Using the school Online Library, find two peer-reviewed articles that are relevant to the research topic you selected in W1 A
Using the school Online Library, find two peer-reviewed articles that are relevant to the research topic you selected in W1 Assignment 2. ATTACHED For each, explain why it is relevant to your research; identify the different sections of it; summarize it in your own words; identify the experimental hypothesis and null hypothesis.
Submission Details
- Please provide your answers in a 3- to 4-page Microsoft Word document.
- Support your responses with examples.
- Cite any sources in APA format.
REVIEW
Diet and the Microbiota–Gut–Brain Axis: Sowing the Seeds of Good Mental Health Kirsten Berding,1 Klara Vlckova,1 Wolfgang Marx,2 Harriet Schellekens,1,3 Catherine Stanton,1,4 Gerard Clarke,1,5
Felice Jacka,2,6,7,8 Timothy G Dinan,1,5 and John F Cryan1,3 1 APC Microbiome Ireland, Cork, Ireland; 2 Deakin University, iMPACT – the Institute for Mental and Physical Health and Clinical Translation, Food & Mood Centre, School of Medicine, Barwon Health, Geelong, VIC,Australia; 3 Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland; 4 Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland; 5 Department of Psychiatry and Neurobehavioural Sciences, University College Cork, Cork, Ireland; 6 Centre for Adolescent Health, Murdoch Children’s Research Institute, Parkville, VIC, Australia; 7 Black Dog Institute, Randwick, NSW, Australia; and 8 College of Public Health, Medical & Veterinary Sciences, James Cook University, Douglas, QLD, Australia
ABSTRACT
Over the past decade, the gut microbiota has emerged as a key component in regulating brain processes and behavior. Diet is one of the major factors involved in shaping the gut microbiota composition across the lifespan. However, whether and how diet can affect the brain via its effects on the microbiota is only now beginning to receive attention. Several mechanisms for gut-to-brain communication have been identified, including microbial metabolites, immune, neuronal, and metabolic pathways, some of which could be prone to dietary modulation. Animal studies investigating the potential of nutritional interventions on the microbiota–gut–brain axis have led to advancements in our understanding of the role of diet in this bidirectional communication. In this review, we summarize the current state of the literature triangulating diet, microbiota, and host behavior/brain processes and discuss potential underlying mechanisms. Additionally, determinants of the responsiveness to a dietary intervention and evidence for the microbiota as an underlying modulator of the effect of diet on brain health are outlined. In particular, we emphasize the understudied use of whole-dietary approaches in this endeavor and the need for greater evidence from clinical populations. While promising results are reported, additional data, specifically from clinical cohorts, are required to provide evidence-based recommendations for the development of microbiota-targeted, whole-dietary strategies to improve brain and mental health. Adv Nutr 2021;12:1239–1285.
Keywords: diet, microbiota, brain, behavior, mental health, mechanisms, gut–brain axis, nutrition
Introduction The human body harbors trillions of microbes [including bacteria, viruses, archaea, lower and higher eukaryotes, and fungi (1)] belonging to hundreds of different species, of which the vast majority reside in the gut. Recent decades have seen an exponential increase in our knowledge of the impact of the gut microbiota on various aspects of human health, including brain health (2). Moreover, it has become clear that diet is one of the key factors involved in shaping the gut microbiota, having marked effects on microbial diversity, as well as the abundance and metabolic capacity of specific microbes (3–5). In addition, there has been an increasing emphasis on the role of dietary habits in supporting optimal mental health (6–8).
