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Published on Leave a comment on Oral Bacteria Linked to Hemorrhagic Stroke

The finding that the oral bacteria Streptococcus mutans, which is found in 10% of the population, is linked with hemorrhagic strokes is big. S. mutans is found in tooth decay or cavities (dental caries). The researchers found a link with cnm-positive S. mutans with both intracerebral hemorrhage (ICH) and also with cerebral microbleeds.

Some risk factors for strokes have long since been known, such as high blood pressure and advanced age, but then there are those hemorrhagic strikes that don't seem to fit the norm, with no apparent risk factors. Well, apparently the presence of cnm-positive S. mutans is one. My understanding of what cnm-positive S. mutans means is S. mutans bacteria that carries the collagen-binding Cnm gene. This bacteria can be found in a person's saliva and in dental plaque, and swabs of both were taken for this study.

This study builds on other studies that find a link between the bacteria Streptococcus mutans and a number of systemic diseases, including bacteremia, infective endocarditis and hemorrhagic stroke. The researchers of this latest study suggest that infection with cnm-positive S. mutans causes constant inflammation (as shown by 2 inflammatory markers: CRP and fibrinogen), which then causes damage to blood vessels (endothelial damage) in the brain. Bottom line: take care of your teeth and gums.

From Science Daily: Oral bacteria linked to risk of stroke

In a study of patients entering the hospital for acute stroke, researchers have increased their understanding of an association between certain types of stroke and the presence of the oral bacteria (cnm-positive Streptococcus mutans).

In the single hospital study, researchers at the National Cerebral and Cardiovascular Center in Osaka, Japan, observed stroke patients to gain a better understanding of the relationship between hemorrhagic stroke and oral bacteria. Among the patients who experienced intracerebral hemorrhage (ICH), 26 percent were found to have a specific bacterium in their saliva, cnm-positive S. mutans. Among patients with other types of stroke, only 6 percent tested positive for the bacterium.

Strokes are characterized as either ischemic strokes, which involve a blockage of one or more blood vessels supplying the brain, or hemorrhagic strokes, in which blood vessels in the brain rupture, causing bleeding.

The researchers also evaluated MRIs of study subjects for the presence of cerebral microbleeds (CMB), small brain hemorrhages which may cause dementia and also often underlie ICH. They found that the number of CMBs was significantly higher in subjects with cnm-positive S. mutans than in those without. The authors hypothesize that the S. mutans bacteria may bind to blood vessels weakened by age and high blood pressure, causing arterial ruptures in the brain, leading to small or large hemorrhages.

"This study shows that oral health is important for brain health. People need to take care of their teeth because it is good for their brain and their heart as well as their teeth," Friedland said. "The study and related work in our labs have shown that oral bacteria are involved in several kinds of stroke, including brain hemorrhages and strokes that lead to dementia."

Multiple research studies have shown a close association between the presence of gum disease and heart disease, and a 2013 publication by Jan Potempa, Ph.D., D.Sc., of the UofL School of Dentistry, revealed how the bacterium responsible for gum disease worsens rheumatoid arthritis. The cnm-negative S. mutans bacteria is found in approximately 10 percent of the general population, Friedland says, and is known to cause dental cavities (tooth decay). Friedland also is researching the role of oral bacteria in other diseases affecting the brain.  http://www.nature.com/articles/srep20074

Published on Leave a comment on Eating An Egg Daily OK For Heart Health?

Remember all the medical advice for years about not eating eggs frequently (high cholesterol! heart disease!) and to instead eat egg white omelettes if one absolutely wanted to eat eggs? Remember the obsession with dietary cholesterol? Well, this recent research followed 1032 men for 21 years and found that a relatively high intake of dietary cholesterol, or eating one egg every day, was not associated with an elevated risk of incident coronary heart disease - not in the entire study population nor in those with the APOE4 phenotype. Also, the study did not establish a link between dietary cholesterol or eating eggs with thickening of the common carotid artery walls. Time to enjoy eggs again! From Science Daily:

High-cholesterol diet, eating eggs do not increase risk of heart attack, not even in persons genetically predisposed, study finds

A new study from the University of Eastern Finland shows that a relatively high intake of dietary cholesterol, or eating one egg every day, are not associated with an elevated risk of incident coronary heart disease. Furthermore, no association was found among those with the APOE4 phenotype, which affects cholesterol metabolism and is common among the Finnish population.

