Updated 1 February 2021
In Part 1 of this special series on covering recently-published research on all things related to pregnancy, birth and breastfeeding, I discussed the most important steps for women to take before they become pregnant.
Part 2 discussed research on pregnancy and birth.
And now, in Part 3, let’s delve into research on breastfeeding.
When pregnant women are considering infant feeding options, their primary concern is usually for the health of their soon-to-be-born baby. But aside from all the health benefits that breastfeeding bestows on babies, it’s also a boon for mothers’ health, as the first 4 articles demonstrate.
1. Breastfeeding hormones reduce mothers’ stress levels and dials up their capacity for happy relationships
The hormone oxytocin, which stimulates the ‘let-down’ of milk when a baby suckles at the breast, has been found to reduce breastfeeding mums’ psychological stress and anxiety levels, dampen their reaction to negative facial expression, and enhance positive feelings towards their baby and their ability to recognise happy adult facial expressions.
Dads who take the motto ‘happy wife, happy life’ seriously would be well-advised to provide their partners with all the support they need while breastfeeding… and don’t forget to smile at your beloved as she nurtures your offspring!
2. Breastfeeding protects women against high blood pressure and diabetes.
According to a meta-analysis that included over 200 000 participants, mums who breastfed their babies for at least 12 months in total (i.e. adding up breastfeeding duration for each child) had a 30% lower risk of developing diabetes and a 13% lower risk of hypertension (high blood pressure) than mums who breastfed for less than 12 months in total.
Furthermore, in a systematic review of 16 other studies that were not included in the meta-analysis, a rather startling statistic emerged: for every additional year of breastfeeding, a woman’s risk of developing diabetes drops by 14%! (Having breastfed my two kids for a total of over 7 1/2 years, I guess I’m virtually diabetes-proof ;-).)
Given that cardiovascular disease is the leading cause of death in women, the authors’ conclusion is noteworthy:
“Breastfeeding is associated with long-term cardiovascular health benefits for women.”
3. Breastfeeding reduces women’s risk of stroke
In a study of almost 130 000 postmenopausal Chinese women, breastfeeding was found to be highly protective against strokes.
The effect of breastfeeding was particularly potent against the clotting type of stroke (ischaemic stroke) which is the most common type in Australia. Women who had ever breastfed were at significantly lower risk of ischaemic stroke.
For the bleeding types of stroke (intracerebral and subarachnoid haemorrhage), longer duration of breastfeeding was necessary to provide a protective effect: at least 7 months for intracerebral haemorrhage and at least 2 years for subarachnoid haemorrhage.
4. Breastfeeding protects women against premature menopause.
Women who go through menopause before the age of 45 are at increased risk of premature death, cognitive decline, osteoporosis, and cardiovascular disease.
So it’s reassuring to know that, according to recent findings from the Nurses Health Study II (a large cohort study which has been tracking the health of female US nurses for several decades), breastfeeding reduces women’s risk of premature menopause.
And the longer, the better: while women who breastfed for a total of 7-12 months had a 13% lower risk of premature menopause than women who breastfed for 6 months or less, breastfeeding for 13-18 months dropped the risk by 19%; 19-24 months by 20%, and 25 months or more by an impressive 27%.
5. Breastfeeding protects women against deadly ovarian cancer
In a pooled analysis of case-control studies including over 24 000 women, breastfeeding was associated with a 24% lower risk of invasive ovarian cancer. The protective effect of breastfeeding was most evident for the high-grade serous subtype (the most deadly form of ovarian cancer) and for endometrioid cancers.
While breastfeeding for 1 to 3 months in a single episode (i.e. breastfeeding one baby for 1-3 months, rather than cumulative breastfeeding duration across multiple children) was associated with 18% lower risk of ovarian cancer, breastfeeding one child for 12 or more months reduced risk by 34%.