Recently, the concept of psychobiotics has emerged, de- scribing exogenous factors that influence the microbiota (e.g., via probiotics, prebiotics, diet) with bacterially medi- ated positive effects on mental health (9–12). It is evident that the consumption of Western-style diets rich in processed,
fried and sugar-rich foods and low in plant foods with their constituent fiber and polyphenols can lead to the loss of microbial diversity and function as well as the extinction of important beneficial microbes and expansion of oppor- tunistic pathogens (13, 14), with far-reaching consequences for human health. It is also recognized that using healthy diets to positively modulate gut–brain communication holds possibilities for both the prevention and treatment of common mental disorders (15). There are emerging studies that focus on the impact of supplementation with single food items, such as fruits and vegetables high in prebiotic fibers, showing some promising results in modulating microbiome– host interactions (16). While such approaches are important in advancing our understanding of how a specific food impacts human microbiota and health and could lead to the discovery of new functional foods, humans consume a combination of food groups with every meal and studying single foods could overlook the potential synergistic effect dietary components might have, not just on overall health,
C© The Author(s) 2021. Published by Oxford University Press on behalf of the American Society for Nutrition. All rights reserved. For permissions, please e-mail: [email protected] Adv Nutr 2021;12:1239–1285; doi: https://doi.org/10.1093/advances/nmaa181. 1239
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but also on microbiota diversity and composition (17). Thus, the study of whole-dietary approaches represents a more realistic path to the development of new dietary interventions and could inform national healthy eating guidelines and policies.
In this narrative review, we summarize the current state of the literature triangulating diet, microbiota, and host be- havior/brain processes. Additionally, potential mechanisms underlying the diet–microbiota–brain interrelationship are discussed. Recent advances highlighting the individual’s microbial profile as a key determinant for the response to a diet intervention are also reviewed. It is envisioned that increasing knowledge in this area will ultimately lead to the development of microbiota-targeted nutrition approaches to mental health.
Impact of Diet on Microbiota Composition and Function What is the gut microbiota? Due to advances in sequencing technology and bioinfor- matics, there has been an increasing understanding of the impact of diet on microbiota composition (18, 19). Bacteria are taxonomically classified into phyla, classes, orders, families, genera, species, and strains. To date, 25 different phyla, ∼2000 genera, and 5000 species have been identified (20). Among the 25 phyla, the most dominant include Firmicutes, Bacteroidetes, Actinobacteria, Cyanobac- teria, Fusobacteria, Proteobacteria, and Verrucomicrobia (21),
Financial support: APC Microbiome Ireland is a research center funded by Science Foundation Ireland (SFI), through the Irish Government’s National Development Plan (grant no. 12/RC/2273 P2). KB has received a postdoctoral fellowship from the Irish Research Council. Author disclosures: APC Microbiome Ireland has conducted studies in collaboration with several companies, including GSK, Pfizer, Cremo, Wyeth, Mead Johnson, Nutricia, 4D Pharma, and DuPont. TGD has been an invited speaker at meetings organized by Servier, Lundbeck, Janssen, and AstraZeneca and has received research funding from Mead Johnson, Cremo, Wellness, Nutricia, and 4D Pharma. JFC has been an invited speaker at meetings organized by Mead Johnson, Yakult, and Alkermes, and has received research funding from Mead Johnson, Cremo, Nutricia, and DuPont. GC has been an invited speaker at meetings organized by Janssen and Probi and has received research funding from Pharmavite. FJ has received industry support for research from Meat and Livestock Australia, Woolworths Limited, the A2 Milk Company, and Be Fit Foods, and travel support and speakers’ honoraria from Sanofi-Synthelabo, Janssen Cilag, Servier, Pfizer, Network Nutrition, Angelini Farmaceutica, Eli Lilly, and Metagenics. FJ has written two books for commercial publication. HS is in receipt of research funding from PepsiCo, Pharmavite, and Cremo. WM is currently funded by an Alfred Deakin Postdoctoral Research Fellowship and a Multiple Sclerosis Research Australia early-career fellowship, has received funding from the Cancer Council Queensland and university grants/fellowships from La Trobe University, Deakin University, University of Queensland, and Bond University, and received industry funding and has attended events funded by Cobram Estate Pty Ltd, received travel funding from the Nutrition Society of Australia, consultancy funding from Nutrition Research Australia, and received speaker’s honoraria from The Cancer Council Queensland and the Princess Alexandra Research Foundation. CS has been an invited speaker at meetings organized by Nutricia and received research funding from Mead Johnson, Cremo, Nutricia, and DuPont. All other authors report no conflicts of interest. Address correspondence to JFC (e-mail: [email protected]). Abbreviations used: ASD, autism spectrum disorder; BBB, blood–brain barrier; BCFA, branched-chain fatty acid; BDNF, brain-derived neurotrophic factor; CMC, carboxymethylcellulose; CNS, central nervous system; C-section, Caesarean section; GABA, γ -aminobutyrate; GF, germ-free; GLP-1, glucagon-like peptide 1; GPCR, G-protein-coupled receptor; HDAC, histone deacetylase; HMO, human milk oligosaccharide; HPA, hypothalamic–pituitary–adrenal; MAC, microbiota-accessible carbohydrate; NMDA, N-methyl-D -aspartate; NU-AGE, European Project on Nutrition in Elderly People; OTU, operational taxonomic unit; P80, polysorbate-80; PYY, peptide YY; TGR5, Takeda G protein-coupled receptor 5; TMA, trimethylamine; TMAO, trimethylamine N-oxide; 5-HT, serotonin.
