The following three research papers have been selected by our Scientific Affairs Analyst at Nestlé, Jean Kim (PhD). They are designed to provide a topline overview and summary of the relevant research paper – they are not a full scientific review. For further details of the research paper, click through to the abstracts in the links provided.
1. Impact of whole grain oat Granola on the human gut microbiota and cardio-metabolic risk factors in at risk individuals
A randomised crossover dietary intervention to test the hypothesis that whole grain oat based Granola breakfast cereal can mediate a prebiotic modulation of the human gut microbiota.
Connolly ML, Tzounis X, Tuohy KM and Lovegrove JA (2016). Hypocholesterolemic and Prebiotic Effects of a Whole-Grain Oat-Based Granola Breakfast Cereal in a Cardio-Metabolic “At Risk” Population. Frontiers in Microbiology, 7, Article 1675.
Several large epidemiological studies, and a number of meta-analyses of nutritional interventions, have reported a positive association between increased wholegrain and oats intake with reduced risk of developing chronic diseases, including the normalisation of plasma cholesterol levels (1,2).
However, few studies have examined the impact of whole grain oat based food products on human gut microbiota and no study to date has measured the ability of dietary oats to modulate the composition and relative abundance of commensal bacteria in vivo. As a result, this study aimed to determine the effectiveness of whole grain oat Granola breakfast cereal, compared to a refined breakfast cereal to beneficially modulate gut microbiota and its metabolic output, plasma lipids, gut satiety hormones and inflammation markers.
SUMMARY OF FINDINGS
Thirty-two volunteers (23-64y; 20 women, 12 men), who were at risk of developing cardio-metabolic disease by virtue of mild hypercholesterolaemia or glucose intolerance, were randomised into two groups consuming either 45g of whole grain oat granola or non-whole grain breakfast cereals daily for two 6-week intervention periods separated by a 4-week wash-out period. Faecal samples, saliva samples, and 20ml fasting venous blood samples were collected from each subject six times before and after each treatment and also 14 days after each of the treatment periods.
The results showed significant time by treatment interaction of whole grain oat for total cholesterol (P=0.0001) and LDL-cholesterol (P=0.02) compared to non-whole grain. There was also a significant time by treatment interaction observed for the relative abundance of faecal bifidobacteria (P=0.0001), lactobacilli (P=0.001) and total bacterial count (P=0.008), which were all elevated after consumption of whole grain oat Granola.
As the mechanisms involved with the observed cholesterol reduction were not clear, a possible limitation of the study was that plasma bile salts and short chain fatty acids (SCFA) were not measured. Although it was observed that faecal SCFA concentrations were similar between treatments, this data may not reflect plasma SFCA concentrations. Further mechanistic studies would be required to examine how prebiotic modulation of the gut microbiota could be linked to cholesterol metabolism, and specifically whether a prebiotic type microbiota modulation would increase bile acid deconjugation.
THE BOTTOM LINE
Daily consumption of whole grain oat Granola resulted in an appreciable prebiotic effect on the human gut microbiota composition and significant reductions in total cholesterol and LDL-cholesterol. These findings provide a step towards understanding a previously unrecognised mechanism that prebiotic modulation of the human gut microbiota may contribute to the hypocholesterolaemic effects of whole grain oat.
“We have shown for the first time in humans that whole grain oat Granola consumption for 6 weeks can stimulate a prebiotic modulation of the gut microbiota selectively increasing faecal bifidobacteria, lactobacilli, and total bacteria compared to a control treatment”.
This study was funded by the Reading Endowment Trust Fund and Jordans Cereals, who supplied the breakfast cereals, however the sponsor had no input into the study hypothesis and design, data analysis and interpretation.
1. Mellen et al. (2008) Whole grain intake and cardiovascular disease: a meta-analysis. Nutr. Metab. Cardiovasc. Dis. 18, 283-90.
2. Queenan et al. (2012) Concentrated oat beta-glucan, a fermentable fiber, lowers serum cholesterol in hypercholesterolemic adults in a randomised controlled trial. Nutr. 6, 6.
2. Effects of oatmeal porridge on gut microflora functions.
A pilot study to see the impact of eating oatmeal porridge every day for 1 week on healthy subjects.
Valeur J, Puaschitz NG, Midtvedt T and Berstad A (2016). Oatmeal porridge: impact on microflora-associated characteristics in healthy subjects. British Journal of Nutrition, 115, 62-7.
Consumption of oats has been shown to have several health benefits (1), including the role of oat β-glucans in the prevention of metabolic syndrome (2), and protection against both organic diseases and functional disorders affecting the gastrointestinal tract (3). In vitro fermentation studies (4), and in vivo animal studies (5,6) also suggest that certain constituents of oats may influence the gut microbiota.
