Date of the last update: 27.07.2023
It has been proven that people who commit acts of violence have low levels of serotonin in their brains. Serotonin influences impulsiveness and overreaction, because any disturbances in the level of this neurotransmitter makes the organism incapable of maintaining the proper level of glucose in the brain. Low level of glucose renders the limbic system (which is responsible for managing emotions), more susceptible to external stimuli. Therefore, sugar deficiency in blood increases our irritability, which in some cases, may lead to more extreme reactions (1). Sugar may help limit hyperactivity and destructive behaviour, especially in the case of children. It has been demonstrated that people prone to aggression become calmer after a meal containing sugar or sweetener.
Research results provide evidence that intake of carbohydrates makes the majority of people more placid and relaxed (2). It has been shown that young men inclined to excessive impulsive behaviour also show symptoms of hypoglycaemia (low blood sugar level). Subsequent research focusing on their reaction to glucose revealed that some of them generated increased amounts of insulin, a hormone that decreases the level of sugar, which remained in their organisms for a relatively long time. This research led to the hypothesis that some people break down sugar abnormally fast, and, as a result, are constantly irritated and liable to react impulsively (3).
When people suffering from stress or emotional disturbances are given carbohydrates, their conditions can improve, and feelings of depression, anxiety, confusion and anger can disappear. The reason this happens is that long-lasting stress – regardless of its source – requires higher amounts of serotonin in the brain (4). Serotonin is one the neurotransmitters (i.e. chemical substances secreted by neurons) that transmit stimulation from cell to cell. As well as serotonin, other important neurotransmitters include histamine, gamma-aminobutyric acid, and catecholamines. Catecholamines have a strong impact on our mood, meaning that many emotion-altering drugs rely on adapting the brain’s levels of catecholamines (5).
Neurotransmitters are made of amino acids. The mixture of amino acids that enter the blood and become available for neurons is determined by the food we eat (6). Therefore, proper functioning of neurotransmitters depends on providing the brain with appropriate amounts of carbohydrates, proteins, and fats. Research carried out in Finland confirmed the relationship between low levels of cholesterol and a tendency towards aggressive and violent behaviour. The research studied 36 convicted murderers, who carried out a test that diagnosed them with an explosive personality, which makes sense, as murder is often the result of a sudden outburst of aggression. The research demonstrated that the impulsive offenders had a considerably lower level of serotonin in comparison to less impulsive participants in the study, and furthermore, almost half of the offenders had attempted suicide (7). Low levels of serotonin is associated with various forms of antisocial behaviour, ranging from hyperexcitability to drug abuse. As pointed out by Hans Selye – and confirmed by recent studies – stress and frustration linked with these imbalanced lead many people to serious illness, pharmacomania, drug addiction, and, sometimes, even to suicide (8). In these cases, our primarily defence mechanisms become mechanisms of destruction.
Low levels of stress can have positive functions and is indispensable, as it manages information and energy stimulation (9). However, it is vital to ensure optimum levels of serotonin and other healthy neurotransmitters in our brains to stop stress escalating into aggressive behaviour. To achieve this balance, we must provide the brain with the necessary amounts of carbohydrates, proteins, and antioxidants that protect it against free radicals.
Our levels of serotonin are also influenced by stress and living conditions. Research carried out on rats indicated that stress substantially lowers the level of serotonin in the amygdala (part of the limbic system responsible for aggressive behaviour). Deficiency of serotonin and intensified aggression has also been observed in mice, when kept in isolation (10). While the deficiency of certain minerals and vitamins in the brain increases stress, stress itself has a negative impact on our brain, for example, by reducing the brain’s level of magnesium, which in turn increases our stress. Therefore, providing the body with all the essential nutrients for proper brain functioning is essential in protecting against stress, as well as aggressive behaviour.
