It is an established medical fact that breastfeeding offers long-term positive medical benefits to babies, which can extend well into adulthood. For instance, breastfed babies are less likely to develop asthma, obesity, and autoimmune disease later in life compared to babies who are exclusively fed formula. Now, a new study reveals new insights into the biological mechanisms that may explain these immunological benefits.
More abundant immune cells
Breast milk contains over 200 different ingredients, including protein, fat, carbs, vitamins, minerals, enzymes, and hormones, although the exact composition will vary from mother to mother and even from one feeding session to another throughout the day.
According to the WHO, breast milk is the natural first food for babies, providing all the energy and nutrients that an infant requires for the first half-year of life. Breast milk continues to be an important part of an infant’s diet, providing half of their nutritional needs during the second half of the year, and one-third during the second year of life.
Breastfeeding transmits elements of the mother’s own microbiome and immune system, providing probiotics to support the growth of beneficial bacteria and kickstarting a baby’s microbiota. The mother transfers her antibodies to her baby through breast milk, and this is particularly true of colostrum, the first milk. For instance, breast milk is high in immunoglobulin A (IgA), which protects the baby from getting sick by forming a protective layer around the nose, throat, and digestive system.
In a new study published this week in the journalAllergy, researchers at the University of Birmingham have discovered that regulatory T cells — a specific type of immune cell which plays a role in regulating or suppressing other cells in the immune system — expand in the first three weeks of life in breastfed babies and are twice as abundant as in formula-fed babies.
According to the authors, these cells control the baby’s immune response so it doesn’t go overboard when it comes into contact with maternal cells transferred through breastmilk, thereby reducing inflammation.
What’s more, the researchers also noticed that bacteria called Veillonella and Gemella, known to support the function of regulatory T cells, are more abundant in the gut of breastfed babies.
“The influence of the type of milk received on the development of the immune response has not previously been studied in the first few weeks of life,” said senior author Gergely Toldi, a researcher at the University of Birmingham and consultant neonatologist at Birmingham Women’s and Children’s NHS Foundation Trust.
“Prior to our research the outstanding importance and the early involvement of this specific cell type in breastfed babies was unknown. We hope this invaluable new insight will lead to an increase in rates of breastfeeding and will see more babies benefit from the advantages of receiving breastmilk.”
“Furthermore, we hope for those babies who are formula-fed, these results will contribute to optimizing the composition of formula milk in order to exploit these immunological mechanisms. We are very grateful for the mums and babies who contributed to this special project.”
A new study reports that breastfeeding might give a boost to baby intelligence. Researchers have found several proteins within breastmilk connected to neurodevelopment, offering new support to the idea that breastfeeding can help babies’ brain development.
The debate around breastfeeding is long and will likely not end anytime soon. Scientific evidence has found that breast milk can protect against infections, and has been associated with a reduced risk of childhood obesity, leukemia, and even cardiovascular health in adulthood. But identifying what effects come directly from the milk is tricky, as other factors can also play an important role.
Regarding breastfeeding’s role in intelligence, results have been mixed and rather inconsistent. There is a myriad factors which can affect intelligence, and drawing a clear cause-effect relationship has proven extremely difficult. However, a new study comes with some convincing new evidence.
“Our previous research established that vulnerable preterm infants who are fed breast milk early in life have improved brain growth and neurodevelopmental outcomes. It was unclear what makes breastfeeding so beneficial for newborns’ developing brains,” says Catherine Limperopoulos, Ph.D., director of MRI Research of the Developing Brain at Children’s National.
Limperopoulos and colleagues at the Children’s National Hospital in Washington, DC, used a sophisticated, non-invasive imaging technique called ‘proton magnetic resonance spectroscopy’ to peer inside newborns’ brains, carrying out a comparison between breastfed babies and babies fed with formula milk. They looked for specific biochemicals in the frontal white matter and the cerebellum — two brain regions that are especially vulnerable in premature babies, which the study focused on.
Specifically, there were increased amounts of inositol (a molecule similar to glucose) and creatine (a molecule which helps to recycle energy inside cells).
