Early Solid Introduction and Sleep in Breastfed Infants

Will starting solid foods early help my baby sleep better? 



The information about solids and sleep varies in quality and can easily leave parents confused

When I was struggling with my infant daughter’s sleep, a piece of advice commonly offered was to start solids early.  Over the course of my daughter’s first year, I quickly learned that there is a lot of conflicting parenting information out there - as well as strong opinions - about the “right” course of action.  While we can be quite certain about some things – such as the importance of back sleeping to protect against Sudden Infant Death Syndrome (SIDS) – solid evidence for other aspects of parenting is often lacking. 

It is a commonly held belief that adding solids to a baby’s diet will help with sleep.  However, there has historically been little evidence to support or refute this claim.  In general, research has shown that solid introduction probably does little, if anything, to help with infant sleep (1-3).  Coming up with an answer to this question has been complicated by the fact that infants typically begin sleeping through the night between 4-6 months, regardless of feeding practices.  This is a situation where we see a correlation (two things appear to be connected to one other – adding solids and sleeping through the night) but we cannot determine causation (that one thing caused the other or vice versa).

Randomized control trials (RCT), by nature of their design, can help determine causation - something that observational studies cannot do.   However, RCT’s have been absent when it comes to studying early solid introduction and sleep - at least until recently.  This is likely one of the reasons why the results from the Enquiring About Tolerance (EAT) study – a RCT with recent data released on early food introduction and sleep in exclusively breastfed infants - is making headlines.  More on the EAT study in a moment - first let's briefly delve into the basics of solid food introduction.


Current consensus suggests adding solids at the 6 month mark

Starting solids marks the gradual transition from an exclusive milk-based diet (breastmilk or formula) to one of table foods.  Oftentimes, these added foods are referred to as “complementary”, reflecting the ongoing importance of breastmilk or formula – in addition to table foods - as the primary form of baby’s nutrition until the end of the first year of life.  Using the World Health Organization (WHO) definition, exclusive breastfeeding means only offering breast milk (including expressed breast milk) but excluding water, breast milk substitutes, other liquids and solids.  Vitamins, minerals and medicines – including the important addition of daily vitamin D - are included in the definition of exclusive breastfeeding.

Similar to the uncertainty around early solid introduction and sleep, there has been an ongoing debate over the optimal time to introduce solids.  The current recommendations from the WHO, the American Academy of Pediatrics (AAP), the Canadian Pediatrics Society (CPS), and Health Canada support exclusive breastfeeding until 6 months of age.  These guidelines have changed over time with Health Canada extending the recommended duration of exclusive breastfeeding from 4-6 months to 6 months in 2004.  This change brought Canadian guidelines in line with the AAP and WHO breastfeeding recommendations and was influenced by research demonstrating the positive health impacts for both infants and mothers from exclusive breastfeeding until 6 months of age.  More recently, there has been a resurgence of interest in the introduction of solids prior to 6 months, stemming largely from evidence that the early introduction of solids may prevent the onset of allergies. 

Despite renewed debate around solid introduction, there remains a reasonably robust consensus that solids can be introduced too early and too late.  Research indicates that solid introduction prior to 3-4 months of age puts infants at greater risk for a number of health ailments including allergies, eczema, type 1 diabetes, celiac disease and childhood obesity (4-8).  Furthermore, waiting longer than 6 months of age to introduce solids, puts a baby at risk for iron deficiency with a number of associated health risks. 


The EAT study: Adding solids early may help with sleep

The Enquiring About Tolerance (EAT) study was a population-based RCT, which was conducted in the United Kingdom over a 7-year period (9).  It included 1303 exclusively breastfed 3-month-old infants who were followed until 3 years of age.  The study is accessible here and I've also included a link to an EAT study summary video.

The primary objective of the EAT study was to look at the effect of introducing allergenic foods, at 3 months verses 6 months of age, on subsequent development of food allergies, in exclusively breastfed infants. A secondary analysis, performed from the study results, looked specifically at the question of whether the early introduction of solids – at 3 months verses 6 months - influences sleep in exclusively breastfed infants (10).  These results of the secondary analysis were published in the July 2018 edition of JAMA Pediatrics and are available here.

To summarize the findings, briefly, the researchers found that early solid introduction was associated with longer sleep duration, fewer overnight awakenings, and lower rates of parent-reported serious sleep difficulties.  All of these results were based on “intention-to-treat” comparisons.  In other words, the researchers included all infants in each of the two study groups, whether or not these infants followed the research protocol. Let’s go through the three conclusions, one by one, including the use of Figures taken from the published paper:

1.     Longer sleep duration: Infants in the 3-month early introduction group (EIG) were found to have significantly longer duration of overnight sleep than the 6-month standard introduction group (SIG).  Longer sleep durations were observed starting at 5 months of age, 2 months after commencing solid food introduction, and observed to persist beyond one year of age.  The difference was, on average, 7.3 minutes more sleep per night, with a peak difference of 16.6 minutes at 6 months of age.  Notably, there was no difference in the amount of daytime sleep between the groups indicating the EIG infants were typically getting slightly more total daily sleep than the SIG babies.

