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Category: healthy living

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Several recent studies have found that constant exposure to high levels of air pollution has negative effects on the brain. The last post described negative effects on the gray matter in brains (resulting in smaller brain volumes) of elderly women from air pollution, but this study found negative effects (lower grade point averages) in young children from high air pollution. From Environmental Health News:

Bad air means lower grade point averages in Texas

Fourth and fifth graders in El Paso, Texas, are more likely to have lower grade point averages if heavily exposed to contaminated air at home, according to a new study.It bolsters a growing body of evidence that air pollution can impair success in school.

They found that for all types of air pollution sources, more exposure corresponded with lower grade point averages. Only one type of pollution—point sources such as factories—was not significantly linked to lower grade point averages.University of Texas at El Paso researchers analyzed the grade point averages of 1,895 children and, using their home location, estimated their exposure to air toxics—such as benzene, arsenic, lead, mercury, hydrochloric acid, toluene, vinyl bromide, xylenes, and diesel particulate matter—using federal data.

“Effects appear to be insidious, since they are mild, unlikely to be perceived, and, hence, unlikely to be addressed in any way … seemingly trivial effects on children’s development may translate into substantial impacts throughout the life course in terms of physical and mental health and personal success,” the authors wrote.The researchers did control for some other things that can affect children’s grades such as poverty, mother’s age, education and ability to speak English, and the child’s race and sex.

Still, the study doesn’t prove that dirty air makes kids do worse in school. It does, however, suggest children’s developing bodies are more susceptible to air pollution, which can harm their respiratory systems and brain.Air pollution might hamper kids’ grades via two primary ways: Illnesses, mostly respiratory, that would make them miss school, and developmental problems resulting from long-term exposure, said Sara Grineski, an associate professor of sociology at The University of Texas at El Paso and co-author of the new study.

Others have found similar links between air pollution and academic performance. Three months ago Columbia University's Perera and colleagues reported that New York City children born to mothers in poverty and exposed to certain air toxics during pregnancy had lower IQs.  Perera, tracking the mothers and children since before birth, said the pollution exposure prior to birth is more strongly linked to learning and behavioral problems. 

In the current study it’s unclear if the children were exposed in their mothers’ womb—an exposure window that is critical to brain development, Perera said....Other studies support this—in February Calderón-Garcidueñas and colleagues reported Mexico City smog was linked to impaired short-term memory and IQ in children.

The city is more than 80 percent Hispanic....Previous studies have shown that El Paso’s minorities are disproportionately impacted by toxics, Grineski said. The city of 675,000 is one of the worst when it comes to particulate matter—a mix of substances emitted by combustion sources, including cars, trucks, industrial plants and wood burning—especially coarse particulates, PM10, those between 2.5 and 10 micrometers (from about 25 to 100 times thinner than a human hair, according to the EPA). El Paso’s 24-hour PM10 average is about 233 micrograms per cubic meter of air, according to the latest EPA data from 2013, which was eighth highest among more than 500 U.S. cities. El Paso, along with Laredo, has the highest carbon monoxide levels in Texas.

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 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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 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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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

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Eating green leafy vegetables and other brightly colored fruits and vegetables containing vitamin K, lutein, folate and beta-carotene were linked to keeping the brain healthy in older adults and slowing cognitive decline. Researchers found that older people who ate one to two servings per day had the cognitive ability of a person 11 years younger than those who consumed none. From Science Daily:

Eating green leafy vegetables keeps mental abilities sharp

Something as easy as adding more spinach, kale, collards and mustard greens to your diet could help slow cognitive decline, according to new research. The study also examined the nutrients responsible for the effect, linking vitamin K consumption to slower cognitive decline for the first time...."Since declining cognitive ability is central to Alzheimer's disease and dementias, increasing consumption of green leafy vegetables could offer a very simple, affordable and non-invasive way of potentially protecting your brain from Alzheimer's disease and dementia."

The researchers tracked the diets and cognitive abilities of more than 950 older adults for an average of five years and saw a significant decrease in the rate of cognitive decline for study participants who consumed greater amounts of green leafy vegetables. People who ate one to two servings per day had the cognitive ability of a person 11 years younger than those who consumed none. When the researchers examined individual nutrients linked with slowing cognitive decline, they found that vitamin K, lutein, folate and beta-carotene were most likely helping to keep the brain healthy.

