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Researchers have known for a while that human breast milk contains hundreds of species of bacteria that a baby ingests while feeding. This is good! The bacteria is seeding the baby's gut microbiome (microbial community). A recent study of breast milk from different continents found that breast milk from healthy mothers also contains species of fungi - which is the breast milk mycobiome. What was noteworthy was that some  types of fungi in breast milk were found among breast milk samples from all locations (a fungi "core group"), while other types of fungi varied among breast milk from the different locations and even how the baby was delivered (vaginal or C-section birth).

After analyzing the 80 samples of breast milk (20 from each country: Spain, Finland, South Africa, China) it was found that some fungi were the same in breast milk from the different locations: Malassezia, Davidiella, Sistotrema, and Penicillium, while others were different. Fungi from the genus Cryptococcus were higher in breast milk from women who delivered vaginally (as compared to those who had a C-section).  [Note: Genus ranks above species, but below family, and the written name is capitalized.]

This study confirms the importance of breast milk as a source of microbes (along with many nutrients and protective compounds) to the infant and infant gut. From Science Daily:

Breast milk microbiome contains yeast and fungi: Do these benefit the infant?  ...continue reading "It Is Normal For Fungi To Be In Breast Milk"

Another excellent reason to breastfeed premature infants - to increase the odds of preventing retinopathy of prematurity (ROP), which is the reason preemies can go blind. It occurs when blood vessels in the retinas of premature infants start to grow out of control. If the abnormal growth continues, the retinas detach, and this can cause blindness.

Sadly, an ROP epidemic occurred in the 1940s and early 1950s when hospital nurseries began using excessively high levels of oxygen in incubators to save the lives of premature infants. During this time, ROP was the leading cause of blindness in children in the US. In 1954, scientists funded by the National Institutes of Health determined that the relatively high levels of oxygen routinely given to premature infants at that time were an important risk factor, and that reducing the level of oxygen given to premature babies reduced the incidence of ROP.

Nowadays ROP is a leading cause of childhood blindness in developed countries. A large US study found that in extremely preterm infants with a gestational age of 22 to 28 weeks, the incidence of ROP was 59% (96% at 22 weeks and 32% at 28 weeks). ROP is considered a  multifactorial disease, and risk factors such as prematurity, low birth weight, oxygen therapy, and oxidative stress have been associated with its development.

This recent study was a meta-analysis of five studies (of 2208 pre-term infants), and it found that the overall incidence of ROP was reduced among infants fed human breast milk compared with those fed formula. The best results in preventing severe ROP was in babies fed exclusively breast milk (up to 90% reduction) or mainly human breast milk feeding. It is thought that breast milk may protect against the development of ROP because of its antioxidant and immune-protective properties.  Note that studies involving donor milk were not included because past studies did not find any advantage for donor milk over formula. This may be possibly related to loss of the breast milk microbes (breast milk normally contains up to 700 species of bacteria) during processing (pasteurizing/heat treatment of milk for 30 minutes) and storage of donor milk. From NPR:

Mother's Milk May Help Prevent Blindness In Preemies

If Stevie Wonder had been born three decades later, we might never have gotten "Superstition" and "Isn't She Lovely" — but the musician might never have gone blind, either. Born premature, Wonder developed retinopathy of prematurity, an eye disease that afflicts more than half of babies born before 30 weeks of gestation.Though treatments were developed in the 1980s, about 400 to 600 U.S. children and 50,000 children worldwide still go blind every year from the condition. Now a study suggests that number could be slashed by more than half if all those preemies received their mothers' milk.

The study, actually a combined analysis of five studies from 2001 through 2013, found that preemies receiving human milk from their mothers had 46 to 90 percent lower odds of retinopathy of prematurity (ROP), depending on how much milk they received and how severe the ROP was. The studies were observational, so they cannot show that breast milk directly caused the lower risk.

Of the infants who develop ROP, most recover and develop well without treatment, but about 10 percent develop severe ROP, increasing their risk of blindness, Chiang said. About half of those infants need treatment, which will prevent blindness in 80 to 90 percent of them.

