Category: Health

{Long before Zika virus made it a household word, the birth defect called microcephaly puzzled scientists and doctors — even as it changed the lives of the babies born with it during the pre-Zika era. But new discoveries may help explain what happens in the developing brains that causes babies to be born with small brains and heads.}

Long before Zika virus made it a household word, the birth defect called microcephaly puzzled scientists and doctors — even as it changed the lives of the babies born with it during the pre-Zika era.

But new discoveries reported by an international team of scientists may help explain what happens in the developing brains of babies still in the womb, causing them to be born with small brains and heads.

The findings may also help scientists who are frantically trying to figure out why the Zika virus causes the same issue in some babies born to mothers who catch the virus from a mosquito bite.

In two new papers in the American Journal of Human Genetics, the researchers report new findings about a key protein involved in the process that generates the many new cells required to build a normal size brain. Though the new studies didn’t involve Zika-related microcephaly, they may provide clues that other scientists can use to investigate how Zika virus disrupts brain development.

Stephanie Bielas, Ph.D., a University of Michigan Medical School assistant professor of human genetics who helped lead the new research, says the findings also provide insight into what is required for brains to develop normally.

“There’s so much we don’t understand about human brain development that we’re just starting to uncover,” she says. “This shows the devastating impact of interrupting cell biology critical for this process.”

Interrupted cell division

Both of the new papers focus on the role of citron kinase, a protein important during the process of mitosis, where one cell divides to make two cells. Cell division is the foundation of normal growth and development.

CIT, as the protein is called for short, helps in the final stages of cell division that separates the two “daughter” cells, called cytokinesis. That’s when the two new cells, each with their own copy of the DNA from the original “parent” cell, sever the connections between them.

Years ago, research in animals showed that problems with the gene that contains the instructions for making the animal form of citron kinase could lead to microcephaly. But until now, that link hadn’t been proven in humans. The researchers now say that CIT is critical to building a normally sized human brain.

To make this discovery, the researchers turned to families from Egypt, France and Turkey that had one or more microcephalic babies. Some of them died soon after birth, the others developed intellectual disabilities that result from having a too-small brain.

Studying these babies’ genes and brain tissue gave clues to the importance of CIT, and the problems that arise when the CIT gene is mutated. Where normal brain cells have only one nucleus — the pouch containing the DNA and other important structures — many cells in microcephalic brain tissue had multiple nuclei. This suggested that something had happened to prevent new cells from dividing properly.

Stem cells help the search

Another tool helped the researchers take the study even further: stem cells. With the parents’ permission, they obtained skin cells from the surviving children and used relatively new techniques to transform them into induced pluripotent stem cells (iPSCs). This essentially turns back the clock on the cells, making them able to develop into nearly any type of cell.

The researchers then grew the iPSCs under special conditions that coaxed them to develop into neural progenitor cells — the kind of cells that in a developing embryo grow and divide rapidly to become the future child’s brain.

“There’s a lot of evidence now that in microcephaly, there aren’t sufficient numbers of neural progenitor cells to build the normal-size brain,” says Bielas. “Since the cells that form the structures of the brain, and develop into the different types of cells are born from this pool of actively dividing cells. This aspect of human brain development is a key issue to study.”

Bielas points out that studying rare spontaneous cases of microcephaly — such as those in the families that took part in the study — offers a chance to identify genes important for brain development and understand the impact of deleterious small genetic mutations.

“Often in genetics, we identify seemingly obscure genes as the genetic basis of disorders; we don’t know what they do or where and when they’re active,” she notes. “But in the case of citron kinase, we knew what a mutation in the gene did in animal models. These newly published findings confirm that CIT mutations are not only linked to severe microcephaly in humans, but are also associated with a smooth, unfolded brain surface — a condition known as lissencephaly — that isn’t usually seen in brain disorders linked primarily to defects in neural progenitor cell mitosis.”

Bielas and her colleagues are now growing brain “organoids” — balls of brain tissue grown from iPSCs or human embryonic stem cells with edited genes — to study this issue further. The hope is that by studying microcephaly’s origins in human cells that mimic the developing brain, they can see what might be going on more clearly in human brain development that wouldn’t be detected in animal models. Some Zika researchers are also using this promising model system to study the virus’s effect on human neural progenitor cells.

