A team of Iranian researchers recently published a meta-analysis seeking to determine what, if any, association there may be between low Vitamin D levels and ADHD in children and adolescents.

Combining the results from thirteen studies with 10,334 participants, they found that youth with ADHD had “modest but significant” lower serum concentrations of 25-hydroxyvitamin D than normally developing children. The weighted mean difference was just under 7 nanograms per milliliter. The odds of obtaining such a result by chance would be less than one in a thousand (p < .001). There was little to no sign of publication bias. Between-study heterogeneity, however, was very high (I2 = 94).

Vitamin D and ADHDThese results suggest an association. But are low serum levels of Vitamin D a cause or effect of ADHD? Causation is vastly more difficult to establish than association. To begin to tease this out, the researchers identified four prospective studies that compared maternal Vitamin D levels with the subsequent development of ADHD symptoms in their children. Two of these used maternal serum levels, and two used umbilical cord serum levels. Together, these studies found that low maternal Vitamin D levels were associated with a 40% higher risk of ADHD in their children. Whether maternal serum or umbilical cord serum measurements were used had little or no effect on the outcome. Study heterogeneity was negligible. But the authors noted that this result “should be considered with caution” because it was heavily dependent on one of the prospective studies included in the analysis. All of which suggests a need for further prospective studies.

In the meantime, the authors suggest it would be prudent to increase sun exposure and Vitamin D supplementation given the prevalence of Vitamin D deficiency.

REFERENCES

Yadollah Khoshbakht, Reza Bidaki, and Amin Salehi-Abargouei, “Vitamin D Status and Attention Deficit Hyperactivity Disorder: A Systematic Review and Meta-Analysis of Observational Studies,” Advances in Nutrition, vol. 9, issue 1, p. 9-20 (2018).

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Mediterranean diet could prevent depression, new study finds” [CNN]; “Mediterranean diet ‘may help prevent depression‘” [BBC]. The publication of Lassale and her colleagues in the prestigious scientific journal Molecular Psychiatry on the association between Mediterranean Diet and depression, received a lot of attention in the media last week.

So, can diet really influence your mental health? The publication of Lassale shows that there are indications that what you eat is related to how you feel. But because this study is an observational study, we can’t conclude anything yet about causation. In other words, we don’t know yet whether eating healthy causes you to feel less depressed, or whether feeling depressed causes you to eat unhealthy.

Causal links between diet and mental health

Diet and mental healthThe researchers of the European consortium Eat2beNICE are investigating exactly this causal link. The way we do this is through clinical trials. In this way, we first let chance decide whether a person receives a particular diet or is part of the control group. Through this randomization we can be sure that the differences that we find between the two groups are really due to the dietary intervention that people received, because all other factors are the same between the two groups.

Specifically for the effects of the Mediterranean diet on behaviour, in the Eat2beNICE project we are using the information and measurements available from the PREDIMED-PLUS trial. In this study, we are looking specifically for the effect of a calorie-restricted Mediterranean diet, combined with physical activity, on several behavioral outcomes related with several psychiatric diseases of adults at high cardiovascular risk.

At the same time, we are conducting three other clinical trials:

  1. In Nijmegen (The Netherlands), we investigate the effects of a very strict, hypo-allergenic diet on behavioural problems in children with ADHD.
  2. We are investigating the effects of vitamin supplements in a clinical trial that will be conducted in Mannheim(Germany) and Groningen(The Netherlands).
  3. Researchers in Barcelona (Spain) and Frankfurt (Germany) are investigating the effects of probiotics (i.e. bacteria that are good for you) on mental health in adults that are highly impulsive and/or aggressive.

Through these studies we hope to be able to identify if these types of food improve mental health and in which circumstances. This can have big implications for psychiatry, where putting someone on a specific, personalised diet may be a way to improve treatment. Also, people who are at a risk for developing mental health problems may benefit from specific diets to reduce this risk. But before this can be put into action, we first need good scientific data on what really works.

How can food drive human behaviour?

A second aim of our large research consortium is to identify the mechanisms between nutrition and the way the brain works. We think that the bacteria that live in your gut play a large role in this, as they interact with other systems in your body, including your brain. So we are collecting poop samples of the people that are participating in our clinical trials to identify which bacteria are more or less common in our participants compared to the control population. We are also measuring our participants’ behaviour and we will scan their brains. We hope that this will help us understanding better why certain types of food can be beneficial for mental health, and why some others increase the risk for mental health problems. This too will help to elucidate, and understand, the causal links between food and behaviour.

In short, we are very thankful for the study of Lassale and her colleagues, for backing up the evidence that what you eat is related to how you feel and behave. Now there’s work for us to do to prove the causal and mechanistic links. We’ll keep you posted here!

 

Authors Jeanette Mostert and Alejandro Arias-Vasquez work at the department of Genetics at the Radboud University Medical Center in Nijmegen, The Netherlands. Alejandro Arias-Vasquez is the project coordinator of the Eat2beNICE project. Jeanette Mostert is the dissemination manager.

 

Further reading

Lassale C, Batty GD, Baghdadli A, Jacka F, Sánchez-Villegas A, Kivimäki M, Akbaraly T. Healthy dietary indices and risk of depressive outcomes: a systematic review and meta-analysis of observational studies. Mol Psychiatry. 2018 Sep 26. doi: 10.1038/s41380-018-0237-8.

 

Blog by Jordi Salas explaining the Lassale paper and the PREDIMED trial:
http://newbrainnutrition.com/category/nutrition/mediterranean-diet/

Blog by Jolanda van der Meer on hypo-allergenic diet (TRACE study): http://newbrainnutrition.com/adhd-and-food-elimination-diet/

Blog by Julia Rucklidge on trials with vitamin supplements: http://newbrainnutrition.com/micronutrients-and-mental-health/

Blog by Judit Cabana on the Gut-Brain axis: http://newbrainnutrition.com/the-gut-brain-axis-how-the-gut-relates-to-psychiatric-disorders/

 

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Vitamin B and ADHDThere is a well-documented relationship between dietary factors, health and human behavior. Severe malnutrition produces neurological and psychiatric symptoms. It is also assumed that dietary factors play a role in common mental disorders, such as ADHD, but this is less established and more difficult to investigate. A few studies have documented a beneficial effect of dietary interventions and vitamin supplements in ADHD in children and adults. To examine the nutritional status in ADHD, Landaas et al.(1) recently compared blood vitamin levels in 133 adult ADHD patients and 131 healthy controls. In the ADHD group there was a clear overrepresentation in the group with low levels of vitamins B2, B6 and B9.

It is yet unclear whether these vitamin levels are a) associated with ADHD symptoms, or b) whether they are the result of altered dietary intake, or c) metabolism in ADHD patients. However, it is possible that the differences reflect dietary habits that are different in a subgroup of ADHD patients and controls. Dietary habits are established early during life and may last into adulthood. It is possible that suboptimal dietary habits may precipitate, exacerbate or maintain symptoms of ADHD. More research in larger samples is obviously needed to clarify these issues. Over the next five years in our project, entitled “Effects of Nutrition and Lifestyle on Impulsive, Compulsive, and Externalizing behaviours,” we expect to gain much more insight into these connections.  We will share our findings with you.  Stay tuned!!

(1) BJPsych Open. 2016 Nov; 2(6): 377–384. Published online 2016 Dec 13. doi:  10.1192/bjpo.bp.116.003491
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5153567/ 

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