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Author: Sima

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Several recent studies found that air pollution has a negative effect on the brain. This study of elderly women in North Carolina found that long-term exposure to higher levels of air pollution (specifically fine particulate matter smaller than 2.5 micrometers (called PM2.5) resulted in smaller brain volumes (especially the brain's white matter). They studied elderly women (aged 71 to 89), but the findings should be of concern to everyone exposed to high levels of air pollution.  White matter connects brain regions (with nerve fibers that pass signals throughout the brain) and determines how information is processed in the brain. The researchers pointed out that other recent studies reported that high air pollution is linked to cognitive decline and accelerated brain aging. From Futurity:

AIR POLLUTION MAY SHRINK BRAIN’S WHITE MATTER

Exposure to air pollution may have a negative impact on how the brain’s white matter ages. Older women who lived in geographic locations with higher levels of fine particulate matter in ambient air had significantly smaller white matter volumes across a wide range of brain areas, new research shows.

Fine particulate matter is smaller than 2.5 micrometers and is known as PM2.5, a form of pollution that easily enters the lungs and possibly the bloodstream. White matter connects brain regions and determines how information is processed in the brain....“Our study provides convincing evidence that several parts of the aging brain, especially the white matter, are an important target of neurotoxic effects induced by long-term exposure to fine particles in the air.”

The study found that older women ages 71 to 89 who had lived in places with greater PM2.5 exposures had significantly smaller volumes of white matter and that this could not be explained by the geographic region where they lived, their race or ethnic background, socioeconomic status, lifestyle, or medical conditions that may also influence brain volumes.

The researchers performed brain magnetic resonance imaging scans of 1,403 women who are part of the Women’s Health Initiative Memory Study (WHIMS), a nationwide report based at Wake Forest Baptist Medical Center in Winston-Salem, NC. The researchers also used residential histories and air monitoring data to estimate the participants’ exposure to air pollution in the previous six to seven years.

White matter contains nerve fibers and connects brain regions with each other by traveling deep within and passing nerve signals throughout the brain. Gray matter is primarily composed of neuronal cell bodies, dendrites, glial cells, and capillaries. The study did not find impacts from exposure to air pollution in participants’ gray matter.

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People fear dementia and Alzheimer's disease, because they are progressive diseases that nothing treats successfully. However, in the past year there have been some studies showing improvements with lifestyle changes (not cures, but for some the progression was slowed or showing some improvements).

The latest studies found that exercise (especially aerobic execise) had some beneficial effects on those with mild cognitive impairment (MCI), Alzheimer's disease, and vascular cognitive  impairment (VCI): neuropsychiatric improvements, improvements in biomarkers for the disease, and improved blood flow to the brain. From Medscape:

Physical Activity May Help Treat Dementia

New research shows that being physically active not only reduces cognitive decline and improves neuropsychiatric symptoms in patients with dementia but may actually reduce Alzheimer's disease (AD) biomarkers, including amyloid and tau protein in the brain. Exercise could also benefit patients with types of dementia other than AD, another study suggests.Some of this promising new research on exercise was presented at the Alzheimer's Association International Conference (AAIC) 2015. 

Danish researchers had already presented cognition-related results of the multicenter ADEX study ...The intervention consisted of 1 hour of aerobic exercise three times a week for 16 weeks. The control group received usual care..... The analysis found that these [neuropsychiatric] symptoms improved in the 66 patients in the "high exercise"group... The NI is a 12-item questionnaire that rates, among other things, depression, apathy, agitation, hallucinations, irritability, weight loss, and sleep."We saw that the control group got worse; there was a small decline in this group, which you would expect because this is progressive disease," said Steen Hasselbalch, MD, Danish Dementia Research Centre, Copenhagen, Denmark. "But the intervention group remained at the same level and even got a little better, so at end of the intervention there was a significant difference."

