The infant feeding schedule reconsidered
In the past, Western "baby experts" often instructed parents to feed their babies at regularly-spaced intervals of 3- or 4-hours.
But today, official medical recommendations have shifted in favor of letting babies decide.
Why the change?
There are a number of reasons, but the simple answer is this: When we let babies determine the timing and the length of their own feeds, they are more likely to get what they need: Not too little, and not too much.
Interfering in this process -- by imposing an infant feeding schedule -- doesn't help babies develop their own intuitions about food (Tylka et al 2015). And it may lead to problems.
instance, newborns should be fed frequently, and whenever they show signs of
hunger -- ideally, before they start to cry. Otherwise, newborns are at higher
risk for dehydration and underfeeding.
Moreover, frequent feeds help breastfeeding mothers establish a good milk supply, and feeding on cue can help breastfed babies adjust for natural variations in milk quality (Institute of Medicine, National Academy of Sciences 1991).
Feeding on cue may also help bottle-fed infants avoid overfeeding. And of course all babies go through growth spurts. All babies experience fluctuations in their energy requirements. Feeding on cue makes it easier for infants to increase or decrease their intake as needed (Tylka et al 2015).
Finally, there may be benefits that extend beyond addressing a baby's hunger and thirst. Babies fed on cue may have an easier time coping with stress. They might even enjoy a cognitive advantage. There are hints that imposing an infant feeding schedule could have a negative impact on cognitive development.
So it seems that the best infant feeding schedule is the one that babies devise for themselves. But what is the evidence? Let's take more detailed look.
everywhere begin life on a diet of milk. But they don't all time their feedings
in the same way. In some species, mothers "park" or "cache"
their young in nests, and leave them there. It's a strategy that allows the
mother to go foraging without the fuss of a tag-along infant. But it only works
if there's a way to keep the babies from starving during those long
separations. How do they cope?
The solution is two-fold.
1. Mothers produce milk that is high in fat, and high in protein -- what we might call super-fuel.
2. Infants have the ability to suckle very fast and efficiently when they finally get to feed.
Together, these elements permit babies to "tank up" on a highly-concentrated food--enough to last them for many hours.
Mammals that follow this strategy are called "spaced feeders," and their milk is very rich indeed. A good example of a spaced feeder is the rabbit, which produces milk that is 18.3% fat and 13.9% protein (Jenness 1974).
By contrast, other mammals keep their babies with them as they forage. Exactly how they do this varies from species to species. Some, like monkeys, carry their babies. Others, like cows, have their infants follow them around on foot.
But regardless, the babies stay close, and along with proximity comes frequent meals. Babies tend to initiate feedings, and suckle at a more leisurely rate. They don't need to tank up on a super-fuel, and so their mothers don't make one. The milk is less caloric, more dilute.
A good example of a continual feeder is a cow, which produces milk that is typically 3.7% fat and 3.4% protein (Jenness 1974).
What about humans?
modern, industrial societies, humans act like spaced feeders. Babies are
"parked" in cribs or cradles and get fed after intervals of 3-4
hours. But were we designed for this strategy? Does the biology of human
breastfeeding have the earmarks of spaced feeding? The answer is no because
So our basic physiology gives us away. We don't produce super-fuel, and our infants lack the spaced-feeder's knack for super-fast milk extraction. And that's consistent with the behavior of other members of our family tree. Continual feeding is the strategy of choice among all of our close relatives -- including bonobos, chimpanzees, and gorillas.
It is also the strategy observed among human beings living in traditional societies. In hunter-gatherer societies, babies aren't just nursed on cue. They are also nursed very frequently -- about 2-4 times an hour (Konner 2006). In other traditional societies, parents don't match this extreme pace, but feedings are nonetheless initiated by the infants. In a survey of non-industrial societies (which included nomadic pastoralists and settled agricultural peoples) anthropologists found that "on demand" feeding was the rule. In every society for which information about the infant feeding schedule was available (25 out of 25), people fed their infants on cue (Severn Nelson et al 2000).
This, then, is our basic physiology and our evolutionary heritage. But how much does it matter? Is this something we can work around?
