Tryptophan intake influences infants' sleep latency.

Area of Science:

• Nutritional Neuroscience
• Infant Nutrition
• Amino Acid Metabolism

Background:

• Formula-fed infants exhibit lower plasma tryptophan concentrations compared to breastfed infants.
• Tryptophan plays a role in regulating sleep-wake patterns in adults.

Purpose of the Study:

• To determine if supplemental tryptophan in infant formula can raise plasma tryptophan levels to those seen in breastfed infants.
• To investigate the behavioral significance of plasma tryptophan and its ratio to other large neutral amino acids (LNAA) on infant sleep patterns.

Main Methods:

• Infants were fed formulas with varying concentrations of added tryptophan (0, 294, 588, 882 mumol/L).
• Human milk-fed and commercial formula-fed infants served as controls.
• Plasma tryptophan concentrations and the tryptophan:LNAA ratio were measured.
• Infant sleep latency was assessed as a behavioral outcome.

Main Results:

• Plasma tryptophan levels in formula-fed infants positively correlated with tryptophan intake.
• Infants receiving the highest tryptophan formula achieved plasma tryptophan:LNAA ratios similar to breastfed infants.
• The tryptophan:LNAA ratio, not absolute tryptophan concentration, predicted sleep latency.
• Higher tryptophan formula intake resulted in significantly shorter sleep latencies (18.7 min vs. 27.7 min).

Conclusions:

• Dietary tryptophan supplementation can normalize plasma tryptophan:LNAA ratios in formula-fed infants.
• The tryptophan:LNAA ratio is a key factor influencing infant sleep latency.
• Modifying infant formula tryptophan content may impact neurobehavioral development through sleep regulation.