The question arises of whether exercise could not just delay worsening of symptoms but actually change brain pathology.The answer, suggests other research, is yes. In a separate study presented at the AAIC 2015, researchers found decreased phosphorylated tau (P tau) in older, previously sedentary persons completing a 6-month regimen of moderate- to high-intensity aerobic exercise.

The study enrolled 70 patients aged 55 to 89 years with prediabetes as well as amnestic mild cognitive impairment (MCI)....We think they are at high, high risk for developing dementia of the Alzheimer's type." These patients were randomly assigned to the aerobic exercise group or to the stretching group. Those in the aerobic group started slowly — 10 minutes of exercise a week — and gradually built the time and intensity up over 6 weeks to the point where they were exercising 45 minutes a day, 4 days a week, at 75% to 85% of their maximum heart rate...."This group had a choice of exercises: treadmill, stationary cycling, elliptical trainer, or preapproved group classes.

The stretching group, whose members could do balance exercises, gentle yoga, and other approved classes in addition to stretching, maintained a maximum heart rate of below 35%. All exercises were adapted to the needs and limitations of individual patients and were done at a local YMCA.

The researchers looked at biomarkers in cerebrospinal fluid (CSF), including P tau protein and amyloid β 42....Most intervention trials don't show such changes in P tau. "But we saw it with exercise and no medications," said Dr. Baker. "Exercise was enough to move a biomarker that indicates the severity of the disease."  It wasn't surprising, she added, that this was true only for older patients. "It may be that before age 70, you have a lot of compensatory mechanisms that help to maintain brain health, and after 70, those start breaking down."

The study also showed that the aerobic activity increased blood flow to the brain...The researchers demonstrated that the increased blood flow was in regions characteristically affected by aging and AD (ie, memory and processing). Cognitive benefits were particularly noteworthy for executive function..."Our brain imaging results are just fantastic; they show some really nice increases in blood flow in the areas of brain that support executive function and areas of the brain that normally show decreased flow for people with MCI, so it's reversing the blood flow detriment in MCI."

AD may not be the only dementia potentially treatable through exercise. Another study discussed at the meeting showed that this intervention may help those with vascular cognitive impairment (VCI). It's the first intervention trial to suggest that exercise can improve cognition in patients with confirmed VCI, said Teresa Liu- Ambrose, PhD, Canada Research Chair, University of British Columbia, Vancouver, Canada, who reported the results.The 6-month study included 71 patients aged 56 to 96 years with mild VCI of varying physical capacities. They were assigned to usual care that included a nutrition component or to an intervention of moderate-intensity walking, 3 times a week for an hour....In a subset of patients who had neuroimaging, there was "evidence of efficiency" in the brain of those who exercised, Dr Liu-Ambrose told Medscape Medical News.

Published on Leave a comment on What’s In the “Natural” Flavors In Our Foods?

I've been reading and thinking about "natural flavors" ever since my earlier posts about food additives (April 20, 2015, August 19, 2014). What exactly are natural flavors and how are they different from artificial flavors?  And why are they even found in organic foods? The more I read, the more I want to avoid them , but it seems to be really, really hard to do so because they seem to be everywhere, even in what we think of as basic foods (e.g., butter). Bottom line: both are chemicals concocted in labs and manufactured in factories. Read labels and try to eat as many unprocessed foods as possible to avoid them.We know very little about many of them, and if they have health effects. Note that the term "natural flavors" may include many chemicals in the "flavor mixtures" (incidental additives) that don't have to be listed on the labels. Currently there are more than 2700 natural flavors being used in the USA. The following are excerpts from articles and a book published in 2015.

From CNN:   What are natural flavors, really?

Look at the food label of almost any packaged good you consume and odds are you'll spot the term "natural flavors." But have you ever wondered what this mysterious additive actually contains? The answer isn't as clear as you might think.Though natural flavors may sound better than their presumably chemical-laden alternative — artificial flavors — it turns out they are not actually all that different.