Mightn't we be able to keep babies equally happy and healthy using a strict infant feeding schedule? Perhaps it's just a matter of tweaking the timing of feeds.
It sounds straightforward, but there are stumbling blocks.
Different babies have different needs, and the same baby experiences fluctuations in energy requirements over time. What if your baby has the urge to be more active, and needs more food to fuel her activities? What if your infant needs more fluids because it's hot, or because he's coming down with a virus? What if your baby is in the middle of a growth spurt?
It isn't merely that you need to adopt a schedule that is individualized to your baby's current needs. You also need a schedule that keeps changing in response his or her future needs. That's pretty hard to do unless you are paying attention to your baby, offering meals when you observe signs of hunger. And if you are doing that, you aren't imposing a strictly-timed infant feeding schedule. By definition, you are feeding on cue.
Moreover, the baby's need for food and fluids is only one side of the equation -- the demand side. There is also the supply side of the equation. If your baby is on formula, it's easy to figure out what your baby is being supplied with. You can read the label, and know your baby is getting the same formulation from one feed to the next.
But breast milk doesn't work that way. Human breast milk is roughly similar in composition from one woman to the next, but there are significant differences. Not only does breast milk vary between individuals. It also varies between milk samples produced by the same woman at different points in time.
When Shelly Hester and her colleagues analyzed 22 published studies on the metabolizable energy content of breast milk, the researchers were able to estimate the calories found per serving: About 65 calories per 100 milliliters (mL) of breast milk.
But hang on. That estimate is the average for milk expressed between 2 weeks and 6 weeks postpartum (Hester et al 2012).
Milk produced earlier is substantially less caloric. Colostrum, the milk produced during the first few days, has only about 53 calories per 100 mL. Then, between approximately 6 and 14 days postpartum, the caloric density increases slightly, averaging 58 calories per 100 mL (Hester et al 2012).
And milk produced later -- after the 6 weeks postpartum -- becomes increasingly caloric as time goes by. That's because the fat content of breast milk tends to increase the longer a woman continues to nurse. When researchers have tracked lactating mothers over time, they've found that the fat content in milk produced at 6 months is higher than it is at 3 months (Szabó et al 2010).
That's a lot of variation already, but we've only scratched the surface because individual mothers vary substantially in the energy content of their milk. Studies indicate that individual woman may range widely in the fat content of their milk -- from 2 grams per 100mL to 5 grams per mL (Institute of Medicine, National Academy of Sciences 1991).
And other research has identified some of the causes of this variation: Diet, body mass index, maternal age, socioeconomic status, and even smoking habits have been linked with differences in the amount of fat in breast milk (Innis 2014; Rocquelin et al 1998; Argov-Argaman et al 2017; Al-Tamer et al 2006; Agostoni et al 2003).
So it shouldn't surprise us if there is no "one size fits all" infant feeding schedule that's going to serve every baby equally well. Babies vary in their needs, and different breastfed babies may be receiving very different types of breast milk. Some get milk that is richer than average. Others get milk that is much lighter.
babies can only drink so much before their stomachs are full, the fat content
of milk is going to make a substantial difference in the calories they obtain
from any given feeding session. Some babies will need more frequent feedings
than other babies do, simply because their milk has fewer calories per serving.
Just as important, milk from the same mother can fluctuate in quality from day to day, and even from hour to hour (Khan et al 2013). So it's possible that an infant feeding schedule that works pretty well one day might leave a baby dissatisfied on another.
Finally, it's worth noting that the quality of breast milk changes during the course of a feed. At the beginning of a feeding session, when the breast appears full, the milk that is released is relatively diluted and low in fat. Then, as the session continues, the breast takes on a softer, emptier appearance, and the milk changes. The earlier "foremilk" gives way to a more concentrated, fattier "hindmilk" (Woolridge 1995), and you can see the difference in this photo.
The foremilk looks watery and bluish. The hindmilk -- produced by the same breast, but later in the session -- is ivory in color, and thicker.