SUMMARY OF FINDINGS
Ten healthy subjects were recruited from hospital staff at Haukeland University Hospital and from students at the University of Bergen (Norway). For 7 days, they ingested a daily portion of 60g oatmeal porridge (1573kJ/100g). Subjects were assessed for the following micro-flora associated characteristics before and after intervention: (i) lactulose-induced intestinal gas production, (ii) faecal levels of short chain fatty acids (SCFA), β-galactosidase and urease, (iii) and rectal levels of prostaglandin E2 (PGE2).
The results of this short term dietary intervention suggested that certain microbial functions were modified within 1 week by eating oatmeal porridge. Microbial fermentation as evaluated by intestinal gas production and excretion of SCFA did not significantly change following dietary intervention, suggesting that there was no alteration of the colonic ability to ferment carbohydrates. Faecal levels of β-galactosidase and urease, however, decreased after eating oatmeal porridge (P=0.049 and 0.031, respectively). Host inflammatory state, as measured by rectal levels of PGE2 also decreased, although the change was not significant (P=0.168).
As this was a pilot study, there was only a small sample size. Further studies on the effect of oatmeal porridge on inflammatory diseases of the colon should be considered, both in conditions characterised by low-grade (ie. irritable bowel syndrome) and overt (eg. inflammatory bowel disease) intestinal inflammation.
THE BOTTOM LINE
The results suggest that oatmeal porridge may modulate gut microbial functions, however, since this was a pilot study further investigation needs to be carried out to see potential prebiotic properties.
“The results of our short dietary intervention suggest that certain microbial functions are modified within 1 week by eating oatmeal porridge”.
This study was funded by the University of Bergen, Norway.
1. Rasane P et al. (2015) Nutritional advantages of oats and opportunities for its processing as value added foods – a review. J Food Sci Technol 52, 662-75.
2. Cloetens L et al. (2012) Role of dietary beta-glucans in the prevention of the metabolic syndrome. Nutr Rev 70, 444-58.
3. Thies F et al. (2014) Oats and bowel disease: a systematic literature review. Br J Nutr 112, Suppl. 2, S31-43.
4. Hughes SA et al. (2008) In vitro fermentation of oat and barley derived beta-glucans by human faecal microbiota. FEMS Microbiol Ecol 64, 482-93.
5. Drzikova B et al. (2005) Dietary fibre-rich oat-based products affect serum lipids, microbiota, formation of short-chain fatty acids and steroids in rats. Br J Nutr 94, 1012-25.
6. Snart J et al. (2006) Supplementation of the diet with high-viscosity beta-glucan results in enrichment for lactobacilli in the rat cecum. Appl Environ Microbiol 72, 1925-31.
3. Using the human gastrointestinal microbiome to personalize nutrition advice: are registered dietitian nutritionists ready for the opportunities and challenges?
Knowledge of the gastrointestinal (GI) microbiome provides the opportunity for registered dietitian nutritionists (RDNs) to offer more personalised nutrition advice to clients.
Harvie R, Chanyi RM, Burton JP and Schultz M (2016). Journal of the Academy of Nutrition and dietetics, 16, S2212-2672.
The GI microbiome is the entire community of microbes, which includes bacteria that live within the GI tract. Individual features of the microbiome may explain why individuals respond differently to standardised nutritional interventions. Every individual has a unique microbiome, which alters over its lifespan. The composition and diversity of the microbiome has been shown to be affected by a variety of personal and lifestyle factors, including diet, exercise, weight, medications, geographical location, stress, age and sex. Manipulating the microbiome to improve health status is becoming increasingly common.
DIET AND THE MICROBIOME
Understanding the role that diet plays in shaping the microbiome provides more evidence that dietitians could use to help patients make healthy choices. For instance, they could encourage the consumption of more fermented foods. The effect of fibre on increasing the diversity of the microbiome is a good reason to encourage patients to not only increase their fibre intake but also to eat a wide variety of fibre sources. The fermentation of fibre by the microbiome involves many different biochemical reactions, with different bacteria having the ability to perform different steps. By incorporating a wider range of fibre sources, it provides a greater range of substrates for the microbiome, giving the opportunity for a wider range of bacteria to become established in the gastrointestinal tracts.
IMPLICATIONS FOR DIETITIANS
Future dietary and microbiological research will require a multidisciplinary approach. Dietitians role in collaborations investigating the microbiome will be to design dietary interventions, provide the dietary education to patients, ensure food composition data are available for the nutrient of interest, and to measure the dietary intake and adherence to the interventions.
THE BOTTOM LINE
“Advances in the understanding of the microbiome offer the opportunity for enhancing our clinical dietetic intervention by incorporating data from the microbiome. Dietitians need to gain some understanding of the metabolic potential of the microbiome so they can incorporate this into their clinical practice”
There was no funding or support directly for this research