Tuesday, November 2, 2010

CLIMATE CHANGE MAY CREATE TIPPING POINTS FOR POPULATIONS, NOT JUST SPECIES

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As Earth's climate warms, species are expected to shift their geographical ranges away from the equator or to higher elevations.

While scientists have documented such shifts for many plants and animals, the ranges of others seem stable.

When species respond in different ways to the same amount of warming, it becomes more difficult for ecologists to predict future biological effects of climate change--and to plan for these effects.

In a study published in the journal Nature, University of Wyoming ecologist Daniel Doak and Duke University ecologist William Morris report on a long-term study of arctic and alpine plants.

The results show why some species may be slow to shift their geographic ranges in the face of climate change, and why we might expect to see sudden shifts as warming continues.

"This study illustrates the critical need for long-term research to address our most pressing ecological challenges," says Saran Twombly, program director in the National Science Foundation (NSF)'s Division of Environmental Biology, which funded the research.

"Without the temporal and spatial scales employed here, we have little hope of understanding the complex ways in which organisms will respond to climate change."

The plant species targeted by Morris and Doak range from populations in the high mountains of Colorado and New Mexico to species growing along the arctic coastline in far northern Alaska.

These regions include habitats that have undergone substantial climate change, leading to the expectation, says Doak, that--especially at the southern edge of their range--populations of the plants should be collapsing.

However, after studying the growth and survival of tens of thousands of individual plants over six years, the researchers show a more complex pattern of responses.

At the southern edge of their ranges, the plants indeed show negative effects of warmer conditions, with lower survival.

"But in most years," says Doak, "these effects are balanced by plants in the south growing more rapidly, so that populations there are no less stable than those in the north."

The opposing trends mean that under current conditions, even across the huge range of conditions Morris and Doak studied, populations of these plants are doing equally well across 30 degrees of latitude--one-third the distance from the equator to the north pole.

However, the researchers' results don't indicate that these plants, or other species, will be unaffected by warming conditions.

By looking at the performance of individual plants in particularly hot and cold years, they found that the compensatory effects across moderately cold to moderately warm years (lower survival balanced by more rapid growth) will not hold up with increased warming.

Instead, in the warmest years at all study sites, both survival and growth of the plants fell.

"Up to a point," says Doak, "we may see little effect of warming for many organisms. But past a climatic tipping point, the balance of opposing effects of warming will likely cease, leading to subsequent rapid declines in populations."

While this tipping point will be different for each species, responses of natural populations to gradual shifts in climate will not necessarily in turn be gradual.

"We shouldn't interpret a lack of ecological response to past warming to mean that little or no effects are likely in the future," says Doak.

The researchers' work also points to a methodology with which to better understand and predict how climate effects on one species will combine to create overall population-wide effects.

"A key part of this approach is the need for long-term studies so we can observe and use the rare years with extreme climates to anticipate what the average future climate will bring," Doak says.

(Photo: Tracy Feldman)

National Science Foundation

FIRST DIRECT EVIDENCE THAT RESPONSE TO ALCOHOL DEPENDS ON GENES

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Many studies have suggested that genetic differences make some individuals more susceptible to the addictive effects of alcohol and other drugs. Now scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory provide the first experimental evidence to directly support this idea in a study in mice reported in the October 19, 2010, issue of Alcoholism Clinical Experimental Research.

The study compared the brain’s response to long-term alcohol drinking in two genetic variants of mice. One strain lacked the gene for a specific brain receptor known as dopamine D2, which responds to dopamine, the brain’s “feel good” chemical, to produce feelings of pleasure and reward. The other strain was genetically normal. In the dopamine-receptor-deficient mice (but not the genetically normal strain), long-term alcohol drinking resulted in significant biochemical changes in areas of the brain well know to be involved in alcoholism and addiction.

“This study shows that the effects of chronic alcohol consumption on brain chemistry are critically influenced by an individual’s pre-existing genetic makeup,” said lead author Panayotis (Peter) Thanos, a neuroscientist with Brookhaven Lab and the National Institute on Alcohol Abuse and Alcoholism (NIAAA) Laboratory of Neuroimaging. “Our findings may help explain how someone’s genetic profile can interact with the environment — in this case, chronic alcohol drinking — to produce these changes only in some individuals, but not in others with a less vulnerable genetic profile. The work supports the idea that genetic screening could provide individuals with valuable information relevant to understanding risks when deciding whether or not to consume alcohol.”