In the Environmental Working Group's Food Scores database of over 80,000 foods, "natural flavor" is the fourth most common ingredient listed on labels. The only ingredients that outrank it: salt, water and sugar. Yet, natural flavoring isn't nearly as simple as these three pantry staples."Natural and artificial flavors play an interesting role in food. They're essentially providing the taste and often they're added to make the food more appealing, or to potentially replace something that's lost through processing, storage or in some cases even from pasteurizing," says David Andrews, senior scientist at the Environmental Working Group. One place you'll often spot natural or artificial flavor is in orange juice; manufacturers will add faux flavor to juice after it's packaged in the plant, to ensure uniformity.

"The differentiation is really down to the origin of those molecules, whether synthetically processed in a lab or purified in a lab but from a natural source," Andrews says. Here's where it gets even muddier: Added flavoring, both natural and artificial, could contain anywhere from 50 to 100 ingredients. And all of the extra ingredients in flavors often aren't as innocent as you'd hope they would be."The mixture will often have some solvent and preservatives — and that makes up 80 to 90 percent of the volume [of the flavoring]. In the end product, it's a small amount, but it still has artificial ingredients," Andrews says.  ...continue reading "What’s In the “Natural” Flavors In Our Foods?"

Published on Leave a comment on A Mix of Bacteria Protect Against Infections?

More research that supports that both more variety (diversity) of microbes and the actual mix of types of microbes are involved in a healthy gut microbiome. Healthy communities don't have just one important species of bacteria, but a mix of bacteria, and some mixes of bacteria work better than others in preventing infections. One can say that some mixes of bacteria are "protective" against infections. And once again, antibiotics screw up the microbial communities and cause imbalances. This study was done in mice looking at gut bacteria and Clostridium difficile (which kills about 14,000 Americans annually), but they are now continuing this research in humans. From Medical Xpress:

It takes a village... to ward off dangerous infections? New microbiome research suggests so

Like a collection of ragtag villagers fighting off an invading army, the mix of bacteria that live in our guts may band together to keep dangerous infections from taking hold, new research suggests. But some "villages" may succeed better than others at holding off the invasion, because of key differences in the kinds of bacteria that make up their feisty population, the team from the University of Michigan Medical School reports. The researchers even show it may be possible to predict which collections of gut bacteria will resist invasion the best—opening the door to new ways of aiding them in their fight.

Working in mice, the team studied one of the most dangerous gut infections around: Clostridium difficile, which kills more than 14,000 Americans a year. C-diff also sickens hundreds of thousands more, mostly hospital patients whose natural collection of gut bacteria—their gut microbiome—has been disturbed by antibiotics prescribed to protect them from other infections.

In a new paper published in the journal mBIO, the team reports the results from tests of seven groups of mice that were given different antibiotics, then were exposed to C-diff spores. The scientists used advanced genetic analysis to determine which bacteria survived the antibiotic challenge, and looked at what factors made it most likely that C-diff would succeed in its invasion.The team also developed a computer model that accurately predicted C-diff's success rate for other mice in the study, based solely on knowing what bacteria the mice had in their natural gut 'village'. The model succeeded 90 percent of the time.

"We know that individual humans all have different collections of gut bacteria, that your internal 'village' is different from mine. But research has mostly focused on studying one collection at a time," says Patrick D. Schloss, Ph.D., the U-M associate professor of microbiology and immunology who led the team. "By looking at many types of microbiomes at once, we were able to tease out a subset of bacterial communities that appear to resist C-diff colonization, and predict to what extent they could prevent an infection."

Schloss, who is a key member of the Medical School's Host Microbiome Initiative, notes that no one species of bacteria by itself protected against colonization. It was the mix that did it. And no one particular mix of specific bacteria was spectacularly better than others - several of the diverse "villages" resisted invasion.

Resistance was associated with members of the Porphyromonadaceae, Lachnospiraceae, Lactobacillus, Alistipes, and Turicibacter families of bacteria. Susceptibility to C. difficile, on the other hand, was associated with loss of these protective species and a rise in Escherichia or Streptococcus bacteria. "It's the community that matters, and antibiotics screw it up," Schloss explains. Being able to use advance genetic tools to detect the DNA of dozens of different bacteria species, and tell how common or rare each one is in a particular gut, made this research possible.

