Issue Date: November 2022
Human Milk and Nutrition Battle Long-term Effects of a Dangerous Intestinal Disease in Preterm Infants
- Previous research has shown that breast milk can help mitigate the deleterious effects of necrotizing enterocolitis (NEC), a life-threatening disease of the gut that can result in the death of intestinal tissue.
- A long-term prospective study assessed whether factors such as nutritional content (preterm- versus term-infant formula), as well as being fed breast milk affected risk of gut infection and intelligence in a cohort of preterm infants.
- Human milk was associated with a lowered risk of infection and NEC in infants.
- Neonatal infection or NEC was associated with subsequent lower IQ at 7 and 30 years.
- Nutritional content of milk fed to infants also had a positive effect on intelligence, whether the nutrients were provided in human milk, preterm- or term-infant formula.
Preterm infant birth can be a stressful ordeal for new parents. Tiny babies can suffer from breathing and cardiovascular failure  and in some cases, two to three weeks after acute conditions appear to be improving ; healthcare professionals must watch for infection and necrotizing enterocolitis (NEC). NEC is a disease in which infection causes the tissue of the intestinal tract to become inflamed and die. Dying tissues are known to release free radicals, and exogenous and endogenous insults, such as ischaemia, inflammation, excitotoxicity, and free-radical insults can damage vulnerable tissues during brain maturation . Previous studies have shown NEC is associated with long-term changes to brain microstructure and a decreased IQ . However, infants fed human milk were six to ten times less likely to develop NEC than those fed cow milk. Still, the roles that nutrition and human milk play in preventing NEC and improving intelligence are unclear.
In a newly published long-term cohort study, scientists at UCL Great Ormond Street Institute of Child Health in London, England, reported their efforts to tease apart the mechanisms behind how infection, nutrition, human milk, and intelligence are interrelated .
“There’s a lot of talk about how breast milk is better for the child and better for brain development,” says Winok Lapidaire, the lead author of the new paper. “But it’s always difficult to tease out why it’s better and the sort of mechanistic pathways behind that—particularly because you can’t really experiment with nutrition.”
Preterm infants miss out on the rapid growth over the third trimester, that is made possible by the nutrients they receive in the womb and without needing to expend calories for temperature regulation or gas exchange. As such, after birth they have higher nutritional requirement than infants born full-term. Human milk contains many important factors such as anti-inflammatory agents, growth factors, and immune cells, but over the first few weeks after preterm delivery, protein levels decrease . This was unknown in the 1980s when Lapidaire’s study began, but what makes this study so interesting is that the infants have now been followed for 30 years.
The study began with 926 preterm infants born in the 1980s across five hospitals in London. Researchers at the time were interested in testing the effects of preterm versus term formulas, so some of the infants were fed the more nutritious preterm formulas, while others were fed term formula. Additionally, some of the infants received banked donor breast milk from the hospital and/or human milk from their mothers. Whether or not the infants developed infections was noted, and the controls were given IQ tests at ages 7, 15, 20, and 30 .
Lapidaire and her colleagues found that a 10 percent increase in milk intake—from either banked or maternal milk—was associated with an 8–12 percent lower chance of developing NEC. Additionally, at ages 7 and 30, subjects who had suffered NEC in infancy had lower Full Scale IQ and Performance IQ scores. Having the less nutritious term formula was associated with increased risk of NEC .
Overall, the researchers found that both human milk and adequate nutrition were important in combatting the maleffects of NEC. Human milk reduced the risk of infection, which subsequently can affect Performance IQ and Full Scale IQ. Nutrient content also had a positive association with higher Verbal IQ scores, regardless of whether the infants were fed human milk .
A long-term randomized control study coming from the same cohort is one of the things that made this study unique, Lapidaire says. “You wouldn’t be able to do this before because there weren’t enough surviving infants,” she explains.
Lapidaire isn’t certain what particular elements of human milk may reduce the risk of infection and subsequently help with brain development, but there are many components in milk that are anti-inflammatory or immunity-boosting and can stave off infection or brain damage.
Lapidaire looks forward to potentially following this cohort as they enter their 40s, and notes that MRI scans on subjects’ brains could also add a level of detail to the present study. In addition, she’s interested in looking at other health outcomes such as cardiovascular health.