with the Bacteroidetes and Firmicutes phyla constituting 70– 90% of the total healthy human gut microbiota (22). Genera within the Firmicutes phylum include Clostridium, Lacto- bacillus, Bacillus, Enterococcus, and Ruminococcus, whereas the Bacteroidetes phylum predominantly consists of the Bacteroides and Prevotella genera. Bifidobacterium is the main representative genus in the Actinobacteria phylum (23).
More than 1000 species of bacteria have been identified in the human gut, although a person on average only carries 160 species (24, 25). While controversies around the specifics of a “healthy microbiota” remain, it has been suggested that it can be defined by resistance (ability to resist perturbations) and resilience (return to baseline state) (26). Similarly, microbial richness (number of microbes) and diversity (the amount of different microbes, i.e., α-diversity) are often associated markers of a healthy microbiota (27). Additionally, certain bacterial genera can be regarded as beneficial symbionts, meaning they live in a mutually beneficial relationship with the human host. At the same time, other bacterial genera have been classified as potential pathogens and an imbalance in the ratio of these bacteria could increase the disease susceptibly of the host. Although this may vary within the specific host context, bifidobacteria and lactobacilli species are generally regarded as the “good” bacteria and are commonly used in probiotic supplements, whereas species like Escherichia coli, strains within the Clostridium genus, and LPS-forming taxa such as Enterobacteriaceae have been linked to disease states and symptomology (28–30). Likewise, the relation between the two dominant phyla, expressed as the Firmicutes:Bacteroidetes ratio, has been associated with several pathological conditions (31, 32), although the association with obesity is still being debated (33). One factor that reflects the difficulties of defining a healthy microbiota is the high variability observed between individuals. Thus, rather than defining a healthy microbiome based on the presence of specific microbes, it has also been suggested that the presence of key microbial functions, described as the “functional core,” could be more important in defining a healthy microbial state (4, 26). This means that metabolic functions can be performed by different microbes, so that in individuals with a different microbiota composition the same microbial functions can be exerted. Likewise, the existing unknowns in the human microbiota make the definition of a healthy microbiota challenging. Although significant advances in sequencing technologies have been made in the last decade, some taxa and strain-level diversity as well as functionality remain unexplored in current microbiota studies (20). This strain-level diversity may be important in determining the associations of a specific bacterial genus with health or disease, which has been a focus of debate within the Prevotella genus (specifically P. copri) (34).