“These biochemicals are markers of brain development,” said Limperopoulos. “For example, higher levels of choline in the brain are associated with improved memory and cognition. We can’t make that direct link here – we don’t have information about memory and cognition in newborns – but our hope is that this is an early marker for improved later intelligence. We’d need to confirm that with our follow-up studies.”
The proteins are useful for all babies, and especially for at-risk babies, such as those born prematurely.
“We’re excited by these results because they’re helping us to understand not only how premature birth can have adverse effects on the developing brain, but also how our caregiving can help to protect the brains of these high-risk infants,” she continues.
However, it should also be noted that if the mother can’t breastfeed for any health reason, there is no need for guilt. Mothers are under huge pressure as it is, and adding more pressure regarding breastfeeding isn’t going to do anyone any favors.
The study “Improved cerebral and cerebellar metabolism in breast milk-fed VLBW infants” has been presented at the Pediatric Academic Societies 2019 Annual Meeting presentation.
There’s no other food that offers more optimal nutrition for babies than breast milk. Nevertheless, in some socio-economic groups, the rate of breastfeeding can be as low as 30% — and this needs to change because breastfeeding is one of the single most undervalued things that a mother can do to ensure that her baby is healthy.
Over the past decades, evidence has piled up showing that breastfeeding dramatically reduces child mortality and provides health benefits that extend into adulthood. Some of these benefits not only apply to the infant but also to the mother.
What is breast milk made of?
Breast milk contains over 200 different ingredients, including protein, fat, carbs, vitamins, minerals, enzymes, and hormones. The exact composition will vary from mother to mother and even from one feeding to another throughout the day.
During the first days after birth, the breasts produce the first form of milk — a thick, yellowish fluid called colostrum. The golden yellow or orange color is due to the high levels of beta-carotene present in the milk. Occasionally, blood may leak from the milk ducts, causing the colostrum to appear red, pink, or rusty in color. This is typically nothing to worry about; however, it’s best to consult your doctor if you notice bloody discharges from the nipples.
Although a mother’s breast produces only two tablespoons of colostrum in the first 24 hours after birth, it is packed full of nutrients.
Sometimes called “liquid gold”, colostrum is high in protein and low in fat and sugar. Antibodies and white blood cells found in the fluid are essential for protecting the newborn against infection and illness. Colostrum is also a natural laxative, allowing the infant’s bowels to move and expel the meconium — a tar-like poop that collects in the bowels before the baby is born.
The colostrum phase of breast milk lasts until the transitional stage begins between the second and fifth day after the birth of the baby.
Transitional breast milk is a combination of colostrum and mature milk that lasts over the course of a few days or a week.
Mature breast milk is the final phase of breast milk that appears once the baby is about two weeks old. Mature breast milk is comprised of foremilk and hindmilk. Foremilk is thin, watery, and lower in fat and calories, and it is the first milk to flow out of the breast when the mother starts nursing her infant. Hindmilk is thicker, creamier, and higher in fat and calories; this starts flowing as the mother continues to breastfeed, following foremilk.
And, if you ever wondered, breast milk tastes sweet (from the milk sugar lactose) and creamy (due to the high amount of fat it contains). A 2019 study found that the taste of breast milk is influenced by the kinds of food the mother eats during the day.
The benefits of breastfeeding
Ideal nutrition for the baby
According to the WHO, breast milk is the natural first food for babies, providing all the energy and nutrients that an infant requires for the first half-year of life. Breast milk continues to be an important part of an infant’s diet, providing half of the nutritional needs during the second half of the year, and one-third during the second year of life.
Breast milk is ‘personalized nutrition’
No two mothers’ milk is exactly the same. One important reason why this happens is that breast milk is specifically produced for her child. What’s more, as the baby’s stomach grows in the first few days after birth, so does the mother’s breast milk production.
Breastfeeding transmits elements of the mother’s own microbiome and immune responses, providing probiotics to support the growth of beneficial bacteria and kickstarting a baby’s microbiota.
