2017 study:whole vs refined grain->microbiota,immune markers
Background: Observational studies suggest an inverse association between whole-grain (WG) consumption and inflammation. However, evidence from interventional studies is limited, and few studies have included measurements of cell-mediated immunity.
Objective: We assessed the effects of diets rich in WGs compared with refined grains (RGs) on immune and inflammatory responses, gut microbiota, and microbial products in healthy adults while maintaining subject body weights.
Design: After a 2-wk provided-food run-in period of consuming a Western-style diet, 49 men and 32 postmenopausal women [age range: 40–65 y, body mass index (in kg/m2) <35] were assigned to consume 1 of 2 provided-food weight-maintenance diets for 6 wk.
Results: Compared with the RG group, the WG group had increased plasma total alkyresorcinols (a measure of WG intake) (P < 0.0001), stool weight (P < 0.0001), stool frequency (P = 0.02), and short-chain fatty acid (SCFA) producer Lachnospira [false-discovery rate (FDR)-corrected P = 0.25] but decreased pro-inflammatory Enterobacteriaceae (FDR-corrected P = 0.25). Changes in stool acetate (P = 0.02) and total SCFAs (P = 0.05) were higher in the WG group than in the RG group. A positive association was shown between Lachnospira and acetate (FDR-corrected P = 0.002) or butyrate (FDR-corrected P = 0.005). We also showed that there was a higher percentage of terminal effector memory T cells (P = 0.03) and LPS-stimulated ex vivo production of tumor necrosis factor-α (P = 0.04) in the WG group than in the RG group, which were positively associated with plasma alkylresorcinol concentrations.
Conclusion: The short-term consumption of WGs in a weight-maintenance diet increases stool weight and frequency and has modest positive effects on gut microbiota, SCFAs, effector memory T cells, and the acute innate immune response and no effect on other markers of cell-mediated immunity or systemic and gut inflammation. This trial was registered at clinicaltrials.gov as NCT01902394.
All randomly assigned participants underwent a 2-wk run-in phase in which they were provided with a Western-style diet (high in saturated fats, red meats, simple carbohydrates, and processed or refined foods and low in fresh fruit and vegetables, WGs, seafood, and poultry). The purpose of the run-in period was to minimize the effect of habitual diet intake before starting the experimental diets. Total daily caloric intake of each participant was initially calculated with the use of the Harris-Benedict formula and was adjusted for physical activity when necessary to maintain the current body weights of subjects. Participants were instructed to maintain their current physical activity levels throughout the study. All meals were based on the USDA Dietary Guidelines 2010, which recommends that 50–55% of energy is derived from carbohydrates, 15–20% of energy is derived from protein, and 25–30% of energy is derived from fat (39). After completion of the run-in phase, participants were assigned to the following experimental diets: an RG diet (8 g/1000 kcal) and a WG diet (16 g/1000 kcal), respectively (Figure 1). The targeted fiber intake that was provided by the WG diet met the recommended Dietary Guidelines for Americans (35 g/d), whereas the fiber intake from the RG diet was slightly above the average intake in adults."
aww, why would you do that.
"The diets were similar in composition with the exception of the source of grain. The WG group received all grains from WG sources, and the RG group received all grains from RG-containing foods. Otherwise, the diets were matched for servings of fruit, vegetables, and protein (e.g., turkey meatloaf with 100% whole-wheat bread crumbs with mixed vegetables or turkey meatloaf with 100% white-bread crumbs with mixed vegetables). Six 240-mL glasses of water or calorie-free drinks were recommended daily. The study dietitian developed 3-d menu cycles at 3 caloric levels (2000, 2500, and 3000 kcal) that used commonly available ingredients and food items. Calories were adjusted (plus or minus) from these calorie amounts on the basis of participants’ weight fluctuations."
ok from wheat to flour to bread to crumbs in the whole grain diet. this is where i start to wonder about relative GI index type stuff.
"In this study, we showed a modest effect of WGs on the composition of microbiota and stool SCFA concentrations. These observations were consistent with 2 (30, 31) of 3 (30, 31, 35) previous studies that investigated the effects of WGs on gut microbiota. We did not observe a difference in the bacterial diversity or phyla between groups, which was in agreement with the other intervention trials that used WG wheat as the main source of WGs (31, 67). In contrast, Martínez et al. (30) used WG barley and brown rice as the main sources of WGs and reported increases in gut microbial diversity and in the Firmicutes:Bacteroidetes ratio. Similar to the results that were reported by Martínez et al. (30) and Vitaglione et al. (31), we observed differences at the genus level whereby there was an increase in the SCFA producer Lachnospira and a decrease in proinflammatory Enterobacteriaceae."
interesting, thank you barley and brown rice for joining the fun
"Note that WG foods contain more micronutrients and phenolic compounds that are known to have various health benefits, including those on immune and inflammatory responses, and we could not determine the contribution of these components, as well as their interactions with fiber, to the final effects in our clinical trial. Therefore, future intervention studies should also consider the inclusion of a variety of grains... "
"... because grains vary in types of fiber and compositions of phytochemicals and micronutrients. In particular, the WG in the current study was predominantly from wheat, whereas oats contributed <5%; however, oats are more prominent sources of soluble fiber, which are known to beneficially alter risk factors for diseases (71). Finally, genomic and epigenetic variations should be determined for the varied responses to WG intake in individuals in terms of changes in gut microbiota, inflammation status, and the immune response."