The new research analyzed the outcomes of 2,208 preterm infants based on whether they received exclusive human milk, any human milk, mainly human milk (more than 50 percent), exclusive formula, any formula or mainly formula. The study did not include donor milk, so all the milk was the mother's pumped or hand-expressed breast milk.

Infants who exclusively received breast milk had 89 percent reduced odds of severe ROP compared to infants who received any formula. Infants who received a mixture of breast milk and formula had roughly half the odds of developing severe ROP compared to infants exclusively receiving formula. The analysis included a very large older study that had found no reduced risk for ROP from breast milk, but most infants in that study received less than 20 percent breast milk.

Until the 1940s and 1950s, ROP did not exist because infants born prematurely rarely survived, Chiang said. As doctors learned to how to keep these tiny babies, usually little more than 3 pounds at birth, alive, they discovered that the blood vessels in their retinas would often start to grow out of control. If the abnormal growth continued, their retinas detached, causing blindness.

The cause of ROP isn't entirely understood, but scientists believe oxidative stress can stimulate the abnormal growth of the blood vessels. Providing preemies with oxygen is often key to their survival, but that oxygen exposure might lead to ROP, according to Jianguo Zhou, a neonatologist in Shanghai, and lead author of the study.

There has been much discussion recently about breastfeeding - why is it so important? Is it really better than formula? The answer is: YES, breastfeeding is the BEST food for the baby, and for a number of reasons. Not only is it nature's perfect food for the baby, but it also helps the development of the baby's microbiome or microbiota (the community of microbes that live within and on humans). Specifically, breast milk transmits about 700 species of bacteria to the baby - bacteria that are important in developing the baby's microbiota, bacteria that are important for the baby's development and health in many ways (including the immune system). No formula does that. Not even close.

There is obviously much we don't know or understand yet, but finding 700 species in breast milk is a big deal. The most variety was in colostrum (the first milk), but even after 6 months (mature milk) they found hundreds of species of bacteria. What was also interesting was that the bacteria species in the breast milk varied whether the baby was born by vaginal birth, unplanned cesarean, or planned cesarean (this last had a somewhat different bacterial community which persisted through the 6 months of the study). By the way, in the original study, the authors made a point of saying that the 700 bacteria species are NOT bacterial contaminants, but meant to be there! (for those who want to sterilize and pasteurize everything because they think that all bacteria are bad).This study is from 2013, but well worth reading. From Science Daily:

Breast milk contains more than 700 species of bacteria, Spanish researchers find

Researchers have traced the bacterial microbiota map in breast milk and identified the species of microbes taken from breast milk by infants. The study has revealed a larger microbial diversity than originally thought: more than 700 species. The breast milk received from the mother is one of the factors determining how the bacterial flora will develop in the newborn baby.

A group of Spanish scientists have now used a technique based on massive DNA sequencing to identify the set of bacteria contained within breast milk called microbiome.  Colostrum is the first secretion of the mammary glands after giving birth. In some of the samples taken of this liquid, more than 700 species of these microorganisms were found, which is more than originally expected by experts.

"This is one of the first studies to document such diversity using the pyrosequencing technique (a large scale DNA sequencing determination technique) on colostrum samples on the one hand, and breast milk on the other, the latter being collected after one and six months of breastfeeding," explain the coauthors, María Carmen Collado, researcher at the Institute of Agrochemistry and Food Technology (IATA-CSIC) and Alex Mira, researcher at the Higher Public Health Research Centre (CSISP-GVA).

The most common bacterial genera in the colostrum samples were Weissella, Leuconostoc, Staphylococcus, Streptococcus and Lactococcus. In the fluid developed between the first and sixth month of breastfeeding, bacteria typical of the oral cavity were observed, such as Veillonella, Leptotrichia and Prevotella....The study also reveals that the milk of overweight mothers or those who put on more weight than recommended during pregnancy contains a lesser diversity of species.

The type of labour also affects the microbiome within the breast milk: that of mothers who underwent a planned caesarean is different and not as rich in microorganisms as that of mothers who had a vaginal birth. However, when the caesarean is unplanned (intrapartum), milk composition is very similar to that of mothers who have a vaginal birth.

These results suggest that the hormonal state of the mother at the time of labour also plays a role: "The lack of signals of physiological stress, as well as hormonal signals specific to labour, could influence the microbial composition and diversity of breast milk," state the authors.