Thus, if the adult terminates the breastfeeding session too soon, or forces a baby to switch breasts too soon, the baby will miss out on hindmilk (Woolridge and Fisher 1988). Babies in this situation will fill up on a low calorie meal, and require more frequent feedings to obtain the energy they need. In addition, they may be at higher risk for symptoms associated with consuming low quality milk. As breastfeeding expert Michael Woolridge (MD and PhD) has pointed out, low-fat milk can contribute to colic, vomiting, diarrhea, and flatulence in infants (Woolridge 1995).
You may have
heard about research linking formula-feeding with rapid infant growth and
an increased risk of childhood obesity. The links have been replicated in many
studies, have prompted concern. Why are formula-fed babies more likely to become overweight?
One answer is that formula might be too energy-dense for some babies (Hester et al 2012).
But it also appears that the delivery system -- drinking from a bottle -- is a contributing factor.
For example, in one study of 1250 American infants, researchers found that bottle-feeding in early infancy was associated with a tendency to eat everything on offer, regardless of whether the babies consumed formula or breast milk. The more frequently babies drank from bottles during their first 6 months, the more likely they were to become big eaters later. As toddlers, they were more likely to completely drain any bottle or cup given to them (Li et al 2010). A smaller study conducted in the United Kingdom reports similar results (Brown and Lee 2012).
It's not clear what this means. Infants can extract milk more quickly from a bottle than they can from a breast. Perhaps the fast pace leads to consuming more during a feed, so babies become accustomed to taking in bigger meals.
But whatever the underlying cause, it invites the obvious question: Isn't this a good reason to impose an infant feeding schedule? Aren't bottle-fed babies better off if we restrict the timing of their meals?
The evidence suggests not.
For instance, experimental research indicates that babies are sensitive to internal cues of hunger and satiety. When allowed to feed on demand, both breastfed (Woolridge and Baum 1992) and formula-fed (Fomon et al 1975) infants adjust their intakes in response to the caloric content of their milk or formula.
And when researchers have tracked infant development over time, they haven't found that feeding restrictions -- including timed feeding schedules -- reduce the risk of a child becoming overweight.
On the contrary, most studies either report no link, or a positive correlation between restrictive feeding and higher body weights (Gubbels et al 2011; DSantis et al 2011b; Dinkevich et al 2015; Gross et 2014). For example, in one study, researchers found that formula-fed babies were more likely to experience rapid weight gain. But they also found that scheduled feeding was a risk factor in its own right (Mihrshahi et al 2011).
Such observations are consistent with studies of older children. Intrusive, restrictive rules about eating may interfere with the development of self-regulation. They may actually increase a child's tendency to engage in emotional overeating (Jani et al 2015; Rodgers et al 2013), and lead to excessive weight gain (Tylka et al 2015).
So researchers suspect that imposing restrictions -- like a strict infant feeding schedule -- are counterproductive for preventing obesity. Kids might learn to ignore their own hunger cues, and eat in response to social cues ("it's time!") or emotions ("I've been denied -- now it's time to make up for that"). By allowing infants to initiate feedings, we may be helping them develop a more healthy relationship with food.
That's an interesting question.
From birth, infants get distressed when their signals to nurse are ignored. And studies indicate brief, token acts of feeding can help newborns bounce back from stress.
Newborns cry less and show signs of reduced pain when they receive small amounts of milk, formula, or sucrose (see review by Shaw et al 2007; also Blass 1997a; Blass 1997b; Blass and Watt 1999; Barr et al 1999). The act of suckling is itself an analgesic (Blass and Watt 1999). And breastfeeding may be a painkiller and stress-reducer.
In one study, newborns subjected to a painful blood collection procedure cried much less if they were permitted to breastfeed (Gray et al 2002). They cried just 4% of time total procedure time, versus 43% for infants in a control group.
Babies who fed during the procedure also showed markedly reduced rates of grimacing (8% v. 50%), and their heart rates increased less (6 beats per minute v. 29 beats per minute).
Some of these differences may be attributable to the extra skin-to-skin contact that the breastfed babies got. But in a follow-up study, the researchers confirmed that breastfeeding was more soothing than skin-to-skin contact alone (Gray et al 2000; Gray et al 2002). And the authors noted that babies who were held without being fed tended to get frustrated, and required much more time to settle down (Gray et al 2002).