In the majority of population, dietary cholesterol affects serum cholesterol levels only a little, and few studies have linked the intake of dietary cholesterol to an elevated risk of cardiovascular diseases. Globally, many nutrition recommendations no longer set limitations to the intake of dietary cholesterol. However, in carriers of the apolipoprotein E type 4 allele -- which significantly impacts cholesterol metabolism -- the effect of dietary cholesterol on serum cholesterol levels is greater. In Finland, the prevalence of the APOE4 allele, which is a hereditary variant, is exceptionally high and approximately one third of the population are carriers.

The dietary habits of 1,032 men aged between 42 and 60 years and with no baseline diagnosis of a cardiovascular disease were assessed at the onset the Kuopio Ischaemic Heart Disease Risk Factor Study, KIHD, in 1984-1989 at the University of Eastern Finland. During a follow-up of 21 years, 230 men had a myocardial infarction, and 32.5 per cent of the study participants were carriers of APOE4.

Published on

 Last fall a study came out that estimated that annually about 3.3 million deaths throughout the world were caused from air pollution. But a study was presented Friday at the American Association for the Advancement of Science (AAAS) that gave a much higher estimate of annual air pollution deaths: 5.5 million. A horrifying number. And yet... governments, companies, and people resist  measures to cut air pollution. Why? It costs money. And also many people are too poor (e.g., China and India) to use cleaner sources of heating and cooking fuel - so they are damaging their own health in their own homes. From Science Daily:

Poor air quality kills 5.5 million worldwide annually

New research shows that more than 5.5 million people die prematurely every year due to household and outdoor air pollution. More than half of deaths occur in two of the world's fastest growing economies, China and India.

Power plants, industrial manufacturing, vehicle exhaust and burning coal and wood all release small particles into the air that are dangerous to a person's health. New research, presented today at the 2016 annual meeting of the American Association for the Advancement of Science (AAAS), found that despite efforts to limit future emissions, the number of premature deaths linked to air pollution will climb over the next two decades unless more aggressive targets are set.

"Air pollution is the fourth highest risk factor for death globally and by far the leading environmental risk factor for disease," said Michael Brauer, a professor at the University of British Columbia's School of Population and Public Health in Vancouver, Canada. "Reducing air pollution is an incredibly efficient way to improve the health of a population."

For the AAAS meeting, researchers from Canada, the United States, China and India assembled estimates of air pollution levels in China and India and calculated the impact on health. Their analysis shows that the two countries account for 55 per cent of the deaths caused by air pollution worldwide. About 1.6 million people died of air pollution in China and 1.4 million died in India in 2013.

In China, burning coal is the biggest contributor to poor air quality. Qiao Ma, a PhD student at the School of Environment, Tsinghua University in Beijing, China, found that outdoor air pollution from coal alone caused an estimated 366,000 deaths in China in 2013....In India, a major contributor to poor air quality is the practice of burning wood, dung and similar sources of biomass for cooking and heating. Millions of families, among the poorest in India, are regularly exposed to high levels of particulate matter in their own homes.

In the last 50 years, North America, Western Europe and Japan have made massive strides to combat pollution by using cleaner fuels, more efficient vehicles, limiting coal burning and putting restrictions on electric power plants and factories. 

Additional facts about air pollution: - World Health Organization (WHO) air quality guidelines set daily particulate matter at 25 micrograms per cubic metre. - At this time of year, Beijing and New Delhi will see daily levels at or above 300 micrograms per cubic meter metre; 1,200 per cent higher than WHO guidelines..... - According to the Global Burden of Disease study, air pollution causes more deaths than other risk factors like malnutrition, obesity, alcohol and drug abuse, and unsafe sex.... - Cardiovascular disease accounts for the majority of deaths from air pollution with additional impacts from lung cancer, chronic obstructive pulmonary disease (COPD) and respiratory infections. Video: https://youtu.be/Kwoqa84npsU 

Published on Leave a comment on Physical Fitness Now and Brain Size Years Later

Another famous long-running study (Framingham Heart Study) finds more bad news for middle-aged coach-potatoes (that is, those who don't exercise or have poor physical fitness). It's an observational study (thus they found an association), but the finding is pretty damn convincing: that poor physical fitness (basically a sedentary life-style) may be linked to a smaller brain size (brain volume) 20 years later. The reason this is significant is because shrinking brain volume means that accelerated brain aging is occurring.

