Recent studies have suggested that the intestinal microbiome plays an important role in modulating risk of several chronic diseases, including inflammatory bowel disease, obesity, type 2 diabetes, cardiovascular disease, and cancer. At the same time, it is now understood that diet plays a significant role in shaping the microbiome, with experiments showing that dietary alterations can induce large, temporary microbial shifts within 24 h. Given this association, there may be significant therapeutic utility in altering microbial composition through diet. This review systematically evaluates current data regarding the effects of several common dietary components on intestinal microbiota. We show that consumption of particular types of food produces predictable shifts in existing host bacterial genera. Furthermore, the identity of these bacteria affects host immune and metabolic parameters, with broad implications for human health. Familiarity with these associations will be of tremendous use to the practitioner as well as the patient.

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Influence of diet on the gut microbiome and implications for human health.

The health benefits of dietary fiber have long been appreciated. Higher intakes of dietary fiber are linked to less cardiovascular disease and fiber plays a role in gut health, with many effective laxatives actually isolated fiber sources. Higher intakes of fiber are linked to lower body weights. Only polysaccharides were included in dietary fiber originally, but more recent definitions have included oligosaccharides as dietary fiber, not based on their chemical measurement as dietary fiber by the accepted total dietary fiber (TDF) method, but on their physiological effects. Inulin, fructo-oligosaccharides, and other oligosaccharides are included as fiber in food labels in the US. Additionally, oligosaccharides are the best known “prebiotics”, “a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microflora that confers benefits upon host well-bring and health.” To date, all known and suspected prebiotics are carbohydrate compounds, primarily oligosaccharides, known to resist digestion in the human small intestine and reach the colon where they are fermented by the gut microflora. Studies have provided evidence that inulin and oligofructose (OF), lactulose, and resistant starch (RS) meet all aspects of the definition, including the stimulation of Bifidobacterium, a beneficial bacterial genus. Other isolated carbohydrates and carbohydrate-containing foods, including galactooligosaccharides (GOS), transgalactooligosaccharides (TOS), polydextrose, wheat dextrin, acacia gum, psyllium, banana, whole grain wheat, and whole grain corn also have prebiotic effects.

Fiber and prebiotics: mechanisms and health benefits.

Objective  To quantify the dose-response relation between consumption of whole grain and specific types of grains and the risk of cardiovascular disease, total cancer, and all cause and cause specific mortality. Data sources  PubMed and Embase searched up to 3 April 2016. Study selection  Prospective studies reporting adjusted relative risk estimates for the association between intake of whole grains or specific types of grains and cardiovascular disease, total cancer, all cause or cause specific mortality. Data synthesis  Summary relative risks and 95% confidence intervals calculated with a random effects model. Results  45 studies (64 publications) were included. The summary relative risks per 90 g/day increase in whole grain intake (90 g is equivalent to three servings—for example, two slices of bread and one bowl of cereal or one and a half pieces of pita bread made from whole grains) was 0.81 (95% confidence interval 0.75 to 0.87; I 2 =9%, n=7 studies) for coronary heart disease, 0.88 (0.75 to 1.03; I 2 =56%, n=6) for stroke, and 0.78 (0.73 to 0.85; I 2 =40%, n=10) for cardiovascular disease, with similar results when studies were stratified by whether the outcome was incidence or mortality. The relative risks for morality were 0.85 (0.80 to 0.91; I 2 =37%, n=6) for total cancer, 0.83 (0.77 to 0.90; I 2 =83%, n=11) for all causes, 0.78 (0.70 to 0.87; I 2 =0%, n=4) for respiratory disease, 0.49 (0.23 to 1.05; I 2 =85%, n=4) for diabetes, 0.74 (0.56 to 0.96; I 2 =0%, n=3) for infectious diseases, 1.15 (0.66 to 2.02; I 2 =79%, n=2) for diseases of the nervous system disease, and 0.78 (0.75 to 0.82; I 2 =0%, n=5) for all non-cardiovascular, non-cancer causes. Reductions in risk were observed up to an intake of 210-225 g/day (seven to seven and a half servings per day) for most of the outcomes. Intakes of specific types of whole grains including whole grain bread, whole grain breakfast cereals, and added bran, as well as total bread and total breakfast cereals were also associated with reduced risks of cardiovascular disease and/or all cause mortality, but there was little evidence of an association with refined grains, white rice, total rice, or total grains. Conclusions  This meta-analysis provides further evidence that whole grain intake is associated with a reduced risk of coronary heart disease, cardiovascular disease, and total cancer, and mortality from all causes, respiratory diseases, infectious diseases, diabetes, and all non-cardiovascular, non-cancer causes. These findings support dietary guidelines that recommend increased intake of whole grain to reduce the risk of chronic diseases and premature mortality.

