Interview with Roland Salesse – “Le cerveau cuisinier

Roland Salesse, you present your latest book “Le cerveau cuisinier”.

Is it simply about recipes for better nutrition, or even for better nutrition of the brain ?

Le cerveau cuisinier n’est pas un livre de recettes ! Le sous-titre est plus explicite : Petites leçons de neurogastronomie .

Our diet is subject to such economic and social pressure (just think of advertising, but also of various advices, injunctions and worries: “lose weight”, “junk food”, “eat this, not that”,” impact of our diet on the climate”) that we forget the physiological bases of nutrition. In writing this book, I wanted to describe how the brain ‘naturally’ dialogues with the body to regulate our food intake. The mechanisms involved are the result of a long evolutionary process that has selected several systems coordinated by the brain :

  • The neuromuscular system of chewing and swallowing.
  • Taste, which is in fact the result of the perception of three systems: olfaction (or smell), gustation (reception of flavours) and the trigeminal nerve system (which provides information on texture, temperature and spiciness).
  • The gastrointestinal system, which functions largely autonomously but communicates with the brain to regulate satiety, digestion, food learning.

Robert Francès was a precursor in France. He worked in Paris at the CNRS and wrote a thesis. Apart from that, there was little information on this subject. So I was interested in tackling this question.

Musicians know the effects of music well, but they describe them with their intuitions. It was necessary for me to look at what these intuitions correspond to. How it is concretely translated in the brain.

When we sit down to eat, are there other mechanisms or systems that we mobilise ?

When I sit down to eat, I don’t just mobilise these systems. I also call upon my learning (since foetal life), my preferences (my ‘tastes’), my psycho-physiological state, my culture and the influence of my socio-economic environment. In short, what was only a survival behaviour takes on emotional, cultural or identity-related meanings that take precedence over ‘simple’ physiological mechanisms.

And it is the brain that integrates all these parameters to preside, consciously or not, over my nutritional behaviour.

Moreover, the human species is a highly social species that has always organised itself on increasing scales, from wandering tribes to globalisation, to supply our insatiable stomachs. In our time, the excesses of overexploitation of the planet, speculation on foodstuffs and overeating driven by advertising have led to global warming, high prices and metabolic (obesity and diabetes ‘epidemic’) and cardiovascular diseases.

How are eating habits established ?

Conditioning starts very young, in an unsuspected way. The foetus, in its mother’s womb, already inherits maternal conditioning. Indeed, certain smells and flavours of the food eaten by the mother pass into the amniotic fluid, thus giving the baby its first olfactory and gustatory experience. But this is not all. The mother herself carries an epigenetic heritage [1], the result of her own lifestyle (including her diet), but also of the conditioning she experienced during her own intra-uterine life with her grandmother. And the little fetus I am talking about already carry in their gonads (ovaries and testicles) the cells that will give rise to the eggs or spermatozoa that will generate the next generation. Thus, from generation to generation, metabolic adjustments are passed on that more or less decide the health of individuals. We now speak of DOHaD, Developmental Origin of Health and Diseases. All is not lost because these epigenetic marks, unlike mutations that change genes, are reversible. In other words, a change in lifestyle can reset and erase the deleterious epigenetic markers.

And for a toddler ?

Let’s go back to our newborn. The composition and quantity of milk, which is essential to the infant’s needs, changes with the duration of breastfeeding. But moreover, in the reassuring atmosphere of the mother’s breast, the baby will continue to learn the senses by breathing in the mother’s smells and the food aromas that pass into the milk. Then, after weaning, the child will gradually become familiar with the family’s eating practices, which will serve as a reference point during the following years, until the changes in the social environment of adolescence and adulthood.

At birth, the babies will receive another “gift”: a good part of the “familiar microbes” of their mother and their environment. We now speak of a microbiome for all microorganisms (bacteria, fungi, viruses, protozoa) and of a microbiota for bacteria only. This “domestic microbiome”, in a way “tamed” – in particular by the mother -, combined with the growth factors contained in the milk, will contribute to the establishment of the infants’ early immunity and promote the development of their immune defences, while teaching them to tolerate the microorganisms that are favourable to physical and mental health. And where is the largest microbial population in our bodies located? In the digestive system, from the mouth to the anus, but with 99% of the total microbial population in the large intestine. Scientific results show that the composition of the microbiota is correlated with the state of health, physical or mental, of individuals. It has even been shown in rodents that a transplant of healthy microbiota can cure a sick mouse and conversely, that a “dysbiosis” microbiota (of abnormal composition) makes a healthy mouse sick.

Epigenetics and microbiota have been studied extensively for the past 20 years or so, and are now emerging in the field of health and medicine as major parameters inherited from conception.

To conclude, how would you summarise the chapters that help us understand how nutrition works ?

Eating mobilises multiple functions of the body. Planning functions to obtain and prepare food, motor functions to bring it to the mouth, chew it and swallow it. Sensory functions to recognise the food and evaluate the food. Largely non-conscious functions of the digestive tract: enzymatic, motor, sensory, neuroendocrine. When we think of “taste” and “gastronomy”, we think of the pleasure experienced when tasting. But the senses (vision, hearing, olfaction, gustation, touch, proprioception (= self-perception)) and the gastrointestinal sensors constitute a veritable laboratory for analysing the ration, which transmits its qualitative and quantitative value to the brain, which in turn controls the act of eating or its cessation. Chronobiology: the brain also regulates the time of meals and orchestrates the relationships between the organs. Memory : the brain also forms the sensory images of food and learns how to eat it. This is how our food choices are determined, as well as their nutritional, symbolic and cultural value, right up to gastronomic appreciation, which involves the same neural circuits as those involved in the aesthetic judgement of works of art, so that science and pleasure can be combined !

[1] Epigenetics (etymologically “over genetics”) is a set of mechanisms that do not change the DNA sequence of genes (called mutation) but change their expression. For example, genes that are expressed during embryonic development are switched off in adulthood or brain cells do not express the same genes as muscle cells.

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