To conduct the study, Morris' research team gathered data from 954 participants from the Memory and Aging Project, which aims to identify factors associated with the maintenance of cognitive health. The participants, whose age averaged 81, reported their daily food and beverage intake by answering a detailed 144-item questionnaire at the beginning of the study.... They followed participants for 2 to 10 years, assessing cognition annually with a comprehensive battery of 19 tests and adjusted for age, sex, education, smoking, genetic risk for Alzheimer's disease and participation in physical activities when estimating the effects of diet on cognitive decline.

"With baby boomers approaching old age, there is huge public demand for lifestyle behaviors that can ward off loss of memory and other cognitive abilities with age," said Morris. "Our study provides evidence that eating green leafy vegetables and other foods rich in vitamin K, lutein and beta-carotene can help to keep the brain healthy to preserve functioning." In addition to green leafy vegetables, other good sources of vitamin K, lutein, folate and beta-carotene include brightly colored fruits and vegetables.

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Women: if you sit at work all day, and then you sit 6 or more hours during your leisure time, then you are at significantly greater risk of developing any cancer (compared to women who sit for fewer than 3 hours a day during leisure time). And the odds for certain cancers (multiple myeloma, ovarian cancer, and invasive breast cancer) are greatly increased. That 30 minutes at the gym doesn't cancel out the negative effects of sitting all day. But interestingly, this pattern didn't apply to men. From Medscape:

Leisure Time Sitting Increases Cancer Risk in Women

Women who sit 6 or more hours a day during their leisure time have a 10% greater risk of developing any cancer compared with women who sit for fewer than 3 hours a day. In addition, they are more likely to develop certain site-specific cancers, such as invasive breast cancer, ovarian cancer, and multiple myeloma. However, no similar pattern emerged for men.

"So when we think about independent risk factors for many types of cancer, and definitely for invasive breast cancer, you want to tell women to maintain a physically active lifestyle, to maintain a healthy weight, to limit their alcohol consumption, and now you also want to tell them to reduce their time spent sitting," she said.

The findings come from an analysis of data on some 69,260 men and 77,462 women enrolled in the American Cancer Society Cancer Prevention Study II Nutrition. All participants were cancer-free on enrolment. Between 1992 and 2009, 18,555 men and 12,236 women were diagnosed with cancer. On average, men were followed for 13.2 years, and women were followed for an average of 15.8 years.

"In women, leisure-time spent sitting was associated with a statistically significant higher risk of total cancer incidence...after adjustment for physical activity, [body mass index (BMI)], and other potential confounders," the authors report. Sitting 6 or more hours a day during leisure time was also associated with a 65% greater risk for multiple myeloma, a 43% greater risk for ovarian cancer, and a 10% greater risk for invasive breast cancer compared with women who sat less than 3 hours a day during leisure time. The association between longer sitting times and endometrial cancer was statistically significant before adjusting for BMI, but was attenuated when adjusted for BMI.

The same pattern was not seen in men in this study. Leisure time spent sitting was not associated with cancer risk in men, with the exception of an 11% higher risk associated with sitting time among obese men.

"There are a lot of individuals whom I would describe as 'an active couch potato.' " Dr Patel said. "People are going to the gym and maintaining a healthy weight, but they spend the majority of the rest of their time in sedentary activities — sitting at work, sitting in the car, sitting at home — so you really have to think not just of that 30 minutes a day where you are intentionally engaging in physical activity, but what does the rest of your day look like?"

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The key finding in this research (they studied mice, but this process would also happen in humans) is that: the presence of microbes specifically blocks the immune cells responsible for triggering allergies. Once again we see the importance of a healthy and diverse microbiota (the community of microbes within us), and the need to nurture it from birth. Studies have shown the importance of the first year of life in establishing a healthy microbiome and the development of the immune system. A number of studies have shown that the presence of pets or animals (e.g., living on a farm) reduces the incidence of allergies in children.From Science Daily:

Role of microbiota in preventing allergies

The human body is inhabited by billions of symbiotic bacteria, carrying a diversity that is unique to each individual. The microbiota is involved in many mechanisms, including digestion, vitamin synthesis and host defense. It is well established that a loss of bacterial symbionts promotes the development of allergies. Scientists at the Institut Pasteur have succeeded in explaining this phenomenon, and demonstrate how the microbiota acts on the balance of the immune system: the presence of microbes specifically blocks the immune cells responsible for triggering allergies. 