https://www.bmj.com/content/bmj/353/bmj.i2716.full.pdf

Whole grain consumption and risk of cardiovascular disease, cancer, and all cause and cause specific mortality: systematic review and dose-response meta-analysis of prospective studies

In the human gut, millions of bacteria contribute to the microbiota, whose composition is specific for every individual. Although we are just at the very beginning of understanding the microbiota concept, we already know that the composition of the microbiota has a profound impact on human health. A key factor in determining gut microbiota composition is diet. Preliminary evidence suggests that dietary patterns are associated with distinct combinations of bacteria in the intestine, also called enterotypes. Western diets result in significantly different microbiota compositions than traditional diets. It is currently unknown which food constituents specifically promote growth and functionality of beneficial bacteria in the intestine. The aim of this review is to summarize the recently published evidence from human in vivo studies on the gut microbiota-modulating effects of diet. It includes sections on dietary patterns (e.g. Western diet), whole foods, food constituents, as wells as food-associated microbes and their influence on the composition of human gut microbiota. The conclusions highlight the problems faced by scientists in this fast-developing field of research, and the need for high-quality, large-scale human dietary intervention studies.

Contribution of diet to the composition of the human gut microbiota.

https://pure.bond.edu.au/ws/files/32288082/AM_Dietary_fiber_intervention_on_gut_microbiota_composition_in_healthy_adults.pdf

Dietary fiber intervention on gut microbiota composition in healthy adults: a systematic review and meta-analysis.

Epidemiological studies have shown an inverse relationship between risk of CVD and intake of whole grain (WG)-rich food. Regular consumption of breakfast cereals can provide not only an increase in dietary WG but also improvements to cardiovascular health. Various mechanisms have been proposed, including prebiotic modulation of the colonic microbiota. In the present study, the prebiotic activity of a maize-derived WG cereal (WGM) was evaluated in a double-blind, placebo-controlled human feeding study (n 32). For a period of 21 d, healthy men and women, mean age 32 (sd 8) years and BMI 23·3 (sd 0·58) kg/m2, consumed either 48 g/d WG cereal (WGM) or 48 g placebo cereal (non-whole grain (NWG)) in a crossover fashion. Faecal samples were collected at five points during the study on days 0, 21, 42, 63 and 84 (representing at baseline, after both treatments and both wash-out periods). Faecal bacteriology was assessed using fluorescence in situ hybridisation with 16S rRNA oligonucleotide probes specific for Bacteroides spp., Bifidobacterium spp., Clostridium histolyticum/perfringens subgroup, Lactobacillus–Enterococcus subgroup and total bacteria. After 21 d consumption of WGM, mean group levels of faecal bifidobacteria increased significantly compared with the control cereal (P = 0·001). After a 3-week wash-out period, bifidobacterial levels returned to pre-intervention levels. No statistically significant changes were observed in serum lipids, glucose or measures of faecal output. In conclusion, this WG maize-enriched breakfast cereal mediated a bifidogenic modulation of the gut microbiota, indicating a possible prebiotic mode of action

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/4BA209E2E74883CF8290DD161A5F46BD/S0007114510002084a.pdf/div-class-title-determination-of-the-span-class-italic-in-vivo-span-prebiotic-potential-of-a-maize-based-whole-grain-breakfast-cereal-a-human-feeding-study-div.pdf

Determination of the in vivo prebiotic potential of a maize-based whole grain breakfast cereal: a human feeding study