- Premature Birth – Symptoms and Causes. Mayo Clinic. [Internet]. Available from: https://www.mayoclinic.org/diseases-conditions/premature-birth/symptoms-causes/syc-20376730.
- Necrotizing Enterocolitis (NEC). National Institute of Health. [Internet]. Available from: https://www.nichd.nih.gov/health/topics/nec#:~:text=Necrotizing%20enterocolitis%2C%20or%20NEC%2C%20is,The%20condition%20typically%20affects%20infants.
- Volpe JJ. Brain injury in premature infants: a complex amalgam of destructive and developmental disturbances. Lancet Neurol. 2009; 8: 110–124.
- Rand KM, Austin NC, Inder TE, Bora S, Woodward LJ. Neonatal infection and later neurodevelopmental risk in the very preterm infant. J. Pediatr. 2015; 170: 97–104.
- Lapidaire W, Lucas A, Clayden JD, Clark C, Fewtrell MS. Human milk feeding and cognitive outcome in preterm infants: the role of infection and NEC reduction. Pediatr Res. 2022;91: 1207–1214.
- Underwood MA. Human milk for the premature infant. Pediatr Clin North Am. 2013; 60(1): 189-207.
- Some kinds of cheese are rich in vitamin K, a nutrient essential to healthy bones.
- Daily consumption of Jarlsberg cheese, but not Camembert, improved several circulatory protein markers of bone health.
- More studies are needed to confirm if Jarlsberg cheese could act as a preventive remedy for osteoporosis.
When treating osteoporosis, a condition where bones become brittle and prone to fractures, doctors usually recommend dietary supplements containing vitamin D, vitamin K2, and calcium. Although milk and milk products are typically rich in these nutrients, cheese is unique in its vitamin K2 content, since the bacteria used in fermentation can produce variants of this nutrient that may be more efficiently absorbed and used by human tissues. The vitamin K2 content of cheese varies depending on the bacterial strains used; the Norwegian cheese Jarlsberg, for instance, is made by lactic acid bacteria that produce a version of vitamin K2 known as MK-9 in high quantities.
In a new study, Helge Einar Lundberg of Skjetten Medical Center in Norway and his colleagues tested whether eating a daily dose of Jarlsberg could boost markers of bone health in healthy women. Before embarking on a clinical trial, the team confirmed that eating about 57 grams of cheese in one day—approximately 4–6 slices of Jarlsberg—increased circulating vitamin K2 concentrations and serum osteocalcin, a blood biomarker of bone health .
The team then recruited 68 healthy, premenopausal women between the ages of 19 and 52. The participants were split into two groups: one group ate 57 grams of Jarlsberg every day for 6 weeks, and the other group consumed Camembert cheese. The Camembert used in the study contained no vitamin K, whereas the Jarlsberg contained approximately 80 μg of vitamin K and its variants per 100 g of cheese. After the initial 6-week period, the Camembert consumers also switched to Jarlsberg for another 6-week span. (TINE SA, a Norwegian dairy product cooperative, provided all the cheese used for the trial and also funded the study). The participants were asked to avoid other cheese for the duration of the study but otherwise continued with their daily diets and routines.
At the end of each 6-week period, the researchers tested blood samples for vitamin K2 and its variants, osteocalcin, a protein named PINP that’s thought to be one of the best biomarkers of bone formation, and certain forms of collagen that indicate bone formation and breakdown. They also measured typical clinical parameters such as cholesterol and blood lipids.
Both groups had slight increases in their levels of serum triglycerides and cholesterol in the first six weeks of participating in the study. The team found higher levels of the PINP protein in the women who ate Jarlsberg. Serum osteocalcin also increased significantly from an average of 21.4 ng/ml to 25.8 ng/ml in the women who ate Jarlsberg daily but not in those who ate Camembert. But after they switched to Jarlsberg for the second half of the study, total serum osteocalcin concentrations rose in this group too . “That’s how we found out this effect is specific to Jarlsberg cheese and not all kinds of cheese,” Lundberg said. “We were very surprised to see these results.”
The data suggest that Jarlsberg has a significant stimulatory effect on serum osteocalcin, according to the authors. The work is “probably the first time” a dietary intervention has shown a significant increase in the total osteocalcin concentration in a randomized controlled trial, they wrote in the paper.
