Reduced crying in term infants fed high beta-palmitate formula: a double-blind randomized clinical trial

Crying is a basic, instinctive response governed by basic neuro-chemical mechanisms that are similar to those that control feeding [1]. Although crying is a common spontaneous behavior, it can induce parental concern, which often results in requests for assistance from health services [1]. Most infants follow a universal crying pattern during the first few months of life, in which crying peaks at 6 weeks of age and then declines until 3 months of age [1‐6]. Crying also has a typical diurnal pattern: 40% of crying episodes occur between 1600 and 2200 h, and after the third month of life, crying episodes are more distributed throughout the day. Infant crying is usually believed to be related to abdominal discomfort, whereas crying for more than 3 hours per day (cumulative), without relation to a medical problem, is termed infantile colic [7]. The prevalence of abdominal discomfort, colic, and their associated potential effects demonstrates the importance of identifying determinants of infant crying behavior, particularly for determinants that can be modified (e.g., feeding choice) [2].

Human milk is the optimal choice for the vast majority of infants. In human breast milk and most infant formulas, approximately 50% of the dietary calories come from fat, with more than 98% in the form of triglycerides (TGs) [8, 9]. Infants easily absorb human milk fat despite its high content of saturated fatty acids (45% of total fatty acids), primarily palmitic acid (C16:0), of which 70-75% is esterified at the sn-2 (beta) position of the TG [8]. This configuration is characterized by a unique, highly specific, positional distribution on the glycerol backbone observed only in TG synthesis in the mammary gland [10]. Studies have shown that palmitic acid is absorbed from human milk as an sn-2 monoacylglycerol [11] and is conserved in that form through digestion, absorption, and chylomicron triacylglycerol synthesis [12]. In contrast, palmitic acid, which is present in the vegetable oils that are commonly used in the manufacturing of infant formulas, is mainly (>80%) esterified to the sn-1 and sn-3 positions [13] and is therefore poorly absorbed by an infant’s intestine. The main cause of this low absorption is the high tendency of palmitic acid esterified at the sn-1 and sn-3 positions to create complexes with dietary minerals, such as calcium [14]. These complexes, known as fatty acid soaps, are insoluble, indigestible, and positively related to stool hardness [15]. The formation of calcium soaps may partly explain the substantial differences in bowel habits and stool consistency between breast- and formula-fed infants [15‐17].

The goal of this study was to compare the effects of high-sn-2 palmitate (beta-palmitate) and low-sn-2 palmitate formulas on infant crying patterns and stool characteristics. We hypothesized that infants who consumed high beta-palmitate formula would demonstrate reduced crying and more frequent, softer stools compared to infants consuming low beta-palmitate formula.

This randomized controlled study showed that term infants who consumed formula with a high beta-palmitate content (HBP) cried less than infants who consumed LBP formula. Additionally, the study showed that the consumption of formula with beta- palmitate improved infant crying patterns during the day. The crying duration and patterns in the HBP group were comparable to those of breastfed infants, and the percentage of crying infants was significantly lower in the HBP group than in the LBP group during the evening and night hours.

Previous studies have shown that the daily duration of crying and fussing in infants increases until 6 weeks of age and then decreases progressively [1‐6, 19]. Our study showed similar peaks of daily crying at 6 weeks for all groups. Harrison et al. found a 50% reduction in daily crying duration from 6 to 12 weeks [20]; however, in their study, the type of feeding was not specified. Our study revealed a similar reduction in daily crying duration, both in the BF group (50%) and the HBP group (80%). In contrast, a small increase in crying time was observed in the LBP group.

Crying commonly clusters in the afternoon and evening [21, 22]. We also observed this peak in this study for all three groups; however, we found that infants in the HBP group cried less during the afternoon and evening hours and had significantly greater reductions in crying duration in the afternoon between 6 and 12 weeks postnatal.

The effects of breastfeeding versus formula feeding on infant crying are controversial. Many studies support breastfeeding as an effective method of calming infants due to its emotional impacts [23]. Kennedy et al. [16] monitored crying duration in infants who consumed formula containing high versus low levels of beta-palmitate. In contrast to our study, they did not find differences in crying between the groups. Savino et al. [24] evaluated the efficacy of formula that was partially hydrolyzed with prebiotic oligosaccharides (OSs) and contained a high level of beta palmitate. The authors found significant differences in crying that were primarily due to a significant reduction in the afternoon crying duration between 6 and 12 weeks postnatal. In their study, however, the formulas contained several different components (partially hydrolyzed whey proteins, prebiotic OSs, and beta palmitate); therefore, the relative contribution of the HBP component could not be determined.

Crying behavior in infants is a complex phenomenon that includes spontaneous "endogenous" crying and “distress-related” crying, which can be linked to separation, hunger, or other physical distresses; therefore, several mechanisms can explain the positive effect of HBP on crying. One mechanism can be attributed to the effect that HBP has on stool characteristics. In this study, HBP-fed infants demonstrated more favorable stool characteristics than LBP-fed infants at 12 weeks. Improvement of stool characteristics is one of the well-known benefits of beta-palmitate [16, 25, 26]. In a previous study, we showed that high beta-palmitate formula beneficially affected infant gut microbiota by increasing the lactobacillus and bifidobacteria counts in stools [27]. This is another possible mechanism because changes in gut microflora induced by probiotic supplementation likely improve infant colic [21].

Animal studies suggest that diet can alter endogenous crying by modifying neuro-endocrine metabolism in the gut (e.g., through the endocannabinoid system, which is associated with a variety of functions, including pain and circadian rhythm). Using a rat model, Banni et al. [27] showed that a diet rich in beta-palmitate led to higher efficiency and enhanced endocannabinoid biosynthesis.

One possible limitation of our study is that we relied on the parents to record crying measurements. Parent diaries of infant crying have become the standard and most widely used tool for studying infant crying [1, 28]; however, this method is still subjective and requires a high degree of parental cooperation. In this study, this limitation was partially overcome by the double-blind nature of our study. We were also limited in this study because crying is known to be highly affected by an infant’s temperament [2], which could have biased our results. We could not, however, overcome this limitation because we did not assess the temperaments of the infants included in this study.

Our study indicates that high beta-palmitate (sn-2 palmitate) formula affects infant crying patterns during the first weeks of life. Comparable to breastfeeding, high beta-palmitate reduced crying duration and frequency, primarily during the afternoon and evening hours, thereby improving the well-being of formula-fed infants and their parents.