In 1986, Rappaport and Levine published an excellent article focusing on the prevention of constipation, integrated with the stages of childhood development [26]. This article emphasizes that parental guidance and education regarding changes in bowel function throughout the first years of life are important strategies for preventing constipation and other bowel-related disorders [26].

Therefore, physicians should provide appropriate parental guidance to foster confidence and competence in interpreting and understanding the normal evolution of a child’s bowel habits. This avoids unnecessary treatment and inappropriate actions resulting from anxiety and fear generated by a lack of knowledge about normal variations in bowel physiology [26].

Generally, the fetus does not pass meconium before birth. Passage of meconium during pregnancy may be indicative of fetal distress. The first passage of meconium occurs within the first 24 h of life. Premature infants weighing < 1500 g at birth may have their first meconium passage after 48 h. Delayed meconium passage is an alarm signal that should be evaluated by a pediatrician [2,5,8,20,21]. After birth, infants are fed colostrum and breast milk, which cause changes in stool characteristics known as transitional stools. Thus, throughout the first few days of life, changes in stool characteristics are observed depending on the type of feeding. Exclusively breastfed infants have looser stools that are passed more frequently (approximately five times per day), whereas formula-fed infants have firmer stools with an average frequency of two bowel movements per day [32–34].

In the first months of life, two conditions may occur that can cause concern in parents. The first is pseudo-constipation, which consists of the elimination of loose stool without pain or difficulty, with a prolonged interval between bowel movements (up to one or two weeks) [35]. Pseudo-constipation is not associated with excessive crying, abdominal distension, or vomiting. Pseudo-constipation should be considered a normal variation in bowel habits that occurs in approximately 5 % of breastfed infants and does not require treatment [31]. The second is infantile dyschezia, which can be seen up to 9 months of age and consists of at least 10 min of straining, crying, and facial flushing before the end of a bowel movement, in the absence of other health problems [1]. Infant dyschezia appears to be caused by a lack of coordination between abdominal muscle contraction and pelvic relaxation and represents a normal phase of childhood development [1]. Therefore, a lack of knowledge about pseudo-constipation and infantile dyschezia can lead to unnecessary and harmful parental behaviors, such as discontinuing breastfeeding or unnecessary changes to infant formula. Unnecessary use of suppositories and other anal stimulants should be avoided [8,26].

More complex motor and cognitive skills, such as walking and talking, appear by the end of the first year of life. At this stage, parental reports of stool retention behavior may emerge, generally beginning with episodes of painful bowel movements [26]. In this situation, the child develops stool retention maneuvers instead of allowing the natural sequence of the normal bowel movement mechanism. Retentive behavior is considered one of the main mechanisms linked to the onset and chronicity of constipation [1–6,8,11].

During the acquisition of anal sphincter control, the lack of a harmonious relationship between parents and children can facilitate the onset or worsening of retentive behaviors [26]. The recommendation is that painful bowel movements should be controlled before starting toilet training [3–6,8,11,26]. The age at which bowel and urination control are acquired varies across cultures. In Western countries, the age for acquiring anal sphincter control has increased from approximately 24 to 36 months [36]. There are several techniques for toilet training [6]. The child-oriented toilet training method is recommended by the American Academy of Pediatrics, the Canadian Society of Pediatrics [6], and the Brazilian Society of Pediatrics [36]. During toilet training, parents should be guided to positively support their children during the various stages of the process [6,36]. Training should generally begin between 18 and 24 months when the child shows signs of readiness, such as staying dry for a couple of hours at a time, showing interest in using the toilet, and being able to follow simple instructions [6,36]. The child should remain in an appropriate position on the potty or toilet with a seat reducer and footrest for periods of approximately 5 min. The gastrocolic reflex can be used during the postprandial period [6,36]. Punishment and immediate expectations should be avoided. Parents should be patient and offer positive reinforcement without exaggeration [6,36]. Imposing and coercive toilet training is classically considered one of the determining factors of withholding behaviors, which can be followed by fecal retention and functional constipation [1–6,8,11].

The pain-retention-pain cycle may begin or recur at school age, owing to phobias caused by a lack of cleanliness and privacy in school bathrooms. Other contributing factors include rigid school schedules and adherence to busy extracurricular activities [26].

Retentive behavior was identified in 70 % of school-age children with constipation in an epidemiological study, and was more frequent than other clinical manifestations, such as increased bowel movement intervals and the passage of stool that clogs the toilet. These data suggest that retentive behavior may trigger the onset of other clinical manifestations of functional constipation [18]. In patients treated at a specialized outpatient clinic, retentive behavior was found in 68 % of preschoolers, 41 % of schoolchildren, and 28 % of adolescents [37]. Therefore, recommending that retentive behavior be avoided by prioritizing defecation may represent a strategy to prevent the onset and progression of functional constipation.

