Represented by a conscious propensity to harm others against their will, aggressiveness is a complex behavior depending on which environmental conditions we have been living in, and the kind of features we have inherited from our ancestors. Humans tend to be an aggressive species.

Among mammals, members of the same species cause only 0.3 percent of deaths of their conspecifics (a member of the same species) [1]. Astonishingly, in Homo sapiens, the rate is nearly 7 times higher, around 2% (1 in 50)!

More than 1.3 million people worldwide die each year because of violence in all of its forms (self-directed, interpersonal and collective), accounting for 2.5% of global mortality. There are two critical conditions that endorse aggressive behavior: being fiercely territorial and living in social groups.

From the evolutionary perspective, aggression is usually described as adaptive. Struggle for resources like habitat, mates and food have had a key role in forming aggressive behavior in humans. Genetic variants that promote aggression have been more likely to be passed on to the next generation because they have increased the chances of survival. Indeed, among tribes of extremely violent hunter-gatherers, men who committed acts of homicide had more children, as they were more likely to survive and have more offspring [2]. This lethal legacy may be the reason we are here today.

Although there are several biological aspects related to aggression, their predictive value continues to be rather low. It is possible to inherit a predisposition to acting violently, but scientists also emphasize that modeling violence in the home environment is the most certain way of propagating aggressive behavior. Children learn to act violently through the simple observation of aggressive models. The way parents manage the inevitable conflicts that arise between themselves and their children is central to the learning of aggression. When parents are unable to stop the child from escalating the intensity of conflict, and when they at least intermittently reinforce the child’s coercive behavior, the child learns that escalation is a viable method of resolving conflict. When this conflict strategy is applied to interactions with siblings or peers, and if it is also reinforced in these contexts, this conflict escalation is likely to include acts of aggression [3].

In addition to being hereditary and learned through social modeling, there is one other crucial component to aggressive behavior: self-control. In humans, the urge to react aggressively stems from the ancient parts located deep in the brain.

The structure capable of controlling those impulses is evolutionally much newer and located just behind the forehead – the frontal lobes. Unfortunately, this “top-down” conscious control of violent impulses is slower to act in contrast with the circuits of eruptive violence deep in the brain. People convicted of murder had been found to have reduced activity in the prefrontal cortex and increased activity in deeper regions [4]. Although there are plenty of examples of people with prefrontal cortex damage who do not commit violent acts, these findings clearly demonstrate that the damage to the prefrontal cortex impairs decision making and increases impulsive behavior.

Early physical aggression needs to be dealt with care. Long-term studies of physical aggression clearly indicate that most children, adolescents and even adults eventually learn to use alternatives to physical violence [5].

Aggression is part of the normal behavioral repertoire of most, if not all, species; however, when expressed in humans in the wrong context, aggression leads to social maladjustment and crime [6]. By identifying mechanisms that predispose people to the risk of being violent – even if the risk is small – we may eventually be able to tailor prevention programs to those who need them most.

This post is adapted from an earlier blog on MiND the Gap/

References

[1] Gómez, J. M., Verdú, M., González-Megías, A., Méndez, M. (2016). The phylogenetic roots of human lethal violence. Nature 538(7624), 233–237.

[2] Denson, T. F., Dobson-Stone, C., Ronay, R., von Hippel, W., Schira, M. M. (2014). A functional polymorphism of the MAOA gene is associated with neural responses to induced anger control. J Cogn Neurosci 26(7), 1418–1427.

[3] Hodges, E.V.E., Card, N.A., Isaacs, J. (2003). Learning of Aggression in the Home and the Peer Group. In: Heitmeyer, W., Hagan, J. (eds) International Handbook of Violence Research. Springer, Dordrecht.

[4] Raine, A., Buchsbaum, M., LaCasse, L. (1997). Brain abnormalities in murders indicated by positron emission tomography, Biol Psychiatry 42(6), 495–508.

[5] Lacourse, E., Boivin, M., Brendgen, M., Petitclerc, A., Girard, A., Vitaro, F., Paquin, S., Ouellet-Morin, I., Dionne, G., Tremblay, R. E. (2014). A longitudinal twin study of physical aggression during early childhood: Evidence for a developmentally dynamic genome. Psychol Med 44(12):2617–2627.