A Clostridium difficile cell.                                                     Credit: Centers for Disease Control and Prevention

Published on Leave a comment on Why Breastfeeding Is So Important

There has been much discussion recently about breastfeeding - why is it so important? Is it really better than formula? The answer is: YES, breastfeeding is the BEST food for the baby, and for a number of reasons. Not only is it nature's perfect food for the baby, but it also helps the development of the baby's microbiome or microbiota (the community of microbes that live within and on humans).

Specifically, breast milk transmits about 700 species of bacteria to the baby - bacteria that are important in developing the baby's microbiota, bacteria that are important for the baby's development and health in many ways (including the immune system). No formula does that. Not even close.

There is obviously much we don't know or understand yet, but finding 700 species in breast milk is a big deal. The most variety was in colostrum (the first milk), but even after 6 months (mature milk) they found hundreds of species of bacteria. What was also interesting was that the bacteria species in the breast milk varied whether the baby was born by vaginal birth, unplanned cesarean, or planned cesarean (this last had a somewhat different bacterial community which persisted through the 6 months of the study).

By the way, in the original study, the authors made a point of saying that the 700 bacteria species are NOT bacterial contaminants, but meant to be there! (for those who want to sterilize and pasteurize everything because they think that all bacteria are bad).

This study is from 2013, but well worth reading. From Science Daily: Breast milk contains more than 700 species of bacteria, Spanish researchers find

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

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

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

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

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

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

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

A Purdue University-led analysis of breast milk concludes that levels of health-promoting compounds known as carotenoids differ by country, with the U.S. lagging behind China and Mexico, a reflection of regional dietary habits. Carotenoids are plant pigments that potentially play functional roles in human development and are key sources of vitamin A, an essential component of eye health and the immune system.

The carotenoid content of a woman's breast milk is determined by her consumption of fruits and vegetables such as squash, citrus, sweet potatoes and dark, leafy greens.

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Published on 2 Comments on Good Books About the Human Microbiome

Recently several good books have been published about the community of microbes within us - our microbiota or microbiome. Originally I mainly saw the term human microbiome used everywhere. It referred to all the organisms living within and on us that are identified by their genomes (genetic material within the organism such as DNA and RNA). However, recently I'm seeing the term microbiota being used more. The microbiota refers to the community of microbes within and on us. Think of it this way: the human microbiota is the collection of all the microbes within and on us, and their genes are called the human microbiome. So there's a difference, but both refer to all the microbes within and on us.

The human body contains over 10 times more microbial cells than human cells - thus 90% microbes (about 100 trillion microbial cells), and 10% human cells (about ten trillion human cells). It is estimated that the weight of all these microbes in an adult is about 3 pounds, which is about the weight of the adult human brain. Different communities of microbes live in different parts of the body - and each little part of the body has its own ecosystem or community. And there is variation from person to person in the types of microbes in each niche in the body. So knowing all this, it is time that to stop thinking about yourself as ME or I, but more of a collective WE.

It is great to see some recently published books that explore this new and emerging field, discuss the importance of feeding and nurturing the microbes (and how), look at current and future medical uses of microbes. Because that's the exciting stuff. As I've been posting all along, our microbes seem to be intimately linked with our health - whether cancer or sinusitis (think how Lactobacillus sakei successfully treats chronic sinusitis) or many other ailments. I enjoyed all the books, I liked that the material was presented a little differently (as well as some different material) by each author, and that each book had reference lists.

