Recently I had a great chance to participate in the 19th WPA World Congress of Psychiatry which took place in Lisbon 21-24 of August 2019. Such an international scientific event summarizes recent findings and sets a trend for future research.

The effect of lifestyle on mental health was one of the topics discussed at the conference. Focusing on nutritional impact in psychiatry I will review here some of the studies – research done in animal models or patients and literature reviews – which were presented at the Congress.

All the poster presentations can be viewed on the conference website https://2019.wcp-congress.com/.

Dietary patterns and mental health

  1. Sanchez-Villegas and colleagues from Spain1 presented research on the Mediterranean diet’s effects in patients recovered from depressive disorders. They found that adherence to Mediterranean diet supplemented with extra-virgin olive oil led to the improvement of depressive symptoms. This new study supports previous reports about positive effects of traditional dietary patterns compared to so-called “Western diet”, and this topic was nicely reviewed in the poster presentation of M. Jesus and colleagues (Portugal)2.

I presented a poster3 on a study done in a mouse model of Western diet feeding. We found that genetic deficiency of serotonin transporter exacerbates metabolic alterations and such behavioural consequences of the Western diet as depressive-like behaviour and cognitive impairment. In human, carriers of a genetic variant that reduces serotonin transporter expression are known to be more susceptible to emotionality-related disorders and prone to obesity and diabetes.

Vitamin D and Mental Health

Nutritional psychiatry was traditionally focused on the effects of vitamins and micronutrients on mental health. Several presentations at this conference were dedicated to the role of vitamin D in mental disorders.

Scientists from Egypt (T. Okasha and colleagues)4 showed their results on the correlation between serum level of vitamin D and two psychiatric disorders: schizophrenia and depression. They found lower serum vitamin D levels in the patients with schizophrenia or depression compared to healthy volunteers. These findings indicate a role of vitamin D in the development of psychiatric disorders.

However, the team from Denmark (J. Hansen and colleagues)5 did not find any effect of 3 months vitamin D supplementation on depression symptoms in patients with major depression. The contrariety of the studies on vitamin D benefits in mental health was presented on the review poster by R. Avelar and colleagues (Portugal)6.

Microbiome and Mental Health

There is increasing evidence that microbiota-gut-brain axis influences behaviour and mental health. N. Watanabe and colleagues (Japan)7 presented the results of a study on germfree and commensal microbiota-associated mice. They found increased aggression and impaired brain serotonin metabolism in germfree mice.

  1. Dias and colleagues (Portugal)8 performed a literature review on this topic exploring possible effects of microbiome and probiotics in mental disorder development. The most robust evidence was found for the association of microbiome alterations and depression/anxiety. Up to date literature is lacking replicated findings on proving positive effects of probiotics in mental disorders treatment.

Diabetes Type 2 and Mental Disorders

Risk factors for type 2 diabetes include diet and lifestyle habits. It is getting more obvious that there is an association between type 2 diabetes and the development of mental disorders.

  1. Mhalla and colleagues (Tunisia)9 reported a study done on patients with type 2 diabetes. They found a high prevalence of depression in women with type 2 diabetes. Also, depression in these patients was associated with poorer glycemic control.

Depression is an important factor influencing insomnia. H.C. Kim (Republic of Korea)10 found insomnia in one-third of patients with diabetes type 2.

The group from Romania (A. Ciobanu and colleagues)11 created a meta-analysis of the medical literature showing an association of diabetes type 2 with Alzheimer’s disease. They highlighted the role of insulin signaling in cognition and proposed glucose blood level control as a therapeutic approach in Alzheimer’s disease.

 

Thus, a lot of studies were recently done on the role of nutrition in psychiatric disorders development and therapy. However, there is still room for future discoveries!

REFERENCES:
From 19th WPA World Congress of Psychiatry proceedings:

  1. Sanchez-Villegas, B. Cabrera-Suárez, M. Santos Burguete, P. Molero, A. González-Pinto, C. Chiclana, J. Hernández-Fleta. INTERVENTION WITH MEDITERRANEAN DIET IN THE IMPROVEMENT OF DEPRESSIVE SYMPTOMS IN PATIENTS RECOVERED FROM DEPRESSIVE DISORDER. PREDI-DEP TRIAL PRELIMINARY RESULTS;
  2. Jesus, C. Cagigal, T. Silva, V. Martins, C. Silva. DIETARY PATTERNS AND THEIR INFLUENCE IN DEPRESSION;
  3. Veniaminova, A. Gorlova, J. Hebert, D. Radford-Smith, R. Cespuglio, A. Schmitt-Boehrer, K. Lesch, D. Anthony, T. Strekalova. THE ROLE OF GENETIC SEROTONIN TRANSPORTER DEFICIENCY IN CONSEQUENCES OF EXPOSURE TO THE WESTERN DIET: A STUDY IN MICE;
  4. Okasha, W. Sabry, M. Hashim, A. Abdelrahman. VITAMIN D SERUM LEVEL AND ITS CORRELATION WITH MAJOR DEPRESSIVE DISORDER AND SCHIZOPHRENIA;
  5. Hansen, M. Pareek, A. Hvolby, A. Schmedes, T. Toft, E. Dahl, C. Nielsen7, P. Schulz8. VITAMIN D3 SUPPLEMENTATION AND TREATMENT OUTCOMES IN PATIENTS WITH DEPRESSION;
  6. Avelar, D. Guedes, J. Velosa, F. Passos, A. Delgado, A. Corbal Luengo, M. Heitor. VITAMIN D AND MENTAL HEALTH: A BRIEF REVIEW;
  7. Watanabe, K. Mikami, K. Keitaro, F. Akama, Y. Aiba, K. Yamamoto, H. Matsumoto. INFLUENCE OF COMMENSAL MICROBIOTA ON AGGRESSIVE BEHAVIORS;
  8. Dias, I. Figueiredo, F. Ferreira, F. Viegas, C. Cativo, J. Pedro, T. Ferreira, N. Santos, T. Maia. EMOTIONAL GUT: THE RELATION BETWEEN GUT MICROBIOME AND MENTAL HEALTH;
  9. Mhalla, M. Jabeur, H. Mhalla, C. Amrouche, H. Ounaissa, F. Zaafrane3, L. Gaha. DEPRESSION IN ADULTS WITH TYPE 2 DIABETES: PREVALENCE AND ASSOCIATED FACTORS;
  10. Kim. FACTORS RELATED TO INSOMNIA IN TYPE 2 DIABETICS;
  11. A. Ciobanu, L. Catrinescu2, C. Neagu3, I. Dumitru3. THE CONNECTION BETWEEN ALZHEIMER’S DISEASE AND DIABETES

 

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Twin studies have been used for decades to estimate the relative importance of genes and environments for traits, behaviors and disorders. A very large meta-analysis of all twin studies conducted during the past 50 years (almost 3000 publications) revealed that across all studied traits the average reported heritability was 49%, meaning that about 50% of the variation in traits is due to genetic factors (1).

1. Methods and theory of classical twin design

By comparing the differences and similarities between twins, researchers use them as a natural experiment to study whether a trait, phenotype or disease is due to nature (genetic predisposition) or nurture (environmental factors).

In order to get a better understanding of twin studies, one must first understand the two types of twins:

  • Monozygotic (MZ) or identical twins were conceived in a single egg, which split and forms two embryos. Therefore, MZ twins share all their genes (100%), and are definitely the same sex.
  • Dizygotic (DZ) or fraternal twins were developing from a separate egg and each egg is fertilized by its own sperm cell, and therefore sharing on average 50% of their genes. DZ twins could be of the same sex or different sex.

Based on the different degree of genetic and the similar extent of prenatal and later environmental factors sharing between MZ and DZ twins, MZ twin pairs may show a higher similarity on a given trait, as compared with DZ twins, if genes significantly influence that trait. On the other hand, if MZ and DZ twin pairs share a trait to an equal extent, it is likely that the environment influences the trait more than genetic factors.

The similarity for a given trait is estimates via intra-class correlations (ICC), and similarity across different traits by the cross-twin cross-trait correlations (CTCT). Comparison of correlations across MZ and DZ pairs allows for the variance (V) of a given trait to be decomposed into three factors:

  • Genetic factors, including additive genetic factors (A), and dominant genetic factors (D)
  • Shared environmental factors (C), that is events that happen to both twins, affecting them in the same way. For example, the socio-economic status of the family, the general personality and general parenting styles and beliefs of the parents.
  • Non-shared or unique environmental factors (E), that is events happen to one twin but not the other one, or the events affect either twin in a different way. For example, school and classroom environment, also including measurement error.