Diet and the gut microbiota The core gut microbiota in adulthood is relatively stable, but environmental factors have been identified that can shape the gut microbial community (23, 35, 36). Both short- (37)
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TABLE 1 Overview of dietary components influencing the microbiota composition
Dietary factors with positive effects on microbiota References
Mediterranean diet1 ↑ Microbial diversity and health-promoting bacterial taxa (i.e., F. prausnitzii, Roseburia, B. adolescentis, B. longum, Prevotella)
(38–41)
Plant-based diet1 ↑ Microbial richness and biodiversity Predominant phyla Bacteroidetes and Actinobacteria Enrichment in Prevotella bacteria ↑ Bifidobacterium, Lactobacillus, Ruminococcus, E. rectale, Roseburia, F.
prausnitzii, Anaerostipes ↓ Clostridium sensu stricto, C. perfringens, C. histolyticum, Odoribacter
(42–50)
Fruits and vegetables1, 2, 3 ↑ Microbial diversity and function Shift in the abundance of bacterial phyla Growth of beneficial bacteria ↓ Potentially harmful bacteria
(51–55)
Fermented foods1 , 2 Positive effects through ingestion of microbes and microbial metabolites ↑ Beneficial microbes (e.g., Bifidobacterium)
(56–59)
Nuts1 “Prebiotic effect” on the genus level ↑ Firmicutes genera, including some butyrate-produces (e.g., Faecalibacterium
and Roseburia), Clostridium and Dialister
(60–62)
Fiber and prebiotics1 , 2 Depending on type of dietary fiber; generally ↑ bacterial diversity and abundance of beneficial microbes
Potential predominance of Prevotella:Bacteroides ↑ Beneficial bacteria (i.e., Bifidobacterium, Lactobacillus, Akkermansia,
Faecalibacterium, Roseburia, Bacteroides, Prevotella) ↓ Potentially pathogenic bacteria (e.g., Enterobacteriaceae)
(63–79)
Plant-based protein1 ↑ Bifidobacterium, Roseburia, and Lactobacillus ↓ Pathogens such as B. fragilis and C. perfringens
(37, 80)
MUFAs/PUFAs1 ↑ Beneficial bacteria, including butyrate producers (e.g., Lactobacillus, Lachnospira, Roseburia, and Bifidobacterium)
(81, 82)
Polyphenols1 , 2 , 3 “Prebiotic”-like effect has been described ↑ Symbionts and ↓ potential pathogens
(83–87)
Dietary factors with negative effects on microbiota
Western diet1 , 2 Potential extinction of beneficial microbes with long-term consumption Dominance of Bacteroides taxa ↑ Firmicutes:Bacteroidetes ratio and Proteobacteria (potentially
mucosa-associated pathogens) ↓ Protective SCFA-producing bacteria
(13, 14, 88–91)
Animal-based protein1 , 2 , 3 Specific microbial changes are observed in relation to different type and source of protein
↓ Beneficial butyrate producing bacterial groups (Roseburia, E. rectale) ↑ Firmicutes and ↓ Bacteroidetes ↑ Potential detrimental gut microbes (e.g., Enterococcus, Streptococcus,
Turicibacter, and Escherichia)
(37, 92–94)
Saturated fatty acids1 , 2 ↓ Total bacterial abundance, microbial diversity and richness ↑ Proinflammatory bacteria (e.g., Alistipes, R. gnavus, Bilophila wadsworthia)
(95–98)
Sweeteners1 , 2 , 3 Ambiguous findings dependent on the type of sweetener and administered dose
Sucralose could induce microbial profile that promotes negative health effects
(99–106)
Emulsifiers2 Detrimental effects have been reported Microbial changes induced by emulsifiers could contribute to inflammatory
diseases ↑ Dorea, Bacteroides, Burkholderia, Clostridium, Veillonella, and Anaeroplasma
(80, 107–109)
1 Data available from human studies. 2 Data available from animal studies. 3 Data from in vitro studies; arrows represent generally reported increases or decreases in the literature.
and long-term (3) dietary habits have been recognized as one of the drivers of microbial composition and diversity and the impact of both individual nutrients and dietary patterns on the microbiota have been extensively explored. The dietary factors influencing the gut microbial community are summarized in Table 1. Although some generalizations
about the impact of diet on microbiota composition can be made, recent work also suggests that the diet–microbe interaction is highly personalized and dependent on the baseline microbiota present (110), indicating that dietary interventions may need to be tailored to one’s individual baseline microbiota (19).