Researcher Nicole Spartano said: "Brain volume is one marker of brain aging. Our brains shrink as we age, and this atrophy is related to cognitive decline and increased risk for dementia. So, this study suggests that people with poor fitness have accelerated brain aging." Bottom line: if you don't get much exercise or lead a sedentary life-style, then increase your activity levels for hopefully better brain health decades later. Just getting out daily (or several times a week) and walking briskly would improve fitness. From Medical Xpress:

Couch potatoes may have smaller brains later in life

Poor physical fitness in middle age may be linked to a smaller brain size 20 years later, according to a study published in the February 10, 2016, online issue of Neurology, the medical journal of the American Academy of Neurology."We found a direct correlation in our study between poor fitness and brain volume decades later, which indicates accelerated brain aging," said study author Nicole Spartano, PhD, with Boston University School of Medicine in Boston.

For the study, 1,583 people enrolled in the Framingham Heart Study, with an average age of 40 and without dementia or heart disease, took a treadmill test. They took another one two decades later, along with MRI brain scans. The researchers also analyzed the results when they excluded participants who developed heart disease or started taking beta blockers to control blood pressure or heart problems; this group had 1,094 people. 

The participants had an average estimated exercise capacity of 39 mL/kg/min, which is also known as peak VO2, or the maximum amount of oxygen the body is capable of using in one minute. Exercise capacity was estimated using the length of time participants were able to exercise on the treadmill before their heart rate reached a certain level. For every eight units lower a person performed on the treadmill test, their brain volume two decades later was smaller, equivalent to two years of accelerated brain aging. When the people with heart disease or those taking beta blockers were excluded, every eight units of lower physical performance was associated with reductions of brain volume equal to one year of accelerated brain aging.

The study also showed that people whose blood pressure and heart rate went up at a higher rate during exercise also were more likely to have smaller brain volumes two decades later. Spartano said that people with poor physical fitness often have higher blood pressure and heart rate responses to low levels of exercise compared to people with better fitness. Spartano noted that the study is observational. It does not prove that poor physical fitness causes a loss of brain volume; it shows the association. (Link to study in journal Neurology.)

Published on Leave a comment on More On Rethinking Cancer Screening

The following is an excellent commentary by Dr. John Mandrola regarding an important British Medical Journal article that I posted about earlier (see Rethinking Cancer Screening). He has a highly regarded web-site and also frequently posts on Medscape. His view is that cancer screening "may be one of Medicine’s largest reversals. A reversal happens when something (testing or treatment) doctors did, and patients accepted, turned out to be non-beneficial." (www.drjohnm.org)

I can't overstate how big a reversal this is in medicine - it's huge, a paradigm change in the making. The reason for this is that studies show that overall death rates are basically the same in screened vs non-screened for mammography, colon, prostate, and lung cancer screening. This means our view of how cancer grows and spreads may have to be reexamined and changed. One possibility suggested by Dr. H. Gilbert Welch is that aggressive cancer is already "a systemic disease by the time it's detectable" (Oct. 28, 2015 post).  From Medscape:

In Cancer Screening, Why Not Tell the Truth?

The problem: cancer screening has not worked. Recent reviews of the evidence show that current-day screening techniques do not save lives. Worse, in many cases, these good-intentioned searches bring harm to previously healthy people.

I realize this sounds shocking. It did to me, too. Millions of women and men have had their breasts squished, veins poked, lungs irradiated, and bowels invaded in the name of "health" maintenance. I've been scolded for forgoing PSA tests and colonoscopy — "you should know better, John."....Anecdotes, however compelling, are not evidence. When you pull up a chair, open your computer, take a breath, suspend past beliefs, and look for the evidence that screening saves lives, it simply isn't there.

One reason that this many people (doctors and patients alike) have been misled about screening has been our collective attachment to the belief that if screening lowers disease-specific death rates, that would translate to lower overall mortality. That is: breast, lung, and colon cancer are bad diseases, so it makes sense that lowering death from those three types of cancer would extend life. It is not so.

In a comprehensive review of the literature[1] published in the BMJ, Drs Vinay Prasad (Oregon Health Sciences University, Portland) and David Newman (School of Medicine at Mount Sinai, New York), along with journalist Jeanne Lenzer, find that disease-specific mortality is a lousy surrogate for overall mortality. They report that when a screening technique does lower disease-specific death rates, which is both uncommon and of modest degree, there are no differences in overall mortality.

