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The study was needed, but my first thought was "Duh! Of course." From Science Daily:

Fist bumping beats germ-spreading handshake

“Fist bumpingtransmits significantly fewer bacteria than either handshaking or high-fiving, while still addressing the cultural expectation of hand-to-hand contact between patients and clinicians, according to a study published in the August issue of the American Journal of Infection Control...

In this study from the Institute of Biological, Environmental, and Rural Sciences at Aberystwyth University in the United Kingdom, researchers performed trials to determine if alternative greetings would transmit fewer germs than the traditional handshake. In this experiment, a greeter immersed a sterile-gloved hand into a container of germs. Once the glove was dry, the greeter exchanged a handshake, fist bump, or high-five with a sterile-gloved recipient. Exchanges randomly varied in duration and intensity of contact.

After the exchange, the receiving gloves were immersed in a solution to count the number of bacteria transferred during contact. Nearly twice as many bacteria were transferred during a handshake compared to the high-five, and significantly fewer bacteria were transferred during a fist bump than a high-five. In all three forms of greeting, a longer duration of contact and stronger grips were further associated with increased bacterial transmission.

“Adoption of the fist bump as a greeting could substantially reduce the transmission of infectious diseases between individuals,” said corresponding author, David Whitworth, PhD. This study expands on the recent call from the Journal of the American Medical Association (JAMA) to ban handshakes from the hospital environment. Healthcare providers’ hands can spread potentially harmful germs to patients, leading to healthcare-associated infections (HAIs). 

Great reason to add more rosemary and oregano to your diet. From Science Daily:

Rosemary, oregano contain diabetes-fighting compounds

The popular culinary herbs oregano and rosemary are packed with healthful compounds, and now lab tests show they could work in much the same way as prescription anti-diabetic medication, scientists report. In their new study, researchers found that how the herbs are grown makes a difference, and they also identified which compounds contribute the most to this promising trait.

Elvira Gonzalez de Mejia and colleagues point out that in 2012, type-2 diabetes affected more than 8 percent of Americans and cost the country $175 billion. ... Recent research has shown that herbs could provide a natural way to help lower glucose in blood. So Gonzalez de Mejia's team decided to take a closer look.They tested four different herbs, either greenhouse-grown or dried commercial versions, for their ability to interfere with a diabetes-related enzyme, which is also a target of a prescription drug for the disease.

They found that greenhouse herbs contained more polyphenols and flavonoids compared to the equivalent commercial herbs. But this didn't affect the concentration required to inhibit the enzyme. Commercial extracts of Greek oregano, Mexican oregano and rosemary were better inhibitors of the enzyme, required to reduce risk of type-2 diabetes, than greenhouse-grown herbs.

Even though it looks to be a modest effect, it is still good news. But they should have added kefir to the list of probiotic containing foods. From Science Daily:

Eating probiotics regularly may improve your blood pressure

Eating probiotics regularly may modestly improve your blood pressure, according to new research in the American Heart Association journal  Hypertension. Probiotics are live microorganisms (naturally occurring bacteria in the gut) thought to have beneficial effects; common sources are yogurt or dietary supplements.

"The small collection of studies we looked at suggest regular consumption of probiotics can be part of a healthy lifestyle to help reduce high blood pressure, as well as maintain healthy blood pressure levels," said Jing Sun, Ph.D., lead author and senior lecturer at the Griffith Health Institute and School of Medicine, Griffith University, Gold Coast, Queensland, Australia. "This includes probiotics in yogurt, fermented and sour milk and cheese, and probiotic supplements."

Analyzing results of nine high-quality studies examining blood pressure and probiotic consumption in 543 adults with normal and elevated blood pressure, researchers found:

  • Probiotic consumption lowered systolic blood pressure (the top number) by an average 3.56 millimeters of mercury (mm Hg) and diastolic blood pressure (the lower number) by an average 2.38 mm Hg, compared to adults who didn't consume probiotics.
  • The positive effects from probiotics on diastolic blood pressure were greatest in people whose blood pressure was equal to or greater than 130/85, which is considered elevated.
  • Probiotics with multiple bacteria lowered blood pressure more than those with a single bacteria.