The proteins and serum biomarkers used in this study serve as proxies to gauge bone health, because it requires approximately a year for changes in bone mass and density to become noticeable. Thus, longer-running studies are needed to confirm whether eating Jarlsberg cheese also affects bone structure in humans. These studies could be conducted in people with borderline, untreated osteoporosis, the authors suggest.
But the increase in osteocalcin isn’t only due to the vitamin K2 present in Jarlsberg, they add. This cheese also contains a compound named 1,4-dihydroxy-2-naphthoic acid (DHNA), formed by propionic acid bacteria in the process of synthesizing vitamin K2. In studies of mice with ovaries removed, researchers have found that vitamin K2 could not stimulate osteocalcin production but DHNA could do so . As a result, the authors of this study suggest that “DHNA is the possible key to the total osteocalcin stimulatory effect of Jarlsberg.” If future studies confirm this effect, the molecule could yield possible new therapies for osteoporosis and to improve bone health.
- Lundberg HE, Holand T, Holo H, Larsen S. Increased serum osteocalcin levels and vitamin K status by daily cheese intake. International Journal of Clinical Trials. 2020 May;7(2):55-65.
- Lundberg HE, Glasø M, Chhura R, Shukla AA, Austlid T, Sarwar Z, Hovland K, Iqbal S, Fagertun HE, Holo H, Larsen SE. Effect on bone anabolic markers of daily cheese intake with and without vitamin K2: a randomised clinical trial. BMJ Nutrition, Prevention & Health. 2022 Jun 30:e000424.
- Kita K, Yamachika E, Matsubara M, Tsujigiwa H, Ishida N, Moritani N, Matsumura T, Mizutani M, Fujita Y, Takabatake K, Ejima K. Anti-osteoporosis effects of 1, 4-dihydroxy-2-naphthoic acid in ovariectomized mice with increasing of bone density. Journal of Oral and Maxillofacial Surgery, Medicine, and Pathology. 2016 Jan 1;28(1):66-72.
- Human milk oligosaccharides (HMOs) promote the growth of beneficial gut bacteria and modulate immune responses.
- In germ-free mice, HMOs boosted immune responses both in intestinal cells and the rest of the body.
- Future studies could reveal a therapeutic use for HMO supplements in pills or infant formula.
In 2013, Laxmi Yeruva was not just a researcher—she was also a new mother trying to figure out the best foods for her baby. Like many parents, Yeruva breastfed her infant and supplemented his diet with formula. The personal experience fueled her wonder about the chemistry of human milk.
As a molecular microbiologist and immunologist at Arkansas Children’s Nutrition Center in Little Rock, part of the United States Department of Agriculture-Agricultural Research Service (USDA-ARS), Yeruva homed in on one component: human milk oligosaccharides, also known as HMOs. These short, complex carbohydrate molecules are the third-most abundant component in human milk, preceded only by lactose and fats. More than 160 different HMOs have been identified thus far. “But only a handful have been extensively studied,” Yeruva said in an interview.
In previous studies, researchers found that HMOs promote the growth of beneficial bacteria in the intestines of animal models and studies of infants. These chemicals also block pathogens from binding to immune cells and can thereby reduce infection rates in the GI tract. In addition to boosting the growth of the gut microbiome, HMOs also appear to modulate immunity, such as by improving responses to the influenza vaccine in a study conducted in mice .
But all these studies were conducted in the presence of gut bacteria, Yeruva said. Could HMOs have direct effects on the immune system in the absence of bacteria?
In a recent study, Yeruva and her colleagues set out to identify the effects of HMOs in the absence of bacteria by studying these molecules in germ-free mice . The team treated 21-day-old germ-free mice with a pool of HMOs isolated from human milk—not just a subset of these molecules. The team fed mice a 15 mg/day HMO dose each day for either 7 or 14 days and then euthanized them either 28 or 35 days later. Another set of mice were kept alive for 50 days. In addition to the HMOs, the mice had unlimited amounts of food and water. For each time span studied, the researchers also maintained a control group of animals as a comparison to understand the effects of HMOs.