The authors cite three reasons why cancer screening might not reduce overall mortality:

  • Screening trials were underpowered to detect differences. I'm no statistician, but doesn't the fact that a trial requires millions of subjects to show a difference, mean there is little, if any, difference?
  • "Downstream effects of screening may negate any disease-specific gains." My translation: harm. Dr Peter Gøtzsche (Nordic Cochrane Center, Copenhagen) wrote in a commentary[2] that "screening always causes harm. Sometimes it also leads to benefits, and sometimes these benefits outweigh the harms." To understand harm resulting from screening, one need only to consider that a prostate biopsy entails sticking a needle through the rectum, or that some drugs used to treat breast cancer damage the heart.
  • Screening might not reduce overall mortality because of "off-target deaths." An illustration of this point is provided by a cohort study[3]that found a possible increased risk of suicide and cardiovascular death in men in the year after being diagnosed with prostate cancer. People die — of all sorts of causes, not just cancer.

Let's also be clear that this one paper is not an outlier. A group of Stanford researchers performed a systematic review and meta-analyses[4] of randomized trials of screening tests for 19 diseases (39 tests) where mortality is a common outcome. They found reductions in disease-specific mortality were uncommon and reductions in overall mortality were rare or nonexistent.

Drs Archie Bleyer and H Gilbert Welch (St Charles Health System, Central Oregon, Portland) reviewed Surveillance, Epidemiology, and End Results (SEER) data from 1976 through 2008 and concluded that "screening mammography has only marginally reduced the rate at which women present with advanced cancer and that overdiagnosis may account for nearly a third of all new breast cancer cases."[5] Likewise, a Cochrane Database Systematic review[6] of eight trials and 600,000 women did not find an effect of screening on either breast cancer mortality or all-cause mortality. This evidence caused the Swiss medical board to abolish screening mammography.[7]

These are the data. It's now clear to me that mass cancer screening does not save lives. But I'm still trying to understand how this practice became entrenched as public-health gospel. It has to be more than fear. Dr Gerd Gigerenzer (Max Planck Institute, Berlin, Germany)...He pointed to language and the ability of words to persuade. Instead of saying "early detection," advocates might use the term "prevention." This, Dr Gigerenzer says, wrongly suggests screening reduces the odds of getting cancer. Doesn't looking for cancer increase the odds of getting the diagnosis of cancer?

Gigerenzer noted two other ways language is used to emphasize screening benefits over harms: -The reporting of benefits in relative, not absolute terms. - The equating of increases in 5-year survival rates with decreases in mortality. I would add to this list of word misuse, the practice of referring to women sent to mammography screening as patients. They are not patients; they are well people. Dr Gigerenzer agreed with the commonsense notion that overall mortality should be reported along with cancer-specific mortality. His editorial included a fact box on breast cancer early detection using mammography provided by the Harding Center for Risk Literacy. I challenge you to tell me why such text boxes should not be shown to people before they undergo screening,

The first action healthcare experts should take is to spread the word that there is nothing about the mass screening of healthy people for cancer that equates to health maintenance. Embrace clear language. Saying or implying that screening saves lives when there are no data to support it and lots to refute it undermines trust in the medical profession.

The second action healthcare experts should take is to stop wasting money on screening. If the evidence shows no difference in overall mortality, why pay for it? I'm not naive to the fact that use of clear language will decrease the number of billable procedures. I am not saying this will be easy. One first move that would be less painful would be to get rid of quality measures or incentives that promote screening.

I want to be clear; I'm not saying all cancer screening is worthless. People at higher baseline risk for cancer, such as those with a family history of cancer or environmental exposures, might derive more benefit than harm from screening. Prasad, Lenzer, and Newman say this group of patients would be a good place to spend future research dollars. That sounds reasonable. I also acknowledge that some people, even when presented with the evidence, will want to proceed with screening. We can argue about who should pay for non–evidence-based medical procedures.

Published on Leave a comment on Researchers Revise The Number of Bacteria in Humans

A recent study has examined the issue of whether the 10 to 1 ratio of bacteria to human cells, which is widely quoted, is actually correct. Weizmann Institute of Science researchers currently feel that based on scientific evidence (which of course will change over time) and making "educated estimates", the actual ratio is closer to 1:1 (but overall there still are more bacterial than human cells). They point out that the 10:1 ratio was originally a "back of the envelope" estimate dating back to 1972.