Under then assumptions of no interaction and no covariance between A, C, D, and E, the total variance of a phenotype (P) can be expressed as:

𝑉𝑎𝑟,𝑃.=𝐴+𝐷+𝐶+𝐸

Narrow sense heritability is defined as the proportion of variance in a trait due to additive genetic effects (A):

,-2.=,𝑉𝑎𝑟(𝐴)-𝑉𝑎𝑟(𝑃).

Broad sense heritability as the proportion of variance due to additive and dominance genetic effects (A+D):

,-2.=,𝑉𝑎𝑟(𝐴+𝐷)-𝑉𝑎𝑟(𝑃).

The classical twin model can be extended to explore bivariate and multivariate traits association, and test for differences between males and females by using sex-limitation models. More information on how to conduct classical and advanced twin model fitting analyses, please refer to (2) and (3).

2. Important advantages of twin studies

  • Estimate the relative importance of genetic factors (i.e., heritability) of one or more traits
  • Help identify shared genetic factors that influence different traits, behaviors and disorders.
  • Explore the causal status of environmental risk factors by controlling for genetic and shared environmental confounding.
  • Offers unique opportunities to study the gene-environmental interplay, including both gene-environmental correlations and gene-environmental interactions.

In summary, the twin study design is considered an important behavioral genetic approach that has been used in many fields, including biology, psychology and sociology. Using a substantial amount of the published twin research (and other genetic informative studies, e.g. sibling comparison, adoption studies), Plomin et al. summarized the top 10 replicated and important findings (4). These findings included:

  • All psychological traits show significant and substantial genetic influence;
  • No traits are 100% heritable, highlighting the importance of environmental factors, and
  • The heritability is caused by many genes of small effect.

Most of these findings or discoveries that could only have been found using genetically sensitive research designs.

In the Eat2BeNice project, we are currently using data from Swedish Twin Register (https://ki.se/en/research/the-swedish-twin-registry) to estimate the heritability of unhealthy eating habits and ADHD symptoms in adults, and also to investigate the relative importance of genetic, shared environmental and non-shared environmental factors for the overlap between adult ADHD symptoms and different dietary habits diets. We will also test specific hypothesis regarding gene-environmental interactions.

Authors:
Lin Li, MSc, PhD student in the School of Medical Science, Örebro University, Sweden.

Henrik Larsson, PhD, professor in the School of Medical Science, Örebro University and Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Sweden.

REFERENCES

  1. Polderman TJ, Benyamin B, de Leeuw CA, Sullivan PF, van Bochoven A, Visscher PM, et al. Meta-analysis of the heritability of human traits based on fifty years of twin studies. Nature genetics. 2015;47(7):702-9.
  2. Neale, M. C. and Meas, H. M. Methodology for genetic studies of twins and families. and the paper Rijsdijk FV & Sham PC. (2002),
  3. Analytic Approaches to Twin Data using Structural Equation Models. Briefings in Bioinformatics, 3 (2), 119 -133.
  4. Plomin, Robert, et al. “Top 10 replicated findings from behavioral genetics.” Perspectives on psychological science11.1 (2016): 3-23.

 

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In the Eat2beNICE project, the researchers aim at studying the effect of diet and mental health and our blogs are meant to enlighten readers.

Every day research findings published in journals will offer an opinion on how to best live our lives. It is simply not possible, nor advised, to change your habit after every piece of new knowledge. On the other hand, researchers do need to publish their results in order to have their findings discussed and reproduced. How do you as a reader navigate?

No single study should alone be enough to change nutritional advice or guidelines. The research into a specific field is best understood when looking at several pieces of knowledge (or publications) as contributing to a bigger picture. Kim Tingley wrote a descriptive picture in the New York Times Magazine on how to view scientific findings. https://www.nytimes.com/2019/05/16/magazine/how-much-alcohol-can-you-drink-safe-health.html Here he writes that the process of understanding the contribution of scientific research should be like looking through a lens and asking yourself if it is clearer or less clear with this particular piece of new information.

Interpreting results from a study isn’t always easy and the limitations of the study can sometimes be difficult to spot. If you are feeling bombarded by the media with constant new findings, be aware that single findings are one piece of information, usually not the full picture and should be interpreted as such. For more information on matters of interests, a good place to start is looking at literature reviews or in the Cochrane Library https://www.cochranelibrary.com/ which will offer views on important publications within a field and help you interpret status quo.

