Constipation in infants: influence of type of feeding and dietary fiber intake

Constipação em lactentes: influência do tipo de aleitamento e da ingestão de fibra alimentar
Andrea Nogueira de Campos Aguirre, Márcia Regina Vitolo,
Rosana Fiorini Puccini
, Mauro Batista de Morais
J Pediatr (Rio J) 2002;78(3):202-8

Introduction

The etiopathogenesis of chronic functional constipation in infants is not fully known. The cause of constipation may involve body composition, genetic, nutritional, psychological or emotional factors, associated or not with intestinal motility disorder(1-3).

Studies carried out at pediatric gastroenterology clinics in Brazil (4,5) and abroad (6), agree that constipation often has an early onset, sometimes in the first six months of life or even at birth. In two studies(4,5) conducted in Brazil with patients aged between four and six years assisted at specialized clinics, approximately 20% of parents or guardians said constipation had developed during exclusive breastfeeding. However, the possibility of constipation during this period is questioned(7). n a previous study(5)we observed that the median for exclusive breastfeeding time was lower in constipated infants than in the control group, which makes us speculate whether breastfeeding can have a protective role against constipation. Nevertheless, this should be carefully analyzed, due to the long interval between the application of the questionnaire and weaning(5).

In infants, a diet low in fibers is a risk for chronic constipation(8,9). To our knowledge, there is no reference in literature that relates bowel habit to the amount of fiber intake in infants.

The present study aimed at evaluating the relationship between the type of breastfeeding, fiber intake and occurrence of constipation in infants.

Methods

The study was carried out at two basic health units in the town of Embu, in the Metropolitan Region of São Paulo, Brazil. The Universidade Federal de São Paulo - Escola Paulista de Medicina (UNIFESP-EPM) has provided the local community with medical assistance through an integrated program since the 1970’s. All infants younger than 24 months, without acute or chronic diseases, consecutively assisted from December 1996 to December 1997 were included in the study. The exclusion criteria were presence of delayed neuropsychomotor development, hypothyroidism, anorectal malformations and use of antacids, anticholinergics and codeine. No infants with such characteristics were found among the assisted patients. As a result, 275 infants were included in the study.

To determine whether or not the infant presented with constipation, a standardized questionnaire including questions related to bowel habits was used. The shape and consistency of stools, as well as pain, difficulty or fear during stool passage were registered. A catalog with 12 pictures of infant’s stools, with different characteristics, was used to help identify their shape and consistency.

Constipation was characterized by necessarily hard stools and by the presence of at least one of the following characteristics: painful stools or difficult stool passage, scybalous stools, cylindrical stools with cracks or thick cylindrical stools, or interval between bowel movements greater than or equal to three days. Intestinal pseudoobstruction occurred when stools were soft, and no painful stools or difficult stool passage were present, at an interval greater than or equal to three days(3). Normal bowel habit was defined as the absence of all characteristics outlined above.

In terms of breastfeeding practice, infants were placed into three categories: (10):

- predominant breastfeeding: infants who were exclusively fed breastmilk, or who were fed breastmilk, water and/or tea;

- mixed breastfeeding: infants who were fed breastmilk and other complementary foods, including cow’s milk, milk-based formulas, or any other kind of food; and

- artificial breastfeeding: infants who were no longer fed breastmilk.

Infant feeding was assessed by the usual daily food intake in infants older than six months(11). The analysis of diet information was made using the Nutrition Support program(12). The amount of dietary fiber intake was assessed through the AOAC (Association of Official Analytical Chemists) table(13).

Weight and height measurements were obtained according to the recommended techniques(14). The comparison between anthropometric parameters of constipated and control infants was performed by z scores, calculated by the EPI-Info program(15), taking into consideration the NCHS (National Center for Health Statistics) weight and height tables(16).

The statistical analysis was made by the EPI-Info program(15). A logistic regression model was used for the multivariate analysis of constipation, using the Stata program (Stata Corporation, Texas, USA)(17). The study was approved by the Ethics and Research Committee of Universidade Federal de São Paulo – Escola Paulista de Medicina, and a written consent form was obtained from parents or guardians.