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Macronutrients Gut microbes are involved in the digestion, absorption, metabolism, and transformation of undigested macronutri- ents, extracting beneficial and bioactive compounds for the human host. Each macronutrient affects the microbial profile in a different way, due to the specialized functionality of microbial taxa. Variations in macronutrient ratios, amounts, and types are large drivers of the effect on microbiota com- position (111), with specific microbes thriving on selective macronutrients, thereby increasing their abundance.
Dietary fiber The most extensively studied macronutrients for shaping the gut microbiota are carbohydrates, specifically dietary fiber. The European Union regulation 1169/2011 defines dietary fiber as
“carbohydrate polymers with three or more monomeric units, which are neither digested nor absorbed in the human small intestine and belong to the following categories: edible carbohydrate polymers (I) naturally occurring in the food as consumed and (II) obtained from food raw material by physical, enzymatic or chemical means with a beneficial physiological effect demonstrated by generally accepted scientific evidence, or (III) edible synthetic carbohydrate polymers which have a beneficial physiological effect demon- strated by generally accepted scientific evidence” (112).
Another well-studied type of dietary fiber is the prebiotic, which is defined as “a substrate that is selectively utilized by host microorganisms conferring a health benefit” (113). It is important to note that whereas most prebiotics can be classified as dietary fiber, not all dietary fibers are prebiotics. Prebiotics are generally fermentable, which is not true for all dietary fibers. Examples of prebiotics include pectins, inulin, fructooligosaccharides, and galactooligosaccharides.
It is generally accepted that the consumption of a high- fiber diet promotes an increase in bacterial diversity and leads to a bloom in the growth of beneficial bacteria (i.e., Bifidobacterium sp., Lactobacillus sp., Akkermansia sp., Faecalibacterium sp., Roseburia sp., Bacteroides sp., and Prevotella) as well as a reduction in potentially pathogenic bacteria (e.g., Enterobacteriaceae) (63–70, 114–116). More specifically, the chemical properties (e.g., polymerization, solubility, and viscosity) of different fibers determine the location of metabolism within the gastrointestinal tract, leading to specific microbial changes in response to their in- gestion. For example, supplementation studies demonstrated that wholegrain products containing β-glucans (soluble nonstarch polysaccharides) support the growth of lactobacilli and bifidobacteria in humans (71) and rats (72), whereas in- tact cereal fibers (e.g., wholegrain cereals, barley fiber, wheat bran, and rye fiber) increase the abundance of Actinobacteria, Bifidobacterium, Clostridium, Lachnospira, Akkermansia, and Roseburia in humans (63, 65, 66, 73). Human consumption of resistant starch led to significant increases in Bifidobac- terium, Faecalibacterium, and Eubacterium, while decreasing some Ruminococcus strains (74, 75). The solubility of a fiber also determines the impact on the microbial profile.
Compared with insoluble fiber, soluble fiber seemed to have a more pronounced effect on the microbial composition and diversity in a piglet model (76). Nevertheless, insoluble, nonfermentable fiber such as cellulose, a prominent source of fiber in fruit and vegetables, can be metabolized by cellulose-degrading microbes (such as Ruminococcus and Fibrobacter), influencing their abundance as well as the abundance of bacteria using the solubilized products (e.g., oligosaccharides and polysaccharides) through cross-feeding (117). In animal studies, cellulose was shown to increase microbial richness (77) and change the microbiota com- position, with a higher abundance of Peptostreptococcaceae, Clostridiaceae, Akkermansia, Parabacteroides, Lactobacillus, Clostridium, Eisenbergiella, Marvinbryantia, Romboutsia, Helicobacter, Enterococcus, or Desulfovibrio (77–79) and lower Sutterellaceae, Lactobacillaceae, or Coriobacteriaceae (77, 79).