REFERENCES

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MoBa is short for The Norwegian Mother and Child Cohort Study which is a large pregnancy observational study. During the years 1999-2008 pregnant women in Norway were recruited to the study. The study is conducted by the Norwegian Institute of Public Health. Questionnaires regarding health, diet and environment were sent out to the women during and after pregnancy. Women are sent regular follow-up questionnaires. As the child grows up, the child also completes questionnaires. In addition, the fathers were invited to participate with a questionnaire when their partner was pregnant. Biological samples were also collected from the mother, father and child. Today there are 114 500 children, 95 000 mothers and 75 000 fathers participating in the study.

https://www.fhi.no/en/studies/moba/

The study was set up to gain knowledge about the causes behind serious disease. The study is unique because it gathers information from fetal (in vitro) life and follows the offspring into adulthood. In this manner it is possible to look at early influences and later disease. The study is prospective, which means that information about mothers, fathers and their offspring is registered before a disease has manifested itself. With this design, women are asked questions several times during her pregnancy and do not have to try to remember what she did when looking back at her pregnancy.

MoBa is population-based and became nationwide with 50 participating hospitals in Norway. For more information on the many publications based on MoBa data, visit this link:

https://www.fhi.no/en/studies/moba/for-forskere-artikler/publications/

The participating women in MoBa also filled in a questionnaire about eating habits before and during pregnancy.

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Recently, I participated in the Radboud Talks 2019, a scientific pitch competition, where I was lucky to be one of the eight finalists.

Why Radboud Talks? It is a perfect opportunity to share my work/ideas with the world and to gain more experience regarding presentation skills. They organized two workshops beforehand, where I had the opportunity to learn presentation techniques from professionals (actors and science communication advisors). We also received a lot of feedback, so I really learned a lot about how to present my scientific work to a general audience.

Below you can find the video from the preliminaries based on which I was chosen as a finalist. There you can hear about my research project which is about gut bacteria and their potential role in ADHD (Attention Deficit Hyperactivity Disorder). ADHD is a common worldwide neurodevelopmental disorder. Every person with ADHD has a unique combination of symptoms and challenges. Importantly, it has a significant social impact on patients’ lives, causing disruption at school, work and relationships. Despite its societal importance, progress in understanding disease biology has been slow.

 

The study of the human microbiome has become a very popular topic, because of their revealed importance in human physiology and health maintenance. Numerous studies have reported that gut bacteria may have an effect on our mental health. Some studies showed a potential role of gut bacteria in a psychiatric disorder like depression, autism or Parkinson (1). Above all, diet showed to have a profound effect of ADHD symptoms. This was earlier described in this blog: https://newbrainnutrition.com/investigating-the-effects-of-a-dietary-intervention-in-adhd-on-the-brain/ and we know that diet is one of the main factors influencing gut bacteria. Taking all together, I am curious (and investigating) if gut bacteria play a role in ADHD and if yes what kind of effect do they have on ADHD symptoms.

REFERENCES:
Bastiaanssen, T., Cowan, C., Claesson, M. J., Dinan, T. G., & Cryan, J. F. (2018). Making Sense of … the Microbiome in Psychiatry. The international journal of neuropsychopharmacology22(1), 37–52. doi:10.1093/ijnp/pyy067

 

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Recent research (1,2) on children and adolescents has reported that elevated levels of ADHD symptoms are positively associated with unhealthy dietary habits, including a higher consumption of refined sugars, processed food, soft drink, instant noodles, and a lower intake of vegetables and fruits. However, the link between low-quality diets and risk of ADHD in adults is still not well established, which would be further explored in the ongoing Eat2beNICE research project.

What is the underlying mechanism for an association between ADHD and unhealthy dietary habits? There is still no clear answer. Nemours’ potential biological pathways, by which dietary intake could have an impact on mental health, has been proposed in the literature (2). For example, iron and zinc are cofactors for dopamine and norepinephrine production (essential factors in the etiology of ADHD), so unbalanced diet with lower levels of iron and zinc may further contribute to the development of ADHD. However, we cannot overlook the possibility of a bi-directional relationship between diet quality and ADHD, especially when the interest in the concept of “food addiction” has received increased attention.