When they ended the treatment, the researchers studied the physical development of intestinal tissues and changes in gene expression that resulted from feeding the HMOs. The intestines of animals fed the HMOs had shallower folds and glands. It’s still a mystery why HMOs in the absence of microbes appear to have this effect, Yeruva says. “I’m still trying to understand what this means.”
In the intestinal tissue, the presence of HMOs triggered the expression of genes necessary for their transport, absorption, and secretion. The researchers also found that HMOs had a strong impact on the immune response even in the absence of microbes—not just within the gastrointestinal tract but affecting immune cells such as T-regulatory cells and macrophages in the bloodstream. “HMOs truly impact the whole body’s immune response, and their presence could help with responding to vaccines,” Yeruva says.
The data suggest that the impact of HMOs is not solely because of their effects on gut bacteria. These milk molecules affect intestinal metabolism and the immune system even in the absence of the microbiome. “I was pleasantly surprised to see this direct effect without microbiota,” Yeruva says. “I’m excited to see there’s a potential benefit.”
If future studies continue to reveal a strong role for HMOs, they could eventually be used as supplements for sick or immunocompromised children to improve their health, Yeruva says.
- Xiao L, Leusink-Muis T, Kettelarij N, Van Ark I, Blijenberg B, Hesen NA, Stahl B, Overbeek SA, Garssen J, Folkerts G, van’t Land B. Human milk oligosaccharide 2′-fucosyllactose improves innate and adaptive immunity in an influenza-specific murine vaccination model. Frontiers in Immunology. 2018 Mar 9;9:452.
- Rosa F, Sharma AK, Gurung M, Casero D, Matazel K, Bode L, Simecka C, Elolimy AA, Tripp P, Randolph C, Hand TW, Williams KD, LeRoith T, Yeruva L. Human milk oligosaccharides impact cellular and inflammatory gene Expression and immune response. Frontiers in Immunology. 2022;13.
- Concentrations of a critical antioxidant called glutathione decrease in the brain as humans age, making the brain vulnerable to oxidative stress.
- An intervention study on adults over 60 years of age found that after just three months, consuming three cups of 1% milk a day increased brain glutathione levels to those associated with younger adults.
- For older adults, consuming the U.S. recommended daily intake for milk has the potential to improve brain health.
Aging adults have long been encouraged to drink milk to maintain bone strength and prevent osteoporosis . But recent research  suggests it isn’t just the skeleton that benefits from this nutritional advice—drinking milk can improve brain health as well.
As our brains age, the concentration of the antioxidant glutathione (GSH) declines and the risk of oxidative stress and the damage it can cause increases . A new study  found that older adults that drank three cups of milk a day increased the concentration of brain GSH, restoring it to concentrations associated with younger adults after just three months. While we wait for science to come up with the fountain of youth, drinking the recommended daily intake of milk offers the potential to stave off age-related declines caused by oxidative stress.
The Dark Side of Oxygen
Oxidative stress is the unavoidable cost of using oxygen for cellular respiration. The process our cells use to turn food into energy for growth, digestion, reproduction, and immune defense creates unstable oxygen-containing molecules called reactive oxygen species (ROS) as byproducts. At low levels, ROS serve important biological purposes within cells, such as cell signaling. If levels aren’t kept in check, however, ROS accumulation in cells can result in oxidative damage to DNA, RNA, proteins, and the cell membrane, and ultimately cellular death.
Here’s where antioxidants, like GSH, come in. Antioxidants are molecules that can break down ROS and repair damage from oxidation. Humans make some types of antioxidants and others are supplied by the diet. But whatever their source, antioxidants have a full-time job and there is always “help wanted;” ROS are constantly produced throughout the body and the antioxidant supply needs to be constantly replenished to keep up.
Don’t Stress Out
Some things get better with age, like wine, whiskey, and cast-iron skillets. Unfortunately, the human body’s ability to keep up with damage caused by ROS declines over time. The brain is particularly vulnerable to oxidative stress; compared with other organs, it has a higher level of oxidative metabolism and lower concentrations of intracellular antioxidants [3, 4]. Over time, this imbalance favoring ROS can lead to declines in function and has been implicated in the development of neurodevelopmental diseases [1, 5]. The finding that GSH concentrations are lower in brains of people with Alzheimer’s disease and Parkinson’s disease prompted researchers to investigate the possibility of restoring intracellular GSH levels to both prevent and treat these diseases .
