on July 01, 2026
The human body is continuously exposed to thousands of food molecules from natural foods, food processing ingredients, microbial metabolites, and compounds generated by industrial food processing.
The digestive and immune systems interpret this vast amount of biological information, distinguishing what provides nourishment, what requires adaptation, and what poses a real threat.
In recent years, research has increasingly reinforced the concept that the relationship between diet and health depends not only on the caloric content of foods but also on their ability to interact with inflammation, the microbiota, metabolism, and cellular signaling systems.
Monosodium glutamate is among the most widely discussed ingredients.
Glutamate is one of the most common amino acids in nature and is naturally present in tomatoes, aged cheeses, mushrooms, meat, breast milk, and numerous fermented foods.
In the food industry, it is used as a flavor enhancer to increase the perception of umami taste.
From a physiological perspective, glutamate is also one of the main excitatory neurotransmitters in the central nervous system.
This fact led for many years to the hypothesis that dietary glutamate could generate direct neurological effects.
Current evidence, however, indicates that dietary glutamate is primarily metabolized in the intestine and does not reach the brain in quantities sufficient to reproduce the effects observed in the central nervous system.
Regarding the so-called “Chinese restaurant syndrome,” now more accurately defined as a syndrome associated with glutamate, studies have not confirmed a consistent and generalizable relationship.
Some individuals may report symptoms such as headache, flushing, a feeling of pressure, or malaise after high exposure under specific conditions, but glutamate is no longer considered a neurotoxic additive at the doses normally consumed.
A more useful approach is to consider the overall context.
Foods that most frequently contain high amounts of flavor enhancers often belong to the category of ultra-processed foods, which are also characterized by higher energy density, high sodium content, and reduced satiety.
A second group of additives that frequently attracts attention concerns nitrites and nitrates.
These compounds are used in meat preservation to limit microbial growth and preserve organoleptic characteristics.
The regulated use of nitrites and nitrates is considered safe within authorized limits.
The main scientific concern does not involve methemoglobinemia in the general adult population—a clinically relevant phenomenon especially in specific contexts and in childhood—but rather the possible formation of nitrosamines under particular processing and consumption conditions.
For this reason, international guidelines suggest limiting the habitual consumption of processed meats without demonizing occasional consumption.
The issue of alcohol also requires a review in light of the most recent evidence.
For many years, observational studies had suggested a possible association between moderate alcohol consumption and reduced cardiovascular mortality.
Subsequent analyses have highlighted important confounding factors.
Major international organizations today do not recommend alcohol consumption for health benefits.
Ethanol has complex effects on metabolism: it alters liver metabolism, influences sleep, disrupts energy regulation, and may contribute to an increased risk of numerous diseases.
The biological differences between men and women in alcohol metabolism are real and depend on body composition, water distribution, and enzymatic activity.
The relationship between alcohol, body composition, and metabolic regulation also appears to be influenced by neuroendocrine signals involving appetite, leptin, insulin sensitivity, and inflammation.
When discussing inflammation, it is important to distinguish physiological processes from pathological states.
Acute inflammation represents an essential biological response for tissue repair.
Heat, redness, edema, and pain reflect the coordinated activation of immune cells and mediators necessary for recovery.
Low-grade chronic inflammation is a different phenomenon.
It may be sustained by multiple factors, including energy excess, physical inactivity, visceral obesity, sleep disturbances, chronic stress, and microbiota alterations.
There is no evidence that repeated consumption of the same food systematically generates a state of chronic inflammation in the general population.
However, some clinical conditions may require specific nutritional strategies.
One particularly important chapter concerns the distinction between food allergy, enzyme deficiency, and non-allergic hypersensitivity.
Lactose intolerance represents an enzyme deficiency due to reduced lactase activity.
It does not involve the immune system.
Classic food allergies, on the other hand, are generally IgE-mediated immune reactions that can cause hives, edema, respiratory symptoms, and, in severe cases, anaphylaxis.
Food allergies must be diagnosed through validated clinical pathways.
In recent years, the term “food sensitivity” has been used to describe symptoms that do not meet the criteria for IgE-mediated allergy.
However, the diagnostic role of dietary IgG and numerous commercial tests remains controversial and is not currently recommended by major allergy societies as a diagnostic tool for allergies.
When a relationship between symptoms and diet is suspected, the most evidence-supported approach remains a structured clinical assessment with possible controlled elimination and subsequent reintroduction diets.
Pharmacological treatment also requires proper contextualization.
Antihistamines and corticosteroids are essential therapeutic tools in many allergic and inflammatory conditions.
They do not “simply mask the symptoms,” but in numerous situations, they reduce the risk of complications and improve quality of life.
Their use must be appropriate and supervised.
One of the most fascinating topics that has emerged in recent decades concerns the intestinal microbiota.
The gastrointestinal tract hosts trillions of microorganisms that participate in digestion, metabolite production, immune modulation, and the protection of the intestinal barrier.
The microbiota is now considered a biologically active ecosystem capable of interacting with metabolism, the brain, and the immune system.
The appropriate use of antibiotics has saved millions of lives.
At the same time, excessive or unnecessary use can alter the composition of intestinal microbes and promote antimicrobial resistance.
Numerous studies have observed associations between early antibiotic exposure and altered risks of certain immune-mediated conditions, although they have not demonstrated simple causal relationships.
The health of the microbiota appears to be supported especially by a high-fiber diet, plant diversity, physical activity, adequate sleep, and prudent use of antibiotics.
Understanding the relationship between diet, immunity, and the microbiota means moving beyond the search for a single responsible ingredient and adopting a systemic view of metabolic health.
Bibliography
Hermanussen M et al. MSG intake and obesity association. Nutr Metab. 2006.
Geha RS et al. Review of monosodium glutamate safety. J Nutr. 2000.
International Agency for Research on Cancer (IARC). Processed meat and cancer. 2015.
World Health Organization. Alcohol and Health Report.
Wood LG et al. Inflammation and nutrition. Nutrients. 2015.
Sampson HA. Update on food allergy. J Allergy Clin Immunol. 2004.
EAACI Position Paper on IgG testing and food allergy.
Blaser MJ. Missing microbes and modern disease. Nature. 2014.
Cho I, Blaser MJ. The human microbiome. Nat Rev Genet. 2012.
Hall KD et al. Ultra-processed diets cause excess calorie intake and weight gain. Cell Metabolism. 2019.
Lynch SV, Pedersen O. The human intestinal microbiome in health and disease. N Engl J Med. 2016.