Food addiction refers to being addicted to certain foods (e.g. highly processed foods, highly palatable foods, sweet and junk foods) in a similar way as drug addicts are addicted to drugs. Animal models (3) have suggested that highly processed foods may possess addictive properties. Rats given high-sugar or high-fat foods display symptoms of binge eating, such as consuming increased quantities of food in short time periods, and seeking out highly processed foods despite negative consequences (e.g. electric foot shocks). One human study (4) found that individuals with high levels of ADHD-like traits (e.g. high levels of impulsively, disorganised, attention problems) were more likely to suffer from problematic eating behaviour with overconsumption of specific highly palatable foods in an addiction-like manner. Therefore, food addiction may, just as substance abuse, be over-represented among individuals with ADHD.

Thus, it seems there could be a vicious cycle between unhealthy dietary habits and ADHD: ADHD may lead to a worse choice of diet, lowering the health quality, which could eventually exacerbate ADHD symptoms. We will further test the bidirectional diet-ADHD associations in the ongoing Eat2beNice project.

This was co-authored by Henrik Larsson, professor in the School of Medical Science, Örebro University and Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Sweden.

AUTHORS:
Lin Li, MSc, PhD student in the School of Medical Science, Örebro University, Sweden.
Henrik Larsson, PhD, professor in the School of Medical Science, Örebro University and Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Sweden.

REFERENCES:
1. Kim KM, Lim MH, Kwon HJ, Yoo SJ, Kim EJ, Kim JW, et al. Associations between attention-deficit/hyperactivity disorder symptoms and dietary habits in elementary school children. Appetite. 2018;127:274-9.

2. Rios-Hernandez A, Alda JA, Farran-Codina A, Ferreira-Garcia E, Izquierdo-Pulido M. The Mediterranean Diet and ADHD in Children and Adolescents. Pediatrics. 2017;139(2).

3. Gearhardt AN, White MA, Potenza MN. Binge Eating Disorder and Food Addiction. Curr Drug Abuse Rev. 2011;4(3):201-7.

4. Ptacek R, Stefano GB, Weissenberger S, Akotia D, Raboch J, Papezova H, et al. Attention deficit hyperactivity disorder and disordered eating behaviors: links, risks, and challenges faced. Neuropsychiatr Dis Treat. 2016;12:571-9.

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A little while ago, this blog featured an entry by Annick Bosch on the TRACE study, an amazing intervention study using the Elimination Diet to treat ADHD in kids (https://newbrainnutrition.com/adhd-and-elimination-diet/). Very shortly summarized, the Elimination Diet entails that participants can only eat a very restricted set of foodstuffs for several weeks, which can greatly reduce the number of ADHD symptoms in some kids. Subsequently, new foodstuffs are added back into the diet one by one, all the time checking that ADHD symptoms do not return. This ensures that every child for which the Elimination Diet proves successful ends up with a unique diet which suppresses their ADHD symptoms.

Now this is a fascinating study, since it indicates a direct influence of diet on ADHD behavior. What we know from the neurobiology of ADHD, is that it is caused by a myriad of relatively small changes in the structure, connectivity and functioning of several brain networks 1. For the most common treatments of ADHD, like medication with methylphenidate 2, we can quite accurately see the changes these interventions have on brain functioning. However, for the Elimination Diet, this has not been studied before at all. This is why we are now starting with the TRACE-MRI study, where kids that participate in a diet intervention in the TRACE program, are also asked to join for two sessions in an MRI scanner. Once before the start of the diet, and once again after 5 weeks, when the strictest phase of the Elimination Diet concludes. In the MRI scanner, we will look at the structure of the brain, at the connectivity of the brain, and at the functioning of the brain using two short psychological tasks. We made a short vlog detailing the experience of some of our first volunteers for this MRI session.

 

 

With the addition of this MRI session, we hope to be able to see the changes in brain structure and function over the first 5 weeks of the diet intervention. This will help us establish a solid biological foundation of how diet can influence the brain in general, and ADHD symptoms specifically. It can also show us if the effect of the Elimination Diet is found in the same brain networks and systems which respond to medication treatment. And lastly, we can see if there is a difference in the brains for those participants for whom the diet has a strong effect versus those where the diet does little or nothing to improve their ADHD symptoms. This can then help us identify for which people a dietary intervention would be a good alternative to standard treatment.

We will update you on the TRACE-MRI study and on the developments in this field right here on this blog!

 

REFERENCES
Faraone, S. V et al. Attention-deficit/hyperactivity disorder ­­­. Nat. Rev. Dis. Prim. 1, (2015).