Results

The infants were classified into two age groups: less than six months and six to 24 months. Table 1 shows the bowel habit pattern and the occurrence or not of constipation. Constipation was present in 25.1% (69/275) of the study population. Scybalous stools were more frequent in constipated infants, representing 63.4% (44/69) of the cases. Stool frequency lower than three times a week was observed in only 5.8% of 69 constipated infants. Constipation was more frequent between the sixth and 24th months (38.8%; 45/116) than in the first six months of life (15.1%), with statistically significant difference (P=0.0000). Mothers noticed their children presented with painful stools or difficult stool passage in 65.2% (15/23) and 25.2% (30/119) of the cases, in the first six months and between the sixth and 24th months of life, respectively. On the other hand, painful stools or difficult stool passage were present in 25.2% (30/119) of the infants with normal bowel habit in the first six months of life and in none of the infants between the sixth and 24th months of life.

Table 1 -
Pattern of bowel habits of breastfed infants seen in basic health unit

The association between breastfeeding practice and occurrence of constipation was analyzed by considering the information obtained from 159 infants in the first six months of life. In this group, 66 (41.5%) were on predominant breastfeeding, 49 (30.8%), on mixed breastfeeding and 44 (27.7%), on artificial breastfeeding. Eight percent (5.1%) of 159 infants had intestinal pseudoobstruction, that is, they passed amorphous stools, with liquid or pasty consistency, at an interval greater than three days; among these infants, six received predominant breastfeeding and two were on mixed breastfeeding. Stool frequency was twice a week in four infants with intestinal pseudoobstruction, once a week in three and once every 15 days in one infant.

Constipation was less frequent in infants on predominant breastfeeding (4.5%) than in those on mixed breastfeeding (18.4%) or on artificial breastfeeding (27.3%; 12/44; P<0.05). In the first six months of life, the incidence of constipation increased with age (5.5% in the first two months, 16.3% in the subsequent two months, and 23.0% in the last two months; P<0.05). Considering that the frequency of constipation increased with age, and that the frequency of predominant breastfeeding decreased; the relationship between these two variables and the occurrence of constipation was analyzed by a logistic regression model, employing three categories for age (first two months, subsequent two months, and last two months of life) and for the type of breastfeeding (predominant, mixed and artificial). Table 2 presents the result of the logistic regression analysis, showing that age is not associated with constipation, in opposition to what was indicated by the statistical test used for separately assessing the association of these variables. On the other hand, the association between type of breastfeeding and constipation (P=0.02) was confirmed. Therefore, according to the odds ratio, artificial versus mixed breastfeeding and mixed versus predominant breastfeeding showed an odds ratio 2.1 times higher for constipation. Artificial breastfeeding, on its turn, showed an odds ratio 4.5 times higher.

Table 2 -
Result of the logistic regression analysis with proportional adjacent categories about the relation between constipation, age and feeding type in 159 breastfed infants during the first semester of life

The study on the association between the intake of nutrients and dietary fibers, and other information about the diet was carried out with infants older than six months. The food intake was assessed according to the usual daily food intake questionnaire, using the information obtained from 75 infants older than six months, who were no longer fed breastmilk. Six (8.0%) questionnaires were not included in the study for having inadequate information. Therefore, the results shown in Table 3 correspond to 31 constipated infants and 38 infants with normal bowel habit. Age and the estimated amounts of food, water and milk volume, energy and protein requirements, and the amounts of protein, carbohydrate, and lipids did not show statistically significant difference between constipated and nonconstipated infants.

Table 3 -
Age (months) and dietary data according to the usual daily diet of breastfed infants with or without constipation

The intake of dietary fiber was estimated according to the AOAC table. This evaluation also included infants who were fed breastmilk, which is not a source of dietary fiber. Among the questionnaires of the 116 infants aged between six and 24 months, nine (7.8%) were not included in the study for having inadequate information. Therefore, the results of 107 questionnaires were considered. Table 4 shows that there was no statistical difference in the intake of dietary fiber by constipated in comparison with nonconstipated infants.

Table 4 -
Estimate of the total fiber intake (g), percentage of adherence to the recommended daily fiber intake (5 g/day) and fiber per 1,000 kcal of diet, according to the usual food intake of breastfed infants with or without constipation

Table 5 shows the anthropometric parameters that did not have statistical difference according to the presence or absence of constipation.