Factors related to family dynamics and the social context can also influence the onset of functional constipation. Certain events can mark the onset of bowel movement disorders, such as the birth of a sibling, exposure to parental marital problems, moving to a new home or school, or the loss of a loved one. These events are milestones that require special attention from parents to address these adversities and prevent children from developing bowel movement disorders [1–6,8,26,36].

Exposure to violence and victimization in children and adolescents is associated with constipation and other gastrointestinal disorders [3–6,8,11]. A study conducted in Brazil using a comprehensive questionnaire revealed a high frequency of exposure and victimization to violence of varying degrees of severity among adolescents [38]. A greater number of questions indicated that violence was associated with a greater risk of functional constipation and irritable bowel syndrome [38]. Violence can influence the interaction between the brain and gut, facilitating the development of functional gastrointestinal disorders [3,4,6]. The possibility that maternal exposure to domestic violence is associated with a greater risk of constipation in children has also been discussed [39]. Therefore, protecting children and adolescents from exposure to violence and victimization can contribute to the maintenance of balanced mental and physical health, including bowel habits.

Other family factors may predispose patients to functional constipation. For decades, it has been emphasized that both children and other family members should have a healthy diet, prioritizing foods rich in dietary fiber and reducing foods rich in fats and simple carbohydrates [26]. In Brazil, an association has been observed between low dietary fiber consumption by mothers and children with constipation [40]. Therefore, it is often difficult for children to adhere to healthy eating habits when their parents and other family members do not do the same [26].

The role of genetic factors in the etiology of functional constipation can also be considered in the family context. A literature review highlights that no genes specifically linked to functional constipation have yet been identified; however, many genetic syndromes have constipation as one of the phenotypic manifestations [41]. In turn, a study of mono- and dizygotic twins has suggested that genetic factors can explain up to 59 % of the concomitant occurrences of constipation [42]. Other evidence compiled in the literature suggests an association between the fingerprint arch pattern and constipation. However, other studies, such as one conducted in Brazil, have not confirmed this finding [43]. In another Brazilian study, only slight agreement was observed between the presence of constipation in adolescents and their mothers or biological fathers, according to the Kappa coefficient (0.12 and 0.05, respectively) [44].

Approximately half of the children with severe functional constipation treated at specialized pediatric gastroenterology clinics experience disease onset in the first year of life [45–47]. During this period, isolated or not gastrointestinal signs and symptoms may occur. These clinical manifestations may fulfill the Rome criteria for functional gastrointestinal disorders in infancy [8,12,13,48]. Regurgitation, colic, and dyschezia in infancy appear to be more closely related to the functional maturation of motility, digestion, and the establishment of intestinal microbiota [8,48]. These clinical manifestations generally disappear during the first year of life. However, functional constipation is more common in the second six months of life [12,13], and the type of nutrition is important for determining bowel habits.

Breastfeeding reduces infant mortality and the risk of developing chronic non-communicable diseases in adulthood [49]. In Brazil, breastfeeding rates have increased [50–52] due to pediatricians’ actions and other public health initiatives [53].

The advantages of breastfeeding should be expanded to include the prevention of constipation. Table 1 presents the main results from articles [13,34,35,54–69] indexed in the PubMed database that linked breastfeeding and constipation.

The first articles were published in Brazil. In 2002, a public primary care-based article from the metropolitan region of São Paulo showed the protective effect of breastfeeding on the development of constipation [35]. The study showed that artificial breastfeeding was associated with a 4.5-fold greater risk of constipation than that of infants who were predominantly breastfed [35]. Another public primary care study also conducted in the metropolitan region of São Paulo showed a 3.0-fold greater risk of constipation in those who received artificial breastfeeding between 6 and 24 months of age [57]. However, a more recent epidemiological study with infants from all regions of Brazil treated in private pediatric practices showed that functional constipation in infants was associated with age and history of prematurity, but not with sex or type of breastfeeding [13]. Whole cow's milk was likely used as a milk source in previous primary care studies [35,51], while in the most recent study [13], in private pediatric practices, >90 % of infants received infant formula as their sole milk source [13,52]. In other words, whole cow's milk may be a risk factor for constipation, which was not observed with the use of infant formula, considering natural breastfeeding as a reference. This hypothesis should be investigated in future studies specifically designed for this purpose.

Table 1 also shows that almost all articles indicate a favorable role for breastfeeding in maintaining normal bowel habits and a lower chance of future constipation. However, it should be noted that there is considerable heterogeneity in the study design, definition of variables, and analytical strategies. Therefore, the specific role of infant formulas with or without added prebiotics and whole cow's milk as risk factors for constipation should be confirmed in future studies specifically designed to answer these questions.

