Nowadays, Diet Therapy is an integral part of treatment plans for Depression, Autism, Epilepsy and other psychiatric disorders as well as Eating and Nutrition Disorders (Bulimia, Anorexia, Binge-Eating). Let's find out what is the connection between what we eat and our brain and why nutrition determines not only our health and appearance but also our mental state.
The discovery of the new organ
Psychobiology is a novel science that studies the connections between our brain (mind) and other organs: how does our health affect our mood and how what we eat can change it? In recent years, a new organism that translates what we eat into brain's messenger-molecules is being widely studied. This organ is called the gut microbiota and is a collection of microorganisms, among which the majority are bacteria (99%) and the rest protozoa, fungi, viruses and helminths. The microbiota is most concentrated in the intestine, especially in its last part called the large intestine.
What does the microbiota do?
When we eat a meal, this goes into the stomach and then into the small intestine where the cell walls are disassembled to extract the substances contained within. These extracts then reach the large intestine and serve as substrates (food) for the microbiota. The microbiota processes these substrates by producing a spectrum of messenger-molecules that directly (neuroactive molecules such as serotonin), or indirectly (pro-inflammatory cytokines and metabolites that stimulate the vagus nerve) act on the central nervous system. These molecules can, on the one hand, stimulate neuroplasticity and thus our ability to adapt to new situations and environments, increase our degree of socialization, our cognitive abilities, reduce anxiety, and increase feelings of general well-being; other molecules, on the other hand, can lead to the opposite result. Thus, the balance between good and bad molecules is determined by those substrates received by the microbiota and thus by what we ate (Berding et al., Adv Nutr 2021).
How are foods classified?
The 2019 FAO (Food and Agriculture Organization of the United Nations) report adopted the NOVA classification of foods and proposes a new concept of nutrition policies.
The NOVA scheme distinguishes four food groups*:
Group 1: Unprocessed and minimally processed foods ― The edible parts of plants (such as fruit, leaves, stems, seeds, roots) or from animals (such as muscle, offal, eggs, milk), and also fungi, algae and water, after separation from nature.
Group 2: Processed culinary ingredients ― Oils, butter, lard, sugar, and salt.
Group 3: Processed foods ― Canned or bottled vegetables or legumes (pulses) preserved in brine; whole fruit preserved in syrup; tinned fish preserved in oil; some types of processed animal foods such as ham, bacon, pastrami, and smoked fish; most freshly baked breads; and simple cheeses to which salt is added.
Group 4: Ultra-processed foods ― Ultra-processed foods are formulations of ingredients, mostly of exclusive industrial use, typically created by series of industrial techniques and processes (hence ‘ultra-processed’). Some common ultra-processed products are represented by: carbonated soft drinks; sweet, fatty or salty packaged snacks; candies (confectionery); mass produced packaged breads and buns; cookies (biscuits), pastries, cakes and cake mixes; margarine and other spreads; sweetened breakfast ‘cereals’ and fruit yoghurt and ‘energy’ drinks; pre-prepared meat, cheese, pasta and pizza dishes; poultry and fish ‘nuggets’ and ‘sticks’; sausages, burgers, hot dogs and other reconstituted meat products; powdered and packaged ‘instant’ soups, noodles and desserts; baby formula; and many other types of product.
*Adapted from: Ultra-processed foods, diet quality, and health using the NOVA classification system, Food and Agriculture Organization of the United Nations, Rome, 2019.
What foods act positively on our mental state?
Numerous researches have identified the dietary pattern (a style of eating, not individual foods), which improves the variety and quality of our gut microbiota. This pattern is not attributed to a particular diet, but summarizes the following rules:
The constant presence of seasonal vegetables in our meals: at least 200g at both lunch and dinner;
The presence of fresh seasonal fruit to maintain the variety of the microbiota, but the amount of fruit should be limited due to the presence of simple sugars: 2 maximum 3 servings per day of fruit is enough (1 serving is equivalent to 150g of product);
The presence of at least 2 servings of legumes (possibly native) in the diet;
The presence of various grains and pseudo-cereals possibly native and unrefined in our diet: whole grain pasta and rice if possible, spelt, barley, oats, buckwheat, quinoa;
Limit the presence of red meat to 1 serving per week, white meat to 2, and increase the presence of fish, especially lean fish, in the diet;
Abundant water: for the female population the recommendation is 1.5-2 liters per day, and for the male population 2-2.5 liters;
Maintain an adequate level of physical activity.
Obviously, all these suggestions must be interpreted for individual cases: food intolerance, allergies, irritable bowel syndrome, celiac disease and other disorders often associated with psychiatric diseases and in any case increasing in the general European population. Diet customization is also influenced by the level of sports activity.
What foods act negatively on our mental state?
"Ultra-processed foods" are industrially processed ready to eat packaged foods and if consumed too much, induces dysfunctions in our body.
Let's see why:
Ultra-processed foods often contain food extracts and thus immediately provide substrates to our microbiota beyond the engagement of the small intestine; therefore, daily consumption of these foods induces the so-called bacterial overproliferation syndrome (SIBO): the migration of the microbiota to the small intestine with induction of intestinal inflammation.
An article published in the British Medical Journal described that high total consumption of ultra-processed foods in men and some subgroups of ultra-processed foods in men and women was associated with an increased risk of colorectal cancer.
Are ultra-processed foods associated with the risk of various diet-related non-communicable diseases (NCDs)?
The FAO “Ultra-processed foods, diet quality, and health using the NOVA classification system” reports the association between ultra-processed food exposures and the following pathologies:
Cardiovascular and metabolic diseases;
There are also studies which found significant direct dose-response associations between the dietary share of ultra-processed foods and death risk due to all causes.
So diet is important for a good mood and a healthy mind?
Absolutely! Multiple studies and clinical cases (Morais et al., Nature reviews, 2021) have shown with certainty that our mood depends on what we eat and our health status. Diet Therapy as an integrated approach is recommended in the treatment of patients with psychiatric diagnoses. Remember, however, that there is no such thing as a one-size-fits-all diet; the diet must be individualized with the aim of resolving any gastro-intestinal, inflammatory, autoimmune diseases, food intolerances, and allergies to increase the patient's degree of well-being. We really are what we eat.