It’s important to emphasise the role of minerals and vitamins needed to maintain optimum serotonin levels in the brain, and protect the organism against stress. These include magnesium, zinc, chromium, vitamins B3 and B5, folic acid, and tryptophan (an amino acid used by the brain to produce serotonin). A nervous impulse is conditioned by the movement of ions of minerals, particularly calcium and magnesium, in nervous tissue. At about 6AM, the adrenal cortex triggers the secretion of hormones that let us stay agile throughout the day. However, a deficiency in magnesium reverses this process, making the body secrete these hormones in the evening, causing fatigue and bad mood in the morning, and higher levels of energy later in the day. The importance of magnesium for our health and mental activity is so high that it may be called a regulator and controller of our organism. Magnesium deficiency is usually the result of insufficient supply through food, impaired absorption from food, or excessive elimination via the kidneys (as can happen with alcoholics and patients treated with diuretic drugs). Increased concentration of thyroid hormones, aldosterones, corticosteroids, and catecholamines brought about by stress also causes excessive elimination of magnesium in urine. Foods rich in magnesium include buckwheat groats, almonds, nuts, poppy seeds, and soybeans.
Zinc is a structural and functional component of about 200 enzymes, and influences all basic living processes. People who commonly have zinc deficiencies include children, pregnant women, nursing mothers, elderly people, people on plant-based diets, and alcoholics. Zinc is easily found in oysters, pumpkin and sunflower seeds.
Chromium stimulates carbohydrate metabolism. In someone with a chromium deficiency, the level of cholesterol and blood sugar increases, and lipid substances precipitate in the aorta. Chromium enhances the effectiveness of insulin, which becomes more active in influencing glucose transformations. Foods high in chromium include broccoli, yeast, liver, wholemeal bread, potatoes boiled with their skins, nuts, cress, and mushrooms.
Vitamin B3 is also indispensable for proper functioning of the brain and peripheral nervous system, as well as for the synthesis of hormones such as cortisol, thyroxine, and insulin. Vitamin B3 is a peculiar anti-stress vitamin, and in addition, it helps get rid of even large concentrations of cholesterol and other fats in blood vessels. Low levels of this vitamin can lead to depression and alcoholism. The main sources of vitamin B3 are tuna fish, yeast, sunflower seeds, peanuts, liver, whole grain cereals, dried beans, and peas.
Vitamin B5 as a constituent of coenzyme A and 4-phosphopantetheine, and takes part in many key physiological reactions connected with the metabolism of carbohydrates, proteins, and fats. It is essential for the synthesis of many compounds, such as sterols (e.g. cholesterol), hormones, neurotransmitters (e.g. acetylcholine, serotonin), phospholipids (components of cell membranes), porphyrins (constituents of haemoglobin), and antibodies. The foods containing vitamin B5 are yeast, liver, bran, oatmeal, and cherries.
Folic acid is necessary for appropriate functioning of the nervous system, the haematopoietic system, and for the development of all systemic cells. Its deficiency leads to depression, frequent irritation, and neurological disorders. The richest sources of folic acid are parsley, beetroot, soybeans, oranges, wholemeal bread, meat, and eggs.
Tryptophan is vital for the production of serotonin, and when its concentration in the brain lowers, the biosynthesis of serotonin decreases. Intake of proteins inhibits tryptophan’s penetration into the brain. It has been found that tryptophan must compete with other amino acids for access to the brain, as all of these amino acids use the same intracellular tract to get through the membrane that surrounds the brain. In a test where rats were fed high-protein food, large quantities of amino acids penetrated into their blood and prevented tryptophan from getting into their brains. This is why, when Wurtman and Fernstrom analysed the brains of rats fed with proteins and carbohydrates, they found very low quantities of serotonin (13). Tryptophan may be found in fish, turkey, milk, peanuts, and bananas (14). When the organism absorbs carbohydrates, insulin captures the amino acids present in blood and transports them to muscle fibres.
The authors of the research referred to above argue that this is how the antistress defence mechanism works. Therefore, when people suffering from stress or emotional disturbances are given carbohydrates, their conditions such as depression, anxiety, irritability, confusion and anger can be improved.
Dissemination of the principles of proper nutrition, by spreading knowledge about food and diet based on up-to-date and credible results of scientific research should be given greater importance. Its aim should be to contribute to the proper mental and physical development of individuals, as well as helping them to remain in good health. Knowledge about nutrition may be disseminated during direct meetings with people in forms of lectures, talks, discussions, shows, courses, or in the form of individual counselling via telephone or mail. The indirect means of spreading the knowledge may include the use of various publications (magazines, books, brochures, leaflets, charts, etc.) as well as mass media, including, first of all, the press, radio, and television.