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2.     Fewer overnight awakenings: Over the course of the study, the EIG infants were found to have 9.1% fewer night-time wakings than the SIG babies. This equates to a decrease from 2.01 to 1.74 wakings per night or, put slightly differently, just shy of 2 fewer awakenings per week.

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3.     Fewer reported sleep problems: Parents in the SIG were significantly more likely to report a small or very serious problem with their child’s sleep than in the EIG.  Researchers found that serious sleep problems were significantly associated with maternal quality of life (e.g., sleep, psychological, social and physical) regardless of group designation.   


We’ve already addressed the value of RCT’s in helping determine causality. Hence, the results of the EAT study are worth carefully considering.  Although the design of the study is robust, the use of a secondary analysis can introduce error.  RCT’s are designed with the primary question in mind, including consideration of potential covariants.  Covariants are factors that can independently affect the outcome of a study.  When this effect is unwanted (i.e., introduce bias) covariants are referred to as "confounders".

In the case of the EAT study, the primary question related to allergy rather than sleep.  Despite this, the secondary analysis included a comprehensive list of potential sleep-related confounders.  In studies such as EAT, when a potential confounder is higher in one study group than the other despite randomization, a statistical adjustment can be made to avoid biasing the study results.  For example, sleep location and method of putting child to sleep were two such variables controlled for at baseline.  This is important, because where a child sleeps (e.g., separate bedroom verses in parent’s bedroom on a separate verses in parent's bedroom on a shared sleeping surface) and how that child is put to sleep (e.g., allowed to fall asleep independently or with sleep props such as breastfeeding) - are known to influence both the quality and quantity of sleep, independent of introducing solids or not.  

Indeed, at the time of study enrollment, infants sleeping in their parents' bedrooms had significantly less sleep than infants sleeping in their own rooms.  Room sharing infants also tended to wake more frequently, 1.28 times more often if sleeping in the parental bed than in their own room.  Infants who were placed to sleep alone rather than soothed to sleep slept an extra 50 minutes longer per night with a similar pattern for overnight awakenings.  The independent sleepers were also significantly less likely to wake at night at enrollment.

At enrollment, there was a slight tendency towards feeding to sleep in the EIG, which was also noted at 4 months.  After 4 months, more SIG mothers fed their infants to sleep and more EIG mothers put their babies down to sleep independently.  Both trends were reported as statistically non-significant but are of interest to note.  Information about sleep location over the course of the study was not readily accessible.  It is possible that the early introduction of solids influenced sleep location and that sleep location, itself, played an independent role in observed sleep patterns.  Notably, given the EAT study focused on exclusively breastfed infants, it does not tell us about the effect of early solid introduction on sleep in formula fed infants.  


When making a decision about early solid introduction, weigh the risks and benefits

Ultimately, as is true for any health care decision - it is important to weigh the potential risks and benefits.  The EAT study demonstrated that early solid introduction may help with sleep - although the positive effects on sleep were arguably small.  Importantly, the EAT study, along with its predecessor - the Learning Early about Peanut Allergy (LEAP) study - demonstrated the potential benefit of early solid introduction in preventing the development of food allergies (11).  Food allergy prevention is an important consideration in favour of early solid introduction, especially given the well-documented morbidity and mortality associated with food allergies.  For example, 1-2% of children suffer from peanut allergy, an oftentimes severe and lifelong condition.  It would be beneficial on both an individual and public health scale to decrease the prevalence of peanut as well as other allergies.  While more information is needed about when and how potential allergenic foods are best introduced, clinical practice guidelines have been developed and are accessible here.

Breastfeeding is known to confer a host of benefits to both infants and mothers. Reduced respiratory and gastrointestinal illnesses for babies in addition to prolonged lactational amenorrhea and maternal weight loss are among the demonstrated benefits of exclusive breastfeeding for the first 6 months (12-14).  However, the impact on gastrointestinal illnesses is likely small, especially in developed countries where there is ready access to safe water and refrigeration.  The importance of lactational amenorrhea and maternal weight loss varies amongst mothers.  Importantly RCT’s studying solid food introduction suggest that the introduction of solid food at 4-6 verses 6 months does not affect infant growth or total energy intake (15-17). 

Ensuring adequacy of maternal milk supply is also a consideration.  By introducing solids early, the amount of breastfeeding is likely to decline.  This decrease may be further hastened in certain situations such as where milk supply is low and mothers are working.  Again, studies in this area are lacking but important to fully understand the implications of early solid introduction.

Lastly, infant readiness for solid introduction must be taken into account. There is a normal range for this milestone, as is true for other developmental step.  Key aspects of solid preparedness include a demonstrated interest in eating, the ability to sit upright comfortably and hold head steady, the capability to lean forward and turn away to indicate wiliness to feed, and the ability to keep the tongue low so as not to push food out.  Advocates of early self-feeding also include an infant's ability to pick up and transfer food into his or her mouth as an important criteria for solid food readiness.


So where does this leave us?

In summary, like other areas of parenting, there is conflicting information about the ideal time to start baby on solids.  Early solid introduction may protect against food allergies and help with infant sleep.  However, it is also important to consider developmental readiness for solids and the potential benefits of delaying complementary foods until 6 months of age.  

Similar to other health care decisions, the unique health needs of babies and mothers should also be considered.  If you have further questions, I encourage you to discuss this important topic with your health care provider.



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