Bielas is also seeking more families whose babies have been born with non-Zika microcephaly, to contribute skin and DNA samples that may yield even more clues about the condition’s origins. “We need to know how microcephaly genes are contributing to such a profound human disorder,” says Bielas. “It’s a puzzle. So let’s figure it out.”

The research was funded by the National Institutes of Health (HD069624) and several sources of funding in France. Full lists of authors and funding sources are available at the links below.

{Researchers are urging surgeons to reconsider using a particular type of thread for a procedure to prevent premature birth, after new research found this thread was associated with an increased rate of premature birth and baby death compared with a thinner thread.}

Researchers are urging surgeons to reconsider using a particular type of thread for a procedure to prevent premature birth, after new research found this thread was associated with an increased rate of premature birth and baby death compared with a thinner thread.

In a new study, researchers at Imperial College London analysed 671 UK women who received a cervical stitch procedure to prevent miscarriage or premature birth.

The procedure, which is performed on around two million women a year globally, is offered to women deemed at high risk of miscarriage or premature birth. The process involves surgeons placing a stitch in the cervix to hold it closed and delay labour. The closed cervix also acts as a barrier to infection, and so shutting it with a stitch prevents bacteria passing through the cervix and into the womb.

Surgeons use one of two types of thread for the stitch — the majority use a thicker woven thread, and around 20 per cent use a thinner thread.

The study results, published in the journal Science Translational Medicine, suggest the thicker thread is associated with a three-fold increase in rate of baby death in the womb when compared to the thinner thread, and is associated with an increased rate of premature birth. It’s thought the thicker woven structure of the thread encourages the growth of dangerous bacteria.

The team suggest switching to the thinner thread for all procedures could prevent 170,000 premature births globally every year, and 172,000 intrauterine baby deaths every year across the world.

Professor Phillip Bennett, lead author of the study from the Department of Surgery and Cancer at Imperial, said: “Although the cervical stitch procedure still holds benefits for women overall, our results suggest the thicker thread may encourage the growth of potentially dangerous bacteria in the cervix. This may lead to premature birth or even loss of the baby. We strongly advise that the thicker thread — which is currently used in the majority of procedures — only be used in a research setting whilst we thoroughly investigate the risks this may hold.”

Around 50,000 babies are born prematurely ever year in the UK. Defined as birth between 24 and 37 weeks of pregnancy, premature birth is the leading cause of neonatal death in the UK. It is triggered by the cervix opening too early in the pregnancy, causing the baby to start moving down the birth canal. The causes are unknown, but infection in the birth canal is thought to be a factor.

Women are recommended to undergo the cervical stitch procedure if they are deemed at high risk of late miscarriage or premature birth — for instance if they have had a previous miscarriage later in pregnancy or a baby who was born too early.

During the procedure, also called cervical cerclage, surgeons use one of two types of thread to close the cervix. One is a thin nylon thread, around 1mm think and very similar to fishing line, called monofilament. The other is a thicker thread — around 5mm thick — that is composed of smaller threads woven together like a shoe lace. The thicker woven thread — called multifilament — is used in around 80 per cent of procedures as surgeons believe it to be stronger, and more efficient at holding the cervix closed.

In the new study, the team looked at 671 women who had the procedure at five UK hospitals over the last ten years. Around half had the thinner ‘fishing line’ thread, while the other half had the thicker ‘shoe lace’ thread.

The results revealed the thicker thread was associated with increased rate of intrauterine death compared to the thinner thread (15 per cent compared to 5 per cent). The rate of intrauterine death in a normal pregnancy is around 0.5 per cent.

The thicker thread was also associated with an increased rate of preterm birth rate compared to the thinner thread — 28 per cent compared to 17 per cent. The rate of preterm birth among the general population is around 7 per cent, but the cervical stitch procedure is only performed on women already deemed at high risk of premature birth.

To understand the difference in outcomes between procedures using the two threads, the team conducted a second study with 50 women who were due to have the cervical stitch procedure. Half received the thinner thread, while half received the thicker thread.