Because many antioxidants come from food, a team of researchers from the University of Kansas  decided to focus on associations between diet and brain concentration of GSH. Using a type of scanning technology called magnetic resonance chemical shift imagining, the researchers created regional maps of GSH concentrations in the living human brain and compared them with data from dietary questionnaires of older adults .
The results were somewhat surprising: GSH concentrations in several brain regions (e.g., frontal, parietal) were correlated with daily intake of dairy foods, despite dairy not being a source of GSH . The researchers offered several possible explanations for the correlation: dairy is a good source of calcium and riboflavin, which are involved in the maintenance of GSH; dairy foods (particularly their whey proteins) are rich in cysteine, an amino acid that is necessary for cells to make GSH; dairy is also a source of two other important amino acids needed to make GSH, glutamate and glycine [1, 3]. Although many other foods contain these vitamins, minerals, and amino acids, dairy foods may have had the strongest correlation because they are one of the few to deliver all of them [1, 5].
Having established a correlation between dairy and brain GSH concenration, the team designed a randomized controlled intervention study to explore a causal relationship: Does dairy consumption increase brain GSH concentration ? They enrolled 66 older adults (60–89 years old) who had a low dairy intake (defined as 1.5 servings or less per day) and assigned them to either the control group, who maintained their usual diet, or the intervention group, who consumed three cups per day of 1% milk for the three-month study period. The intervention servings were selected to match the recommended daily intake of dairy (per the Dietary Guidelines for Americans). Magnetic resonance chemical shift imaging was performed on each study participant at baseline and at the end of the intervention period.
Over the three-month study period, the control group had no significant changes in brain GSH concentration. In contrast, the intervention group had a 7.4% increase in parietal GSH, 4.7% increase in fronto-parietal GSH, and an overall brain GSH increase of 4.7% (all of which were statistically significant) . The researchers believe the results were also clinically significant. To put these numbers in perspective, GSH concentrations in brains of older adults are approximately 10% lower than in younger adults, suggesting that just three months of milk drinking was effectively able to restore GSH concentration in some brain regions .
Milk for Longevity
The researchers cleverly named their study MILK (for Milk Intervention for Longevity at the University of Kansas). But does milk drinking actually increase your life span? The study was not designed to test for the effects of higher brain GSH levels on aging and longevity, and there are certainly many factors (e.g., genetics) that determine whether an individual will develop a neurodegenerative disease such as Alzheimer’s. However, if higher levels of brain GSH are associated with lower levels of oxidative stress in the brain, it stands to reason that milk drinking could play a role in mitigating the damage caused by ROS and slowing the associated declines in neural function.
This study is one of only a few intervention studies that have demonstrated an increase in brain GSH concentration and the only one to do so with a dietary intervention (as opposed to a drug intervention) . The ability to influence brain GSH concentration with a commonly consumed food that is widely available offers a simple and safe alternative to drug trials . The fact that they used the recommended daily intake demonstrates that small dietary changes could potentially have large impacts on brain health.
Choi IY, Taylor MK, Lee P, Alhayek SA, Bechtel M, Hamilton-Reeves J, Spaeth K, Adany P, Sullivan DK. Milk intake enhances cerebral antioxidant (glutathione) concentration in older adults: A randomized controlled intervention study. Frontiers in Nutrition. 2022: 1778.
Bains JS, Shaw CA. Neurodegenerative disorders in humans: the role of glutathione in oxidative stress-mediated neuronal death. Brain Research Reviews. 1997 Dec 1;25(3): 335-58.
Choi IY, Lee P, Denney DR, Spaeth K, Nast O, Ptomey L, Roth AK, Lierman JA, Sullivan DK. Dairy intake is associated with brain glutathione concentration in older adults. The American Journal of Clinical Nutrition. 2015 Feb 1;101(2): 287-93.
Cobley JN, Fiorello ML, Bailey DM. 13 reasons why the brain is susceptible to oxidative stress. Redox Biology. 2018 May 1;15: 490-503.
Cacciatore I, Baldassarre L, Fornasari E, Mollica A, Pinnen F. Recent advances in the treatment of neurodegenerative diseases based on GSH delivery systems. Oxidative Medicine and Cellular Longevity. 2012 Oct; 2012.