We believe probiotics might help lower blood pressure by having other positive effects on health, including improving total cholesterol and low-density lipoprotein, or LDL, cholesterol; reducing blood glucose and insulin resistance; and by helping to regulate the hormone system that regulates blood pressure and fluid balance," Sun said.

After posting yesterday "Probiotic Misconceptions", I was pleasantly surprised that today's NY Times had an article (by Jane Brody) raising similar concerns. What was good is that she wrote about supplements not being regulated. She also left out that probiotic beneficial organisms are found in more than the gut. A case in point being the sinuses - because healthy sinuses also have Lactobacillus sakei (according to the Abreu et al study of 2012), and which has been the basis for my family's successful kimchi treatment for sinusitis (see Sinusitis treatment link for the method). From the NY Times:

Probiotic Logic vs. Gut Feelings

The label on my bottle of Nature’s Bounty Advanced Probiotic 10 says it contains 10 probiotic strains and 20 billion live cultures in each two-capsule dose. The supplement provides “advanced support for digestive and intestinal health” and “healthy immune function.” I have no way to know if any of this is true. Like all over-the-counter dietary supplements, probiotics undergo no premarket screening for safety, effectiveness or even truth in packaging. 

To be sure, lay and scientific literature are filled with probiotic promise, and I am hardly the only consumer who has opted to hedge her bets. The global market for probiotic supplements and foods is expected to reach $32.6 billion this year,with a projected annual growth of 20 percent or more.

 Beneficial micro-organisms have since been shown to inhabit three main locations in the digestive tract: the stomach, the lower part of the small intestine and the large intestine. To better understand the current enthusiasm for enhancing the body’s supply of these micro-organisms, some definitions are needed.

Prebiotics are nondigestible carbohydrates that stimulate the growth and activity of beneficial micro-organisms (that is, probiotics) in the gut. They are found naturally in oats, wheat, some fruits and vegetables (bananas, onions, garlic, leeks, asparagus, soybeans, honey and artichokes), and in breast milk, and they are added to some infant formulas.

Probiotics are defined by the World Health Organization as “live micro-organisms which when administered in adequate amounts confer a health benefit on the host.” The ailments that probiotics are said to benefit range from infection-caused diarrhea, inflammatory bowel diseases and irritable bowel syndrome to asthma, allergy and Type 1 diabetes.

Synbiotics are a combination of prebiotics and probiotics. They are found in so-called functional foods like yogurt and kefir, fermented foods like pickles and some cheeses, and in some supplements.

That probiotic organisms are important to health is not questioned. As researchers at the Institute for Immunology at the University of California,Irvine have written intestinal micro-organisms play “an important role in the development of the gut immune system, digestion of food, production of short-chain fatty acids and essential vitamins, and resistance to colonization from pathogenic microorganisms.”

Dr. Walker has explained that probiotics enhance defensive action by the cells that line the gut. When a person takes antibiotics, especially the broad-spectrum antibiotics most often prescribed, many of these beneficial microbes are destroyed along with the disease-causing bacteria. Patients on antibiotics are often told to consume yogurt with active cultures to replenish the beneficial organisms.

In an extensive review of the evidence published in 2010 in the journal Pediatrics, an expert committee concluded that probiotics might limit the course of virus-caused diarrhea in otherwise healthy infants and children. But the committee said there was not sufficient evidence to justify routine use of probiotics to prevent rotavirus-caused diarrhea in child care centers. Nor did the committee endorse taking probiotics during pregnancy and nursing or giving them to infants to prevent allergic disorders in those at risk.

Only a small percentage of probiotic foods and supplements have the backing of peer-reviewed published research. They include Dannon’s Activia yogurt and DanActive drink and the supplements Culturelle and Align. Although kefir contains even more probiotic strains than yogurt, clinical studies have not shown it to be effective in preventing or treating infectious diarrhea.

The challenge in taking probiotics is to get the microbes past the stomach, where most are killed by gastric acid, said Robert Dunn, a biologist at North Carolina State University. Once in the intestines, they must compete effectively with the microbes already present.