Martin Blaser, MD - Missing Microbes: How the Overuse of Antibiotics is Fueling Our Modern Plagues   This is the most scholarly of the books (published 2014, and with lots of references), because he is writing not just from his own extensive personal and professional experiences, but also as director of the New York University Human Microbiome Program. He discusses the dangers of some modern medical advances (such as frequent use of antibiotics and Cesarean sections)  to the human microbiome and how this may ultimately result in various diseases (modern plagues). I have posted about him various times, including an NPR interview about his book. The CDC (Centers for Disease Control) book review page also said: "Despite his emphasis on missing microbes, however, Blaser is wary of using probiotics, prebiotics, and synbiotics to restore microbial balance. He reasonably cites the challenges arising from the unsubstantiated claims of manufacturers and the paucity of well-designed trials to evaluate probiotics."

Justin Sonnenburg and Erica Sonnenburg, PhDs - The Good Gut: Taking Control of Your Weight, Your Mood, and Your Long-term Health This interesting book written is  meant for the general reader, and they incorporate their personal stories (they are both PhDs working at Stanford University while raising 2 children) as well as what the latest microbiota research is regarding our health and bodies. They make the case that "caring for our gut microbes may be the most important health choice we make". They, like Dr. Blaser, argue that our microbiota are in peril from changes to the diet, overuse of antibiotics, and oversterilization, and is facing a "mass extinction event" which is leading to a number of modern ailments (allergies, asthma, etc). They even provide some menus and recipes to feed our microbes, recipes that stress dietary fiber. Some posts in the past year mentioned his research (especially the importance of dietary fiber in health).

Alanna Collen -  10% Human: How Our Body's Microbes Hold the Key to Health and Happiness  (Published 2015) This book is written in a chatty style by Alanna Collen, a British science writer with a PhD in evolutionary biology. She incorporates both her personal story and experiences with the scientific literature. There was much to like about the book and that it was "easy to read", but there were a few moments that I thought that the research in a discussion was incomplete (urinary tract infections come to mind).

This last one I haven't yet read, but Dr. Rob Knight is such a BIG name in this emerging field  (and I heard his wonderful lectures in the Coursera course on the human microbiome) that I'm including this TED talk book. He is also a co-founder of the American Gut Project. I've mentioned his work in a number of posts this past year. Rob Knight with Brendan Buhler - Follow Your Gut: The Enormous Impact of Tiny Microbes (TED BOOKS) (Published 2015)

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 The following article supported what I have been reading over the past few years: that medical tests and treatments also have downsides, that it is possible to "know too much", that more harm than benefits can occur from certain tests, procedures, and medicines, and lifestyle changes (eat a less processed more plant-based diet, move more, and don't smoke) can be better than some medicines or certain procedures. The doctor mentioned in this article (Dr. H. Gilbert Welch) recently published a book aimed at the general public which I just read and highly recommend: Less Medicine, More Health. Dr. Welch is an academic physician, a professor at Dartmouth Medical School, and a nationally recognized expert on the effects of medical testing. In 2012 he published the well regarded and more technical and in-depth book on this issue: Overdiagnosed: Making People Sick in the Pursuit of Health. From The Atlantic:

The Downside of Medical Screening

If you had a disease, and you could find out sooner rather than later, why wouldn’t you?Medicine has long focused on early detection of diseases as part of a move toward preventive care. But imperfect tests, false positives, and overdiagnosis mean that sometimes the tests do more harm than good, and in recent years, there have been more recommendations to reduce some kinds of screening, including pap smears, colonoscopies, mammograms, and even annual pelvic exams.

“This is something we all need to understand, the two sides of early detection. It does help people, but it’s almost guaranteed to harm others,” said H. Gilbert Welch, a professor of medicine, public policy, and business administration at Dartmouth College, and author of the book Should I Be Tested for Cancer? (He reveals his answer in the book’s subtitle: “Maybe not.”)

The more you look for disease, the more you find it. And in the case of cancer, it’s hard for doctors to know if what they find is dangerous and needs to be addressed, or if it’s just a small tumor that won’t grow and poses no threat. “We can’t be sure which is which, so we treat everybody,” Welch explained at the Aspen Ideas Festival’s Spotlight Health session. “That means we’re treating people who will never experience problems from their disease.”

