); [EMAIL_ADDRESS] (B.Y.)  
[PERSON]  
2 Department of Future Technologies, University of Turku, 20520 Turku, Finland; [EMAIL_ADDRESS] (S.H.); [EMAIL_ADDRESS] (B.Y.)  
[PERSON]  
3 Functional Foods Forum, University of Turku, 20520 Turku, Finland; [EMAIL_ADDRESS] (M.Kalliomaki@utu.  
strict GFD may be challenging to maintain due to social and economic burdens. Even when maintained, GFD may be restricted and nutritionally suboptimal, since many gluten-free products have high fat and sugar but low fiber content. Such a diet predisposes patients to constipation, obesity and cardiovascular diseases [3; 4; 5].  
The use of nutritious and fiber-rich whole-grain oats would diversify the GFD and improve the palatability, texture and fiber-content of the diet. Pure oats are being grown and produced following strict agricultural practices to minimize the contamination with other cereals. In Finland, oats are a major ingredient in the traditional daily diet and since the year 2000, pure oats have been considered suitable for the gluten-free diet [6]. Nowadays, oat products are widely used among Finnish celiac disease patients [7]. Although the inclusion of oats on GFD is recommended in Nordic countries, it is still not globally applied, possibly due to the debate regarding the safety of oats for CeD patients [8; 9].  
The intestinal microbiota primes the immune system and provides enzymes that expand the metabolic capacity of the host. The conversion of dietary components, such as dietary fiber, that escape the digestion of the host enzymes, support also the growth of microbes themselves. Intestinal microbiota and its metabolites play a major role in defining the antigen milieu of enterocytes, since they are able to interfere with the cells of the intestinal epithelium and modulate the signaling pathways through specific receptors [10]. It is assumed that a decreased microbiota diversity and relative abundances of specific bacterial taxa may lead to functional imbalance where the mutualistic relationship between the host and his microbes is disturbed. Indeed, deviations in the microbiota community structure have been associated with several local and systemic diseases, possibly contributing to the pathogenesis and/or clinical manifestation of these diseases (reviewed in [11]). In addition, GFD as such has been associated with potentially harmful alterations in microbiota, such as decreased microbiota richness, decreased amounts of bifidobacteria, lactobacillus as well as _Faecalibacterium prausnitzii_ and increased amounts of _Proteobacteria_[12; 13]. However, currently, the majority of the studies published on the fecal microbiota of celiac disease patients have been conducted with pediatric patients or by using conventional methods with limited throughput (reviewed in [14]).  
To our understanding, the present study is one of the first on the gastrointestinal well-being and intestinal microbiota of persons with NCGS and within the few evaluating the intestinal microbiota of adult oat-using CeD subjects. The aim of this study was to evaluate the effect of oat consumption on the dietary status and gut well-being among adult subjects with gluten-related disorders who consume oat products on daily basis compared to healthy, oat consuming controls by using fecal microbiota signatures and its metabolites (short-chain fatty acids (SCFAs), ammoniacal nitrogen and \(\beta\)-glucuronative activity) as biomarkers.