Table 5 -
Median and 25th and 75th percentils (between parentheses) of weight-for-age, weight-for-height and height-for-age z scores of children with and without constipation

Discussion

In Brazil, several recently reviewed studies (3) showed that constipation frequently occurs in infants, with a rate of 25.1% in infants younger than two years – an age group that was not much investigated in previous studies. In the present study, the incidence of constipation increases progressively in the first six months of life. However, the prevalence of constipation between the sixth and 24th months is statistically higher than that observed during the first six months. A study(18)conducted with a community in northeastern Brazil showed a 21.8% prevalence of constipation in infants, which is similar to the result obtained in the present study. It is not easy to compare the results of different studies on the prevalence of constipation due to the different concepts adopted in each one of them. In the present study, constipation is characterized by the elimination of necessarily hard stools and by at least one of the following characteristics: painful stools or difficult stool passage, scybalous or cylindrical stools with cracks, or still, interval between bowel movements greater than or equal to three days. This concept is in agreement with the proposition of a workgroup that included representatives from different continents(19).

Our results showed that constipation in infants was usually characterized by the passage of hard, scybalous stools, followed by painful stools or difficult stool passage. A reduction in stool frequency occurred in only 5.8% of constipated infants. On the other hand, painful stools and/or difficult stool passage was reported by 25.2% of the mothers whose children were younger than six months, without constipation, showing that this diagnostic information is not so specific in this age group. With regard to intestinal pseudoobstruction, there are no references in literature on its frequency, which was 5.1% in the 159 infants younger than six months, who corresponded to 7.3% (8/110) of the infants on predominant breastfeeding. It is important to emphasize that intestinal pseudoobstruction is not a pathological condition, and therefore, it requires no treatment, but only some guidelines or instructions to the family and maintenance of breastfeeding. The constipated infants included in this study were not receiving any specific treatment. This is different from the practice used in pediatric gastroenterology clinics which, in general, treat older children and more severe conditions, of which constipation is the major complaint. Constipation complications, such as fecal soiling, stool retention, painful and sporadic passage of bulky stools, and chronic abdominal pain are commonly observed in these specialized clinics(4-6). In patients with chronic constipation assisted at specialized services, the problem is often observed in the first year of life. For that reason, infants are investigated for the association between constipation and two dietary aspects that might be related to its onset: type of breastfeeding and amount of dietary fiber in the weaning diet.

The absence of breastfeeding in the first six months of life is associated with constipation, according to the logistic regression test. In other words, the chances of an infant on artificial breastfeeding presenting constipation is 4.5 times higher than in infants on predominant breastfeeding. According to literature(20,21), stool frequency is higher in the first year of life, decreasing with age. Stool frequency in infants on natural breastfeeding is higher than in infants on artificial breastfeeding. Motilin can be responsible for altered bowel habits(20). Another aspect to be considered is the good digestibility of lipids contained in human milk versus milk-based formulas, which produces softer stools(22). After weaning, some cases of constipation can be attributed to intolerance of or allergy to cow’s milk protein(23-25). If we add these physiological(20,21) and pathological(21-23) evidence to the results obtained through our study, natural breastfeeding should be considered a protection factor against constipation.

Another diet-related factor that can influence the development of constipation in infants is the content of dietary fibers in weaning foods. However, there is no reference in literature that relates the intake of dietary fiber to bowel habits in this age group. The information on the intake of dietary fiber in infants is scarce. There is some concern that the high intake of dietary fiber may have negative effects on growth for causing early satiation or for interfering with mineral uptake.

The only recommendation for dietary fiber intake involving infants found in literature was proposed by Agostoni et al.(26), who suggested the daily intake of at least five grams of dietary fibers a day. In the present study, there was no association between constipation and reduced fiber intake, which is different from the results obtained from other studies carried out in Brazil(8) and abroad (9), whose study population consisted of children older than two years.

Although there is some reference in literature(27-30) that a high intake of dietary fiber can cause anorexia, thus interfering with the amount of energy intake, in our study, the infants had a median intake of energy and fiber greater than the minimal recommendation, and the weight and height values showed that the nutritional status of the study population was satisfactory. The fact that constipated and nonconstipated infants did not have different estimates for fiber intake does not mean that the administration of fibers to those who are prone to constipation does not normalize bowel habits.

Our study showed that the estimated intake of dietary fiber was not different between constipated and nonconstipated infants. With respect to natural breastfeeding, we can affirm that its protective role against constipation in the first six months of life is one more advantage in relation to artificial breastfeeding.

Acknowledgements

We thank all the support received from the State of São Paulo Research Foundation (FAPESP). We also thank Mr. Fernando A.B. Colugnati for carrying out the statistical analysis and the logistic regression test.