But they may experience problems from the treatment.The panel gave the example of prostate cancer, which is very common in men—one in seven American men will be diagnosed with it in their lifetimes. “But it turns out a lot of these cancers are very indolent,” said Jessica Herzstein, a preventive-medicine consultant and member of the U.S. Preventive Services Task Force. Around 30 to 40 percent of men who’ve been treated for prostate cancer likely had “slow-growing tumors that would never have become a threat to the man’s lifespan or health,” according to the Prostate Cancer Foundation.

In other words, “you’re going to die with them, not of them,” Herzstein said, “and the treatments are very very harmful.” Radiation therapy, for example, can cause incontinence and erectile dysfunction, and hormone therapy can cause osteoporosis and depression.

The possibility of a false positive is another downside. Not only could it lead to more invasive follow-up tests or treatments that aren’t needed, but it can also give patients unnecessary anxiety.“If we resolve the test by saying ‘The test was wrong, you’re fine!’, that’s one thing,” Welch said. “But most false alarms aren’t resolved that way. [It’s more like] ‘You don’t have cancer, but you have some abnormality that possibly puts you at a higher risk for cancer, but we’re not going to do anything about it. I think that’s where there can be [mental] harm.”

Ultimately, it comes down to a weighing of the benefits and the harms, and, in the absence of clear evidence, the preferences of the patient. The U.S. Preventive Services Task Force helps identify which tests are beneficial by evaluating and grading them. It gives tests an A if there’s a high certainty of substantial benefit, a B if there’s moderate certainty of substantial benefit, a C if there’s moderate certainty of a small benefit, a D if there’s moderate or high certainty of no benefit, and an I if the evidence is just too insufficient to say.

The task force gave prostate cancer screening a D. HIV screening got an A. For breast cancer screening, an always-controversial topic, the results vary. Breast self-exams got a D. Mammograms got a B, but only for women between 50 and 74 years old. For women in their 40s, the grade is a C, meaning the task force recommends patients and physicians discuss and decide together.

Before getting a screening test, patients should think about what would happen if they get a positive result, and if they’d be ready for it, Welch advised. “If I were to go through this, and have this diagnosis, would I want to have this surgery?” Herzstein asked, posing a hypothetical. Would you want to undergo the biopsy, the chemo, whatever treatments come next? “Maybe you don’t even want to go there if there is no treatment for the disease,” she added. Welch gives an example. “With Alzheimer’s disease that’s a fundamental question: What are you going to do with a positive result?” he asked. 

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Recently I've seen a number of published studies that found benefits to someone being bilingual or benefits in learning a new language. Some benefits recently found in bilinguals (or the "billngual advantage"): more gray matter in the executive control area of the brain, 4 to 5 year delay in onset of Alzheimer's symptoms, processing of information more efficiently and more easily, and young bilingual children are more likely to think that everything is learned (while monolinguals more likely to think things are innate). From Science Daily:

Bilinguals of two spoken languages have more gray matter than monolinguals

A new study published in the journal Cerebral Cortex suggests people who speak two languages have more gray matter in the executive control region of the brain...Early on, bilingualism was thought to be a disadvantage because the presence of two vocabularies would lead to delayed language development in children. However, it has since been demonstrated that bilingual individuals perform better, compared with monolinguals, on tasks that require attention, inhibition and short-term memory, collectively termed "executive control."

This "bilingual advantage" is believed to come about because of bilinguals' long-term use and management of two spoken languages. But skepticism still remains about whether these advantages are present, as they are not observed in all studies...."Given this concern, we took a different approach and instead compared gray matter volume between adult bilinguals and monolinguals. We reasoned that the experience with two languages and the increased need for cognitive control to use them appropriately would result in brain changes in Spanish-English bilinguals when compared with English-speaking monolinguals. And in fact greater gray matter for bilinguals was observed in frontal and parietal brain regions that are involved in executive control."

Gray matter of the brain has been shown to differ in volume as a function of people's experiences. A prominent finding of this type was a report that London taxi drivers have more gray matter in brain areas involved in spatial navigation.