The researchers also point out that the ratio may vary over the course of each day - as a person defecates out huge amounts of bacteria with each bowel movement. However, this study - which is not the final word - is an educated guess about bacteria only. What about the viruses, the fungi, etc that also reside on and within us? We know much less about all the other microbes. I am disturbed that article after article, and headline after headline, equates microbes and bacteria. Microbes does not mean only bacteria.  From Science Daily:

Germs, humans and numbers: New estimate revises our microbiome numbers downwards

How many microbes inhabit our body on a regular basis? For the last few decades, the most commonly accepted estimate in the scientific world puts that number at around ten times as many bacterial as human cells. In research published in the journal Cell, a recalculation of that number by Weizmann Institute of Science researchers reveals that the average adult has just under 40 trillion bacterial cells and about 30 trillion human ones, making the ratio much closer to 1:1.

The rising importance of the microbiome in current scientific research led the Weizmann Institute's Prof. Ron Milo, Dr. Shai Fuchs and research student Ron Sender to revisit the common wisdom concerning the ratio of "personal" bacteria to human cells.

The original estimate that bacterial cells outnumber human cells in the body by ten to one was based on, among other things, the assumption that the average bacterium is about 1,000 times smaller than the average human cell. The problem with this estimate is that human cells vary widely in size, as do bacteria. For example, red blood cells are at least 100 times smaller than fat or muscle cells, and the microbes in the large intestine are about four times the size of the often-used "standard" bacterial cell volume. The Weizmann Institute scientists weighted their computations by the numbers of the different-sized human cells, as well as those of the various microbiome cells. 

Some excerpts from the original journal article from Cell: Are We Really Vastly Outnumbered? Revisiting the Ratio of Bacterial to Host Cells in Humans

The human microbiome has emerged as an area of utmost interest....One of the most fundamental and commonly cited figures in this growing field is the estimate that bacteria residing in the human body outnumber human cells by a factor of 10 or more (Figure 1A). This striking statement often serves as an entry point to the field. After all, if a human being is a cell population composed of at least 90% bacteria, it is only natural to expect a major role for them in human physiology.

Both the numerator (number of microbial cells) and the denominator (human cells) of this 10:1 ratio are based on crude assessments. Most sources cite the number of human cells as 1013 or 1014.....We performed a thorough review of the literature and found a long chain of citations originating from one “back of the envelope” estimate (Figure 1). This estimate, though illuminating, was never meant as the final word on the question.

Recently, the estimate of a 10:1 bacterial to human cell ratio (B/H) ratio has received criticism (Rosner, 2014). Therefore, an alternative value and an estimate of the uncertainty range are needed. Bacteria are found in many parts of the human body primarily on the external and internal surfaces, including the gastrointestinal tracts, skin, saliva, oral mucosa, and conjunctiva. The vast majority of commensal bacteria reside in the colon, with previous estimates of about 1014 bacteria (Savage, 1977), followed by the skin, which is estimated to harbor ∼1012 bacteriaBerg, 1996). Less than 1012 bacteria populate the rest of the body.....Almost all recent papers in the field of gut microbiota directly or indirectly rely on a single paper (Savage, 1977) discussing the overall number of bacteria in the gut. Interestingly, review of the original Savage 1977 paper demonstrates that it actually cites another paper for the estimate (Luckey, 1972)....The estimate, performed by Luckey in 1972, is an illuminating example of a back-of-the-envelope estimate, which was elegantly performed, yet was probably never meant to serve as the cornerstone reference number to be cited decades later.

Updating the ratio of bacteria to human cells from 10:1 or 100:1 to closer to 1:1 does not take away from the biological importance of the microbiota. ...Although we still appear to be outnumbered, we now know more reliably to what degree and can quantify our uncertainty about the ratios and absolute numbers. The B/H ratio is actually close enough to one, so that each defecation event, which excretes about 1/3 of the colonic bacterial content, may flip the ratio to favor human cells over bacteria. This anecdote serves to highlight that some variation in the ratio of bacterial to human cells occurs not only across individual humans but also over the course of the day.