The scientists were particularly interested in the dopamine system because a wide range of studies at Brookhaven and elsewhere suggest that deficiency in dopamine D2 receptors may make people (and animals) less able to experience ordinary pleasures and more vulnerable to alcoholism, drug abuse, and even obesity. The ability to breed mice completely lacking the D2 gene — and carefully control and monitor their alcohol intake — made it possible to test the effect of this genetic influence on the brain’s response to chronic alcohol drinking for the first time in this study.

The scientists studied mice lacking the dopamine D2 gene and genetically normal mice, all males. They divided these groups further, giving half of each group only water to drink, and the other half a solution of 20 percent ethanol to simulate heavy drinking.

After six months, the scientists compared the levels of a different kind of brain receptor known as cannabinoid type 1 (CB1) in various parts of the brain in all four groups. CB1 receptors are located near dopamine receptors and are also known to play a role in alcohol consumption and addiction. Many findings indicate that the two types of receptors may influence one another.

In the current study, the scientists found that water-drinking animals without D2 receptors had increased, or up-regulated, levels of CB1 receptors in brain regions associated with addiction, compared with water-drinking normal control animals. “That may mean that active D2 receptors in normal mice somehow inhibit the expression of the CB1 gene; and therefore, the absence of D2 leads to increased CB1 expression,” Thanos said.

Chronic alcohol consumption, however seemed to negate this effect: D2-deficient mice that drank alcohol showed about half the CB1 levels compared to the D2-deficient water drinkers.

“We observed an up-regulation of CB1 in D2-deficient mice that was reversed by chronic ethanol intake,” Thanos said. “This down-regulation of CB1 after alcohol intake in the D2-deficient animals could underlie the lower reinforcing effects of ethanol in these mice,” he added.

Individuals experiencing lower-than-normal reinforcement, or reward, in response to a drug may be more likely than those experiencing a normal response to seek out further stimulation of the brain’s reward centers by continued or increasing use of the drug.

To test this hypothesis, future research will explore the effects of CB1 down-regulation on animals’ drinking behavior when given a choice between alcohol and water. The scientists will also conduct similar studies in female mice to investigate the role of gender on the observed findings.

“Further research on the relationship and interaction between genetic makeup and environment will help us better understand the chronic disease of addiction in terms of a series of risk factors that may elevate a person’s vulnerability. This information will be imperative to the public and will help people make more informed decisions about their behaviors,” Thanos said.

(Photo: BNL)

Brookhaven National Laboratory

COMPUTER MODELING OF SWIMMING FISH COULD LEAD TO NEW ROBOTS AND PROSTHETICS

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Scientists at the University of Maryland and Tulane University have developed a computational model of a swimming fish that is the first to address the interaction of both internal and external forces on locomotion. The interdisciplinary research team simulated how the fish's flexible body bends, depending on both the forces from the fluid moving around it as well as the muscles inside. Understanding these interactions, even in fish, will help design medical prosthetics for humans that work with the body's natural mechanics, rather than against them.

This research is published in the October 18, 2010 online early edition of the Proceedings of the National Academy of Sciences.

"When a fish moves in a fluid, muscles contract, but the fluid also moves against the body. So, the amount the body moves depends on the internal muscle force and the external reaction of fluids," explained Eric D. Tytell, who conducted this research as a postdoctoral researcher in the laboratory of Professor Avis Cohen, Department of Biology and Institute for Systems Research. "Previous studies examined body mechanics separately from fluid mechanics because it is a very hard problem to solve. This is the first time that anyone has put together a computational framework to simulate this for large, fast animals like fishes.

Understanding the general principles of animal movement could help to design and inspire engineered systems, including robots and medical prosthetics. This simulation was developed for the lamprey, a primitive vertebrate whose nervous system is being used as a model by Cohen and colleagues to develop prosthetic devices for people with spinal cord injuries.