What about being bilingual leads to these advantages?....The researchers compared gray matter in bilinguals of American Sign Language (ASL) and spoken English with monolingual users of English...."Unlike the findings for the Spanish-English bilinguals, we found no evidence for greater gray matter in the ASL-English bilinguals," Olulade says. "Thus we conclude that the management of two spoken languages in the same modality, rather than simply a larger vocabulary, leads to the differences we observed in the Spanish-English bilinguals."

Science Daily: Bilingualism delays Alzheimer's manifestation by more than four years

The symptoms of Alzheimer disease (AD) manifest themselves about four to five years later in bilinguals as opposed to monolinguals. In bilinguals, the disease onset was estimated at the age of 77, while in monolinguals, this was at the age of 73.

From Science Daily:  Bilingual brains better equipped to process information

Speaking more than one language is good for the brain, according to new research that indicates bilingual speakers process information more efficiently and more easily than those who know a single language. The benefits occur because the bilingual brain is constantly activating both languages and choosing which language to use and which to ignore, said a researcher.

From Science daily:  Bilingualism changes children's beliefs

Most young children are essentialists: They believe that human and animal characteristics are innate. That kind of reasoning can lead them to think that traits like native language and clothing preference are intrinsic rather than acquired. But a new study suggests that certain bilingual kids are more likely to understand that it's what one learns, rather than what one is born with, that makes up a person's psychological attributes.

White and gray matter of the human brain. Credit: Medline Plus, US National Library of Medicine

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Huh - all that talk and research for years about the first born being the smartest and most responsible. Yes...but according to this large study comparing 377,00 high school students from different families, the differences are so small as to be meaningless (1 IQ point!). Researchers looking within-families (studying siblings within families) say that the effects are larger. Depends on who you want to believe. And this study did not look at the siblings later in life - at achievements, etc. From Medical Xpress:

Birth order has no meaningful effect on personality or IQ, massive study reports

For those who believe that birth order influences traits like personality and intelligence, a study of 377,000 high school students offers some good news: Yes, the study found, first-borns do have higher IQs and consistently different personality traits than those born later in the family chronology. However, researchers say, the differences between first-borns and "later-borns" are so small that they have no practical relevance to people's lives. The analysis found - as a previous large-scale study did - that first-borns enjoy a one-IQ-point advantage over later-borns, Damian said. The difference is statistically significant but meaningless, she said.

The analysis also revealed consistent differences in personality traits between first-borns and later-borns - first-borns tended to be more extroverted, agreeable and conscientious, and had less anxiety than later-borns, for example - but those differences were "infinitesimally small," amounting to a correlation of 0.02, Roberts said. "But in terms of personality traits and how you rate them, a 0.02 correlation doesn't get you anything of note. You are not going to be able to see it with the naked eye. You're not going to be able to sit two people down next to each other and see the differences between them.."

The study controlled for potentially confounding factors - such as a family's economic status, the number of children and the relative age of the siblings at the time of the analysis - that might skew the results, Damian said. For example, wealthier families tend to have fewer children than other families, and so have a higher proportion of first-borns who also have access to more resources that may influence their IQ or personality, she said.

Many previous studies of birth order suffered from small sample sizes, Damian said. Many compared children with their siblings - a "within-family" design that some assert is better than comparing children from different families, as the new analysis did.

The team also evaluated a subset of the children in the study - those with exactly two siblings and living with two parents. This allowed the researchers to look for specific differences between first- and second-borns, or second- and third-borns. The findings confirmed those seen in the larger study, with specific differences between the oldest and a second child, and between second and third children. But the magnitude of the differences was, again, "minuscule," Roberts said.

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A recent report found that when a person is exposed to a little bit (or low doses) of a lot of different commonly encountered chemicals, than the combinations over time may cause changes that increase the risk of cancer (they may initiate cancer). Think about it - we are not exposed to just one chemical at a time (which is how chemicals are tested), but to mixtures or a "chemical soup". It is almost impossible to avoid them. As one of the researchers said: "We urgently need to focus more resources to research the effect of low dose exposure to mixtures of chemicals in the food we eat, air we breathe and water we drink." Testing mixtures of chemicals is currently not required by law.