Besides changing microbial composition, different di- etary fibers also influence microbial enzymatic capacity and metabolite concentration. Chemical properties such as solubility and fermentability determine the degree and location of microbial fermentation as well as the type of metabolite produced (76). Soluble, fermentable fiber can increase microbial enzymatic capacity to degrade com- plex carbohydrates and produce health-promoting SCFAs, namely acetate, propionate, and butyrate (114, 118). SCFAs, specifically butyrate, have been implicated in gastrointestinal (main energy source of colonocytes, supporting gut barrier function) and metabolic (glucose homeostasis, lipid oxida- tion) health, exert anti-inflammatory and immunomodula- tory properties, and can influence central functioning (as outlined in detail below) (119, 120). Numerous intervention studies in humans show that reducing the consumption of carbohydrates and wholegrain cereals lowers the abundance of important butyrate-producing bacteria, including the pro- biotic bifidobacteria, as well as SCFAs themselves (121–123). While insoluble fiber does not have a pronounced effect on SCFA production, alterations in the linoleic acid, nicotinate and nicotinamide, glycerophospholipid, glutathione, and sphingolipid pathways as well as the valine, leucine and isoleucine metabolic pathways were observed in response to insoluble fiber (e.g., cellulose) intake (78, 79).
Dietary lipids and fatty acids Although most fatty acids are absorbed in the small intestine, dietary lipids and fat also exhibit a marked impact on the microbial profile. Whether these alterations are beneficial or harmful depends on the type of fat. Different degrees of saturation have been reported to differentially shape microbial composition. For example, high SFA intake has been shown to be associated with reduction in total bacterial abundance in humans (95) and in microbial diversity and richness (95, 96), as well as an increase in proinflammatory bacteria (e.g., Bilophila wadsworthia) (96–98) in mice. In humans, healthier polyunsaturated fatty acids (e.g., omega- 3 PUFAs) promote the growth of beneficial bacteria, includ- ing butyrate producers such as Lactobacillus, Lachnospira,
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Roseburia, and Bifidobacterium (81), and are correlated with higher microbial diversity as well as taxa from the families Lachnospiraceae and Ruminococcaceae (82). Besides the degree of saturation, chain length also determines the impact of fatty acids on the gut microbiota. Results from animal studies show that medium-chain fatty acids (7– 12 carbons) increase the abundance of Bifidobacterium, Bacteroides, and Prevotella and decrease the abundance of Clostridium histolyticum or Helicobacter (119, 124–126). Long-chain fatty acids (13–18 carbons), on the other hand, alter the abundance of Blautia, Clostridium, Coprococcus, Dialister, Lactococcus, Roseburia, or Bacteroides (119, 127– 129) in animal models. While a recent controlled feeding study in Chinese adults showed that adopting a higher- fat, lower-carbohydrate diet led to unfavorable changes in gut microbiota, fecal metabolomic profiles, and plasma proinflammatory factors (130), the fat type administered was primarily soybean oil, limiting conclusions about other types of dietary fat intake in humans. Indeed, there is currently a dearth of human interventions investigating the impact of amounts and different types of dietary lipids on the gut microbiota and associated metabolites, representing an important gap in the literature.
The benefits of ω-3 (n–3) fatty acids for central func- tioning range from enhanced memory, mood, attention, and cognitive performance to a reduced risk of developing de- pression and regulation of stress sensitivity (131–138). While most of these benefits can be linked to PUFA involvement in brain membrane structure, function and signal transduction, modulation of neurotransmitter turnover, neurogenesis, or anti-inflammatory and anti-apoptotic effects (139), the notion that PUFAs could be considered prebiotics (140) suggests another indirect mechanism through microbial alterations. Indeed, ω-3 fatty acids have been proposed to restore the eubiotic state in pathological conditions by increasing the beneficial bifidobacteria and decreasing enterobacteria, which in turn supports an anti-inflammatory environment through the production of SCFAs and suppres- sion of endotoxemia (81, 141). This cascade of events in turn could have upstream effects on brain and behavior, specifi- cally in inflammation-related disorders such as depression. Indeed, in an animal model, specific microbial changes (e.g., increased abundance of Lactobacillus and bifidobacteria and altered ratio of bifidobacteria to enterobacteria) associated with ω-3 fatty acid supplementation were closely related to changes in behavior (142).