And yes, what you eat while breastfeeding has an effect on the breast milk. From Science Daily:  Carotenoid levels in breast milk vary by country, diet

A Purdue University-led analysis of breast milk concludes that levels of health-promoting compounds known as carotenoids differ by country, with the U.S. lagging behind China and Mexico, a reflection of regional dietary habitsCarotenoids are plant pigments that potentially play functional roles in human development and are key sources of vitamin A, an essential component of eye health and the immune system.The carotenoid content of a woman's breast milk is determined by her consumption of fruits and vegetables such as squash, citrus, sweet potatoes and dark, leafy greens.

Read the labels on personal care products, and do NOT buy those with triclosan! (See earlier posts for other reasons to avoid triclosan.) From Science Daily:

The 'dirty' side of soap: Triclosan, a common antimicrobial in personal hygiene products, causes liver fibrosis and cancer in mice

Triclosan is an antimicrobial commonly found in soaps, shampoos, toothpastes and many other household items. Despite its widespread use, researchers report potentially serious consequences of long-term exposure to the chemical.The study, published Nov. 17 by Proceedings of the National Academy of Sciences, shows that triclosan causes liver fibrosis and cancer in laboratory mice through molecular mechanisms that are also relevant in humans.

"Triclosan's increasing detection in environmental samples and its increasingly broad use in consumer products may overcome its moderate benefit and present a very real risk of liver toxicity for people, as it does in mice, particularly when combined with other compounds with similar action," said Robert H. Tukey, PhD, professor in the departments of Chemistry and Biochemistry and Pharmacology. 

Tukey, Hammock and their teams, including Mei-Fei Yueh, PhD, found that triclosan disrupted liver integrity and compromised liver function in mouse models. Mice exposed to triclosan for six months (roughly equivalent to 18 human years) were more susceptible to chemical-induced liver tumors. Their tumors were also larger and more frequent than in mice not exposed to triclosan.

The study suggests triclosan may do its damage by interfering with the constitutive androstane receptor, a protein responsible for detoxifying (clearing away) foreign chemicals in the body. To compensate for this stress, liver cells proliferate and turn fibrotic over time. Repeated triclosan exposure and continued liver fibrosis eventually promote tumor formation.

Triclosan is perhaps the most ubiquitous consumer antibacterial. Studies have found traces in 97 percent of breast milk samples from lactating women and in the urine of nearly 75 percent of people tested. Triclosan is also common in the environment: It is one of the seven most frequently detected compounds in streams across the United States.

More about this study plus a discussion about the FDA's lack of action. From The Atlantic:

The Ingredient to Avoid in Soap

Breast milk contains hundreds of species of bacteria.From the December 8, 2013 Scientific American:

The bacteria in breast milk

Several recent studies have found that breast milk contains a healthy dose of commensal bacteria; all the staphylococci, streptococci, and lactic acid bacteria that are found in the infant gut. This isn’t just bacteria from the skin which have contaminated the samples, but bacteria that have come from inside the breast as an integral component of the milk.

In a study of 16 women it was found that while each milk sample contained hundreds of different bacterial species, around half of the microbiotic community was made up of nine species present in all samples. The other half varied from person to person. This pattern is also found in human gut microbes; a core set present in all individuals along with a large diversity of separate species to make up a unique individual microbiome.

So how do bacteria get into breast milk? Some of them may come from the mouth of the baby. During feeding the skin of both the mother and baby will be in contact with the baby’s open mouth and a certain amount of flow-back can occur between the mouth and nipple. More excitingly it’s been suggested that immune cells in the mothers gut may be able to pick up bacteria and carry them around the body using the lymphatic system. The lymphatic system is a network of vessels used to transport blood plasma. It’s a main highway for immune cells inside the body and is also involved in the absorption and transports of fats.

Like all humans, infants have a range of bacteria within their gut. It looks like these bacteria are initially supplied from the mother’vaginal and skin bacteria, before being replaced by bacteria from the breast milk. Researchers also found that when babies started eating solid food a whole new range of bacteria was introduced, forming the gut microbiome that persisted into adulthood.