"The devices may one day help people regain control over their legs and walk again, Cohen said. "We understand to first order the neural circuit that controls the muscles for swimming or walking. Now, for neuroprosthetics, we need to understand how the muscles interact with the body and the environment - our model helps us do that.

Chia-yu Hsu, a postdoctoral researcher at Tulane University, and Tytell performed simulations with different values for various body and fluid properties. One property that they discovered was particularly important in determining how well a fish swims is body stiffness.

Take a lamprey and a barracuda as examples -- if you hold a freshly dead lamprey, it just drops, because it is a very floppy fish, Tytell explains. But if you take a fish like a barracuda, their bodies are stiffer and don't flop much. We wanted to know what difference does the floppy vs. stiff body make? If their muscles produced the same amount of force, then the floppy body, since it bends more, should accelerate more rapidly, but also expend more energy. And the stiff body should accelerate more slowly because it bends less, but once it gets going, it should use less energy.

But in reality, this doesn't happen -- barracudas generally accelerate faster than lampreys. The simulations show that barracudas' muscles are probably stronger than lampreys', matched to the higher body stiffness. That may be why barracudas strike so quickly, Tytell said.

Lisa Fauci, professor of mathematics at Tulane University, has been developing the mathematical models and computational simulations required to gain insight into complex biological systems where flexible structures interact with a surrounding fluid.

"It is incredibly rewarding to work with biologists who embrace scientific computing as an essential facet of research, and to see that our simulations can address fundamental questions in physiology," Fauci said.

"The simulations demonstrate that matching the mechanical properties of future prosthetic devices to the body's natural mechanics will be crucial. We'll have to get the mechanics right," Cohen said.

But the research also provides biologists with quantitative information that can be applied to understand the biodiversity and evolution of fishes.

Evolutionary biologists are interested in figuring out what the selective pressures were that led to a species having certain characteristics, and one of the things that it very important is locomotion. How animals move relates to their ability to find food, locate mates, and to escape predators," explained Tytell. "So this information is likely to have evolutionary importance in how fish evolved mechanically."

The team plans to continue working with the model, using it to examine why different fishes are shaped differently.

"What difference does it make to be shaped like an eel or shaped like a trout?" Tytell says. "We understand pretty well the difference that shape makes for things like submarines that don't bend, but not so well for fishes."

They will also simulate sensory systems to try to figure out how fish maneuver so agilely through turbulent water.

"The first line of defense against external perturbations such as eddies in the water for fishes, or tripping on a rock for humans, isn't the nervous system, but rather the body's mechanics, kind of like the shocks on a car. If we can translate the mechanical stability that living organisms exhibit into the design of robots or prosthetics, we could really advance the technology," Tytell said.

(Photo: U. Maryland)

University of Maryland

SINS OF THE FATHER

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Medical researchers have for the first time shown a link between a father’s weight and diet at the time of conception and an increased risk of diabetes in his offspring.

The finding, reported in the prestigious journal Nature, is the first in any species to show that paternal exposure to a high-fat diet initiates progression to metabolic disease in the next generation.

“We’ve known for a while that overweight mums are more likely to have chubby babies, and that a woman’s weight before and during pregnancy can play a role in future disease in her children, partly due to the critical role the intrauterine environment plays in development,” said study leader Professor Margaret Morris, from UNSW’s School of Medical Sciences.

“But until now, the impact of the father’s environment – in terms of his diet – on his offspring had not been investigated.” The work formed the basis of the PhD study of Dr Sheau-Fang Ng, who showed that paternal environmental factors such as diet and weight are important contributors to disease in the next generation

In the Nature study, male rats were fed a high fat diet to induce obesity and glucose intolerance and then mated with normal weight females. The resulting female offspring exhibited impaired glucose tolerance and insulin secretion as young adults.

“This is the first report of non-genetic, intergenerational transmission of metabolic consequences of a high fat diet from father to offspring,” Professor Morris said.

“A family history of diabetes is one of the strongest risk factors for the disease; however until now, the extent of any influence of non-genetic paternal factors has been unclear.”

Professor Morris said the research showed that overweight fathers can play a role in “programming” epigenetic changes in their offspring, possibly through effects on their sperm caused by their consumption of high-fat food. Epigenetics is a process whereby changes in gene expression – and hence function – can occur even when there are no alterations in the DNA sequence.