Breastfeeding enhances the baby immune system
The mother transfers her antibodies to her baby through breast milk, and this is particularly true of colostrum, the first milk. For instance, breast milk is high in immunoglobulin A (IgA), which protects the baby from getting sick by forming a protective layer around the nose, throat, and digestive system.
It is due to this principle of antibody transfer that having a mother sick with the flu may actually be a good thing. By breastfeeding, she actually provides all the antibodies a baby needs to fight the flu-causing virus.
In other words, even if a baby gets an illness, or the mother does, the protective effect of her milk tends to amplify. A breastfed baby is thus more likely to recover faster than a formula-fed baby because the mother will produce specific antibodies against whatever infection the baby contacted.
Breastfeeding reduces disease risk in babies
There are numerous studies that have found a link between exclusively breastfeeding and a reduction in a baby’s risk of disease.
For instance, babies fed a diet exclusively consisting of breast milk for their first six months of life were 63% less likely to get serious cold or throat infections.
Studies have linked breastfeeding with a 50% reduction in the risk of sudden infant death syndrome (SIDS) — the unexplained death, usually during sleep, of a seemingly healthy baby less than a year old — after one month a 36% reduction in risk in the first year.
Breastfed babies also fair better in terms of allergies, with one study finding that babies that were nursed at their mothers’ breast for 3-4 months had a 27-42% reduced risk of asthma and eczema.
Exclusive breastfeeding for at least 4 months reduces the risk of hospitalization for respiratory tract infections by up to 72%.
Not only that, when a baby is hit by an infection or disease, breastfeeding has been shown to reduce their severity.
Breastfeeding reduces the risk of disease in mothers, too
Breastfeeding not only protects babies from disease, but also the mother. The more a mother breastfeeds her child, the stronger the protective effect against breast and ovarian cancer, studies have shown.
What’s more, women who breastfeed for at least one year have a 10% to 50% lower risk of high blood pressure, arthritis, high blood fats, heart disease and type 2 diabetes.
Most recently, researchers have found an association between breastfeeding and a reduced risk of metabolic syndrome, which is a cluster of conditions that occur together, increasing your risk of heart disease, stroke, and type 2 diabetes.
Breastfeeding promotes healthy brain and cognitive development
Researchers at the Children’s National hospital in Washington, DC have shown that breast milk increases the amount of biochemicals that are important for brain growth and development. Although the study focused on extremely premature babies born at a gestational age of between 23 and 32 weeks, they might apply to healthy babies born at term.
Researchers at Brown University reported in 2013 that breastfeeding alone produces the best results for boosting a baby’s brain growth — even by as much as 20% to 30%.
Another study performed by researchers at Boston Children’s Hospital found that for each additional month a baby was breast-fed, verbal ability was higher at age 3, and verbal and nonverbal IQ scores were higher at age 7.
It’s not just the nutritional effects that may contribute to brain development. Breastfeeding mothers tend to spend more time engaging in emotional care than mothers who feed their infants formula; and these differences in mother-infant interactions could explain differences in infant brain development.
Breastfeeding is taxing on the body’s energy balance, requiring about 500 extra calories daily. The hormonal response is also altered during this time, increasing appetite and making mothers more prone to store fat for lactation.
As a result, it’s quite normal for a breastfeeding mother to gain weight. In fact, studies have found that breastfeeding mothers tend to gain more weight than women who don’t breastfeed — but only during the first three months after delivery. After three months of lactation, breastfeeding mothers go through an increase in fat burning that helps them lose weight easier than mothers who don’t breastfeed.
Sleep is sweeter for breastfed babies
Contrary to what you might have heard, formula-fed babies don’t actually sleep more — that’s a myth. Research suggests that both formula-fed and breast-fed babies sleep just as much and are equally as likely to wake up for food during the night.
That being said, the quality of sleep for breastfed babies may be superior as they go back to sleep sooner, a study suggests. This might be due to oxytocin produced in the baby’s body during breastfeeding, which helps him feel sleepy.