Dr. Dunn, author of "The Wild Life of Our Bodies," says there is good reason to remain skeptical of probiotics“There are hundreds of kinds of prebiotics and probiotics in stores,” he said. “As a consumer, it’s almost impossible to figure out what is best. What are the specific species in your intestines, and how will what you take compete with them?” Still, he added, taking them doesn’t seem harmful. 

There is growing evidence for the role of the appendix in restoring a healthful balance of microbes in the body. Though long considered an expendable, vestigial organ, the appendix is now being looked at as “a storehouse of good bacteria,” Dr. Dunn said. In a study of recovery rates from Clostridium difficile, which causes a severe form of infectious diarrhea, often following antibiotic therapy, patients whose appendixes had been removed were more likely to have a recurrent infection than those who still had appendixes.

The study found real differences between organic and conventionally grown foods - organic foods have lower levels of pesticides, higher levels of antioxidants, and lower levels of cadmium. From NY Times:

Study of Organic Crops Finds Fewer Pesticides and More Antioxidants

Adding fuel to the debates over the merits of organic fooda comprehensive review of earlier studies found substantially higher levels of antioxidants and lower levels of pesticides in organic fruits, vegetables and grains compared with conventionally grown produce.

However, the full findings, to be published next week in the British Journal of Nutrition, stop short of claiming that eating organic produce will lead to better health. Still, the authors note that other studies have suggested some of the antioxidants have been linked to a lower risk of cancer and other diseases.

Organic farming, by and large, eliminates the use of conventional chemical fertilizers and pesticides. Those practices offer ecological benefits like healthier soils but produce less bountiful harvests. 

In the new study, an international team of scientists did not conduct any laboratory or field work of their own. Instead, they compiled a database from 343 previously published studies and performed a statistical procedure known as a meta-analysis, which attempts to ferret robust bits of information from studies of varying designs and quality.

Over all, organic crops contained 17 percent more antioxidants than conventionally grown crops, the new study found. For some classes of antioxidants, the difference was larger. A group of compounds known as flavanones, for example, were 69 percent higher in the organic produce. (At very high quantities, as in some supplements, some antioxidants have been shown to be harmful, but the levels in organic produce were not nearly that high.)

The researchers said they analyzed the data in several different ways, and each time the general results remained robust. Charles M. Benbrook, a professor at Washington State University and another author of the paper, said this analysis improved on earlier reviews, in part because it incorporated recent new studies.

The study also found that organically produced foods, particularly grains, contain lower levels of cadmium, a toxic metal that sometimes contaminates conventional fertilizers. Dr. Benbrook said the researchers were surprised by that finding; there was no difference in other toxic metals like mercury and lead.

A topic that is rarely mentioned is the human virome (the collection of resident viruses in the human body). We all have many viruses, but almost nothing is known about them.This is an introductory article about the human virome. From the January 11, 2014 Science News:

The vast virome

 The microbiome — what scientists refer to as the collection of bacteria, fungi and other single-celled organisms that live in and on the body — has been a hot research topic for more than a decade. But bacteria aren’t the only microbes with which we humans share space.

The most abundant inhabitants of what many researchers are calling “the human ecosystem” are the virusesViruses are deceptively simple organisms consisting of genetic material packed in a protein shell. They are tiny and can’t replicate on their own, relying on human or other cells to reproduce.

And yet, scientists estimate that 10 quintillion virus particles populate the planet. That’s a one followed by 31 zeros. They outnumber bacteria 10-to-1 in most ecosystems. And they’re ubiquitous in and on humans.

Pérez-Brocal and others are learning that viruses, once seen only as foreign invaders that make people sick, are an integral part of human biology. Some cause major diseases, including influenza, AIDS and some cancers. Others, conversely, may promote health. Some may even help us gauge how well the human immune system works.

The study of people’s resident viruses, known collectively as the human virome, is “a whole new frontier in the understanding of humans,” and could become important for the future of medicine, says Forest Rohwer, an environmental microbiologist at San Diego State University.