Another interesting observation regarding constipation prevention was obtained from a study conducted in Porto Alegre, Brazil [70]. This randomized cohort study showed that infants cared for in the first two years of life by professionals who had received training in the Ten Steps to Healthy Eating had a 38 % reduced risk of constipation at the age of 6 years [70].

In summary, the premature cessation of breastfeeding is a risk factor for constipation. In this situation, infant formulas should be used, especially those containing prebiotics such as a mixture of fructooligosaccharides (FOSs) and galactooligosaccharides (GOSs), which decrease stool consistency and increase bowel movement frequency [71,72]. There is still very little evidence on the role of synthetic oligosaccharides identical to those found in breast milk (human milk oligosaccharides [HMOs]) added to infant formulas. The results of two clinical trials showed that a dose of 5.8 g/L of HMOs increased bowel movement frequency and decreased stool consistency, a finding not observed in another clinical trial that used infant formula with a lower HMO content [72].

Another concern is the lipid profiles of cow's milk and some infant formulas, which may be associated with the increased formation of calcium soaps with palmitic acid esterified at the sn-1 and sn-2 glycerol positions. Thus, the addition of palmitic acid esterified at the sn-2 position in infant formulas results in better absorption, increases the bioavailability of calcium, and provides stools with less consistency by reducing soponification [73,74].

In summary, the first year of life provides an excellent opportunity for defining food preferences and preventing constipation. In infants, constipation generally begins with pain or difficulty passing hard, separate hard lumps (like nuts) without an increase in the interval between bowel movements [13,35,37]. These clinical manifestations do not meet the Rome IV [8] criteria for functional constipation; however, they serve as warnings that dietary changes should be implemented promptly. After the introduction of complementary foods, dietary fiber can be a key factor in preventing constipation. The addition of prebiotics to infant formula may decrease stool consistency and increase bowel movement frequency compared to formulas without prebiotics and cow's milk, thus reducing the chance of painful bowel movements that can trigger the onset of functional constipation. On the other hand, there is no evidence to justify the recommendation of probiotics in the prevention or treatment of functional constipation according to the ESPGHAN guidelines [75]. The same position is adopted by ESPGHAN for the use of prebiotics in the treatment of functional constipation [76].

The benefits of dietary fiber have been recognized since the Hippocratic era; however, to date, there is no fully accepted definition [77–84]. Dietary fiber can be defined as polymeric carbohydrates with >10 monosaccharide units that are resistant to enzymatic hydrolysis in the human intestine [77–80]. More recently, a broader definition has also been proposed that adopts the term “functional fiber”, which includes oligosaccharides with a lower degree of polymerization that are not absorbed by the intestine and are fermented in the intestinal lumen by the intestinal microbiota [84]. Generally, soluble fibers are more fermentable, have greater osmotic power, and a greater capacity to stimulate the growth of bacterial mass, while insoluble fibers provide an increase in fecal volume/bulk [77–84]. Many tables of insoluble and soluble dietary fiber composition in foods are based on the analytical determination recommended by the Association of Official Agricultural Chemists’ methods, which provide the levels of soluble and insoluble fiber [81]. The Dietary Reference Intake (DRI) recommendations include the following definitions: dietary fiber consists of nondigestible carbohydrates and lignin that are intrinsic and intact in plants; functional fiber consists of isolated, nondigestible carbohydrates that have beneficial physiological effects in humans; total fiber is the sum of dietary fiber and functional fiber [84].

For the pediatric age group, there are two commonly used recommendations for dietary fiber intake. In 1995, for children over 2 years of age, the minimum consumption recommended in grams/day was equal to the age expressed in years plus 5, and the maximum was the age plus 10 g [85]. This recommendation has been adopted in Brazil, both for research [46,86] and also by the Brazilian Society of Pediatrics [87]. In turn, the DRIs recommend higher values based on the concept of “adequate intake” for total fiber, as shown in Table 2 [84]. It must be noted that there are no dietary fiber recommendations for infants in the first year of life [35,57,84,85].