Protein and amino acids The source, concentration, and amino acid balance of dietary protein are primary factors influencing the com- position, structure, and function of gut microbes. In hu- man intervention studies, animal-based protein elicits a more pronounced effect on microbiota composition than plant-based protein (37). In mice, animal-based protein increases potential detrimental gut microbes, e.g., Peptostrep- tococcaceae, Ruminococcaceae, Enterococcus, Streptococcus, Turicibacter, or Escherichia (92), and plant-based protein
boosts the abundance of Bifidobacterium, Roseburia, and Lactobacillus and lowers the abundance of pathogens such as Bacteroides fragilis and Clostridium perfringens (37, 42, 80). More specifically, the different sources of animal-based protein have been associated with distinct changes in the relative abundances of specific bacteria. For example, using rats and in vitro studies with human fecal inoculum, it was demonstrated that chicken protein could increase Actinobac- teria, Bifidobacterium, and Bacteroides, whereas beef protein was linked to elevated levels of Proteobacteria and Oscil- libacter and decreased C. perfringens and C. histolyticum (93, 94). Additionally, different amounts of protein intake have varying effects on microbial abundance. In a piglet model, reduction of protein concentration in the diet resulted in decreased bacterial richness and Clostridium_sensu_stricto_1 abundance, whereas Escherichia–Shigella abundance in- creased and moderate protein restriction was associated with elevated Peptostreptococcaceae (143). Lastly, microbial metabolites are also affected by the amount of protein consumed. Switching to a high-protein, low-carbohydrate diet reduces the abundance of butyrate-producing bacteria and increases colonic protein fermentation and metabolites detrimental to health, such as branched-chain fatty acids (BCFAs) and concentrations of phenylacetic acid and N- nitroso compounds (121).
Micronutrients Vitamins and minerals. Vitamins and minerals are important cofactors in the synthesis and metabolism of neurotransmitters as well as in the energy metabolism of neurons. It is well appreciated that the gut microbiota can synthesize certain vitamins, most notably vitamin K and B-group vitamins [e.g., cobalamin (B12), folate, and riboflavin (144, 145)], some of which might be directly absorbed. Because vitamins and minerals are mostly absorbed in the upper gastrointestinal tract and usually only small amounts will reach the colon (146), studying the impact of these nutrients on the colonic microbiota in humans is challenging and some inconsistent results have been reported (147). Nevertheless, there is now accumulating evidence that the vitamins that reach the distal colon can serve as an important …
,
Contents lists available at ScienceDirect
Food Quality and Preference
journal homepage: www.elsevier.com/locate/foodqual
The effects of actor-partner’s meal production focus on satisfaction with food related life in cohabiting couples
Berta Schnettlera,b,c,d,⁎, Edgardo Miranda-Zapatad, Ligia Orellanac,d, Tino Bech-Larsene,⁎, Klaus G. Grunerte
a Universidad de La Frontera, Facultad de Ciencias Agropecuarias y Forestales, Temuco, Chile b Visiting Professor and Researcher at the Universidad Católica de Santiago de Guayaquil, Guayaquil, Ecuador c Universidad de La Frontera, Scientific and Technological Bioresource Nucleus (BIOREN-UFRO), Temuco, Chile d Universidad de La Frontera, Núcleo Científico y Tecnológico en Ciencias Sociales, Centro de Excelencia en Psicología Económica y del Consumo, Temuco, Chile e Aarhus University, MAPP Centre, Aarhus, Denmark
A R T I C L E I N F O
Keywords: Satisfaction with food-related life Meal preparation Dyadic analysis Different-sex couples
A B S T R A C T
This paper reports the estimation of an Actor-Partner Interdependence Model
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