Breastfeeding protects mothers from depression
Approximately 15% of women experience feelings of sadness and anxiety after delivering their baby, a condition known as postpartum depression.
The benefits of breastfeeding extend into adulthood
A history of breastfeeding during a baby’s early life can predict success later in life. A study performed by British researchers found that 16-year-olds who were breastfed for six months as infants were more likely to get higher grades in their school exam than their colleagues who were formula-fed, even after the results were adjusted to take into account household income and parents’ education.
Feed your baby soon after birth, preferably within the first hour.
Place the undressed baby directly onto your chest (skin-to-skin).
Make sure your baby is well attached to the breast
Before the milk ‘comes in’ many babies may feed up to 12 times in 24 hours.
Ideally, you and your baby should remain together after the birth so the baby can breastfeed throughout the day and night.
If your baby is having difficulty attaching to the breast, hand express and give colostrum to them.
Breastfeeding is a learned skill and you may need help. Don’t be afraid to ask.
Avoid the use of dummies, teats and infant formula unless a medical professional has advised you to use them.
Bottom line: Breast milk is the most nutritious and healthy kind of food a baby can receive. It’s well worth breastfeeding your child rather than using formula. That being said, this article does not constitute medical advice and you should always consult your doctor about what’s right for both you and your baby.
Mothers’ breast milk may be dramatically more important to the health of infants than previously thought. In a new study, doctors found that momma mice who breastfed their pups transferred immune cells that offered protection against infections long after breastfeeding stopped.
Doctors were aware that breastfeeding raises the immunity of an infant, but the assumption has always been that this protection is only temporary, lasting just for the time that infants are breastfed. What’s more, it was always thought that this immunity was due to antibodies transferred from the mother to neutralize bacteria and viruses.
These assumptions have been now been toppled by a new study published today in the journal Science Advances. Researchers at the University of Birmingham in the UK studied rodent offspring nursed by mothers who had a preconception helminth infection. Unexpectedly, the research team found that the protection against the worm infection was passed onto the infants by cells in the milk rather than through proteins such as antibodies. Most striking of all, these transferred cells offered protection throughout the body well into adulthood.
“This is the first demonstration that infection prior to pregnancy can transfer life-long cellular immunity to infants,” said Dr. William Horsnell, lead author of the study and a researcher at the University of Birmingham’s Institute of Microbiology.
“The work shows that exposure to an infection before pregnancy can lead to a mother transferring long term immune benefits to her offspring. This is remarkable and adds a new dimension to our understanding of how a mother can influence our health.”
In the future, the researchers would like to use this newfound knowledge to create vaccines that prevent infections. The reasoning is simple: if the immune system of mothers and would-be-mothers is primed against infectious diseases through vaccination, then babies could reap the same protective effects through breastfeeding. This new study suggests that this protection could be permanent, which is simply remarkable.
“We hope this research will lead to human investigations into how maternal exposure to pathogens prior to pregnancy can influence infant health,” added Professor Kai-Michael Toellner, of the University of Birmingham’s Institute of Immunology and Immunotherapy.
Breast milk offers excellent, balanced, and healthy nutrition for babies providing all the proteins, fats, vitamins, minerals, and enzymes that young bodies need to stay healthy. Mothers create new antibodies in real time, which help strengthen young immune systems. But that’s not all. Recent studies have shown that breast milk is more beneficial than we think.
The HAMLET molecule. HAMLET (Human alpha-lactalbumin made lethal to tumor cells)
In 2014, researchers from the US and Australia found that feeding an exclusively human milk (EHM) diet to premature infants reduces the incidence of necrotizing enterocolitis (NEC), a serious condition primarily affecting preemies.
A study in 2018 from the University of Helsinki showed that babies breastfed for at least six months have less antibiotic-resistant bacteria in their gut compared with infants breastfed for a shorter period of time.
Researchers at the University of Cologne in Germany have observed that breast milk administered intranasally (via the nose) could protect preemies who have experienced severe brain injuries. This is the first report on additional nasal breast milk application in very low birth weight preterm infants with severe brain injury observing a beneficial effect on neurodevelopment in preterm infants.