“Breastfeeding is associated with a significant decrease in risk of ovarian cancer overall and for the high-grade serous subtype, the most lethal type of ovarian cancer.”
6. Breastmilk enhances infants’ cognitive development
It has long been known that breastfed babies have higher intelligence test scores in childhood than bottle-fed babies, and the longer they’re breastfed, the higher the scores.
While there are many components of human breast milk that may enhance cognitive development, recent research zeroed in on a human milk oligosaccharide (HMO – a complex sugar that is indigestible by babies, but serves as a fuel source for their gut bacteria) known as 2’-fucosyllactose (2’FL).
Animal studies had previously shown that exposure to 2’FL enhanced cognitive outcomes of learning, memory, and attention in rodents.
To find out whether the same effects occurred in humans, researchers recruited 50 Hispanic mother-infant pairs from maternity clinics in Los Angeles County.
Women who breastfed their 1 month old babies more frequently were found to have higher levels of 2’FL in their breast milk, and the higher the level of 2’FL in milk, the higher the children scored on the Bayley-III (a standardised test of child development) at the age of 2.
“We found that maternal and breast milk characteristics were associated with infant cognitive development at 24 months of age, an outcome that prior studies have suggested tracks across the life course to mitigate risk for psychiatric disorders and maximize scholastic potential and vocation.”
Interestingly, breastfeeding frequency and 2’FL content of breast milk at 6 months of age was not associated with test scores, indicating that the first month of life is a sensitive period for cognitive development, and that women should be breastfeed their newborns ‘on demand’ rather than trying to feed them on a predetermined schedule.
This study also confirmed previous research which has found that the babies of women who were obese before becoming pregnant with them, had poorer cognitive development at age 2 than babies born to normal-weight women, reinforcing the need for women to attain a healthy weight before they start their families.
7. Breastfeeding fine-tunes babies’ immune systems, reducing their risk of developing asthma and autoimmune diseases
While it has been known for decades that breastfed babies have a lower risk of asthma and autoimmune disorders, the mechanisms underlying this protective effect were unclear.
Research published in the journal Allergy has begun to solve the mystery. In the first 3 weeks after birth, the proportion of regulatory T cells (Tregs) – a type of white blood cell that modulates the immune system, maintaining tolerance to self-antigens, and helping to prevent autoimmune disease – . circulating in newborns’ bloodstream increases rapidly.
However, the proportion of Tregs is nearly two‐fold higher in exclusively breastfed newborns compared to those who received formula milk only.
Moreover, T cells drawn from the blood of exclusively breastfed babies showed a reduced inflammatory response to non‐inherited maternal antigens – molecules from their mother that foetuses are exposed to while in utero, and which are implicated in the development of autoimmune disease.
The researchers analysed stool samples from the babies, and found that breastfed babies’ gut microbiomes were more abundant in two key species of bacteria, Veillonella and Gemella, which produce short-chain fatty acids that promote the growth of Tregs.
Putting all the pieces together, human breastmilk contains all the components to build a healthy immune system in newborns, right down to providing the right prebiotics (bacterial fuel sources) to feed the precise species of gut bacteria that promote healthy immune function.
8. Human breast milk helps babies tell the time, so that they can develop normal circadian rhythm
As any parent will tell you, newborn babies have absolutely zero sense of day and night; they wake up, feed, and sleep at all hours.
However, breastfeeding helps to establish normal circadian rhythm in babies, by delivering time-setting cues from mother to baby.
The composition of breast milk varies quite dramatically throughout the day:
- Cortisol (a hormone that promotes alertness) – occurs at levels three times higher in morning milk than in evening milk.
- Melatonin, which promotes sleep and digestion, is barely detectable in daytime milk, but rises in the evening, peaking around midnight.
- Nucleotides that promote healthy sleep are also more abundant in night milk than day milk.
- Levels of individual amino acids (building blocks of protein) show consistent oscillations across the 24 hour day, echoing their roles in activity, growth and development.
