Whole-Grain Rye and Wheat Affect Some Markers of Gut Health without Altering the Fecal Microbiota in Healthy Overweight Adults: A 6-Week Randomized Trial

Abstract

Whole grains have shown potential for improving gut health, but evidence comparing different whole-grain types is lacking. We investigated whether whole-grain wheat (WGW) and whole-grain rye (WGR) improve gut health in different ways compared to refined wheat (RW), with the primary outcomes of microbiota composition and gastrointestinal (GI) symptoms. In a randomized parallel trial, 70 healthy adults (in means ± SDs; aged 51.0 ± 9.4 y, body mass index [BMI (in kg/m)] 27.8 ± 1.9, 32:38 men:women) replaced cereal foods from their habitual diet with WGR, WGW, or RW (control). Before and after a 6-wk intervention, a spot stool sample was collected and analyzed for short-chain fatty acids and microbiota composition through the use of 16S ribosomal RNA gene-targeted high-throughput amplicon sequencing. GI symptoms and stool regularity were evaluated by questionnaires at baseline and after weeks 2, 4, and 6. Intakes of whole grains were 145.2 ± 75.9, 124.2 ± 57.3, and 5.4 ± 3.2 g/d in the WGW, WGR, and RW groups, respectively. Gut microbiota composition was not affected by diet. The relative change in fecal butyrate decreased in the RW (-38%) group compared to the WGW (25%, = 0.014) and WGR groups (-1%, = 0.037). Other short-chain fatty acids were unaffected. Flatulence was more frequent following intake of WGW (OR: 2.06, 95% CI: 1.03, 4.17) and WGR (OR: 2.62, 95% CI: 1.35, 5.22) compared to RW, whereas bloating was less frequent following WGW (OR: 0.38, 95% CI: 0.18, 0.80) and WGR (OR: 0.34, 95% CI: 0.16, 0.72). Stool frequency increased following WGR but not WGW, compared to RW in weeks 2 (0.4 defecations/d, = 0.049) and 4 (0.5 defecations/d, = 0.043), but not in week 6. The WGW and WGR groups did not differ from each other in any of the variables tested. Regular consumption of WGR and WGW affected fecal butyrate concentration and gastrointestinal symptoms in healthy overweight adults, supporting the hypothesis that WGR and WGW can be included in the diet equally to maintain gut health. This trial was registered at clinicaltrials.gov as NCT02358122.

Randomised clinical trial: effect of low-FODMAP rye bread versus regular rye bread on the intestinal microbiota of irritable bowel syndrome patients: association with individual symptom variation

“…Our study adds to the previous evidence that the addition or substitution of specific, high-fibre grains/cereals while the individual continues with his/her otherwise habitual diet does not alter the microbial diversity or cause other community-wide microbiota effects [22][23][24][25]. Instead, specific changes in individual bacterial taxa were observed when comparing the baseline versus post-intervention microbiota (Fig.…”

“…2). Recently, Swedish researchers studied the effects of refined wheat, whole grains wheat and rye in 70 healthy volunteers [23]. The intestinal microbiota composition was not affected by any of these grain products in that 6-week cross-over study.…”

A new rye‐based beverage with high polyphenols and amino acids: Production and study of physicochemical and sensory properties

“…Rye grains also contain ferulic and diferulic acids as the major phenolic compounds in rye, contributing to the antioxidant effects of rye (Bondia‐Pons et al, ). Consuming rye‐based foods/beverages with high insoluble fiber and higher phenolic compounds, may result in: free radicals scavenging, inhibition of human LDL cholesterol oxidation (Abdel‐Aal & Rabalski, ), reduction in gallstones generation, promoting weight loss (Afzal et al, ), lowering the risk of breast cancer and diabetes (Adlercreutz, ; Van Dam, Hu, Rosenberg, Krishnan, & Palmer, ), attenuating the cardiovascular diseases, and promoting the gastrointestinal health (Vuholm et al, ). Other protective effects of high fiber‐containing diet includes protection from breast cancer (Pietinen et al, ), prostate cancer (Torfadottir et al, ), and colon cancer (Kyrø et al, ), childhood asthma (Tabak et al, ), and inflammation in people with metabolic syndrome have been reported (Kallio et al, ).…”

Differential Physiological Responses Elicited by Ancient and Heritage Wheat Cultivars Compared to Modern Ones

“…Human studies showed changes in the amount of bacterial family and species linked to whole wheat consumption. In particular, an increase in Bifidobacterium, Lactobacillus, Enterococcus, and Prevotella species [70,71] and a decrease of Dialister, Blautia, and Collinsella [71] have been linked to whole wheat consumption, even if no changes resulted at genus or higher taxonomic levels [71,72]. However, while providing interesting data taken as a whole, these studies show a strong heterogeneity in the experimental design and in the methods used, as pointed out by Koecher and collaborators [73].…”