The research, published in The European Journal of Pediatrics, was based on the idea that breastmilk has stem cells (neurotrophins and mesenchymal stem cells) which can potentially repair brain injuries in preemies. Neurotrophins are molecules that can promote growth and survival of neural cells. Stem cells are pluripotent cells, meaning that they can develop into virtually any cell type that is needed by the body. The research is still in its early stages and the study is small (with only 31 extremely low birth weight preemies) but the concept is promising and deserves further studies.
If the international community is serious about meeting the health targets set by the United Nations Sustainable Development Goals (SDGs), it must focus its efforts to encourage more mothers to feed their newborns breast milk and make it easier for mothers to actually breastfeed (it’s not easy!).
A new study from the University of Helsinki showed that babies breastfed for at least six months have less antibiotic-resistant bacteria in their gut compared with infants breastfed for a shorter period of time. Moreover, the study showed that antibiotics used by mothers increased the number of antibiotic-resistant bacteria in infants.
Schematic by MeMed.
Bacteria resistant to antibiotics are everywhere — including the human gut, regardless of whether a person has taken antibiotics or not. Antibiotic resistance (or antimicrobial resistance, a.k.a. AMR) is one of the main global threats to public health. Being colonized by opportunistic pathogens carrying antibiotic resistance genes (ARGs) increases the risk of acquiring infections that are difficult to treat. Worldwide, an estimated 214,000 neonatal deaths each year are due to septic infections caused by antibiotic-resistant pathogens. Bacteria resistant to antibiotics are transmitted between individuals similar to how bacteria, viruses and other pathogens are: through direct contact or through food.
In this recently completed study, the researchers investigated the amount and quality of bacteria resistant to antibiotics in breast milk and the gut of mother-infant pairs, resulting in three important findings.
Infants who were breastfed for at least six months had a smaller number of resistant bacteria in their gut than babies who were breastfed for a shorter period or not at all. This shows that breastfeeding seems to be able to protect infants from such bacteria.
Antibiotic treatment of mothers during delivery increased the amount of antibiotic-resistant bacteria in the gut of infants. The effect was still noted even six months post-delivery and post-treatment.
Breast milk also contains bacteria that are resistant to antibiotics and the mother is likely to pass these bacteria on to the child through milk. However, breastfeeding reduced the number of resistant bacteria in the infant gut — an indication of the benefits of breastfeeding for infants.
— 8 months — The baby now weighs about 4 3/4 pounds. His layers of fat are filling him out, making him rounder, and his lungs are well developed.
Another study by investigators at the University of Edinburgh reported that babies born before their due date (premature infants, also known as preemies) show better brain development when fed breast milk rather than formula. Premature birth has been linked to an increased risk of problems with learning and thinking skills in later life, which are thought to be linked to alterations in brain development.
The investigators studied magnetic resonance imaging (MRI) brain scans from 47 babies who had been born before 33 weeks gestation with scans that took place when they reached term-equivalent age. The team also collected information about how the infants had been fed while in intensive care — either formula milk or breast milk from either the mother or a donor. They found that babies who exclusively received breast milk for at least three-quarters of the days they spent in the hospital showed improved brain connectivity compared with others. The effects were greatest in babies who were fed breast milk for a greater proportion of their time spent in intensive care. The study suggests that brain development in the weeks after preterm birth is improved in babies who receive greater amounts of breast milk.
A 30-year-old transgender woman successfully breastfed her baby for six weeks, until her milk production had to be supplemented with formula. How is that possible?
First, let’s look at her case: she took hormonal treatment for six years before her baby was born. She hadn’t undergone any gender-affirming surgery, such as orchidectomy (the surgical removal of testicles) or vaginoplasty (the construction or reconstruction of the vagina). Basically, the testicles were still there and functioning.
To suppress the testosterone production, alongside the feminizing hormone regimen, she took spironolactone, a drug generally used for treating fluid build-up in heart conditions, but which also lowers the production of testosterone and promotes gynecomastia (breast growth in men or transgender women).