So what might happen to a baby who finds her signals for quick comfort are routinely ignored?
While I've found no studies that bear directly on this question, responsive care has been linked with development of better stress regulation skills -- even among highly irritable, "at risk" babies.
Moreover, a variety of studies suggest that sensitive, responsive parenting contributes to secure attachment relationships and better child outcomes.
And there is intriguing research regarding cognitive development.
In what is perhaps the largest study yet to investigate the effects of an infant feeding schedule, Maria Iacovou and Almudena Sevilla (2013) tracked the development of more than 10,000 British children -- breastfed and bottle-fed alike -- from birth to age 14.
There were no experimental manipulations. The researchers merely noted whether babies had been fed on schedule or on demand, and then followed their cognitive and academic progress. And the results favored feeding on demand:
At every age, kids who'd been subjected to an infant feeding schedule performed more poorly on standardized tests. Moreover, their IQs were, on average, 4.5 points lower.
Correlation doesn't prove causation, of course, and this is just one study. It needs to be replicated.
But it's interesting to note that the study's results remained much the same even after controlling for a variety of potential confounds, like parents' education levels, economic factors, health, breastfeeding, maternal smoking, and the children's exposure to negative discipline tactics. There wasn't any obvious reason for the difference between groups. Just the distinction between feeding on cue and following an infant feeding schedule.
As with most science, we still have a lot left to learn. We don't yet understand all the determinants of breast milk quality, or why the composition of breast milk changes over time. We don't yet understand all the causes of increased obesity risk in formula-fed and bottle-fed infants. And it isn't yet clear how much impact an infant feeding schedule might have over the long term.
In particular, we need more research on the possible effects an infant feeding schedule might have on stress regulation and cognitive development.
We also need more research regarding physical growth rates. When researchers analyzed the growth records of 48, one-year-old babies, they found no "pervasive" effect of feeding style on infant weight gain during the first six months postpartum (Saxon et al 2010). However, this study relied on retrospective reports from mothers (asking them to characterize their feeding styles 12 months before), which introduces some uncertainty. And the study didn't control for breastfeeding, which differed between groups.
That's important, because -- as we've seen -- imposing an infant feeding schedule could have opposite effects on weight gain depending on whether a baby is breastfed or formula-fed. It may help breastfed babies avoid being underfed, and help formula-fed babies avoid excess weight gain. By lumping together all babies fed on cue, we lose the ability to detect these opposing, but potentially important effects. Future, carefully controlled studies can help us resolve the question.
Meanwhile, what we do know is that human beings exhibit the characteristics of continual feeders, and it's a sure bet that relatively frequent, "on demand" feedings have been the historic and evolutionary norm for our species.
It's also clear that breast milk can vary substantially in fat composition and caloric density, so that babies will benefit from being able to schedule the timing of their own feeds. And all babies -- whether they consume breast milk or formula -- experience fluctuations in their needs for fluids and energy. When we are responsive to their cues of hunger and thirst, we're more likely to meet these needs.
How can you tell if a newborn is hungry? Find answers to this and other questions in my article, "The newborn infant feeding schedule: A review of the evidence against regimented feedings."
In addition, you can read more about this topic in "Breastfeeding on demand: A cross-cultural perspective." And for more information about the composition of breast milk, read this review.
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Note: Portions of this article, "Jettisoning the infant feeding schedule: Why babies are better off feeding on cue," are taken from an earlier Parenting Science article, "The infant feeding schedule: Why babies benefit from feeding on demand." The material here has been updated and substantially revised.
For more references pertaining to the infant feeding schedule, see my article on breastfeeding on demand.
Image credits for "The best infant feeding schedule"
Friend with mother nursing infant - US Dept. Agriculture (creative commons license)
Grandmother, infant, and mother - Philippe Parr / flickr (creative commons, no derivations)
Image of mother nursing outdoors - Aurimas Mikalauskas /flickr (creative commons)
Breast milk by Azoreg / wikimedia commons (creative commons license)
Baby bottle by nerissa's ring / flickr (creative commons license)
Newborn sleeping by Jason Barles / flickr (creative commons license)
Content of "The best infant feeding schedule" last modified 3/2017