Spreading simple nutritional knowledge should start as early as in nursery school, where children learn about fruit and vegetables, also by helping in gardening. Proper habits ought to be formed by emphasising the principles and methods of healthy diet from early childhood, because in this period of life it is most effective. In primary and lower secondary schools the issue of nutrition is a component of the syllabi of several subjects (science, biology, chemistry, technology), but there is a lack of well-qualified teachers.
In upper secondary schools (with the exception of gastronomy schools) nutrition is sometimes the subject of optional courses (e.g. housekeeping). The introduction of classes focused on human nutrition into school curricula could prove difficult as students’ timetables are very busy. Nevertheless, introduction of various kinds of lectures or practical classes focused on nutrition into the syllabi of other subjects or extra-curricular activities seems vital (15). At this point, the adequate training of teachers about nutrition becomes essential. Given that the prevention of antisocial behaviour can be largely influenced by nutrition, social workers and workers in penal institutions should also be well informed on the topic.
In teaching nutrition, the influence of diet on brain functioning should be particularly emphasised. The brain is the most important of our organs: the seat of our intelligence and personality. Its functioning determines our success and satisfaction in life. Obvious as this may seem, and despite calling the 21st century “the new era of the brain,” little attention has been paid to the relationship between nutrition and brain functioning.
- (1) J. Carper: Zywnosc, twoj cudowny lek (Food – Your Miracle Medicine), London 1995; A. Moir, D. Jessel: Zbrodnia rodzi sig w mozgu (A Mind to Crime. The Controversial Link between the Mind and Criminal Behaviour). Warszawa 1998.
- (2) J. Carper, op. cit.
- (3) A. Moir, D. Jessel, op. Cit. 
- (4) J. Wurtman, S. Suffes: Serotonina – prze/om w dietetyce (The Serotonin Solution). Warszawa 1997.
- (5) E. Solomon, D. Martin, L. Berg, C. Villee: Biologia (Biology). Warszawa 1996.
- (6) J. Gaw^cki: Spozywanie pokarmu – mechanizmy regulacyjne (Nutrition — Regulatory Mechanisms). Warszawa 1998.
- (7) A. Moir, D. Jessel, op. dt.
- (8) H. Selye: Stress iycia (The Stress of Life). Warszawa 1963; H. Selye: Stres okielznany (Stress without Distress). Warszawa 1978; S. Hoffmann, G. Hochapfel: Neurosenlehre, psychoterapeutische und psychosomatische Medizin (The Study of Neurosis, Psychotherapeutic and Psychosomatic Medicine). Stuttgart 1995.
- (9) A. Koi^taj: Pochwala stresu (The Blessed Stress). Kielce 1993.
- (10) B. Holyst: Wiktymologia (Victimology). Warszawa 1997.
- (12) K. Kopczynski: Wplyw zywienia na prac^ mozgu i aktywnoii psychicznq czlowieka (The Influence of Nutrition on Human Brain and Mental Activity). “Zdrowie Psychiczne” 1997, 3^4.
- (13. J. Wurtman, S. Suffes, op. cit.
- (14) A. Brzozowska: Skladniki mineralne (Minerals). Warszawa 1998; M. Wartanowicz: Witaminy (Vitamins). Warszawa 1998; W. Kierst: Nauka o zywieniu zdrowego i chorego czlowieka (Nutrition in Health and Illness). Warszawa 1989; I. Gumowska: Bqdi zdrow – smaeznego! O odiywczych i ieczniezych wlaiciwoiciach roslin (Be Healthy – Enjoy your Meal! The Nutritious and Therapeutic Properties of Plants). Warszawa 1987; H. Kunachowicz, J. Nadolna, B. Przygoda, K. Iwanow: Tabele skladu i wartotci odzywczej iywno&ci (The Charts of Composition and Nutritious Value of Food). Warszawa 2005.
- 15. W. Roszkowski: Upowszechnianie wiedzy o zywieniu. Zalecenia zywieniowe (Dissemination of Knowledge about Nutrition. Dietary Counselling). Warszawa 1998.