Professor Morris said the study expands our understanding of the role environmental factors might play on a child’s physiology and metabolism.

“It adds another level to our understanding of the causes of the growing epidemics in obesity and diabetes,” she said. “While here we studied female offspring, we need to examine whether the effect is also found in males”.

The work was carried out in collaboration with scientists in the UNSW Schools of Medical Sciences and Biotechnology and Biomolecular Sciences, the Garvan Institute, and the University of Adelaide.

(Photo: UNSW)

University of New South Wales

THE REAL MOMMY BRAIN: NEW MOTHERS GREW BIGGER BRAINS WITHIN MONTHS OF GIVING BIRTH

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Motherhood may actually cause the brain to grow, not turn it into mush, as some have claimed. Exploratory research published by the American Psychological Association found that the brains of new mothers bulked up in areas linked to motivation and behavior, and that mothers who gushed the most about their babies showed the greatest growth in key parts of the mid-brain.

Led by neuroscientist Pilyoung Kim, PhD, now with the National Institute of Mental Health, the authors speculated that hormonal changes right after birth, including increases in estrogen, oxytocin and prolactin, may help make mothers’ brains susceptible to reshaping in response to the baby. Their findings were published in the October issue of Behavioral Neuroscience.

The motivation to take care of a baby, and the hallmark traits of motherhood, might be less of an instinctive response and more of a result of active brain building, neuroscientists Craig Kinsley, PhD, and Elizabeth Meyer, PhD, wrote in a special commentary in the same journal issue.

The researchers performed baseline and follow-up high-resolution magnetic-resonance imaging on the brains of 19 women who gave birth at Yale-New Haven Hospital, 10 to boys and nine to girls. A comparison of images taken two to four weeks and three to four months after the women gave birth showed that gray matter volume increased by a small but significant amount in various parts of the brain. In adults, gray matter volume doesn’t ordinarily change over a few months without significant learning, brain injury or illness, or major environmental change.

The areas affected support maternal motivation (hypothalamus), reward and emotion processing (substantia nigra and amygdala), sensory integration (parietal lobe), and reasoning and judgment (prefrontal cortex).

In particular, the mothers who most enthusiastically rated their babies as special, beautiful, ideal, perfect and so on were significantly more likely to develop bigger mid-brains than the less awestruck mothers in key areas linked to maternal motivation, rewards and the regulation of emotions.

The mothers averaged just over 33 years in age and 18 years of school. All were breastfeeding, nearly half had other children and none had serious postpartum depression.

Although these early findings require replication with a larger and more representative sample, they raise intriguing questions about the interaction between mother and child (or parent and child, since fathers are also the focus of study). The intense sensory-tactile stimulation of a baby may trigger the adult brain to grow in key areas, allowing mothers, in this case, to “orchestrate a new and increased repertoire of complex interactive behaviors with infants,” the authors wrote. Expansion in the brain’s “motivation” area in particular could lead to more nurturing, which would help babies survive and thrive physically, emotionally and cognitively.

Further study using adoptive mothers could help “tease out effects of postpartum hormones versus mother-infant interactions,” said Kim, and help resolve the question of whether the brain changes behavior or behavior changes the brain – or both.

The authors said that postpartum depression may involve reductions in the same brain areas that grew in mothers who were not depressed. “The abnormal changes may be associated with difficulties in learning the rewarding value of infant stimuli and in regulating emotions during the postpartum period,” they said. Further study is expected to clarify what happens in the brains of mothers at risk, which may lead to improved interventions.

In their “Theoretical Comment,” Kinsley and Meyer, of the University of Richmond, connected this research on human mothers to similar basic research findings in laboratory animals. All the scientists agreed that further research may show whether increased brain volumes are due to growth in nerve cells themselves, longer and more complex connections (dendrites and dendritic spines) between them, or bushier branching in nerve-cell networks.

American Psychological Association

NEW INDUSTRIAL APPLICATION FOR REVOLUTIONARY FORENSIC METAL FINGERPRINTING TECHNIQUE

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Groundbreaking research into fingerprint detection developed at the University of Leicester now has an industrial application, thanks to a new invention by the scientist who developed the technique.