Rohwer’s research indicates that viruses are part of the human defense system. Mucus studded with bacteria-infecting viruses called bacteriophage, or phage, may help protect host cells from invasive microbes, he and his colleagues reported June 25 in the Proceedings of the National Academy of Sciences. 

“We know a lot about the bacteria that inhabit humans,” says David Pride, an infectious disease doctor at the University of California, San Diego. In comparison, “we know absolutely nothing about the viruses.” Not that scientists haven’t been interested in viruses. Until recently there was just no good way to identify them, an important first step toward understanding the biology of health and disease. As a consequence, virome research is in its infancy.

Researchers have gotten a head start on cataloging bacterial denizens of the body because all bacterial cells contain a version of the 16S ribosomal RNA gene. Virus hunters aren’t so lucky. There is no analogous virus-identification tag. Instead, to look for viruses, researchers must sequence hundreds of thousands of bits of DNA from a sample — skin swabs, saliva, feces or mucus, for example. Scientists have gotten really good at generating these DNA sequences; the trick is figuring out what they are.

Every time Frederic Bushman samples a new person’s virome, he says, he finds new viruses. A microbiologist at the University of Pennsylvania Perelman School of Medicine in Philadelphia, Bushman has shown that no two people’s gut viruses are exactly alike. But once a person has picked up a community of bacteria-infecting phage, it tends to stick around. Fully 80 percent of the viruses present when the researchers first started tracking one man’s virome were still there more than two years later.

Maybe researchers can use bacteriophage to shape the human microbiome in healthier ways. Using phage to control bacteria is a resurgence of an old idea. In the 1920s, doctors in the former Soviet Union and other Eastern European countries began using phage to treat specific bacterial infections. Unlike antibiotics, which kill bacteria indiscriminately, phage target only certain microbes for destruction.

“Healthy subjects are just loaded with viruses,” Wylie says. Even viruses known to cause diseases such as the common cold were found in healthy kids. That makes it difficult to determine whether a particular virus is really making someone sick.

Some viruses previously thought innocent may cause harmTo figure out which viruses are friends, foes or neutral passengers on the human body, scientists first need to identify them. Researchers still aren’t very good at recognizing new viruses, says Brian Jones, a molecular biologist at the University of Brighton in England. 

Based on what researchers have learned so far about the virome, Jones is convinced that viruses and other microbes “should be viewed as a part of us rather than something that lives in or on us.” They are part of the puzzle, the intricate ecosystem composed of human and microbial cells, all pushing and pulling at one another and subject to local conditions, such as diet and environment.

This is Part 3 on how lifestyle influences aging. Many recent research reports tell of a link between our lifestyle and how we'll age - whether we'll be active and healthy well into our 80s or in terrible shape and dying young. Mind you, these are not "definites" because nothing can give you a guarantee, but they are ways we can improve our odds in living a long and healthy life. From Medical Xpress:

Having a sense of purpose may add years to your life, study finds

Feeling that you have a sense of purpose in life may help you live longer, no matter what your age, according to new research. The research has clear implications for promoting positive aging and adult development, says the lead researcher.

The researchers looked at data from over 6000 participants, focusing on their self-reported purpose in life (e.g., "Some people wander aimlessly through life, but I am not one of them") and other psychosocial variables that gauged their positive relations with others and their experience of positive and negative emotions.

Greater purpose in life consistently predicted lower  across the lifespan, showing the same benefit for younger, middle-aged, and older participants across the follow-up period. "To show that purpose predicts longer lives for younger and older adults alike is pretty interesting, and underscores the power of the construct," he explains.

From Science Daily:

Education boosts brain function long after school, study shows

Education significantly improves mental functioning in seniors even four decades after finishing school, shows a new study. The study shows that people who attended school for longer periods performed better in terms of cognitive functioning than those who did not. Using data from individuals aged around 60, the researchers found a positive impact of schooling on memory scores. The fact that young people or their parents did not choose whether to go longer to school strongly suggests that schooling is the cause rather than personal characteristics that would affect this choice and could also explain the differences in cognitive function.

