Background: Breastfeeding is considered the most optimal mode of feeding for neonates and mothers. Human milk changes over the course of lactation in order to perfectly suit the infant’s nutritional and immunological needs. Its composition also varies throughout the day. Circadian fluctuations in some bioactive components are suggested to transfer chronobiological information from mother to child to assist the development of the biological clock. This review aims to give a complete overview of studies examining human milk components found to exhibit circadian variation in their concentration. Methods: We included studies assessing the concentration of a specific human milk component more than once in 24 h. Study characteristics, including gestational age, lactational stage, sampling strategy, analytical method, and outcome were extracted. Methodological quality was graded using a modified Newcastle-Ottawa Scale (NOS). Results: A total of 83 reports assessing the circadian variation in the concentration of 71 human milk components were included. Heterogeneity among studies was high. The methodological quality varied widely. Significant circadian variation is found in tryptophan, fats, triacylglycerol, cholesterol, iron, melatonin, cortisol, and cortisone. This may play a role in the child’s growth and development in terms of the biological clock.

/pdf/circadian-variation-in-human-milk-composition-a-systematic-5cenl8z6pf.pdf

Circadian Variation in Human Milk Composition, a Systematic Review

The purpose of this study was to evaluate the circadian variation of human milk macronutrients and energy content depending upon pregnancy duration. One hundred eighty fresh human milk samples from 45 mothers (27 of preterm and 18 of full-term newborns) were collected on a single day chosen between the 14th to 16th day after delivery. The samples were taken four times per day at 12 PM, 6 PM, 12 AM and 6 AM. Only lactating women, who could not breastfeed their hospitalized newborns and expressed milk by breast pump, were enrolled in the study. Human milk macronutrient composition and energy count were evaluated by mid-infrared spectrophotometry. Significant differences in macronutrient content were observed between 6 AM and 12 PM for mean protein content (t = − 4.62, df = 44, p < 0.001), for mean fat content (t = − 2.10, df = 44, p = 0.04) and for mean energy content (t = − 2.24, df = 44, p = 0.03); between 6 AM and 6 PM for mean protein content (t = − 2.41, df = 43, p = 0.02), for mean fat content (t = − 3.76, df = 43, p = 0.001) and for mean energy content (t = − 3.85, df = 43, p < 0.001); between 12 PM and 12 AM for mean protein content (Wilcoxon test V = 75.5, p = 0.001), for mean fat content (t = 2.50, df = 44, p = 0.02) and for mean energy content (t = 2.74, df = 44, p = 0.01); between 6 PM and 12 AM for mean protein content (V = 229, p = 0.02), for mean fat content (t = 4.39, df = 43, p < 0.001) and for mean energy content (t = − 4.57, df = 43, p < 0.001). The average content of carbohydrates did not change significantly during the 24 h. The samples of preterm newborns’ mothers had more apparent diurnal fluctuations in macronutrient content. Our study revealed significant diurnal variations in protein and fat in human milk, and these circadian fluctuations were more apparent in the milk of mothers of preterm infants.

/pdf/circadian-changes-in-the-composition-of-human-milk-5f5zzdhxar.pdf

Circadian changes in the composition of human milk macronutrients depending on pregnancy duration: a cross-sectional study

Evolution of the circadian profile of human milk amino acids during breastfeeding

Over the last century significant advances in technology and science have provided us with a better understanding of the regulation and control of the sleep-wake cycle. Characterization of normal sleep and wakefulness has naturally led to the identification and classification of normal variants and a myriad of sleep disorders. Recent discoveries have begun to uncover the intricate relationships between nutrition, diet, and sleep. This chapter provides a very basic review of sleep-wake regulation, states of alertness, and physiologic correlates to lay the foundation in sleep medicine for which the reader will build upon as they delve into subsequent chapters.

Handbook of nutrition, diet and sleep

Rapid sample preparation procedure for determination of retinol and α-tocopherol in human breast milk.