Dr John Bond's method of identifying fingerprints on brass bullet-casings, even after they have been wiped clean, was based on the minuscule amounts of corrosion which can be caused by sweat. First announced in 2008, this breakthrough was cited as one of the technologies 'most likely to change the world' by a panel of experts for BBC Focus magazine and was included in Time magazine's list of '50 best inventions of the year'.

Now, working with scientists in the University of Leicester Department of Chemistry, Dr Bond has applied the same technique to industry by developing a simple, handheld device which can measure corrosion on machine parts. Corrosion leads to wear and tear and needs to be carefully monitored so that worn parts are replaced at the appropriate time so this invention should prove a boon to the manufacturing sector.

"This is a new, quick, cheap and easy way of measuring the extent of corrosion on copper and copper based alloys, such as brass," explains Dr Bond, who is an Honorary Research Fellow in the University's Forensic Research Centre and Scientific Support Manager at Northamptonshire Police.

"It works by exploiting the discovery we made during the fingerprint research – that the corrosion on brass forms something called a 'Schottky barrier' – and we use this to see how much the metal has corroded.

"Such measurements can already be made but this is quick, cheap and easy and can be performed 'in the field' as it works off a nine-volt battery."

Dr Bond said: "Measuring corrosion of metal such as brass is important to ensure that machinery does not operate outside its safe limits.

"This could be anything from checking that a water pipe will not burst open to ensuring that the metal on an airplane is not corroded. This could lead, for instance, to the wheels falling off a jet. Having a corrosion measurement means for copper and alloys such as brass that is quick portable and cheap enables metals to be tested in situ with no prior set up of a corrosion measuring device.

"Also, rather than simply saying that the brass is corroding (as a technique such as weighing the brass would) this technique enables the type of corrosion to be determined (i.e. copper oxide or zinc oxide corrosion). As to which one it is gives clues as to how severe the corrosion is.

"This can be done already with something like X-ray photoelectron Spectroscopy (XPS) but that is lab based and very expensive to use. Our technique works off a 9-volt battery. In that sense, it won't tell you any more than XPS can, it is just quicker, cheaper and easier.

"A common use of brass in industry is heat exchangers as brass is a good conductor of heat. If these are water based, then seeing how the water is corroding the brass is useful. Also, you simply need to be able to touch the brass with a probe, there is no other setting up required. It's as easy as taking your temperature with a thermometer."

There is much research on inhibiting the corrosion of brass because of its use in heat exchangers and industrial pipe work, this technique enables the degree of corrosion to be easily measured.

A description of the prototype device has been published in the journal Review of Scientific Instruments. Dr Bond and his colleagues are now looking for a company which could exploit the invention and place it on the market.

(Photo: U. Leicester)

University of Leicester

EAT SAFER: NOVEL TECHNOLOGY DETECTS UNKNOWN FOOD PATHOGENS

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Technologies for rapid detection of bacterial pathogens are crucial to maintaining a secure food supply.

Researchers from the School of Science at Indiana University-Purdue University Indianapolis (IUPUI) and the Bindley Bioscience Center at Purdue University have developed a novel approach to automated detection and classification of harmful bacteria in food. The investigators have designed and implemented a sophisticated statistical approach that allows computers to improve their ability to detect the presence of bacterial contamination in tested samples. These formulas propel machine-learning, enabling the identification of known and unknown classes of food pathogens.

The study appears in the October issue of the journal Statistical Analysis and Data Mining.

"The sheer number of existing bacterial pathogens and their high mutation rate makes it extremely difficult to automate their detection," said M. Murat Dundar, assistant professor of computer science in the School of Science at IUPUI and the university's principal investigator of the study. "There are thousands of different bacteria subtypes and you can't collect enough subsets to add to a computer's memory so it can identify them when it sees them in the future. Unless we enable our equipment to modify detection and identification based on what it has already seen, we may miss discovering isolated or even major outbreaks."