The case report states that she was in good health, but had a history of panic attacks, for which she was taking occasional clonazepam, and insomnia, for which she was taking zolpidem — drugs that aren’t recommended during pregnancy or breastfeeding. The report doesn’t mention if she continued the treatment during breastfeeding.
Easier said than done. Inducing lactation in non-pregnant cisgender women is a fairly common procedure, however, so the challenge was to the liking of New York transgender-medicine doctors Tamar Reisman and Zil Goldstein, the authors of the study published in the journal Transgender Health.
First, the researchers had to convince the patient’s body that she was pregnant, so they enhanced the dosage of estrogen and progesterone, the two feminine hormones implicated in pregnancy. Later, the doctors reduced those hormones to mimic childbirth. Additional to this treatment, they gave her a galactagogue — domperidone — to increase the secretion of prolactin, the hormone responsible for milk production. Domperidone is generally used to treat nausea, but this drug is banned in the US because in some intravenous instances it produced cardiac arrhythmias, cardiac arrest, and sudden death. The woman procured domperidone from Canada.
To increase milk production, doctors also recommended using a breast pump that enhanced levels of oxytocin and prolactin. After one month of treatment, she started producing milk droplets, and after three months of treatment, 2 weeks before the baby’s due date, the patient was making 8 oz. of breast milk per day.
“The patient breastfed exclusively for 6 weeks. During that time the child’s pediatrician reported that the child’s growth, feeding, and bowel habits were developmentally appropriate. At 6 weeks, the patient began supplementing breastfeedings with 4–8 oz of Similac brand formula daily due to concerns about insufficient milk volume” write the authors.
“At the time of this article submission, the baby is approaching 6 months old. The patient continues to breastfeed as a supplement to formula feeding, and she continues to adhere to the medication regimen described earlier.”
The wonders of breastfeeding are irreplaceable. The study enumerating many advantages to breastfeeding. But I’m just left with one question: Knowing all these things about breastfeeding, why didn’t the birth-mother breastfeed the baby herself? It boggles the mind.
Another question arises: Did the induced milk have the same nutritional and immunologic properties as the milk that would have come from a pregnant woman?
Colostrum, known as the first milk, is different from the usual breast milk. Colostrum is produced only at the last stage of pregnancy and during the first days postpartum, and its qualities are different from breast milk. Human first milk is rich in immunologic components such as secretory IgA, leukocytes, lactoferrin, and developmental factors such as epidermal growth factor. It contains low concentrations of lactose, indicating its primary functions to be immunologic and trophic rather than nutritional.
Madeline Deutsch, director of clinical services at the UCSF Center of Excellence for Transgender Health, believes there has not been adequate research on the matter. Deutsch, also a transgender woman with a 6-month-old child, said she understands transgender mothers, but trying to induce lactation is “not something I would do”.
Doctor Deutsch is reluctant on this matter because there is no available information as to whether the medication used was transferred to the baby. She is also concerned about the nutritional values of the breast milk produced by transgender women.
A new study of over 10,000 women has shown that women who breastfeed after giving birth have significantly lower chances of post-natal depression than their counterparts who didn’t.
There are still many things we don’t yet understand about breastfeeding, as this study highlights – mothers who planned to breastfeed and were actually able to do it were around 50% less likely to become depressed than mothers who had not planned to and did not. The relationship between breastfeeding and post-natal depression was most pronounced when babies were 8 weeks old and started to lose its weight quickly after that.
The research analyzed 13,998 births in the Bristol area in the early 1990s. Maternal depression was measured using the Edinburgh Postnatal Depression Scale when babies were 8 weeks, and 8, 21 and 33 months old. Doctors also took into consideration any preexisting conditions to rule out any potential external influence. It also controlled for socioeconomic factors such as income and relationship status, and for other potential confounders such as how babies were delivered, and whether they were premature. It’s one of the biggest studies of the kind, and also one of the few to control for external stimuli.
