Unlocking the Link between Ultra-Processed Foods and Depression: How Our Plate Affects Our Mood and Anxiety

2023-05-19 14:02:31

The contents of our plates may well impact our emotions, mood and anxiety. Among the threats, several studies highlight a link between the consumption of so-called ultra-processed products and the risk of depression. Explanations.

An apple every morning keeps the doctor away, they say. The adage is less valid when the fruit is replaced by an industrial white bread, a chocolate bar, crisps, a soda or a frozen ready meal. These foods belong to the family of so-called ultra-processed foods, otherwise products made from an industrial process and whose composition is low in nutrients, high in sugars, fat and additives. If we have known for several years that their consumption is associated with risks of overweight, obesity, diabetes and even cancer, scientific research is closely studying the connections between these products, more specifically their ingredients, and mental disorders.

Thus, according to an American study published in July 2022 in review Public Health Nutrition , “people who eat this type of food have a very markedly increased risk of triggering anxious and depressive symptoms”, reports today Guillaume Fond, psychiatrist and teacher-researcher at the FondaMental foundation and at the university hospitals of Marseille. How is it possible ? Are we really “what we eat”? How does our digestive tract interact with our brain?

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Generalized chronic inflammation

As the German doctoral student Giulia Enders pointed out in 2015, author of the best-selling The discreet charm of the gut, our digestive system is our “second brain”. It hosts a veritable ecosystem made up of billions of bacteria and called the microbiota. The latter is in symbiosis with the intestine, it facilitates our digestion but also plays an important role in the metabolic, immune and neurological functions of the body. Only certain ingredients contained in particular in ultra-processed foods and of poor nutritional quality threaten this balance and, by domino effect, our mood.

More specifically, a diet high in sugars, saturated fats and low in fibre, modifies the permeability of the intestinal barrier which therefore allows more toxins to pass into the blood. “This phenomenon will then create chronic inflammation which will weaken the immune system and disrupt all the organs, including the brain”, underlines Guillaume Fond.

When inflammation spreads to all levels and you are sick, all functions are impaired, from the ability to think to sleep

Gabriel Lepousez, neurobiologist specializing in brain plasticity at the Pasteur Institute

Once the body is weakened, the vicious circle begins. To understand it, one only has to think of the sensation of a brain that turns in slow motion when one has a cold or suffers from gastroenteritis. “When inflammation spreads at all levels and you are sick, all functions are altered, from the ability to think to sleep, informs Gabriel Lepousez, neurobiologist specializing in brain plasticity at the Pasteur Institute. Some scientific hypotheses suggest that this inflammatory context would be conducive to cognitive decline, such as that observed during aging.

Researchers from the Institut Pasteur, Inserm, and CNRS have been able to observe the effects of this deregulation in the context of work published in Nature Communications in December 2020. Through a laboratory experiment, scientists have thus discovered that if the microbiota of a mouse in a state of chronic stress and depression is transferred to another healthy rodent, the latter develops after 8 weeks the same symptoms and then becomes depressed in turn. “If the microbiota is damaged, it leads to poor absorption of lipids essential for the proper functioning of the brain, the Omega 3 and 6, says neurobiologist Gabriel Lepousez, who participated in the study. In the event of a deficiency of these unsaturated fatty acids, the brain experiences a deficit of certain neurotransmitters in the hippocampus, a key region of the brain involved in the formation of memories and emotions. This dysfunction can then lead to depressive behavior.

Frustration and low energy

On a behavioral and emotional level, too much ultra-processed food is not without consequences. High in sugar, fat and salt, these products are carefully formulated to be so palatable and satisfying, they’re almost addictive. “Because it brings together tasty ingredients, the ultra-processed food causes the release of dopamine (pleasure hormone, editor’s note), which conditions the pleasure associated with fatty, salty and/or sweet food and pushes us to come back to it at the next meals”, observes the neurobiologist Gabriel Lepousez.

More concretely, when biting into a cookie or a pizza, a comfort circuit is set up. The pleasure felt activates the reward system and increases the production of dopaminergic neurons responsible for the production of the pleasure hormone in the brain. To naturally guard against addiction, “this system regulates itself in the event of excess and will seek to reduce the feeling of reward if the food is ingested again. Result, this pushes some eaters to consume more and more to try to find this feeling, ”notes the neurobiologist.

What ultimately lead to its share of frustration, guilt but also weight gain, just as devastating on morale. “The more weight you gain, the less motivation and psychic energy you have to play sports. And to compensate for this lack, food will become a means of emotional regulation. Some will then turn to processed and sweet products such as cookies or chocolate. There too, this will be translated at the level of the brain by anxiety up to depression, mild to very marked”, summarizes the psychiatrist Guillaume Fond.

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How to cure it ?

To try to turn the tide, the first reflex is to regain control over your diet. If the total eviction of ultra-processed products is impossible, the psychiatrist Guillaume Fond recommends granting them a very marginal share in the diet, around 5%. For the specialist, also author of the book Eat well to stop feeling depressedr (1), it is preferable the rest of the time to favor a diet rich in seasonal fruits and vegetables, without forgetting legumes, rich in vegetable proteins, complex carbohydrates and minerals. “Several meta-analyses confirm it: eating fruit every day reduces the risk of depression by 15% and by 9% if you eat vegetables daily,” he reports.

Eating fruit every day reduces the risk of depression by 15% and by 9% if you eat vegetables daily

Guillaume Fond, psychiatrist

As mentioned above, omega-3s are also essential fatty acids for the proper functioning of the brain. They are found in vegetable oils but also in fatty fish such as sardines or mackerel. “We choose them fresh or preferably canned because frozen fish no longer contain omega 3 after 6 months,” says the psychiatrist.

Finally, the health professional praises the nutritional benefits of foods with a “probiotic effect”, named after these “good bacteria” that are generally taken in the form of food supplements to rebalance their microbiota (or intestinal flora). They have a multiple anti-inflammatory effect: on immunity, digestion, the porosity of the intestine, specifies Dr. Guillaume Fond. They can be found in dairy products or lacto-fermented products, such as soy sauce, kimchi or miso soup.

(1) Eat well to stop feeling depressed, by Guillaume Fond, Odile Jacob editions, 272 pages, 22.90 euros.

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