To detect and identify colonies of pathogens such as listeria, staphylococcus, salmonella, vibrio and E. coli based on the optical properties of their colonies, the researchers used a prototype laser scanner, developed by Purdue University researchers. Without the new enhanced machine-learning approach, the light-scattering sensor used for classification of bacteria is unable to detect classes of pathogens not explicitly programmed into the system's identification procedure.

"We are very excited because this new machine-learning approach is a major step towards a fully automated identification of known and emerging pathogens in real time, hopefully circumventing full-blown, food-borne illness outbreaks in the near future. Ultimately we would like to see this deployed to tens of centers as part of a national bio-warning system," said Dundar.

"Our work is not based on any particular property of light scattering detection and therefore it can potentially be applied to other label-free techniques for classification of pathogenic bacteria, such as various forms of vibrational spectroscopy," added Bartek Rajwa, the Purdue principal investigator of the study.

Dundar and his colleagues believe this methodology can be expanded to the analysis of blood and other biological samples as well.

(Photo: IUPUI School of Science)

Indiana University-Purdue University Indianapolis

STUDY CONFIRMS: WHATEVER DOESN'T KILL US CAN MAKE US STRONGER

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We've all heard the adage that whatever doesn't kill us makes us stronger, but until now the preponderance of scientific evidence has offered little support for it.

However, a new national multi-year longitudinal study of the effects of adverse life events on mental health has found that adverse experiences do, in fact, appear to foster subsequent adaptability and resilience, with resulting advantages for mental health and well being.

The study, "Whatever Does Not Kill Us: Cumulative Lifetime Adversity, Vulnerability and Resilience," to be published in the forthcoming issue of the Journal of Personality and Social Psychology, is available on the website of the American Psychological Association at http://psycnet.apa.org/psycinfo/2010-21218-001/.

It examined a national sample of people who reported their lifetime history of adverse experiences and several measures of current mental health and well being.

Authors are Mark Seery, PhD, assistant professor of psychology at the University at Buffalo; E. Alison Holman, PhD, assistant professor of nursing sciences, University of California, Irvine; and Roxane Cohen Silver, PhD, professor of psychology and social behavior and medicine at UC Irvine.

Seery, senior author of the study, says previous research indicates that exposure to adverse life events typically predicts negative effects on mental health and well-being, such that more adversity predicts worse outcomes.

But in this study of a national survey panel of 2,398 subjects assessed repeatedly from 2001 to 2004, Seery and co-researchers found those exposed to some adverse events reported better mental health and well-being outcomes than people with a high history of adversity or those with no history of adversity.

"We tested for quadratic relationships between lifetime adversity and a variety of longitudinal measures of mental health and well-being, including global distress, functional impairment, post-traumatic stress symptoms and life satisfaction," Seery says.

"Consistent with prior research on the impact of adversity, linear effects emerged in our results, such that more lifetime adversity was associated with higher global distress, functional impairment and PTS symptoms, as well as lower life satisfaction.

"However," says Seery, "our results also yielded quadratic, U-shaped patterns, demonstrating a critical qualification to the seemingly simple relationship between lifetime adversity and outcomes.

"Our findings revealed," he says, "that a history of some lifetime adversity -- relative to both no adversity or high adversity -- predicted lower global distress, lower functional impairment, lower PTS symptoms and higher life satisfaction."

The team also found that, across these same longitudinal outcome measures, people with a history of some lifetime adversity appeared less negatively affected by recent adverse events than other individuals.

Although these data cannot establish causation, Seery says the evidence is consistent with the proposition that in moderation, experiencing lifetime adversity can contribute to the development of resilience.

"Although we studied major lifetime adversity," he says, "there is reason to believe that other relatively mundane experiences should also contribute to resilience.

"This suggests that carefully designed psychotherapeutic interventions may be able to do so, as well, although there is much work that still needs to be done to fully understand resilience and where it comes from."

(Photo: U. Buffalo)

University of Buffalo

BREAST MILK STUDY FURTHERS UNDERSTANDING OF CRITICAL INGREDIENTS

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In a study published online in advance of print in Breastfeeding Medicine, the official journal of the Academy of Breastfeeding Medicine, researchers at The University of Texas Health Science Center at Houston (UTHealth) announced the results of an observational study showing that the levels of nitrite and nitrate in breast milk change during the initial days after birth, which the scientists argue is to accommodate the changing physiologic requirements of developing babies.