Published on Leave a comment on Some Have Pain From Electromagnetic Fields

 For years I have heard anecdotal stories about some people who sensed electromagnetic fields and were bothered by them. Many considered such stories a little woo-woo....but now comes this study on rats that was based on people with nerve injuries, who have weird sensations and pain from electromagnetic fields of power lines, cell towers, and cell phones on roam. The nerve injured rats had pain from electromagnetic fields similar to what people with nerve-injuries (such as post amputation) report. From Science Daily:

Energy from cellphone towers amplify pain in amputees

For years, retired Maj. David Underwood has noticed that whenever he drove under power lines and around other electromagnetic fields, he would feel a buzz in what remained of his arm. When traveling by car through Texas' open spaces, the buzz often became more powerful. "When roaming on a cellphone in the car kicked in, the pain almost felt like having my arm blown off again," said Underwood, an Iraq War veteran who was injured by an improvised explosive device (IED). His injuries have resulted in 35 surgeries and the amputation of his left arm.... "I didn't notice the power lines, cellphones on roam or other electromagnetic fields until I first felt them in my arm."

Until a recent study led by researchers at The University of Texas at Dallas was published online last month in PLOS ONE, there was no scientific evidence to back up the anecdotal stories of people, such as Underwood, who reported aberrant sensations and neuropathic pain around cellphone towers and other technology that produce radio-frequency electromagnetic fields.

"Our study provides evidence, for the first time, that subjects exposed to cellphone towers at low, regular levels can actually perceive pain," said Dr. Mario Romero-Ortega, senior author of the study and an associate professor of bioengineering in the University's Erik Jonsson School of Engineering and Computer Science. "Our study also points to a specific nerve pathway that may contribute to our main finding."

This is one of the first studies to look at the effects of electromagnetic fields (EMFs) in a nerve-injury model, said Romero-Ortega....There are nearly 2 million amputees in the United States, according to the Centers for Disease Control and Prevention, and many suffer from chronic pain. After interacting with Underwood, Romero-Ortega decided to study the phenomena that Underwood described.

The team hypothesized that the formation of neuromas -- inflamed peripheral nerve bundles that often form due to injury -- created an environment that may be sensitive to EMF-tissue interactions. To test this, the team randomly assigned 20 rats into two groups -- one receiving a nerve injury that simulated amputation, and the other group receiving a sham treatment. Researchers then exposed the subjects to a radiofrequency electromagnetic antenna for 10 minutes, once per week for eight weeks. The antenna delivered a power density equal to that measured at 39 meters from a local cellphone tower -- a power density that a person might encounter outside of occupational settings.

Researchers found that by the fourth week, 88 percent of subjects in the nerve-injured group demonstrated a behavioral pain response, while only one subject in the sham group exhibited pain at a single time point, and that was during the first week. After growth of neuroma and resection -- the typical treatment in humans with neuromas who are experiencing pain -- the pain responses persisted.

"Many believe that a neuroma has to be present in order to evoke pain. Our model found that electromagnetic fields evoked pain that is perceived before neuroma formation; subjects felt pain almost immediately," Romero-Ortega said....Romero-Ortega said since the research produced pain responses similar to those in anecdotal reports and a specific human case, the results "are very likely" generalizable to humans.

"There are commercially available products to block radio frequency electromagnetic energy. There are people who live in caves because they report to be hypersensitive to radiomagnetism, yet the rest of the world uses cellphones and does not have a problem. The polarization may allow people to disregard the complaints of the few as psychosomatic," he said. "In our study, the subjects with nerve injury were not capable of complex psychosomatic behavior. Their pain was a direct response to human-made radiofrequency electromagnetic energy."

At one point in the study, members of the research group showed Underwood video of subjects in the experiment and their response to radiofrequency electromagnetic fields. "It was exactly the same type of movements I would have around cellphones on roam, power lines and other electromagnetic fields," said Underwood, who has served on congressional medical committees and been exposed to some of the best doctors in the world.

Published on Leave a comment on Will the Blue Light From Device Screens Damage Our Eyes?

Now and then I hear people wondering whether the many hours we spend staring at computer, cell phone, and tablet screens is damaging our eyes. And what about fluorescent lighting (which seems to bother many people) and LED lights? After all, the blue light of all our device screens seems intense, and researchers have long known that blue light is toxic to the retina.