Increased whole grain intake has been shown to reduce the risk of many non-communicable diseases Countries including the USA, Canada, Denmark and Australia have specific dietary guidelines on whole grain intake but others, including the UK, do not Data from 1986/87 and 2000/01 have shown that whole grain intake is low and declining in British adults The aim of the present study was to describe whole grain intakes in the most current dietary assessment of UK households using data from the National Diet and Nutrition Survey rolling programme 2008–11 In the present study, 4 d diet diaries were completed by 3073 individuals between 2008 and 2011, along with details of socio-economic status (SES) The median daily whole grain intake, calculated for each individual on a dry weight basis, was 20 g/d for adults and 13 g/d for children/teenagers The corresponding energy-adjusted whole grain intake was 27 g/10 MJ per d for adults and 20 g/10 MJ per d for children/teenagers Whole grain intake (absolute and energy-adjusted) increased with age, but was lowest in teenagers (13–17 years) and younger adults up to the age of 34 years Of the total study population, 18 % of adults and 15 % of children/teenagers did not consume any whole-grain foods Individuals from lower SES groups had a significantly lower whole grain intake than those from more advantaged classifications The whole grain intake in the UK, although higher than in 2000/01, remains low and below that in the US and Danish recommendations in all age classes Favourable pricing with increased availability of whole-grain foods and education may help to increase whole grain intake in countries without whole-grain recommendations Teenagers and younger adults may need targeting to help increase whole grain consumption

/pdf/low-whole-grain-intake-in-the-uk-results-from-the-national-17tjvszbbh.pdf

Low whole grain intake in the UK: results from the National Diet and Nutrition Survey rolling programme 2008-11

Epidemiological evidence suggests an inverse association between whole grain consumption and the risk of non-communicable diseases, such as CVD, type 2 diabetes, obesity and some cancers. A recent analysis of the National Diet and Nutrition Survey rolling programme (NDNS-RP) has shown lower intake of whole grain in the UK. It is important to understand whether the health benefits associated with whole grain intake are present at low levels of consumption. The present study aimed to investigate the association of whole grain intake with intakes of other foods, nutrients and markers of health (anthropometric and blood measures) in the NDNS-RP 2008–11, a representative dietary survey of UK households. A 4-d diet diary was completed by 3073 individuals. Anthropometric measures, blood pressure levels, and blood and urine samples were collected after diary completion. Individual whole grain intake was calculated with consumers categorised into tertiles of intake. Higher intake of whole grain was associated with significantly decreased leucocyte counts. Significantly higher concentrations of C-reactive protein were seen in adults in the lowest tertile of whole grain intake. No associations with the remaining health markers were seen, after adjustments for sex and age. Over 70 % of this population did not consume the minimum recommend intake associated with disease risk reduction, which may explain small variation across health markers. Nutrient intakes in consumers compared with non-consumers were closer to dietary reference values, such as higher intakes of fibre, Mg and Fe, and lower intakes of Na, suggesting that higher intake of whole grain is associated with improved diet quality.

/pdf/whole-grain-intake-and-its-association-with-intakes-of-other-fpi4q0vh3x.pdf

Whole grain intake and its association with intakes of other foods, nutrients and markers of health in the National Diet and Nutrition Survey rolling programme 2008-11.

Increased whole grain intake has been shown to reduce the risk of many non-communicable diseases such as cardiovascular disease, type 2 diabetes, obesity and some cancers. In response to the evidence, some countries including the US, Canada, Denmark and Australia have dietary guidelines on whole grain intake. However, there is no whole grain specific dietary recommendation in the UK and analysis of dietary survey data from 1986 and 2000 showed that whole grain intake was low and declining in British adults. The aim of this study was to describe the whole grain intake in the most current dietary assessment of the UK, The National Diet and Nutrition Survey (NDNS) 2008-11. The NDNS is a representative dietary survey of households in the UK. Four-day diet diaries were completed by 3073 individuals between 2008 and 2011, along with details of socio-economic status (SES). Daily whole grain intake was calculated for each individual on a dry weight basis. Median whole grain intake was 19·6 g/d and 13·4 g/d for adults (18+ years) and children/teenagers (1·5–17 years), respectively (Fig. 1). Whole grain intake increased with age but was lowest in teenagers (13–17 years) and younger adults up to age 34 years, for whom intakes were lower than those in all other age groups. There were 18% and 15% non-consumers of any wholegrain foods, for adults and children/teenagers, respectively. After adjustment for energy intake, adult females had higher whole grain intake than males. Those from lower SES groups had significantly lower whole grain intake than those more advantaged classifications.