The team then monitored the women at 4, 8 and 16 weeks after the procedure through ultrasound scans and analysis of bacteria collected using vaginal swabs.

The results suggested that women who received the thicker thread had increased inflammation around the cervix. There was also increased blood flow, which is associated with the cervix opening before labour.

Crucially, the team also found women who received the thicker thread had more potentially harmful bacteria in the vagina and around the cervix.

Dr David MacIntyre, scientific lead of the study, also from the Department of Surgery and Cancer at Imperial explained: “At the beginning of the trial, all women had similar types of naturally-occurring bacteria, called Lactobacillus, in their birth canal and around their cervix. However four weeks after the procedure 45 per cent of the women who received the thicker thread had these harmless bacteria replaced with potentially dangerous bacteria that have previously been associated with poor outcomes during pregnancy, like preterm birth and infection in babies. Women who received the thinner thread maintained normal levels of harmless Lactobacillus bacteria in the birth canal or cervix.”

The team also performed lab-based experiments to examine how easily bacteria grew on the two types of thread. Dr MacIntyre added: “We found potentially dangerous bacteria grew more easily on the thicker thread. This may be because bacteria can latch onto the woven structure of the thick thread more easily than the smooth thin thread. ”

There is a randomised clinical trial of 900 patients currently underway, organised by University of Birmingham, which is looking at the comparative risks of the two threads.

Professor Bennett added: “Our current study suggests the thick multifilament thread is associated with increased risk of complications. Even after factoring in the age and overall health of the patient, this effect still existed. However there are other factors that may influence the risks, such as surgical technique. Only by performing a large randomised clinical trial can we confirm whether the thicker thread itself is triggering complications, to ensure this procedure is as safe and effective as possible for the mother and baby.

Professor Bennett added that anyone concerned about the cervical stitch procedure should speak to their healthcare team.

Professor Jeremy Nicholson, head of the Department of Surgery and Cancer at Imperial, explained the research also provides insights into how a women’s naturally occurring bacteria may influence pregnancy: “This research showed that all 50 women in the second part of the study had a higher level of potentially dangerous bacteria in their birth canal than a healthy pregnant woman — even before undergoing the cervical stitch procedure. This links to our ongoing work that suggests a woman’s bacterial mix in the birth canal — called the microbiome — has an important role in pregnancy. It also shows, for the first time, that treatments that change the bacteria in the vagina may lead to bad outcomes in pregnancy. We need to further investigate the role of a woman’s vaginal microbiome in pregnancy to help ensure more babies are born healthy, and at the right time.

“This is part of a much broader work programme in our department aimed to understand the normal microbial composition of the body, and how changes to this may link to a range of non-infectious diseases.”

Jane Brewin, chief executive of the charity Tommy’s, added: “The really good news is that a safe and proven treatment to prevent pre-term birth has just been made safer by this new finding. A treatment which has been around for many years has been shown to prevent pre-term birth but no-one really understood why it seemed so effective in some people but not in others; now we have a plausible explanation and success rates should improve as a result of this work. It’s important that women who have this procedure ask their obstetrician about what stitch they will receive because clinical practice can take time to catch up with research findings.”

The research was funded by the Genesis Research Trust and the NIHR Imperial Biomedical Research Centre. Dr David MacIntyre was supported by a Career Development Award from the Medical Research Council.

{From middle-age, the brains of obese individuals display differences in white matter similar to those in lean individuals ten years their senior, according to new research led by the University of Cambridge. White matter is the tissue that connects areas of the brain and allows for information to be communicated between regions.}

Our brains naturally shrink with age, but scientists are increasingly recognising that obesity — already linked to conditions such as diabetes, cancer and heart disease — may also affect the onset and progression of brain ageing; however, direct studies to support this link are lacking.

In a cross-sectional study — in other words, a study that looks at data from individuals at one point in time — researchers looked at the impact of obesity on brain structure across the adult lifespan to investigate whether obesity was associated with brain changes characteristic of ageing. The team studied data from 473 individuals between the ages of 20 and 87, recruited by the Cambridge Centre for Aging and Neuroscience. The results are published in the journal Neurobiology of Aging.