“This research shows the essential nature of nitrite in breast milk,” said Nathan Bryan, Ph.D., the study’s senior author and an assistant professor at the UTHealth Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases (IMM). “While the nitrite and nitrate composition of breast milk has been reported, this is the first study to demonstrate the changing levels of nitrite and nitrate early on.”

Dietary nitrite and nitrate are part of a normal diet. When people eat nitrate-rich vegetables, the bacteria in their mouths and stomachs converts the nitrate into nitrite, which in turn aids in the production of nitric oxide. Nitric oxide keeps blood pressure levels normal, fights infection and supports the nervous system. Animal studies suggest nitric oxide might even guard against heart attack and stroke.

The scientists measured nitrite and nitrate levels in breast milk during the first three days of birth (colostrum), days three to seven (transition milk) and eight or more days (mature milk). Seventy-nine patient samples were analyzed and they were donated by mothers who were either admitted to Memorial Hermann - Texas Medical Center (TMC) in Houston for childbirth or who were visiting a UT Physicians’ clinic in the TMC.

Bryan said colostrum has significantly higher concentrations of nitrite and significantly lower concentrations of nitrate than both transition and mature milk, which he believes may be nature’s way of providing nitric oxide to the newborns whose gastrointestinal tract is not yet colonized by bacteria that convert nitrate to nitrite. Nitrite-rich colostrum overcomes this deficit, he said.

Human milk concentrations of colostrum, transition milk and mature milk were 0.08 mg/100ml nitrite and 0.19 mg/100ml nitrate, 0.001 mg/100ml nitrite and 0.52 mg/100ml nitrate, and 0.001 mg/100ml nitrite and 0.3 mg/100ml nitrate, respectively.

To corroborate their findings, researchers analyzed milk samples taken from two women on 14 consecutive days and the scientists observed the same change in the nitrite and nitrate levels.

Some women cannot nurse their children due to health issues. Other women may choose not to breastfeed so the investigators also measured the level of dietary nitrite and nitrate in alternative sources of newborn nutrition: formula, cow milk and soy milk.

Noting that breast milk is considered more beneficial to newborns than these others sources of nutrition, Bryan said the study revealed that colostrum contains the highest amount of nitrite of any of the milk products tested.

“This is another difference that has been noted between mother’s milk and formula,” said Pamela Berens, M.D., one of the study’s authors and a professor of obstetrics, gynecology and reproductive science at the UTHealth Medical School. “Studies like this help us better understand the benefits of breast milk.”

The World Health Organization (WHO) and the American Academy of Pediatrics recommend exclusive breastfeeding for the first six months of life. It is good for both mothers in that it can reduce the risk of breast and ovarian cancers and for babies in that it protects against disease and infection.

Bryan said the concentration of nitrite and nitrate found in breast milk calls into question the amount recommended by the Joint Food and Agricultural Organization/WHO Acceptable Daily Intake (WHO ADI) standards. Total daily nitrite intake for nursing infants is 20 times that recommended by the WHO ADI, he said.

Too much nitrite/nitrate or too little nitrite/nitrate can be bad for health, Bryan said. Much of the concern about nitrite/nitrate levels stems from a condition associated with too much nitrite in the blood system called methemoglobinema (blue baby syndrome). Typically, this is caused by infant formulas made from bacteria and nitrate contaminated well water. The levels of nitrite and nitrate that cause blue baby syndrome are much higher than what is present in breast milk, he said.

“These data, considered together with nitrite and nitrate exposure estimates from foods, show that humans are exposed from birth to dietary sources of nitrite and nitrate. The presence of nitrite and nitrate in breast milk argues for a fundamental role in physiology, which is supported by a number of basic science studies and some clinical trials,” Bryan said.

“Contrary to the prevailing scientific opinion about the biological effects of nitrite and nitrate, our data support the view that humans may require these dietary components from birth - from nature's most perfect food,” said Norman G. Hord, Ph.D., M.P.H., R.D., the study’s lead author and an associate professor of food science and human nutrition at Michigan State University (MSU).

(Photo: U. Texas)

The University of Texas Health Science Center at Houston

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