From Medscape:

Lifetime of Intellectual Enrichment Keeps Aging Brain Sharp

A lifetime of intellectual enrichment helps delay onset of cognitive decline in older individuals, new data from the Mayo Clinic Study on Aging show.

In this longitudinal study, researchers found ties between higher levels of education and working in mentally stimulating jobs in early- to mid-life, as well as higher levels of mid- to late-life cognitive activity, such as using a computer, reading, and participating in social activities, and better cognition with age..."We also found that an individual with low education/occupation benefited more by engaging in high mid-/late-life cognitive activity than an individual with high education/occupation," Dr. Vemuri noted.

A number of research results were reported at the Alzheimer's Association International Conference 2014.  From Science Daily:

Potential Alzheimer's disease risk factor and risk reduction strategies become clearer

Participation in activities that promote mental activity, and moderate physical activity in middle age, may help protect against the development of Alzheimer's disease and dementia in later life, according to new research.

From Science Daily:

Physical activity is beneficial for late-life cognition

Physical activity in midlife seems to protect from dementia in old age, according to a study. Those who engaged in physical activity at least twice a week had a lower risk of dementia than those who were less active. The protective effects were particularly strong among overweight individuals. In addition, the results showed that becoming more physically active after midlife may also contribute to lowering dementia risk.

This is Part 2 on how lifestyle influences aging. Many recent research reports tell of a link between our lifestyle and how we'll age - whether we'll be active and healthy well into our 80s or in terrible shape and dying young. Mind you, these are not "definites" because nothing can give you a guarantee, but they are ways we can improve our odds in living the long and healthy life that we want. From February 2014 Medscape:

Cancers Caused by Lifestyle Behaviors: Experts Urge Action

In launching the World Cancer Report 2014 earlier this week, the editors emphasized the need for prevention and highlighted lifestyle behaviors that lead to cancer, including smoking tobacco, drinking alcohol, overweight/obesity, and lack of exerciseThe report, issued by the International Agency for Research on Cancer (IACR), contains contributions from more than 250 scientists worldwide, many of them leading experts in their fields. 

In the United States, 1 in 3 cancer deaths is related to obesity, poor nutrition, or physical inactivity, and the problem will only increase as more countries and regions adopt the diet and lifestyles of more economically developed economies."

Tobacco, both smoked and smokeless, remains the world's leading cause of cancer morbidity and mortality, the report notes. The IACR and also the US Surgeon General have concluded that the relationship with smoking is causal for cancers of the nasal and oral cavities, hypopharynx, larynx, trachea, esophagus, lung, bronchus, bone marrow (leukemia), stomach, kidney, pancreas, ureter, uterus, bladder, and cervix. The IACR expands this list to also include paranasal sinuses, liver, colon, rectum, and ovary (mucinous), but says it is unclear if there is a link with breast cancer.

Still under-recognized, and not acted on, is the association between drinking alcohol and cancer. The agency says cancers caused by drinking alcoholic beverages include those of the oral cavity, pharynx, larynx, esophagus, liver, colorectum, and female breast.

Excess body fat increases the risk for cancers of the esophagus, colon, pancreas, endometrium, and kidney, as well as postmenopausal breast cancer. The evidence for obesity increasing the risk for these cancers is "convincing," the agency comments, and there is a dose–response relationship, so being overweight is less risky than being obese.

Regular physical activity reduces the risk for multiple cancers by contributing to weight control, and also reduces the risk for colorectal and breast cancer by additional mechanisms. The general consensus among researchers is that exercise should be of moderate intensity and average at least an hour each day.

High consumption of red meat, especially processed meat, is associated with a risk for colorectal cancer. "A diet high in fruit and vegetables and whole grains does not appear to be as strongly protective against cancer as initially believed," the report notes. "However, this dietary pattern is still advisable because of the benefits for diabetes and cardiovascular diseases, and some possible reductions in cancer incidence."

From Science Daily:

Watching too much TV may increase risk of early death: Three hours a day linked to premature death from any cause

Adults who watch TV three hours or more a day may double their risk of premature death from any cause. Researchers suggest adults should consider getting regular exercise, avoiding long sedentary periods and reducing TV viewing to one to two hours a day.