The researchers divided the data into two categories based on weight: lean and overweight. They found striking differences in the volume of white matter in the brains of overweight individuals compared with those of their leaner counterparts. Overweight individuals had a widespread reduction in white matter compared to lean people.

The team then calculated how white matter volume related to age across the two groups. They discovered that an overweight person at, say, 50 years old had a comparable white matter volume to a lean person aged 60 years, implying a difference in brain age of 10 years.

Strikingly, however, the researchers only observed these differences from middle-age onwards, suggesting that our brains may be particularly vulnerable during this period of ageing.

“As our brains age, they naturally shrink in size, but it isn’t clear why people who are overweight have a greater reduction in the amount of white matter,” says first author Dr Lisa Ronan from the Department of Psychiatry at the University of Cambridge, “We can only speculate on whether obesity might in some way cause these changes or whether obesity is a consequence of brain changes.”

Senior author Professor Paul Fletcher, from the Department of Psychiatry, adds: “We’re living in an ageing population, with increasing levels of obesity, so it’s essential that we establish how these two factors might interact, since the consequences for health are potentially serious.

“The fact that we only saw these differences from middle-age onwards raises the possibility that we may be particularly vulnerable at this age. It will also be important to find out whether these changes could be reversible with weight loss, which may well be the case.”

Despite the clear differences in the volume of white matter between lean and overweight individuals, the researchers found no connection between being overweight or obese and an individual’s cognitive abilities, as measured using a standard test similar to an IQ test.

{A study published in the journal Epidemiology has found that women who douche have double the risk of ovarian cancer.}

Prior studies have linked douching to yeast infections, reduced fertility, pelvic inflammatory disease, but this is the first study to link douching to ovarian cancer.

Douching is the act of cleaning the vagina with scented sticks, sprays and other materials. The vagina is known to clean itself naturally and douching can cause an overgrowth of harmful bacteria.

The researchers followed more than 41,000 women in the United States and Puerto Rico during their research.

Many women who douche see it as a necessary part of good hygiene and this is wrong. Some women douche to prepare for s*x and to clean up after s*x but the researchers have warned women to discontinue this act as it interferes with nature’s balance.

{Researchers have identified evidence of bacteria in sterilely obtained breast tissue and found differences between women with and without breast cancer.}

A team of Mayo Clinic researchers has identified evidence of bacteria in sterilely-obtained breast tissue and found differences between women with and without breast cancer. The findings are published in the Aug. 3 issue of Scientific Reports.

“Our research found that breast tissue samples obtained in the operating room under sterile conditions contain bacterial DNA, even when there is no sign of infection. Furthermore, we identified significant differences in the breast tissue microbiome of women with cancer versus women without cancer,” says Tina Hieken, M.D., a breast surgical oncologist at Mayo Clinic. “Our work confirmed the presence of a distinct breast tissue microbiome and that it is different than the microbiome of the overlying breast skin.”

According to the National Cancer Institute, a microbiome is a collection of microorganisms and viruses that live in a specific environment in the human body.

Dr. Hieken says, globally, breast cancer accounts for nearly one quarter of all cancers and is the leading cause of cancer death among women. She says that while there are established risk factors for breast cancer, at least 70 percent of breast cancer cases occur in women of average risk, and current prediction models are poor at identifying risk for individual women.

“Differences in the microbiome have been implicated in cancer development at a variety of body sites including stomach, colon, liver, lung and skin,” says co-investigators Amy Degnim, M.D. a breast surgical oncologist at Mayo Clinic. “There is mounting evidence that changes in the breast microbiome may be implicated in cancer development and the aggressiveness of cancer and that eliminating dangerous microorganisms or restoring normal microbiota may reverse this process,” adds Nick Chia, Ph.D., a microbiome researcher at Mayo Clinic.

Dr. Hieken says it remains unclear whether small shifts in microbial communities, the presence of a virulent pathogenic strain or the absence of a beneficial one might be responsible for promoting the development of cancer in the breast microbiome. However, she says the findings of this study will spur further research to identify potential causes of breast cancer development and new microbial-based prevention therapies.

