There are many reasons for normal babies needing to feed at night. Three possible ones are: (1) breast milk and infant formula are relatively low in energy requiring babies to feed often, (2) the growing brain needs a lot of glucose which babies need to replenish frequently, and (3) babies are born very immature and require contact with parents, day and night. In short, human biology doesn’t support a pattern of sleeping through the night early in life.
A) Describing why babies need to feed at night and the role of breastfeeding
It is not fully understood why babies need to wake and feed during the night, but it may be because:
In short, it is unreasonable to expect a baby to sleep through the night because our biology doesn’t support this pattern.
Breastfeeding has a role in infant sleep. Breastfeeding can help a baby fall asleep, thus limiting the length of the night waking. Some breast milk components will increase and decrease at various times during the day and night. These variations may be providing nutrients when they are most needed by the baby and also teaching and supporting the baby’s internal clock. For these reasons, breast milk can be called chrononutrition.
B) Human milk is relatively low in energy
Mammals are named for the Latin word for breast. Milk secretion may have started as early as 300 million years ago (Oftedal 2012). Now, there are about 4000 species of mammals today that inhabit a wide range of environments (McClellan 2008). Each type of mammalproduces a distinctive type of milkto meetthe needs of itsyoung. The range in milk types is actually astonishing.
1) The hooded seal
Marine mammals such as whales, seals, and sea lions have milk that is high in fat. For example, hooded seal milk is 60 to 70% fat. By comparison, human milk is about 4% fat. Hooded seal mothers only breastfeed their pupsfor about one week.During this time, thepupgains 7 kilograms (15 pounds) to double its birth weight at the time of weaning (Oftedal 1988). The high fat content helps the pup gain weight quickly to keep warm, allowing it to leave the Arctic iceand enter the sea, safe from unstable sea ice and polar bears (Boyd 1998).
2) The Malaysian tree shrew
The Malaysian tree shrewproduces milk with afat content of about 25%, so the mother needs to spend only about two minutes with her young every other day to provide them with enough calories (Hubrecht2010). As a result, she is less likely to give away the location of her young to predators, and can spend more time foraging for food.
Armadillos are mammals found in the south central U.S.A. and Central and South America. Their bodies are covered with bony plates. Their milk is very high in protein (8-11%) compared to the milk of other mammals. Human milk, by comparison, is only about 1.5% protein (Power 2018). The protein serves as a vehicle for calcium and phosphorus, which are needed to build the young armadillos’ armour.
4) Human milk
Human milk has relatively little fat, about four per cent, and its energy content is lower, like the milk of many land-based mammals. Yet, even compared with otherlandmammals, our babiesgrow slowly.They don’t need extra rich milk.
Because the baby’s stomach can take in only a small amount of this relatively low-energy milk, babies need to feed regularlyto get enough nutrients to grow. If they slept through thenight, they would go one-thirdof a 24-hour period without food.This is a long time, given the low energy of human milk.
C) The human brain needs a lot of milk sugar to work
Human milkhas a lot ofmilk sugar(lactose) and fewer nutrients compared with the milk of other non-primate mammals (Sellen 2007).The baby’s body turns lactose intoglucose, which is then used by the brain for energy.
The human brain is large and complicated compared with the brains of other mammals oursize (Cairo2011). It accounts for only 2%of an adult’s weight but consumes 20%of all the energy our bodies use (Mergentahler2013). A baby’s brainis about 10% of its body weight but uses a remarkable 50% of the energy used (Grande Covián1979).
The human brain grows quickly during the first year, tripling its weight from about 300 grams (10 ounces) to about 900 gm (30 oz) (Dekaban1978).The average adult brain weighs 1,300 to 1,400 gm (around 3 lbs).
In the first year of life,whilethe brain triples in size, the average baby’s height increases only by half, from about 50 centimetres (20 inches) to 75 cm (30 in).
Given thelargesizeof thehuman brain, itshighenergy demands,anditsrapid growth during the first year, it’s most likely that babies wake up to feed at night to get the glucose necessary for their brains to work and grow.
D) Babies are born immature
Compared with the young of other species,humanbabies are extremely immatureat birthand take a long time to mature. Indeed, our brains are not truly mature until we are 25 years of age (Arain 2013).
As a result, human babies need close contactwith their parents over a long period. Unlike other mammals, human babies can’t walk, can’t feed themselves, can’t keep themselves warm, and so on.This is true during the night as well as the day, so many babies won’t sleep through the night.
A lack of contact and thestress caused by separation can havelong-termhealth consequences.
E) Other reasons for waking
Babies may also wake up other reasons such as painful tummy cramps as they digest milk, feeling too warm or cold, needing a diaper change, or unfamiliar sounds.
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