Results of a large study published in the Mayo Clinic Proceedings. From Science Daily:

Large waist linked to poor health, even among those in healthy body mass index ranges

Having a big belly has consequences beyond trouble squeezing into your pants. It’s detrimental to your health, even if you have a healthy body mass index (BMI), a new international collaborative study has found. Men and women with large waist circumferences were more likely to die younger, and were more likely to die from illnesses such as heart disease, respiratory problems, and cancer after accounting for body mass index, smoking, alcohol use and physical activity.

Some good news for those who have to sit for long periods every day at work - being physically fit may help. From Science Daily:

Physical fitness associated with less pronounced effect of sedentary behavior

Physical fitness may buffer some of the adverse health effects of too much sitting, according to a new study. Sedentary behavior has been linked to an increase risk of obesity, metabolic syndrome, type 2 diabetes mellitus, cardiovascular disease, some cancers, and premature death. But previous studies of the association have not taken into account the protective impact of fitness, a strong predictor of cardiovascular disease incidence and mortality.

I've been seeing research report after report looking at how our lifestyle determines how we'll age - whether we'll be active and healthy well into our 80s or in terrible shape and dying young. Mind you, these are not "definites" because nothing can give you a guarantee, but they are ways we can improve our odds in living the long and healthy life that we want. From Medical Xpress:

A healthy lifestyle adds years to life

Live longer thanks to fruit, an active lifestyle, limited alcohol and no cigarettes. This is the conclusion of a study by public health physicians at the University of Zurich who documented for the first time the impact of behavioural factors on life expectancy in numbers. 

...Brian Martin and his colleagues from the Institute of Social and Preventive Medicine (ISPM) at the University of Zurich have examined the effects of these four factors – both individual and combined – on life expectancy. An individual who smokes, drinks a lot, is physically inactive and has an unhealthy diet has 2.5 fold higher mortality risk in epidemiological terms than an individual who looks after his health. Or to put it positively: "A healthy lifestyle can help you stay ten years' younger", comments the lead author Eva Martin-Diener.

"The effect of each individual factor on life expectancy is relatively high", states Eva Martin-Diener. But smoking seems to be the most harmful. Compared with a group of non-smokers, smokers have a 57 percent higher risk of dying prematurely. The impact of an unhealthy diet, not enough sport and alcohol abuse results in an elevated mortality risk of around 15 percent for each factor.

According to Martin an unhealthy lifestyle has above all a long-lasting impact. Whereas high wine consumption, cigarettes, an unhealthy diet and physical inactivity scarcely had any effect on mortality amongst the 45 to 55-year-olds, it does have a visible effect on 65 to 75-year-olds. The probability of a 75-year-old man with none of the four risk factors surviving the next ten years is 67 percent, exactly the same as the risk for a smoker who is ten years younger, doesn't exercise, eats unhealthily and drinks a lot.

From Medical Xpress:

Picking up healthy habits in your 30s and 40s can slash heart disease risk

The heart is more forgiving than you may think—especially to adults who try to take charge of their health, a new Northwestern Medicine study has found. When adults in their 30s and 40s decide to drop unhealthy habits that are harmful to their heart and embrace healthy lifestyle changes, they can control and potentially even reverse the natural progression of , scientists found. On the flip side, scientists also found that if people drop  or pick up more bad habits as they age, there is measurable, detrimental impact on their coronary arteries.

For this paper, scientists examined healthy lifestyle behaviors and coronary artery calcification and thickening among the more than 5,000 participants in the Coronary Artery Risk Development in Young Adults (CARDIA) study who were assessed at baseline (when participants were ages 18 to 30) and 20 years later.The healthy  assessed were: not being overweight/obese, being a nonsmoker and physically active and having low alcohol intake and a healthy diet. 

By young adulthood (at the beginning of the study), less than 10 percent of the CARDIA participants reported all five healthy lifestyle behaviors. At the 20-year mark, about 25 percent of the study participants had added at least one healthy lifestyle behavior. Each increase in healthy lifestyle factors was associated with reduced odds of detectable  and lower intima-media thickness—two major markers of cardiovascular disease that can predict future cardiovascular events. Adulthood is not too late for healthy behavior changes to help the heart."