{People infected with a common parasitic worm may be twice as likely to acquire the HIV virus that causes AIDS.}

People infected with a common parasitic worm may be twice as likely to acquire the HIV virus that causes AIDS, a field study from Tanzania reported Wednesday.

The parasite, Wuchereria bancrofti, is found in many areas in Africa where HIV infection rates are high, and can cause elephantiasis, a disease that horribly deforms the limbs and other parts of the body.

Also endemic in Asia, the western Pacific and parts of the Caribbean and South America, the parasite has infected 120 million people worldwide.

The mosquito-borne worm can live in the human lymphatic system for years without symptoms emerging.

The new findings, published in The Lancet medical journal, added a compelling reason for tackling elephantiasis, known to scientists as lymphatic filariasis, the authors argued.

“The long disease duration of W. bancrofti infection — around 10 years — creates an ongoing immune response,” which could make people more susceptible to HIV infection, said Inge Kroidl, a tropical medicine specialist at the University of Munich in Germany.

Mosquito threats

For the study, conducted between 2006 and 2011, researchers analysed 2,699 people in the Kyela district of Mbeya, southwest Tanzania.

Lymphatic filariasis affects one in four people in the country, and has long been suspected as a factor driving the HIV epidemic in sub-Saharan Africa.

Participants were examined annually over a five year period — blood, urine, stool, and sputum samples were collected to test for HIV and W. bancrofti infection. Interviews determined if sexual activity could have heightened their risk of contracting HIV.

The researchers found that people carrying the parasite were twice as likely to also have the AIDS virus. The impact was highest among adolescents and young adults.

For now, the observed link is merely a correlation, with no proven cause-and-effect, the researchers pointed out.

It does, however, highlight the need for an elephantiasis cure.

“Lymphatic filariasis elimination programmes in the past decade have focused on the reduction of transmission but made only limited efforts to cure W. bancrofti infection,” Kroidl said.

Prevention currently focuses on the use of bed nets and other mosquito repellents.

Other infections such as chlamydia, herpes and syphilis are known to increase susceptibility to HIV.

Jennifer Downs and Daniel Fitzgerald of the Center for Global Health at Weill Cornell Medicine in New York, writing in a commentary, said further study was urgently needed to confirm the findings.

“Controlling lymphatic filariasis has the potential not only to decrease morbidity from the disease itself, but could additionally prevent incident HIV infections among the 120 million people living with this chronic infection,” they said in The Lancet.

Lymphatic filariasis is classified by the World Health Organization (WHO) as one of about 20 “neglected tropical diseases” that collectively affect more than a billion people in developing countries.

{When you are having indigestion, there are certain foods you should avoid.}

Here are 7 foods you should avoid when you are having tummy issues

{{1. Ice cream }}

Ice cream should be avoided when you are having problems with digestion because ice cream is known to cause cramping, bloating and indigestion.

{{2. Spicy foods}}

Spicy foods can stimulate the digestive system so they should be avoided when you are experiencing nausea, vomiting and diarrhea.

{{3. Beans }}

Beans is another food you should avoid if you are having problems with digestion. While high in fibre and protein, beans also contain a type of sugar known as oligosaccharide which is difficult to digest.

{{4. Citrus fruits}}

Citrus fruits such as lemon, oranges and grapefruits should be avoided when you have a stomach upset because they are known to cause digestive problems due to their acidic nature.

{{5. Fried foods }}

Fried foods are another food you should avoid when having issues with digestion because they are high in fat and full of grease.

{{6. Processed foods }}

Processed foods should be avoided if you are having issues with digestion because they lack fibre which helps regulate bowel movements. Some processed foods also contain lactose which can worsen the situation.

{{7. Alcohol
}}

Drinking too much alcohol can cause indigestion and it should be avoided when you are feeling nauseated.

{Using a laboratory device that can deliver concussive impacts to cell cultures and image the aftermath in real time, researchers are gaining new insight into how brain cells react to trauma.}

A team of Brown University researchers has been able to watch in real time what happens to neurons after they experience the kinds of forces involved in a blow to the head. Their findings, published in the journal Scientific Reports, could help scientists to understand how traumatic brain injury unfolds at the cellular level.