Konrad, K., Neufang, S., Fink, G. R. & Herpertz-Dahlmann, B. Long-term effects of methylphenidate on neural networks associated with executive attention in children with ADHD: results from a longitudinal functional MRI study. J. Am. Acad. Child Adolesc. Psychiatry 46, 1633–41 (2007).

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Have you ever noticed that the type of food you eat can affect how you feel afterwards? Some food might make you wish to rest and relax, some food might give you the little extra energy you just needed. Evidence is accumulating that also in the long run, diet may play a pivotal role for your mental health. For example, it might have an effect on impulsive and compulsive behaviour [1].
But it’s not only the diet that affects our body, mind and brain – it’s also the amount of what we eat. Research shows that people don’t necessarily know what a suitable amount of food might be. Sure you can imagine that this can easily lead to obesity – which in turn can impair our general health.

A meta-analysis (that is, a study that investigates an effect among many independent studies that have been conducted so far) from 2018 came to the conclusion that serving size and the size of the tableware has an effect on the amount we eat: When offered larger-sized portions, packages or tableware, participants ate or drank more than when offered smaller-sized versions [2].

British nutritional scientists now developed a guideline for the British Nutrition Foundation (BNF) to help people estimate the suitable serving size. For example, they recommend that when having a pasta dish, you should take as much pasta for one person as fits into both of your hands (before cooking). A portion of fish or meat should be about half the size of your hand. However, this does not mean that when you eat more than one portion, you are an overeater.

According to their tipsheets, which can be found here,
https://www.nutrition.org.uk/healthyliving/find-your-balance/portionwise.html
one should compose his or her daily menu based on a mixture of different portions. For example, 3-4 portions of starchy carbohydrates (such as the above-mentioned pasta) are recommended daily. Their guidelines, however, offer a few handy (literally!) advises to help you get a sense of how much food you should consume, thus preventing you from overeating. With a few simple tips kept in mind, you can do some good for your physical and mental health, daily.

REFERENCES
[1] Sarris J, Logan AC, Akbaraly TN, Amminger GP, Balanzá-Martínez V, Freeman MP, et al. Nutritional medicine as mainstream in psychiatry. Lancet Psychiatry. 2015; 2(3):271-4.
View here:
https://www.thelancet.com/journals/lanpsy/article/PIIS2215-0366(14)00051-0/fulltext

[2] Hollands GJ, Shemilt I, Marteau TM, Jebb SA, Lewis HB, Wei Y, Higgins JPT,
Ogilvie D. Portion, package or tableware size for changing selection and consumption of food, alcohol and tobacco. Cochrane Database of Systematic
Reviews 2015, Issue 9. Art. No.: CD011045. DOI: 10.1002/14651858.CD011045.pub2
View here:
https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD011045.pub2/full

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Increasing evidence is showing that the gut microbiota can alter the brain and behavior, and thus may play a role in the development of psychiatric and neurodevelopmental disorders, such as autism and schizophrenia.

Animal models are a useful tool to study this mechanism. For example, germ-free (GF) mice, which have never been exposed to microorganisms, are compared with mice exposed to microorganisms, known as conventional colonized mice (CC). Recent studies have schizophrenia and autismreported that GF animals show increased response to stress, as well as reduced anxiety and memory. In most cases, these alterations are restricted to males, in which there are higher incidence rates of neurodevelopmental disorders compared with females.

Mice, like humans, are a social species and are used to study social behavior. A recent study compared GF and CC mice using different sociability tests. GF mice showed impairments in social behavior compared with CC mice, particularly in males. Interestingly, they demonstrate that social deficits can be reversed by bacterial colonization of  the GF gut (GFC), achieving normal social behavior.

Microbiota seem to be crucial for social behaviors, including social motivation and preference for social novelty. Microbiota also regulate repetitive behaviors, characteristic of several disorders such as autism and schizophrenia.

Bacterial colonization can change brain function and behavior, suggesting that microbial-based interventions in later life could improve social impairments and be a useful tool to effect the symptoms of these disorders.

This blog was co-authored by Noèlia Fernàndez and Judit Cabana

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Real time measurements of intestinal
gases: a novel method to study how food is being digested

Researchers in Wageningen (The
Netherlands), have been able to identify for the first time, how gut microorganisms
process different types of carbohydrates by measuring in real time the intestinal
gases of mice. This is not only a novel method to understand how food is
digested but could also tell us more about the role of gut microorganisms in
gut health.

