Some 30% of pre-weaning infants present problems of sleep during the night, especially those who are bottle-fed. The solution is for them to be breast-fed for as long as possible, or, if this is not possible, for the formula milk to reproduce breast-milk's natural circadian variations in the concentrations of tryptophan and those nucleotides which have a beneficial effect in consolidating the circadian sleep-wake cycle.
Objective: To study in pre-weaning infants the effect on nocturnal sleep of the administration of formula milk dissociated into its day/night components.
Materials and methods: A prospective study was carried out on 30 pre-weaning infants of 4-20 weeks in age who preferentially showed sleep problems. The day dissociated formula, administered from 06:00-18:00, had lower levels of tryptophan and carbohydrates, and higher levels of proteins together with cytosine-5P, guanosine-5P, and inosine-5P. The night dissociated formula, administered from 18:00-06:00, had lower levels of proteins and medium-chain triglycerides, higher levels of tryptophan and carbohydrates, together with adenosine-5P and uridine-5P. In a random, double-blind, design, three one-week diets were administered: Diet A (Control): normal initiation milk; Diet B: 06:00-18:00 normal initiation milk, 18:00-06:00 dissociated night formula; and Diet C: day/night formulas with the schedule given above. The sleep patterns were analyzed by means of actimeters (Actiwatch). Statistical analysis consisted of an ANOVA with a Scheffe F-test, taking a value of p<0.05 to be statistically significant.
Results: The children receiving the week of Diet C (with the day/night formulas in synchrony with the environment) showed increased hours of actual sleep (7.68 +/- 0.54 h vs. 6.77 +/- 0.12 h for the Diet A control) and improved sleep latency (0.44 +/- 0.04 h vs. 0.60 +/- 0.08 h for the Diet A control). The same children receiving the Diet B in another different week showed an improvement in sleep efficiency (76.43 +/- 3.4% vs. the Diet A control 69.86 +/- 0.94%) and sleep latency (0.45 +/- 0.04 h vs. the Diet A control 0.60 +/- 0.08h) The parents also reported, in response to follow-up questions, an improvement in the sleep of their infants during the Diet C week.
Conclusion: Day/night infant formula milks designed according to the principles of chrononutrition help to consolidate the sleep/wake rhythm in bottle-fed infants.