The study was done using a custom-built laboratory device that can compress neurons inside 3-D cell cultures while using a powerful microscope to continuously monitor changes in cell structure.

“This is the first study that applied this kind strain to brain cells and followed them over time,” said Christian Franck, an assistant professor in Brown’s School of Engineering and the paper’s corresponding author. “We’re excited because we can finally get some concrete information about when cells start to degenerate, when they die and what the process looks like.”

Among the study’s key findings was that after a compression event with forces similar to those involved in traumatic brain injury (TBI), it takes approximately six hours for neurons to develop irreparable structural damage. That suggests that there may be a window for therapeutic intervention aimed at minimizing further damage, Franck said.

The study also found two different types of structural damage occurring in cells following compression. One type, called diffuse axonal injury, scientists know well as a hallmark manifestation of cellular TBI. But the second form, which also led to cell death, has not previously been associated with TBI. That finding suggests that the full extent of TBI damage in the brain could be underestimated in some cases.

“We hope that this work provides some fundamental guideposts for future research on TBI,” Franck said. “Once we understand how this works at a basic cellular level, then we can start to think about adding the complexity back in and understanding how it works in the brain.”

A new approach

What made the research possible was an experimental technique Franck’s lab has been developing over the past few years. Most lab studies on neuronal injury are done using two-dimensional cell cultures grown on slides or petri dishes. To see what happens when cells are placed under strain, researchers either stretch them or expose them to shearing forces. But 2-D techniques can’t evaluate compressive force, which is known to be important in blows to the head.

“We wanted to add this other facet of compression to our laboratory work,” Franck said. “The only way you can do that is in 3-D.”

Franck and his colleagues grew rat neurons in 3-D collagen cultures about the diameter of a quarter. They then placed the cultures in their device, which has a hydraulic piston apparatus that sits atop a laser-scanning microscope. The piston delivers precisely tuned compressive force to the culture, while the microscope generates continuous images of cell structures.

That real-time observation was a key part of the work, Franck said.

“If we can look at this continuously, then we can get a much better idea of when permanent damage begins and when cells finally die,” he said.

Researchers have known for a while that much of the damage and cell death in TBI does not occur at the moment of impact. Instead, there appears to be a biochemical cascade that, over a period of time, causes damage to accrue in the cells and eventually leads to death. One problem, however, is that nobody knows exactly how long that process takes after a compressive strain, or whether it occurs slower or faster depending on the severity of the impact.

Franck’s work found that it take about six hours for neurons to show signs of irreparable damage from the amount of compression thought to be typical of blows to the head. But the timing from the onset of damage to cell death varied according to the amount of compression. For example, cells exposed to a 7 percent strain died after about 12 hours, while those exposed to a 12 percent strain died in around seven hours.

“Our system doesn’t have nearly the complexity of a real brain, so we’re not saying that it plays out exactly this way in TBI patients,” he said. “But we wanted to start simply and get fundamental data on how neurons respond to these strains. We think it provides a good starting point for further research.”

Different kinds of damage

A particular advantage to Franck’s device is that is that it enables precise control over the total amount of compression and how long it is applied (called strain rate). The study showed that both of those factors influenced cellular injury in different ways. While the total amount of compression was responsible for the timing of cell death, strain rate was responsible for how many cells were damaged and what kind of damage they suffered.

At the higher strain rates used in the study, neurons developed diffuse axonal injury (DAI) — the hallmark of TBI in which cellular appendages called axons swell and eventually break, forming bubbles or “blebs” at the breaking points. But at slower strain rates, the structural damage took a different form. Instead of breaking and forming blebs, the axons and neurite extensions simply retracted as the cells died.

“Pathologists look for blebs and other signs of DAI to assess whether a TBI has occurred and how widespread the damage is,” Franck said. “But what this suggests is that they may be missing this other type of morphology.”

The effect of strain rate is important because while scientists know generally how fast TBI-related impacts are (in the National Football League, for example, impacts are about 15 milliseconds), it’s not clear how that energy wave is transmitted through the brain. The strain rate applied to the outside of the head could be very different from what is transmitted through the brain, and this study suggests that the manifestation of injury could be different depending on the rate.