Intestinal gases

The intestinal microbiota is a diverse and
dynamic community of microorganisms which regulate our health status. The
advancement of biomolecular techniques and bioinformatics nowadays allows
researchers to explore the residents of our intestines, revealing what type of microorganisms
are there. However, studying only the microbial composition of an individual
provides limited insights on the mechanisms by which microorganisms can
interact with the rest of our body. For example, far less is understood about
the contribution of the gut microorganisms in the production of intestinal
gases such as hydrogen, methane and carbon dioxide through the breakdown of
food and how these gases affect the biochemical pathways of our bodies.

Intestinal gases consist mostly of
nitrogen, and carbon dioxide, which originate primarily from inhaled air. Hydrogen
and methane though, are produced as by-products of carbohydrate fermentation
(break down), by intestinal microorganisms. However, not all carbohydrates are
digested in the same way. For instance, food with simple sugars can be rapidly absorbed
in the small intestine unlike complex carbohydrates such as fibers, which reach
the colon where they are digested by the colonic microbiota.

Lower_digestive_system

Measuring hydrogen in mouse intestines

To study these interactions and gain
knowledge on how microorganisms process carbohydrates, the research team led by Evert van
Schothorst from the Human and Animal Physiology Group of Wageningen University
(WU) in collaboration with the WU-Laboratory of Microbiology fed mice two
different diets with the same nutritional values but with different types of carbohydrates
(1). The first diet contained amylopectin,
a carbohydrate which can be digested readily in the small intestine while the
second diet contained amylose, a slowly digestible carbohydrate that is
digested by intestinal microorganisms in the colon.

Animals fed the easily digestible carbohydrates
showed minimal production of hydrogen whereas the group fed with the complex
carbohydrates presented high levels of hydrogen. Moreover, the two groups were
characterized not only by distinct microbial composition (different types of
bacteria present) but also distinct metabolic profiles (short chain fatty acids),
suggesting that the type of carbohydrate strongly affects microbial composition
and function.

The importance of
hydrogen

Hydrogen consumption is essential in any anoxic
(without oxygen) microbial environment to maintain fermentative processes. In
the intestine it can be utilised through three major pathways for the
production of acetate, methane and hydrogen sulphide. These molecules are
critical mediators of gut homeostasis, as acetate is the most predominant short
chain fatty acid produced in mammals with evidence suggesting a role in inflammation and obesity (2). Methane, which is produced by a specific type of microorganisms,
called archaea, has been associated with constipation related diseases, such as
irritable bowel syndrome(3) and also recently with athletes’ performance (4)! Finally hydrogen sulphide
is considered to be a toxic gas, although recent findings support the notion
that it also has neuroprotective effects in neurodegenerative disorders such as
Parkinson and Alzheimer diseases (5).

To the best of our knowledge, this is the first time that food-microbiota interactions have been studied continuously, non-invasively and in real time in a mouse model. Hydrogen is a critical molecule for intestinal health and understanding its dynamics can provide valuable information about intestinal function, and deviations in conditions such as Crohn’s disease or irritable bowel syndrome (IBS).

Further reading

1. Fernández-Calleja, J.M., et al., Non-invasive continuous real-time in vivo analysis of microbial
hydrogen production shows adaptation to fermentable carbohydrates in mice.

Scientific reports, 2018. 8(1): p.
15351.

https://www.nature.com/articles/s41598-018-33619-0

2.
Perry, R.J., et al., Acetate mediates a
microbiome–brain–β-cell axis to promote metabolic syndrome.
Nature, 2016. 534(7606): p. 213

3. Triantafyllou, K., C. Chang, and M. Pimentel,
Methanogens, methane and gastrointestinal
motility.
Journal of neurogastroenterology and motility, 2014. 20(1): p. 31.

4. Petersen, L.M., et al., Community characteristics of the gut microbiomes of competitive
cyclists.
Microbiome, 2017. 5(1):
p. 98.

5. Cakmak,
Y.O., Provotella‐derived hydrogen sulfide, constipation,
and neuroprotection in Parkinson’s disease. Movement Disorders, 2015. 30(8): p.
1151-1151.

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Welcome to New Brain Nutrition. You can enjoy FREE Online Courses when you Log In or Join here.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 728018

New Brain Nutrition is a project and brand of Eat2BeNice, a consortium of 18 European University Hospitals throughout the continent.

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