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

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!

From 19th WPA World Congress of Psychiatry proceedings:

  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;
  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;
  11. A. Ciobanu, L. Catrinescu2, C. Neagu3, I. Dumitru3. THE CONNECTION BETWEEN ALZHEIMER’S DISEASE AND DIABETES


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The bacteria in your gut affect blood insulin levels and may influence your chances of developing type 2 diabetes

Developing type 2 diabetes is for a large part influenced by your diet but also genes. However, a recent study has now shown that your gut microorganisms might also play an important role in the risk of developing type 2 diabetes (T2D). The article published in Nature Genetics entitled “Causal relationships among the gut microbiome, short-chain fatty acids (SCFA’s) and metabolic diseases”, claims evidence that bacterial metabolites such as SCFA’s are able to influence insulin levels and increase the risk of getting T2D.

Various studies have suggested that increased SCFA production benefits the host by exerting anti-obesity and antidiabetic effects, however, results of different studies are not always in agreement. Moreover, there is also evidence that increased production of SCFAs in the gut might be related to obesity, due to energy accumulation. Resolving these conflicting findings requires a detailed understanding of the causal relationships between the gut-microbiome and host energy metabolism, and the present study contributes to this.

The authors analyzed data from a large population study based in Groningen (The Netherlands), comprising 952 individuals with known genetic data, as well as information on parameters associated with metabolic traits such as BMI and insulin sensitivity. In addition, data were acquired for the type and the function of the bacteria which were present in the gut of the study participants. Combining this data, the authors tried to answer the question of whether changes in microbiome features causally affect metabolic traits or vice versa?

A technique called Mendelian randomization (MR) which is increasingly accepted to establish cause-effect relationships in the onset of diseases was applied. The primary outcome of the analysis was that host genes influence the production of the SCFA butyrate in the gut, which is associated with improved insulin response in the blood after an oral glucose tolerance test. In addition, abnormalities in the production or absorption of propionate, another SCFA, were causally related to an increased risk of T2D.

So far available data suggest that overweight humans or those with type 2 diabetes may have different microorganisms in their gut compared to healthy people. These microorganisms which are commonly found in healthy people are absent from the T2D patients. Whether the differences in the microbiota between healthy and T2D patients are an effect of the disease development or account for causality is challenging to be answered. With the data from the present study, authors are able to go one step further and demonstrate potential routes by which microorganisms are able to regulate our metabolic status underlying their importance for our wellbeing.

Collectively the present article suggests that production of bacterial SCFA’s play a pivotal role in the regulation of metabolic traits such as blood insulin levels and are associated with the onset of T2D.

Since the study was observational and did not include any T2D patients, confirmation of the results is essential. Follow up studies including T2D patients would be highly informative. With the rising prevalence of obesity in adults, which is reaching epidemic levels, the prevalence of T2D will also continue to rise. In the past years, scientists have mainly focused on the role of human gene data, but this has not led to major breakthroughs. Perhaps knowledge of the microbiome will elucidate molecular mechanisms which can be translated to novel effective treatments for metabolic disorders such as T2D.

Sanna, S., van Zuydam, N. R., Mahajan, A., Kurilshikov, A., Vila, A. V., Võsa, U., . . . Oosting, M. (2019). Causal relationships among the gut microbiome, short-chain fatty acids and metabolic diseases. Nature genetics, 1.

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