Dietary fiber is traditionally recommended as part of the maintenance treatment of constipation, as recommended by the UK National Institute for Health and Care Excellence [22], the World Gastroenterology Organization [23], and also in documents from the Brazilian Society of Pediatrics [80,87]. In this context, in Brazil, since the 1990s, a diet rich in dietary fiber has been considered part of the treatment of constipation [1,45,88]. However, the recommendation of a diet rich in dietary fiber for the treatment of constipation is not based on scientific evidence from clinical trials. Systematic reviews of controlled clinical trials have shown that there is no evidence that dietary fiber contributes to the treatment of constipation [77,79,89]. In this regard, the ESPGHAN, published in 2014, states that a normal dietary fiber intake is recommended in children with constipation [2]. The immediate interpretation of this recommendation is that increasing dietary fiber consumption is not indicated for the treatment of constipation. However, in real-life settings, a large portion of the population, including children and adolescents, consumes insufficient dietary fiber compared to the recommendations, indicating the need to increase dietary fiber consumption in patients with constipation who consume insufficient dietary fiber. In addition, most clinical trials on the efficacy of dietary fiber in the treatment of constipation have been conducted in specialized services where patients with severe constipation are treated. Therefore, the lack of dietary fiber efficacy in patients treated with specialized services should not be extrapolated to the entire population. In specialized services, patients with more severe conditions require a therapeutic program that includes disimpaction and laxatives [2,4–6,19,20], which could make it difficult to demonstrate the specific effects of dietary fiber.

Another interpretation of the relationship between dietary fiber intake and constipation focuses on the possibility that habitually insufficient dietary fiber consumption is a risk factor for constipation. In the late 1990s, a population-based epidemiological study [90] and another case-control study [46] demonstrated for the first time that low dietary fiber consumption is associated with constipation in children and adolescents. In Greece, a negative relationship between dietary fiber consumption and constipation was observed [90]. In Brazil, a case-control study showed an odds ratio of 4.1 linking low dietary fiber consumption and constipation [43]. Other studies have confirmed these findings both in Brazil [91] and in other Eastern countries [92–96]. In contrast, other Brazilian studies [86,97–99] did not confirm the association between lower dietary fiber consumption and constipation. However, no epidemiological studies have shown an association between excessive dietary fiber intake and an increased risk of constipation.

Interventions, such as dietary fiber and prebiotics, can increase stool frequency and improve fecal consistency in non-breast-fed infants [71,72] and children with isolated symptoms of constipation [100].

Thus, considering the available epidemiological evidence, insufficient fiber consumption is high in the general population and is associated with constipation in several studies. Therefore, a diet that meets the dietary fiber recommendations should be considered to prevent constipation.

Water is essential for life and is the most abundant component of the human body. Water participates in several metabolic processes, including the transport of substances across membranes, cellular homeostasis, temperature regulation, and circulatory physiology. Total body water represents 75 % of an infant's weight and approximately 55 % of an adult’s weight. Water is not stored in the body, and the amount produced during metabolic processes is insufficient to meet the body’s needs. Therefore, it should be consumed throughout the day to ensure adequate hydration. Water needs are influenced by several factors such as age, sex, body mass, physical activity levels, and environmental factors [101–103]. In the first months of life, exclusive breastfeeding fully meets water needs [101–103]. Table 3 presents the water consumption recommendations according to the Institute of Medicine's DRIs [84]. From the age of 9 years, total water needs are higher for boys. In women, the recommended water intake is higher during pregnancy, particularly during lactation. It should be noted that, from an epidemiological point of view, more than half of the pediatric population does not meet the minimum water intake recommendations [103]. For this reason, hypohydration was also observed in more than half of the children included in studies conducted in Israel, France, the USA, Italy, and Brazil [104,105].

In this context, the hypothesis that hypohydration is related to the etiology of constipation has been discussed in the literature [106]. In clinical practice, increasing fluid consumption is part of some guidelines for the treatment of constipation [22,23]. However, the NASPGHAN/ESPGHAN guidelines, published in 2014, established, based on expert opinion, that increasing fluid consumption should not be part of the therapeutic program for functional constipation [2].

In turn, a literature review identified only five articles that explored the efficacy of fluid intake in the treatment of constipation [31]. These studies had heterogeneous designs. The results of some studies have suggested a positive effect; however, none of them allowed for an unquestionable position [31]. A significant practical limitation in planning a randomized controlled study on this topic is the difficulty of determining an adequate placebo.

In contrast, only five articles have linked habitual fluid consumption and constipation [31]. All of which showed lower fluid intake among children with constipation, and in three, the difference was statistically significant [31].

The relationship between hypohydration and constipation has been evaluated in only two studies conducted in Brazil [107,108]. The first, a school-based study, evaluated children with and without constipation aged 7–10 years [107]. Children with constipation, compared to the control group, had lower fluid intake and higher mean urinary osmolarity, while the association between hypohydration and constipation did not reach statistical significance (p = 0.073) [107]. The second, a case-control study, showed an association between severe constipation and hypohydration in girls in the bivariate analysis. However, statistical significance was not maintained (p = 0.082) in the multivariate analysis, including age [108].

Further studies are required to investigate the relationship between hypohydration and constipation. However, available evidence suggests that adequate water intake may protect against the development of constipation.