Recently researchers measured the blue light on various device screens and lamps (including over extended time periods) and compared it to looking at a clear blue sky in June (but not looking at the sun). They found that most devices put out less blue light than the blue sky on a clear day and all were less than international standards for blue light exposure limits. Whew...we're all OK. But don't use them for a long time at night because their bright emissionInternational Commission on Non-Ionizing Radiation Protectisuppresses melatonin (needed for sleep). From Medscape:

Blue Light From Screens, Bulbs Won't Damage Retina

Despite concerns that staring at devices putting out high amounts of the blue light wavelength could damage human retinas, a recent study finds that most devices put out less of that light than the blue sky on a clear day. "Even under extreme long-term viewing conditions, none of the low energy light bulbs, computers, tablets and mobile phones we assessed suggested cause for concern for public health," said lead author John O'Hagan, head of the Laser and Optical Radiation Dosimetry Group of Public Health England in Chilton, U.K., in an email.

As people are using computers and phones more often and low-energy lighting like fluorescent and LED bulbs is becoming more common, the types of light human eyes are encountering is changing, the researchers pointed out January 15 online in the journal Eye. Compared to traditional incandescent bulbs, electronic screens and low-energy light bulbs tend to emit more blue light, which has long been known to be toxic to the retina, they write.

Based on that toxicity research, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has proposed a safe exposure limit, below which blue light is unlikely to harm a viewer's eye. O'Hagan and his team measured the blue light emitted by several sources, including mobile phones, tablet computers, laptops and lamps, over time periods similar to the way people use the devices. Then they compared the emissions to the ICNIRP's exposure limits.

After comparing multiple colors on device screens, the researchers found that a white screen had the highest blue light emissions, so they used a white screen set at maximum brightness for their measurements.They also compared the blue light emissions from various devices to the levels people would encounter when looking at a clear blue sky in summertime in Chilton, in southern England, and also to an overcast winter sky in the same location.

The blue light exposure on a clear day in June was around 10 percent of the ICNIRP safe limit. A cloudy day in December produced around 3 percent of the limit. Comparing these natural exposures with light from lamps, computer screens and mobile devices like smartphones, the study team found that the artificial light produced even lower exposures than people normally encounter outdoors. That is, provided they're staring just at the sky, not directly at the sun.

 

Even considering that people may stare at computer screens for hours in the course of work or play, the study team concludes that there's no danger to the retina.They caution, however, that the amount of light that gets transmitted from the surface of the eye to the retina is age-related, so children may be more sensitive to blue light. Light sources that are comfortable for adults could be distressing for children, the authors warn.

Published on

This study is noteworthy and relevant to humans (it was done on mice) because it may explain why so many people taking antibiotics get frequent viruses or seem more susceptible to infections. Once bacteria (both good and bad) are killed by antibiotics, then the community becomes unbalanced (dysbiosis), so that viruses may gain a foothold and a viral infection develops. In a healthy microbial community all sorts of microbes can be found, even ones we typically consider pathogenic, but the whole community keeps them in balance. One can say that "depletion of commensal microbiota also affects antiviral immunity".

The study researchers said that the study findings were relevant to humans: that oral antibiotics could result in increased susceptibility to sexually transmitted infections, as well as other infectious viruses. Note: commensal microbes or commensalism is a the living together of two organisms (different species) in a relationship that is beneficial to one and has no effect on the other. Dysbiosis is microbial imbalance, the microbial community being "out of whack". From Science Daily:

Antibiotics may increase susceptibility to sexually transmitted infections

Commensal microbiota, populations of bacteria that inhabit the tissues of larger organisms, often have complex relationships with their hosts. Researchers have been aware for some time that commensal microbiota play a role in antiviral immunity by producing immune inductive signals that trigger inflammasome responses, among other things.

However, the role of dysbiosis on antiviral immunity hasn't been studied. Dysbiosis describes the loss of bacterial diversity within a microbiome, and the direct role that commensal microbiota play in antiviral immunity suggests that such loss would facilitate viral infections. Recently, a collaborative of Korean and Japanese scientists conducted a study into the effects of antibiotic-induced dysbiosis on antiviral immunity, and have published their results in the Proceedings of the National Academy of Sciences.

The researchers investigated the mechanisms of commensal microbial immunity on the genital mucosa by treating mice with antibiotics for four weeks and then exposing them to HSV-2. A control group received placebo. They report that the antibiotics caused dysbiosis within the vaginal microbiota, and resulted in a dramatic increase in innate immune response—specifically, they noted increases in an alarmin called IL-33, which blocked effector T cells from migrating into the vaginal tissues and secreting antiviral cytokines.