6] Asherson, P., Cormand, B. (2016). The genetics of aggression: Where are we now? Am J Med Genet B Neuropsychiatr Genet 171(5), 559–561.

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Have you experienced drowsiness after eating a large meal? Has an important presentation made your stomach turn? Seeing a special someone made you feel butterflies in your stomach? If you have (and you most likely have), then you know how strong the connection between the brain and the gut is.

Scientists have found that many chronic metabolic diseases, type 2 diabetes, mood disorders and even neurological diseases, such as Parkinson’s disease, Alzheimer’s disease, amyotrophic lateral sclerosis (ALS) and multiple sclerosis, are often associated with functional gastrointestinal disorders (1). The importance of the association between the gut and the brain is gaining momentum with each new study. However, the way HOW the signaling between these two integral parts of the body exactly works hasn’t been clear until recently.

It was thought for a long time that the only “communication channel” between the gut and the brain was the passive release of hormones stimulated by the consumed nutrients. Hormones entered the bloodstream and slowly notified the brain that the stomach is full of nutrients and calories. This rather slow and indirect way of passing messages takes from minutes to hours.

But now, a recent study (2) has elegantly proven that the gut can message the brain in seconds! Using a rabies virus enhanced with green fluorescence, the scientists traced a signal as it traveled from the intestines to the brainstem of mice, crossing from cell to cell in under 100 milliseconds – faster than the blink of an eye.

The researchers had also noticed that the sensory cells lining the gut were quite similar to the receptors in the nose and on the tongue (3). The effects, however, differ. In the mouth, the taste of fatty acids triggers signals to increase hunger, whereas in the small intestine, fatty acids trigger signals of satiety. This means that the discovered “gut feeling” might be considered as a sixth sense, a way of how the brain is being signaled when the stomach is full.

This new knowledge will help to understand the mechanism of appetite, develop new and more effective appetite suppressants and help those struggling with weight and problematic eating patterns.

REFERENCES
(1) Pellegrini C et al (2018) Interplay among gut microbiota, intestinal mucosal barrier and enteric neuro-immune system: a common path to neurodegenerative diseases? Acta Neuropathol 136:345. doi:10.1007/s00401-018-1856-5

(2) Kaelberer et al (2018) A gut-brain neural circuit for nutrient sensory transduction. Science 361(6408):eaat5236. doi:10.1126/science.aat5236

(3) Bohórquez and Liddle (2015) The gut connectome: making sense of what you eat. J Clin Invest 125(3):888–890. doi:10.1172/JCI81121

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Psychobiotics are helpful bacteria (probiotics) or support for these bacteria (prebiotics) that influence the relationship between bacteria and brain. The human digestive system houses around 100 trillion of these bacteria, outnumbering the human body cells 10:1. Probiotics provide a great deal of functions vital to our well-being, like supporting the digestion process and improving the absorption of nutrients. Based on the latest research, helpful gut bacteria that can also positively affect the brain – psychobiotics – benefit people suffering from chronic stress, poor mood, or anxiety-like symptoms (1).

There are 3 ways psychobiotics can affect your mental health:

  • Brain chemicals like serotonin, dopamine, and noradrenaline can be produced in the intestines directly by gut microbiota.
  • Battling with and protecting from stress by modifying the level of stress hormones.
  • When an inflammation occurs, inflammatory agents are elevated throughout the body and brain and can cause depression and other mood and cognitive disorders. Psychobiotics can affect the brain by lowering inflammation.

Lactobacillus and Bifidobacterium are the most popular probiotics with respect to mental health (1).

Disruption of the balance of gut bacteria is quite common due to the use of different kinds of medications, antibiotics, artificial preservatives, poor food and water quality, herbicides, stress, and infections (2, 3, 4).