“Breastfeeding has well-established benefits to babies, in terms of their physical health and cognitive development; our study shows that it also benefits the mental health of mothers,” says Dr Maria Iacovou, from the University of Cambridge’s Department of Sociology and a Bye Fellow at Fitzwilliam College. “In fact, the effects on mothers’ mental health that we report in this study are also likely to have an impact on babies, since maternal depression has previously been shown to have negative effects on many aspects of children’s development.”
Doctor Iacovou believes that mothers should not only be encouraged to breastfeed when their health allows it, but governments should also provide a level of support that will help mothers who want to breastfeed succeed.
“Lots of mothers and babies take to breastfeeding pretty easily. But for many others, it doesn’t come naturally at all; for these mothers, having someone with the training, the skills, and perhaps most importantly the time to help them get it right, can make all the difference,” she adds. “However good the level of support that’s provided, there will be some mothers who wanted to breastfeed and who don’t manage to. It’s clear that these mothers need a great deal of understanding and support; there is currently hardly any skilled specialist help for these mothers, and this is something else that health providers should be thinking about.”
Just yesterday we were telling you about a change in diet 3.5 million years ago, modifying the way our hominid ancestors evolved and, in turn, how we evolved. Now, we’re moving a little closer to the present day – researchers calculating the barium levels in fossil teeth claim that they’ve found a difference in the way humans and Neanderthals were breastfeeding their babies.
Image by Ian Harrowell, Christine Austin, and Manish Arora Molar tooth model with the cut face showing color-coded barium patterns merging with a microscopic map of growth lines, which have been accentuated to reflect their ringlike nature.
Tanya Smith, an associate professor of human evolutionary biology, and Katie Hinde, an assistant professor of human evolutionary biology, worked with colleagues at the Icahn School of Medicine at Mount Sinai in New York and Westmead Hospital in Australia found a correlation between barium levels in teeth and an increase in breastfeeding, confirming what many anthropologists already suspected. As they explain, barium levels can survive unhampered for thousands of years, meaning the test can show breast-feeding changes among both early humans and Neanderthals.
“There’s an ongoing debate about whether Neanderthal and contemporary Homo sapiens would have practiced different behaviors in terms of their breast-feeding,” Smith said. “People have speculated that an early weaning process in modern humans may have been part of their evolutionary advantage. We don’t have the data to answer that question yet, but we now have the method to be able to start collecting that data. It’s clear that there are developmental differences between Neanderthals and modern humans — we’ve amassed good evidence for that in the fossil record,” she continued. “What we haven’t been able to do is make a direct comparison using a biomarker like first reproduction age, or life span, or weaning age. That’s why this is so exciting, because now we can get at one of these ‘life history’ variables directly.”
But that’s not all they did – they calculated weaning age, taking advantage of the unique way in which teeth grow. Pretty much like trees, teeth grow in concentric layers – various substances (such as calcium, oxygen and small amounts of metal) get deposited in the tooth enamel.
Using both chemical analysis and microscopic studies, they showed that initially, barium levels are very low, because very little of it passes through the placenta. Then, as the baby is born and is breastfed, the barium levels rise significantly, only to drop as he starts supplementing his meal with other foods. It then drops again, significantly, once breastfeeding is stopped.
“We can see when the barium shows up in the tooth after birth, and we see it increase over time, because an infant will take more milk as they get bigger and more active, and then you see it drop off in this beautiful, inverted U-shaped function,” Hinde said. “This is a game-changer in many ways, because this will allow us to go to museum collections and look at this as a proxy for how much milk different infants got from their mothers and what their weaning process was like. We can now look at that within species, but we can also look at that among species. That will tell us about the evolution of how mothers invest in their young.”
Some researchers believe that this also provided an evolutionary advantage over the Neanderthals – one of the many things which ensured our survival as a species.
“This can give us a window into one aspect of life that may have separated modern humans from Neanderthals,” she said. “This topic has been debated for a long time in the scientific community. What does it mean that human and Neanderthal cranial development was different? What does it mean that their dental development was different? We haven’t been able to get at these questions in the fossil record, but now we can actually get at a real developmental benchmark. That’s why this is so exciting.”