"That loss of healthy habits had a measurable negative impact on their coronary arteries," Spring said. "Each decrease in healthy lifestyle factors led to greater odds of detectable  calcification and higher intima-media thickness.

Spring said the healthy changes people in the study made are attainable and sustainable. She offers some tips for those who want to embrace a  at any age:Keep a healthy body weight; Don't smoke; Engage in at least 30 minutes of moderate to vigorous activity five times a week; No more than one alcoholic drink a day for women, no more than two for men; Eat a healthy diet, high in fiber, low in sodium with lots of fruit and vegetables.

From Science Daily:

Adults who lose weight at any age could enjoy improved cardiovascular health

Weight loss at any age in adulthood is worthwhile because it could yield long-term heart and vascular benefits, suggests new research. For the first time, the findings indicate that adults who drop a BMI category -- from obese to overweight, or from overweight to normal -- at any time during adult life, even if they regain weight, can reduce these cardiovascular manifestations. The findings are from a study examining the impact of lifelong patterns of weight change on cardiovascular risk factors in a group of British men and women followed since birth in March 1946. 

This article summarizes some of the same things I've been posting here. From NY Times:

We Are Our Bacteria

We may think of ourselves as just human, but we’re really a mass of microorganisms housed in a human shell. Every person alive is host to about 100 trillion bacteria cells. They outnumber human cells 10 to one and account for 99.9 percent of the unique genes in the body.

Our collection of microbiota, known as the microbiome, is the human equivalent of an environmental ecosystem. Although the bacteria together weigh a mere three pounds, their composition determines much about how the body functions and, alas, sometimes malfunctions. Like ecosystems the world over, the human microbiome is losing its diversity, to the potential detriment of the health of those it inhabits.

Dr. Martin J. Blaser, a specialist in infectious diseases at the New York University School of Medicine and the director of the Human Microbiome Program, has studied the role of bacteria in disease for more than three decades. In his new book, “Missing Microbes,"Dr. Blaser links the declining variety within the microbiome to our increased susceptibility to serious, often chronic conditions,  from allergies and celiac disease to Type 1 diabetes and obesity. He and others primarily blame antibiotics for the connection.

The damaging effect of antibiotics on microbial diversity starts early, Dr. Blaser said. The average American child is given nearly three courses of antibiotics in the first two years of life, and eight more  during the next eight years. Even a short course of antibiotics like the widely prescribed  Z-pack (azithromycin, taken for five days), can result in long-term shifts in the body’s microbial environment.

But antibiotics are not the only way the balance within us can be disrupted. Cesarean deliveries, which  have soared  in recent decades, encourage the growth of microbes from the mother’s skin, instead of from the birth canal, in the baby’s gut, Dr. Blaser said in an interview.

This change in microbiota can reshape an infant’s metabolism and immune system. A recent review of 15 studies involving 163,796 births found that, compared with  babies delivered vaginally, those born by cesarean section were 26 percent more likely to be overweight and 22 percent more likely to be obese as adults. 

The placenta has a microbiome of its own, researchers have discovered, which may also contribute to the infant’s gut health and help mitigate the microbial losses caused by cesarean sections.

Further evidence of a link to obesity comes from farm animals. About three-fourths of the antibiotics sold in the United States are used  in  livestock. These  antibiotics change the animals’ microbiota, hastening their growth. When mice are given the same  antibiotics used on livestock, the metabolism of their liver changes, stimulating an increase in body fat, Dr. Blaser said.

Even more serious is  the increasing number of serious disorders now linked to a distortion in the microbial balance in the human gut. They include several that are becoming more common in developed countries: gastrointestinal ailments like Crohn’s disease, ulcerative colitis and celiac disease; cardiovascular disease; nonalcoholic fatty liver disease; digestive disorders like chronic reflux; autoimmune diseases like multiple sclerosis and rheumatoid arthritis; and asthma and allergies.