In order to support a healthy microbiota, one should start from eating a diverse range of foods rich in different plant sources. Foods that contain lots of fiber or are fermented also promote the growth of beneficial gut bacteria. Excessive consumption of sugar and artificial sweeteners should be minimized. Managing stress levels, exercising on a regular basis, not smoking and getting enough sleep are also important for keeping microbiota in good condition. When taking antibiotics, one should make sure to consume probiotics so the body can maintain the bacteria it needs to stay healthy.

For people needing help regarding mental health problems, psychobiotics may be a promising relief. Psychobiotics are well-adapted to the intestinal environment and naturally modulate gut–brain axis communications, thereby reducing the chance of adverse reactions.

It is possible that even simple prescribing of a particular diet may be sufficient to promote the selective proliferation of natural or therapeutically introduced psychobiotics (5). Further research focusing on the strain and dosage of psychobiotics, duration of treatment, and the nature of mental disorders will help to determine the most efficient ways of helping people to improve their mental health.

REFERENCES
Abhari A, Hosseini H (2018) Psychobiotics: Next generation treatment for mental disorders? J Clin Nutr Diet. 4:1. doi:10.4172/2472-1921.100063

Carding et al (2015) Dysbiosis of the gut microbiota in disease. Microb Ecol Health Dis. 26: 10.3402/mehd.v26.26191

Lozano et al (2018) Sex-dependent impact of Roundup on the rat gut microbiome. Toxicol Rep. 5:96–107. doi: 10.1016/j.toxrep.2017.12.005

Paula Neto et al (2017) Effects of food additives on immune cells as contributors to body weight gain and immune-mediated metabolic dysregulation. Front Immunol. 8:1478. doi:10.3389/fimmu.2017.01478

Kali (2016) Psychobiotics: An emerging probiotic in psychiatric practice. Biomed J. 39(3):223-224. doi:10.1016/j.bj.2015.11.004

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Food is addictive. It has been an addiction that has kept mankind alive for thousands of years. Today, hunger is no longer a problem in the developed world; it is quite the opposite. According to the World Health Organization, worldwide obesity has nearly tripled since 1975. Obesity has reached epidemic proportions globally, with at least 2.8 million people dying each year as a result of being overweight or obese.

In order to maximize the nutritional value, humans are hard-wired to prefer foods that have either a high sugar or fat content. The amount of energy obtained from food is measured in kilocalories (kcal) per gram. Fats have the most energy (9 kcal) and carbohydrates (sugars and starches) have the same amount of energy as proteins (4 kcal). However, these nutrients differ in how quickly they supply energy. Sugars and starches have the advantage of being converted into energy faster than fats and protein. Protein is preferentially used for building and repairing different tissues, not as an energy source.

Once a beneficial adaptation of preferring fast digesting or the most energy-rich nutrients, has now become a risk factor for both physical and also mental health (1), making it an inevitable research focus.

In a recent study at the Yale University School of Medicine (2) it was determined that people not only favour fatty or sugary foods, but place the highest value on those that combine both. Participants (tasked to make monetary bids on different food items) were ready to pay the most for cookies, chocolate, cake and other treats that had both high sugar and also fat content. Equally familiar, liked and caloric fatty (e.g., cheese, salami) or sugary foods (e.g., lollipops) were assigned lower values.

Based on surges of activity, brain scans revealed that foods high in both fat and sugar were more rewarding than foods rich in only one category of nutrient.

Unexpectedly, it was also observed that participants were very accurate at estimating the energy density (kcal) of fatty foods, but poor at estimating the energy density of sugar-containing foods.

Once rare, but nowadays common and abundant treats high in both fat and sugar are most rewarding and therefore can very likely contribute to overeating. In addition, it has turned out to be difficult for people to assess the amount of calories in foods with a high sugar content. These findings taken together can help to understand and also hopefully find new treatment options for people struggling with obesity.

  • Hoare E et al (2015) Systematic review of mental health and well-being outcomes following community-based obesity prevention interventions among adolescents. BMJ Open 2015;5:e006586. doi:10.1136/bmjopen-2014-006586
  • DiFeliceantonio et al (2018) Supra-additive effects of combining fat and carbohydrate on food reward. Cell Metabolism 28, 1–12. doi:10.1016/j.cmet.2018.05.018
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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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