Can the composition of breastmilk affect the quality of sleep in exclusively breastfed infants?
Benefits of breastfeeding
Breastfeeding is called the gold standard for infant nutrition, both for those born on time and those born prematurely (<37 weeks of pregnancy). According to the recommendations of the World Health Organization, the European Society for Paediatric Gastroenterology, Hepatology and Nutrition, and the Polish Expert Group, exclusive breastfeeding should apply to the first 6 months of life. After this time, complementary foods should be introduced to the child's diet, and breastfeeding should be continued for as long as desired by the mother and the child. These recommendations result from the numerous, well-documented benefits that this type of feeding brings to both the child and the mother.
The benefits are conditioned by the ideal composition of mother's milk at the nutritional level. And also thanks to the ingredients contained in milk that demonstrate biological activity, including: enzymes (supporting digestive processes), hormones (regulating metabolism), antibodies (beneficially influencing the functions of the immune system) and finally pro- and prebiotics supporting the development and functions of intestinal microbiota.
The results of numerous studies indicate that breastfed children have a lower risk of necrotizing enterocolitis (especially in children born prematurely), respiratory diseases, otitis media, metabolic diseases in later life (including adulthood). For the mother, breastfeeding reduces the risk of breast and ovarian cancer and hypertension. It also promotes a faster return to pre-pregnancy body weight.
What do we know about breastfeeding rates in Poland?
Unfortunately, epidemiological data related to breastfeeding rates are not routinely collected in our country. Therefore, there is a lack of detailed information on what percentage of children were ever breastfed and how long breastfeeding lasted (both exclusive and any). However, the results of the nationwide PITNUS study published in 2016 indicate that only 6% of infants were exclusively breastfed at 5-6 months of age.
One of the most common reasons given by mothers for stopping breastfeeding is the belief that the amount of milk produced is insufficient, which translates into, among other things, restless sleep for the child, frequent waking at night, very short naps during the day. This very often determines the decision to introduce breast milk substitutes (so-called formula milks) into the child's diet, which, unfortunately, completely replace mother's milk over time. This is partly because taking food from a bottle is easier for the child, requires less effort and becomes preferential for him.
What influences the composition of breastmilk?
It is known that the composition of breastmilk is dynamic, determined by factors of various origins, including physiological (time since delivery, time of day/night, week of delivery), maternal (health status, nutritional status) and environmental (diet, latitude). The best documented influence is the physiological factors, indicating, among others, a significantly higher protein content in the milk of mothers of premature babies compared to the milk of mothers who gave birth on time, or a higher fat content in milk samples taken in the early morning hours.
Knowledge of these relationships allowed me to design a study and attempt to answer the question "can the composition of breast milk affect the quality and length of sleep of exclusively breastfed infants?" This question seems all the more relevant because numerous studies conducted among older children and adults have shown that the way of feeding (including the consumption of specific groups of products or nutrients) is related to the quality of sleep. Particular attention is paid, among others, to the consumption of one of the amino acids - tryptophan. One of the recently published meta-analyses showed that its supplementation can facilitate falling asleep and extend the time of sleep. Other components indicated by the authors of the meta-analysis are: simple carbohydrates (negative effect), fats (contradictory results) and total protein (positive effect). Of course, it should be remembered that translating these results to the population of infants is impossible, among others due to the significantly different nutritional needs of this group, the period of intensive growth and development.
How does nutrition relate to sleep?
Serotonin (known as the “happiness hormone”) and melatonin play a key role in regulating sleep and mood. Variations in their levels may underlie sleep and mental health disorders. Both compounds are synthesized from one of the essential amino acids – tryptophan. For the proper course of biosynthesis (as cofactors), vitamin B6, vitamin D, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are necessary. Tryptophan is converted into 5-hydroxytryptophan (5-HTP) by tryptophan hydroxylase 2 (TPH2), an enzyme transcriptionally activated by vitamin D. 5-HTP can then be converted into serotonin, which is facilitated by vitamin B6. Serotonin is further metabolized into melatonin, which in turn is facilitated by omega-3 fatty acids – EPA and DHA. This means that a number of nutrients contribute to the proper synthesis of serotonin and melatonin, and their consumption can affect the regulation of sleep and mood.
Which components of breastmilk can affect the quality and length of infant sleep?
There is a certain belief that children fed with breastmilk substitutes sleep better and longer, among others due to their higher (compared to breastmilk) caloric value and protein content. Therefore, in the milk samples used in my study, it is planned to assess, among others, the energy value and content of macronutrients (proteins, fats and carbohydrates) and their correlation with the length and quality of infant sleep, which will be assessed using a validated tool.
In addition, the content of tryptophan and other essential amino acids and their metabolites, including melatonin and 6-hydroxymelatonin, will be analyzed. It is also planned to determine the concentration of selected hormones in breastmilk - leptin and ghrelin, which affect the hunger and satiety center (leptin inhibits the feeling of hunger, and ghrelin increases it). It is suggested that in the case of insufficient sleep, the concentration of leptin in the blood decreases, while the amount of ghrelin increases, which consequently increases appetite. Due to the fact that the concentration of adipokines in the mother's blood may positively correlate with the concentration of this hormone in the milk she produces, the quality and length of the mother's sleep will also be assessed.
In summary, the way of feeding can be an important factor determining the quality and length of sleep. In the case of exclusively breastfed infants, the only source of energy and nutrients (as well as biologically active ones) is mother's milk. So far, no study has been conducted to assess whether the composition of breastmilk affects the quality of sleep in the youngest population group. I am all the more pleased that in the Laboratory of Breastmilk and Lactation Research we will be implementing a project that will allow us to answer this question.