The effects may be synergistic  - an enhanced effect that is more than the sum of the individual chemicals. And some chemicals may have bigger effects at smaller doses (typical of endocrine or hormone disruptors), than at larger doses - which is not how chemicals are typically viewed (typical view: the more you are exposed to a chemical, the greater the effect). A global task force of 174 scientists looked at 85 common everyday chemicals (at everyday low doses), and 50 were found to support cancer-related mechanisms (processes essential to cancer development). Examples of problematic chemicals that are common in everyday life: triclosan (in many soaps and personal care products), bisphenol A (in many plastics, including can linings), and atrazine (common herbicide or weedkiller). From the LA Times:

Combinations of 'safe' chemicals may increase cancer risk, study suggests

Lots of chemicals are considered safe in low doses. But what happens when you ingest a little bit of a lot of different chemicals over time? In some cases, these combinations may conspire to increase your risk of cancer, according to a new report. “Many [chemicals] have the possibility, when they are combined, to cause the initiation of cancer,” said Hemad Yasaei, a cancer biologist at Brunel University in England, one of the authors of the report. “They could have a synergistic or enhanced effect.”

This is not the way regulators typically think about cancer risk when they evaluate a compound’s safety.Normally, they test an individual chemical on laboratory animals, exposing them to progressively smaller amounts until it no longer causes malignant tumors to grow. Then they take that dose, determine the equivalent for humans, and apply what is called a “margin of safety” by declaring that some small fraction of that low dose is safe for people.

The big assumption driving the margin of safety is that a smaller amount of a chemical is less dangerous than a larger amount. (Think of the familiar axiom, “The dose makes the poison.”) But that’s not true for all chemicals, experts say. Some chemicals, such as those that mimic hormones, may actually be more dangerous at lower doses because the human body is exquisitely attuned to respond to minute amounts of natural hormones such as estrogen and testosterone.

And regulators haven’t required testing of mixtures of chemicals at all...Leroy Lowe, president of Canadian nonprofit Getting to Know Cancer and leader of the report published this week by the journal Carcinogenesis. The new report raises questions about whether this approach is adequate...Humans are exposed to about 80,000 man-made chemicals over their lifetimes, experts say. These chemicals are in the foods we eat, the water we drink and the air we breathe. "We live in a chemical soup,” said toxicologist Linda Birnbaum, director of the National Institute of Environmental Health Sciences, who was not involved in the new study.

The research team — a coalition of 174 researchers from 28 countries — set out to determine whether mixtures of these chemicals, at the very tiny concentrations found in the environment, could plausibly trigger the formation of cancerous tumors. They focused on 85 particular chemicals that were impossible to avoid in modern life, that were likely to disturb biological function and were not thought to pose cancer risks at the very low doses that people tend to ingest them.

The researchers scoured the scientific literature to understand how each of these chemicals could affect 10 important processes that are essential to cancer development. Among them: tumor-promoting inflammation, resistance to cell death and the formation of new blood vessels to feed malignant cells. In addition, they categorized whether each of the chemicals exerted biological effects at very low doses to which humans are ubiquitously exposed. (These doses are so small that they tend to be measured in parts per million or parts per billion.)
Of the 85 chemicals researchers examined, 50 were found to affect cancer-causing processes in the body, even at very low doses.

These 50 everyday chemicals included bisphenol A (used in manufacturing plastics), triclosan (often found in hand sanitizer and anti-bacterial soap) and atrazine (a commonly used herbicide). Since each of these chemicals affects different processes that could lead to cancer — bisphenol A makes cells less sensitive to signals to stop reproducing, for example, while atrazine encourages inflammation — it’s plausible that consuming mixtures of these chemicals is riskier than consuming any one individually.

More details about this report. From Science Daily: Cocktail of common chemicals may trigger cancer