Human Milk and Chrononutrition
By Brian W. Donnelly, M.D., F.A.B.M.
Chrononutrition is the study of the interaction between biological rhythms and nutrition, along with the relationship between these factors and human health. It encompasses the distribution of energy, meal frequency and regularity, duration of the eating period, and the relative importance of these factors for metabolic health and risk of chronic disease.
Many people have learned some of the simple effects of chrononutrition on their own. A breakfast high in protein is likely to more effectively activate your brain. An after-dinner serving high in fat (like dessert) is likely to make you want to go to sleep.
Over the past decade there has been considerable research on chrononutrition in adults. And lately, there have been some studies looking at this phenomenon in nursing babies. Breast milk produced in the morning differs from breast milk produced at night. For example, the hormone cortisol and several brain-stimulating amino acids (tyrosine, methionine, glycine, and phenylalanine) are present in morning samples, but very low in evening samples. Breast milk produced in the evening contains high levels of melatonin, purine nucleotides, and the amino acid tryptophan. Tryptophan is the precursor of both serotonin and melatonin, brain neurotransmitters important for relaxation and sleep. Key immune factors are present in day samples of breast milk but not in night samples, corresponding to the likelihood of encountering microbes during the day as compared to the night.
The importance of these findings is that the timing of receiving morning milk versus night milk may have impact on babies who are not breastfed, but are receiving expressed breast milk. For example, the baby receiving expressed “night milk” during the day might be sleepier than expected, whereas the one who receives “morning milk” at night might have a more difficult than expected time getting to sleep. There are other effects on the baby’s immune system that are just starting to be figured out.
For the time being, it is wise for mothers who are expressing their milk to not just include the date the milk was expressed, but the time of day as well. Receiving appropriately time- matched milk can help the baby better develop its circadian rhythm, and keep the whole family healthier and happier.
Learn more about “Breast Milk and the Importance of Chrononutriton” in Frontiers in Nutrition here.
Dr. Brian Donnelly has a special interest in breastfeeding. He was the initial recipient of the Allegheny County Health Department’s Breastfeeding Advocacy Award. He is a Fellow of the Academy of Breastfeeding Medicine and can perform the frenulotomy procedure for tongue-tied infants who have trouble nursing. Dr. Donnelly sees patients at the AHN Pediatrics Northland office.