- The iron content of breast milk hits its peak around noon; vitamin E peaks in the evening.
- Minerals like magnesium, zinc, potassium and sodium are all highest in the morning.
- Infection-fighting immunoglobulins and complement (immune proteins), and white blood cells delivered from the mother’s circulation are higher in day milk than night milk, presumably to provide extra protection to babies at the time when they are most likely to be exposed to potential pathogens. In addition, the levels of cytokines (chemicals that modulate the immune system’s activity) fluctuate in predictable rhythms across the course of the day.
The take-home messages from this fascinating field of research into human breast milk as ‘chrononutrition’ are
- Breastfeeding may help babies to develop a normal, healthy circadian rhythm, while formula, with its unchanging composition, may not.
- Breast milk that is expressed for later feeds should be labelled with the time of day that is was expressed, to avoid sending confusing circadian signals to their babies.
9. Co-sleeping, or bed-sharing, promotes breastfeeding and can be done safely
According to new evidence-based recommendations issued by the Academy of Breastfeeding Medicine, bedsharing or co-sleeping promotes the initiation and duration of exclusive breastfeeding.
Provided parents avoid risky cosleeping behaviour (sleeping with their baby on a sofa or armchair; having their baby sleep next to an adult impaired by alcohol, medications, or illicit drugs, or who smokes; cosleeping with a baby who was born prematurely; cosleeping in a bed with soft furnishings (e.g. multiple pillows) or heavy covers; and cosleeping with a baby who has never having initiated breastfeeding), cosleeping is safe and beneficial for both baby and mother.
The ‘cuddle curl’ position that breastfeeding mothers naturally adopt when sleeping with their infants (illustrated below) protects infants from slipping up the bed under pillows, or down the bed where they might become suffocated under bedclothes:
The authors of the guidelines make some interesting observations:
“In industrialized countries until the early 20th century, most infants were bedsharing and breastfeeding. After that time, solitary sleep developed as an ideal among the middle classes, reinforced by the growing trends of artificial feeding and medicalization of childbirth, separating infants from mothers. Sleep training also became increasingly popular in some industrialized societies…
Concerns about infant sleep duration and location did not appear until after the late 19th and early 20th centuries in industrialized countries, indicating that infant sleep research has taken place within an historical context in which feeding of human milk substitutes and solitary sleep promotion were normative.”
Cosleeping in safe circumstances has not been found to increase the risk of Sudden Infant Death Syndrome (SIDS) and a significant protective effect against SIDS for nonhazardous bedsharing has been found in infants above 3 months of age.
10. Consuming a high-sugar diet (especially sugar-sweetened beverages) during the breastfeeding period can impair your baby’s cognitive development
Breastfed children whose mothers who consumed the most fructose (primarily from sugar-sweetened beverages such as soft drinks/sodas and sweetened iced tea, and fruit juice) in the first month after they were born, were found to have lower scores on tests for cognitive development when they were two years old. Interestingly, consumption of breastfeeding mothers had no measurable impact on babies’ cognitive development when they were only 6 months old, indicating that the harm done by poor diet choices in breastfeeding mothers is cumulative and long-term.
Putting it all together
To summarise, breastfeeding is beneficial to the health of both mother and baby, and promotes the baby’s cognitive development, conveying lifelong advantages. Mothers who eat a wholesome, nutrient-rich diet while breastfeeding will not only lose their baby weight faster, but also benefit their babies’ development.
The Australian Breastfeeding Association (ABA) is an invaluable resource. I strongly advise all of my pregnant clients to join the ABA, get to know their local group leader and attend meetings before they give birth. The womanly art of breastfeeding is best learnt by spending time with women who have practised it!
No formula can ever substitute for human breast milk. Mothers who are unable to breastfeed their babies are advised to seek donor milk from appropriately screened mothers, via an accredited milk bank such as that run by the Australian Red Cross, or the MothersMilkBank.
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