The etiology of digestive pathologies such as irritable bowel syndrome (IBS), inflammatory bowel diseases (IBD) and cancer is not yet fully understood. In recent years, several studies have evidenced circadian variations in mechanisms involved in digestive health. In situations of disturbed circadian rhythms (chronodisruption) where the central clock and the peripheral clocks receive incoherent signals, the synchronicity is lost producing implications for health. This lack of coordination could alter the tissue function and cause long term damage to the organs. Life habits such as sleep, physical exercise, social interaction, and feeding times are determinants for stability and integrity of circadian rhythms. In recent years, experimental and clinical studies have consistently evidenced that the alteration of circadian rhythms is associated with the development of digestive pathologies mainly linked to dismotility or changes in microbiota composition. Likewise, it seems reasonable to deep into the importance of chronodisruption as a factor that may participate in the development of pathologies such as IBS, IBD and digestive cancers. Moreover, life habits respecting circadian rhythms should be promoted for the prevention of these diseases. Further studies will allow us a better understanding of the mechanisms acting at molecular level, and the development of new therapeutic targets.

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Breastfeeding protects against adverse cardiovascular outcomes in the long term. Melatonin is an active molecule that is present in the breast milk produced at night beginning in the first stages of lactation. This indoleamine appears to be a relevant contributor to the benefits of breast milk because it can affect infant health in several ways. The melatonin concentration in breast milk varies in a circadian pattern, making breast milk a chrononutrient. The consumption of melatonin can induce the first circadian stimulation in the infant’s body at an age when his/her own circadian machinery is not functioning yet. This molecule is also a powerful antioxidant with the ability to act on infant cells directly as a scavenger and indirectly by lowering oxidant molecule production and enhancing the antioxidant capacity of the body. Melatonin also participates in regulating inflammation. Furthermore, melatonin can participate in shaping the gut microbiota composition, richness, and variation over time, also modulating which molecules are absorbed by the host. In all these ways, melatonin from breast milk influences weight gain in infants, limiting the development of obesity and comorbidities in the long term, and it can help shape the ideal cellular environment for the development of the infant’s cardiovascular system.

The aim of this review is to describe adolescent nutritional requirements from a scientific, nutritional, and psychosocial point of view, emphasizing the main risks of malnutrition at this age. Currently, too many teenagers are alone at home and prepare their own meals. The influence of friends replaces parental rules. The habits of adolescents are characterized by a tendency to skip meals, especially breakfast, and, less frequently, the midday meal; to purchase carry-out meals away from home; to consume snacks, especially sweets; to eat at fast food restaurants, almost always with high-calorie content; and to eat fried foods, soft drinks, and sweets. Toxic habits, such as smoking, alcohol, and drugs, interfere with a healthy diet, as well. Physical activity usually decreases during adolescence, particularly in girls. The lack of physical activity is due to a precarious knowledge of the benefits associated with practicing physical activity, low motivation, time constraints, and, in many cases, the lack of adequate facilities. Adolescents interested in a body image in accordance with modern ideals follow restrictive and unbalanced diets without any nutritional basis, which they themselves planned. These behaviors increase the risk of nutritional alterations, such as noncompliance with nutritional requirements, meal pattern irregularities, nutritional problems due to low nutrient intake, and self-esteem issues and frustration. In general, in this age group, there is an increase in protein consumption and salt content, often with a supply of unbalanced nutrients, high-fat diets (35–50% of total calories), and low polyunsaturated/saturated fat ratio. In addition, adolescents consume a low level of complex carbohydrates, fiber, fruits, and vegetables.

Objective: Cesarean section rates are increasing in developed countries and could be performed as an emergency or elective procedure. Our research aim was to determine whether elective cesarean section influences the melatonin content, the main circadian hormone, in human milk. Methods: Twenty-one women after vaginal delivery and 18 women after elective cesarean section were included. Only healthy mothers with normal newborns exclusively breastfed were recruited. Two samples of human milk were collected for each woman at three stages of lactation: colostrum, transitional milk, and mature milk; at each stage, one daytime sample and another nighttime sample were obtained. In total, 228 milk samples were studied. The melatonin content was analyzed by enzyme-linked immunosorbent assay. Results: Melatonin rhythmicity with higher melatonin content at night was maintained at each of the three stages of lactation, regardless of the type of delivery. A higher melatonin content was found in daytime colostrum after cesarean section with respect to colostrum obtained from mothers after vaginal delivery (30.3 pg/mL versus 14.7 pg/mL, p = 0.020). Melatonin content decreased progressively throughout the course of lactation in both groups. This decrease was significant when comparing transitional milk to colostrum in the cesarean group, both in the daytime (p = 0.016) and nighttime samples (p = 0.048). Conclusions: Cesarean section is associated with an increase in daytime colostrum melatonin. No difference was observed in mature milk with respect to vaginal delivery. Melatonin values in human milk decrease during the first month of lactation and circadian rhythmicity was observed irrespective of the mode of delivery.

Melatonin, the hormone of circadian rhythm regulation, is involved in the modulation of mitochondrial activity through its antioxidant and anti-inflammatory properties. Alteration of circadian rhythms such as sleep is related to obesity and metabolic pathogenesis in adulthood, but studies during childhood are scarce. The present study investigated the association of melatonin with metabolic and inflammatory markers in children with (n = 113) and without obesity (n = 117). Melatonin was measured in saliva four and two hours before bedtime, and after one hour of sleep. Cardiometabolic factors, high sensitivity C-reactive protein, immune markers (monocyte chemoattractant protein-1, plasminogen activator inhibitor-1, tumor necrosis α and interferon-γ), leptin and ghrelin were determined. Sleep duration was recorded by a questionnaire. The melatonin level at 1 h after sleep was found to be increased more than twofold in children with obesity (90.16 (57.16–129.16) pg/mL) compared to controls (29.82 (19.05–61.54) pg/mL, p < 0.001) and was related to fat mass (rho = 0.294, p < 0.001); melatonin levels at 1 h after sleep were inversely correlated with high-density lipoprotein cholesterol. Positive correlation was found with apolipoprotein B, adipokines, high sensitivity C-reactive protein, plasminogen activator inhibitor-1 and tumor necrosis factor-α. Shorter sleep duration and earlier waking times were recorded in children with obesity. In conclusion, melatonin in children with obesity appears to be involved in the global metabolic and inflammatory alteration of this condition.

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Circadian rhythms are the changes in biological processes that occur on a daily basis. Among these processes are reactions involved in metabolic homeostasis. Circadian rhythms are structured by the central clock in the suprachiasmatic nucleus of the hypothalamus via the control of melatonin expression. Circadian rhythms are also controlled by the peripheral clocks, which are intracellular mechanisms composed of the clock genes, whose expression follows a circadian pattern. Circadian rhythms are impacted by signals from the environment called zeitgebers, or time givers, which include light exposure, feeding schedule and composition, sleeping schedule and pattern, temperature, and physical exercise. When the signals from the environment are synchronized with the internal clocks, metabolism is optimized. The term chronodisruption is used to describe the opposite situation. The latest research has demonstrated that life habits coherent with the internal clocks should be adopted, especially during childhood, to prevent metabolic diseases. Nevertheless, a few studies have investigated this link in children, and key information remains unknown.