The hygiene hypothesis suggests a link between the decline in infectious diseases and the increase in allergic diseases in industrialized countries. Improvements in hygiene levels necessarily lead to reduced contact with microbes that is paralleled by an increased incidence in allergic and autoimmune diseases, such as type 1 diabetes.

Epidemiological studies have substantiated this hypothesis, by showing that children living in contact with farm animals -- and therefore with more microbial agents -- develop fewer allergies during their lifetime. Conversely, experimental studies have shown that administering antibiotics to mice within the first days of life results in a loss of microbiota, and subsequently, in an increased incidence in allergy.

However, until now, the biological mechanisms underlying this phenomenon remained unclear. In this study published in Science, the team led by Gérard Eberl (head of the Microenvironment and Immunity Unit at the Institut Pasteur) shows that, in mice, symbiotic intestinal microbes act on the immune system by blocking allergic reactions.

Several types of immune response can be generated in order to defend the organism. The presence of bacterial or fungal microbes provokes a response from immune cells known as type 3 cells. These immune cells coordinate the phagocytosis and killing of the microbes. However, in the case of infection by pathogenic agents that are too large to be handled by type 3 cells (such as parasitic worms and certain allergens), the cells that organize the elimination of the pathogen, but also allergic reactions, are known as type 2 cells.

In this study, scientists at the Institut Pasteur have shown that type 3 cells activated during a microbial aggression act directly on type 2 cells and block their activity. Type 2 cells are consequently unable to generate allergic immune responses. This work demonstrates that the microbiota indirectly regulates type 2 immune responses by inducing type 3 cells.

These results explain how an imbalance in microbiota triggers an exaggerated type 2 immune response normally used to fight large parasites, but that also leads to allergic responses....In terms of allergy treatment, a hitherto unexplored therapeutic approach consists therefore in stimulating type 3 cells by mimicking a microbial antigen in order to block allergy-causing type 2 cells.

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It turns out that we also have microbes called archaea living in and on our bodies. They are part of our microbiome (community of microbes living in and on us, which also includes bacteria, viruses, and fungi). Archaea constitute a domain or kingdom of single-celled microorganisms. These microbes are prokaryotes, meaning that they have no cell nucleus or any other membrane-bound organelles in their cells. Archaeal cells have unique properties that separate them from bacteria and eukaryotes. Archaea were initially classified as bacteria and thought to only exist in extreme environments (such as hot springs and salt lakes), and given the name archaebacteria, but this classification is now outdated. We now know that archaea live in less extreme places, including oceans, marshlands, animals, and humans.

So little is known about archaea that not even medical schools discuss this topic. This may be due to the fact that we currently don't know of any archaea that are human pathogens (that is, that cause illness) or parasitic. They are generally viewed as mutuals (the relationship is beneficial to both organisms) or commensals (they benefit, but don't help or harm the other organism). Humans appear to have low levels of archaea, and so far they have  been found in the human gut (part of digestion and metabolism), on the skin, and in subgingival dental plaque (and perhaps involved with periodontal disease). But studies rarely look for them. We don't know the importance or roles that they play in our bodies (but there are suspicions), but it turns out that drugs such as statins and the antibiotic metronidazole  are eliminating them.

Note that methanogens are archaea that excrete or produce methane as a metabolic byproduct in anoxic (no oxygen) conditions such as the gut. They help digest our food. The species Methanobrevibacter smithii  has been shown to be present in up to 95.7% of humans studied, and found to be the most abundant methanogen in the human gut, comprising up to as much as 10% of all anaerobes found in a healthy individual's colon. Anaerobes are organisms that require oxygen-free conditions to live. Some of the June 2015 article (by M. N. Lurie-Weinberger and U. Goph) excerpts from PLOS:

Archaea in and on the Human Body: Health Implications and Future Directions

Although they are abundant and even dominant members of animal microbiomes (microbiotas), from sponges and termites to mice and cattle, archaea in our own microbiomes have received much less attention than their bacterial counterparts. The fact that human-associated archaea have been relatively little-studied may be at least partially attributed to the lack of any established archaeal human pathogens. Clinically oriented microbiology courses often do not mention archaea at all, and most medical school and biology students are only aware of archaea as exotic extremophiles that have strange and eukaryotic-like molecular machinery. Since archaea have been known to be associated with the human gut for several decades, one would think that human microbiome studies may unravel new facets of archaea–human interactions...  ...continue reading "We Have Archaea In and On Our Bodies"