Breast milk is changing with the progression of lactation
and during a 24-h period. To determine the effect of
diurnality or nocturnality on total nitrogen and protein
content of the breast milk. We collected human milk samples
from health mothers living throughout Community
of Extremadura (Spain) from January 2008 to December
2008 with less than two months of lactation. We divided
the samples in three groups: calostral group (1-5 days
postpartum), transitional group (6-15 days postpartum)
and mature group (> 15 days postpartum). All samples
were stored in a freezer at -80oC. We considered as day
period between 08:00-20:00h and night period 20:00-
08:00h. Analysis of the human milk samples was based on
the Kjeldahl method. Protein contents were calculated
from total nitrogen x 6,25. The statistical analysis of the
data was descriptive (mean ± standard deviation) and
inferential (T-Student test). No differences (P > 0,05)
were found to exist among the contents of individual
human milk samples. The mean contents of each component
were as follows: Total nitrogen of calostral, transitional
and mature group was 0,30 ± 0,06 g/dL (night
period), 0,29 ± 0,05 g/dL (day period); 0,26 ± 0,04 g/dL
(night period), 0,25 ± 0,04 g/dL (day period); 0,22 ± 0,05
g/dL (night period), 0,20 ± 0,04 g/dL (day period) respectively,
in this mature group with a statistical variation
(P<0,05). Protein content of calostral, transitional and
mature group was 1,88 ± 0,4 g/dL (night period), 1,81 ±
0,3 g/dL (day period); 1,62 ± 0,3 g/dL (night period), 1,59
± 0,3 g/dL (day period); 1,35 ± 0,3 g/dL (night period),
1,26 ± 0,3 g/dL (day period) respectively, in this mature
group with a statistical variation (P < 0,05). Although we
observed differences in the nitrogen and protein content
during the individual stages of lactation, it is just in the
population of mature lactating women, where the components
analyzed varied significantly between day and
night.

/pdf/analisis-del-contenido-en-nitrogeno-y-proteinas-de-leche-4k0xzzcyb9.pdf

Análisis del contenido en nitrógeno y proteínas de leche materna, día vs noche

Breast milk is changing with the progression of lactation and during a 24-h period. To determine the effect of diurnality or nocturnality on total nitrogen and protein content of the breast milk. We collected human milk samples from health mothers living throughout Community of Extremadura (Spain) from January 2008 to December 2008 with less than two months of lactation. We divided the samples in three groups: calostral group (1-5 days postpartum), transitional group (6-15 days postpartum) and mature group (> 15 days postpartum). All samples were stored in a freezer at -80 oC. We considered as day period between 08:00-20:00 h and night period 20:00-08:00 h. Analysis of the human milk samples was based on the Kjeldahl method. Protein contents were calculated from total nitrogen x 6,25. The statistical analysis of the data was descriptive (mean ± standard deviation) and inferential (T-Student test). No differences (P > 0,05) were found to exist among the contents of individual human milk samples. The mean contents of each component were as follows: Total nitrogen of calostral, transitional and mature group was 0,30 ± 0,06 g/dL (night period), 0,29 ± 0,05 g/dL (day period); 0,26 ± 0,04 g/dL (night period), 0,25 ± 0,04 g/dL (day period); 0,22 ± 0,05 g/dL (night period), 0,20 ± 0,04 g/dL (day period) respectively, in this mature group with a statistical variation (P < 0,05). Protein content of calostral, transitional and mature group was 1,88 ± 0,4 g/dL (night period), 1,81 ± 0,3 g/dL (day period); 1,62 ± 0,3 g/dL (night period), 1,59 ± 0,3 g/dL (day period); 1,35 ± 0,3 g/dL (night period), 1,26 ± 0,3 g/dL (day period) respectively, in this mature group with a statistical variation (P < 0,05). Although we observed differences in the nitrogen and protein content during the individual stages of lactation, it is just in the population of mature lactating women, where the components analyzed varied significantly between day and night.

[Nitrogen and protein content analysis of human milk, diurnality vs nocturnality].

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Análisis del contenido en nitrógeno y proteínas de leche materna, día vs noche

[Nitrogen and protein content analysis of human milk, diurnality vs nocturnality].