Antibiotic-treated mice succumbed to HSV-2 infection dramatically faster than control mice. They exhibited more severe pathology and all mice treated with antibiotics prior to viral exposure died within 11 days of infection. "Taking these data together, we find that depletion of commensal bacteria results in a severe defect in antiviral protection following mucosal HSV-2 infection," the researchers write.

By analyzing stool and vaginal washes from both groups of mice, they determined that antibiotic treatment induced an imbalance in the microbial composition of the vaginal mucosa. Further, they were able to determine that no single species of bacteria was responsible for the antiviral immunity effects of the commensal microbiome; rather, it was the imbalance of the microbiotic population that accounted for the effects.

 

The human mouth hosts a variety of microbes, some taking up residence on the mouth lining (blue) within days after birth. Credit: Martin Oeggerli (National Geographic)

Published on Leave a comment on BPA Free and BPA Plastic Have Similar Effects

Once again, research shows that "BPA-free" plastic does not mean it is safer than BPA plastic. Both BPA and BPS (the usual replacement for BPA) leach estrogenic chemicals into the foods and beverages, which means negative health effects when ingested. Both BPA and BPS mimic the effects of estrogen, as well as the actions of thyroid hormone. Yes, this study was done on zebrafish, but think of them as "the canaries in the mine" - if it affects them, it could affect humans also, especially developing fetuses and young children.

BPA  and BPS can leach into food, particularly under heat, from the lining of cans and from consumer products such as water bottles, baby bottles, food-storage containers, sippy cups, and plastic tableware. BPA can also be found in contact lenses, eyeglass lenses, compact discs, water-supply pipes, some cash register and ATM receipts, as well as in some dental sealants. A good way to minimize exposure to BPA , BPS, and other estrogenic chemicals is to try to avoid food and beverages in plastic containers and cans, but instead try to buy and store food in glass containers, jars, and bottles. From Science Daily:

'BPA-free' plastic accelerates embryonic development, disrupts reproductive system

Companies advertise "BPA-free" as a safer version of plastic products ranging from water bottles to sippy cups to toys. Many manufacturers stopped used Bisphenol A to strengthen plastic after animal studies linked it to early puberty and a rise in breast and prostate cancers.Yet new UCLA research demonstrates that BPS (Bisphenol S), a common replacement for BPA, speeds up embryonic development and disrupts the reproductive system.

Using a zebrafish model, Wayne and her colleagues found that exposure to low levels of BPA and BPS -- equivalent to the traces found in polluted river waters -- altered the animals' physiology at the embryonic stage in as quickly as 25 hours. "Egg hatching time accelerated, leading to the fish equivalent of premature birth," said Wayne, who is also UCLA's associate vice chancellor for research. "The embryos developed much faster than normal in the presence of BPA or BPS."

The UCLA team, which included first author Wenhui Qiu, a visiting graduate student from Shanghai University, chose to conduct the study in zebrafish because their transparent embryos make it possible to "watch" cell growth as it occurs.... In a second finding, the team discovered that the number of endocrine neurons increased up to 40 percent, suggesting that BPA overstimulates the reproductive system.... "We saw many of these same effects with BPS found in BPA-free products. BPS is not harmless."

After uncovering her first finding about BPA in 2008, Wayne immediately discarded all of the plastic food containers in her home and replaced them with glass. She and her family purchase food and drinks packaged in glass whenever possible. "Our findings are frightening and important," emphasized Wayne. "Consider it the aquatic version of the canary in the coal mine."

Finally, the researchers were surprised to find that both BPA and BPS acted partly through an estrogen system and partly through a thyroid hormone system to exert their effects. "Most people think of BPA as mimicking the effects of estrogen. But our work shows that it also mimics the actions of thyroid hormone," said Wayne. "Because of thyroid hormone's important influence on brain development during gestation, our work holds important implications for general embryonic and fetal development, including in humans."

Researchers have proposed that endocrine-disrupting chemicals may be contributing to the U.S.' rise in premature human births and early onset of puberty over the past couple of decades. "Our data support that hypothesis," said Wayne. "If BPA is impacting a wide variety of animal species, then it's likely to be affecting human health. Our study is the latest to help show this with BPA and now with BPS."