/pdf/whole-grain-intake-in-the-uk-remains-low-results-from-the-acq19g4qt6.pdf

Whole grain intake in the UK remains low: results from the National Diet and Nutrition Survey rolling programme years 1, 2 and 3

There is much epidemiological evidence to suggest an inverse association of whole grain consumption with the risk of many noncommunicable diseases. The risk of cardiovascular disease, type 2 diabetes, obesity and some cancers has been shown to be reduced in higher consumers against low or non-consumers of whole grain. We have previously shown that whole grain intake in the National Diet and Nutrition Survey (NDNS) 2008–2011 population is low, with 18% of adults and 15% of children/teenagers consuming no whole grain. It is important to understand whether the health benefits associated with intake of whole grains are still present at low levels of consumption. The aim of this study was to investigate the association of daily whole grain intake with intakes of other foods and nutrients, and markers of health (anthropometric and blood measures) in the NDNS 2008–2011 population. The NDNS is a representative dietary survey of households in the UK. Four-day diet diaries were completed by 3073 individuals between 2008 and 2011, along with the collection of anthropometric measures (height, weight, waist/hip ratio and body mass index (BMI)), blood pressure and blood samples. Daily whole grain intake was calculated for each individual, considering foods with any whole grain content, on a dry matter basis. Whole grain intake was also categorised by number of servings, with one serving classified as 16 g of whole grain, according to the US definition. Over half (57%) of and children/teenagers (1·5–18 years) and 44% of adults (19+ years) did not consume one serving of whole grain per day. Around a quarter of adults (24%) and children/teenagers (26%) consumed one serving of whole grain per day. Significant trends across increasing whole grain servings (0, 1, 2, 3 or more) were seen with decreasing C-reactive protein concentrations in adults, decreasing white blood cell count in both adults and children/teenagers and decreasing weight and BMI in children/teenagers. No significant trends were seen with the other blood measures (blood pressure, cholesterol (total, HDH, LDL), triglycerides, creatinine and haemoglobin) and anthropometric measures in adults. Increased intakes of whole grain was correlated with increasing intakes of milk, yogurt, bread, ready to eat cereal and fruit and vegetable intake. Significantly higher mean intakes of fibre, iron, calcium, potassium, phosphorus, magnesium, thiamin and riboflavin were seen in both adult and child/teenager whole grain consumers compared with non-consumers. In this population increased whole grain intake was positively associated with white blood cell count, C-reactive protein (in adults only) and anthropometric measures (in children and teenagers only), but not with other markers of health. Whole grain intake was generally low, with over 80% of adults, teenagers and children not consuming the minimum US recommendation (48 g or 3 servings a day), which may explain the small variation across other markers of health. The nutrient intakes of wholegrain consumers compared with the non-consumers were closer to dietary reference values, particularly for fibre intake, suggesting that increasing whole grain intake is associated with improved diet quality.

Whole grain intake is associated with intakes of other foods and nutrients and some markers of health in the National Diet and Nutrition Survey rolling programme years 1, 2 and 3

Brigid McKevith

Papers

Determination of the in vivo prebiotic potential of a maize-based whole grain breakfast cereal: a human feeding study

Low whole grain intake in the UK: results from the National Diet and Nutrition Survey rolling programme 2008-11

Whole grain intake and its association with intakes of other foods, nutrients and markers of health in the National Diet and Nutrition Survey rolling programme 2008-11.

Whole grain intake in the UK remains low: results from the National Diet and Nutrition Survey rolling programme years 1, 2 and 3

Whole grain intake is associated with intakes of other foods and nutrients and some markers of health in the National Diet and Nutrition Survey rolling programme years 1, 2 and 3