{{Further research}}

Franck and his colleagues plan to continue using their apparatus to explore cellular TBI. In the future they intend to use more complex culture media in order to better simulate the differing tissue structures in the brain. They are also interested in using their device to evaluate possible therapeutic measures.

“The nice thing is we have a very well-controlled system to cause injury that can also be used to evaluate therapeutic interventions,” Franck said. “We can inject drugs into the culture, for example, and see how the cells respond.”

Franck hopes that the results from these kinds of lab studies will eventually guide clinical research aimed at reducing the devastating effects of TBI.

{Increased death risk primarily associated with red meats, eggs and dairy — not found among those with healthy lifestyle.}

The largest study to examine the effects of different sources of dietary protein found that a high intake of proteins from animal sources — particularly processed and unprocessed red meats — was associated with a higher mortality rate, while a high intake of protein from plant sources was associated with a lower risk of death.

The largest study to examine the effects of different sources of dietary protein found that a high intake of proteins from animal sources — particularly processed and unprocessed red meats — was associated with a higher mortality rate, while a high intake of protein from plant sources was associated with a lower risk of death. Results from the study — which analyzed data from two long-term epidemiologic studies — appears in the August 1 issue of JAMA Internal Medicine.

“Overall, our findings support the importance of the sources of dietary protein for long-term health outcomes,” says Mingyang Song, MD, ScD, a research fellow in the Massachusetts General Hospital (MGH) Clinical and Translational Epidemiology Unit (CTEU) and Division of Gastroenterology and corresponding author of the report. “While previous studies have primarily focused on the overall amount of protein intake — which is important — from a broad dietary perspective, the particular foods that people consume to get protein are equally important. Our findings also have public health implications and can help refine current dietary recommendations about protein intake, in light of the fact that it is not only the amount of protein but the specific food sources that is critical for long-term health.”

While several studies have suggesting that substituting proteins for carbohydrates in the diet has several health benefits — including weight management, reducing blood pressure and other cardiovascular risk factors — the authors note, few studies have examined the specific sources of protein. Those that have were relatively small and based on one-time assessment of participants’ diets. The current study analyzes data from the Nurses’ Health Study (NHS) and the Health Professionals Follow-up Study (HPFS), which have compiled comprehensive health data on more than 170,000 participants since the 1980s. In addition to completing overall health questionnaires every two years, participants provide information on their dietary intake — specifically how often they consumed portions of particular types of food during the preceding year — every four years.

The researchers analyzed more than 30 years of data for NHS participants and 26 years of data for HPFS participants, totaling more than 3.5 million person-years. During those time periods more than 36,000 deaths were documented among study participants — almost 9,000 from cardiovascular disease, around 13,000 from cancer and about 14,000 from other causes. After adjustment for lifestyle and other dietary risk factors, a high consumption of protein from animal sources — any types of meat, eggs or dairy — was weakly associated with an increased rate of death, while high consumption of protein from plant sources — breads, cereals, pasta, beans, nuts and legumes — was associated with a lower mortality rate.

More careful analysis revealed that the association of animal protein intake with an elevated mortality risk only applied to participants with at least one factor associated with an unhealthy lifestyle — being either obese or underweight, heavy alcohol consumption, a history of smoking, or physical inactivity. In fact, the association disappeared in participants with a healthy lifestyle. Analysis based on specific sources of protein indicated that the animal-protein-associated mortality risk applied primarily to processed and unprocessed red meats, which include both beef and pork products, and not to protein from fish or poultry.

“While we expected we might find the associations to be weaker in the healthy lifestyle group, we did not expect them to completely disappear,” says Song. “But when we looked deeper into the data, we found that — at similar levels of animal protein intake — those in the unhealthy lifestyle group consumed more red meats, eggs and high-fat dairy, while the healthy lifestyle group consumed more fish and poultry. So we suspect the different sources of animal protein between the two groups may contribute to the stronger results in the unhealthy lifestyle group.”

He adds, “Our findings suggest that people should consider eating more plant proteins than animal proteins, and when they do choose among sources of animal protein, fish and chicken are probably better choices. Future studies should examine the mechanisms underlying the different effects of plant and animal proteins — along with different sources of animal proteins — on overall health.”