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Category: healthy living

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Flatulence is good, and up to 18 a day is totally normal! From NPR:

Got Gas? It Could Mean You've Got Healthy Gut Microbes

We know that air often comes after eating nutrient-packed vegetables, such as cabbage, kale and broccoli. And researchers have found that fiber-rich foods, like beans and lentils, boost the levels of beneficial gut bacteria after only a few days, as we reported in December.

So all this got us wondering: Could passing gas, in some instances, be a sign that our gut microbes are busy keeping us healthy? Absolutely, says Purna Kashyap, a gastroenterologist at the Mayo Clinic in Rochester, Minn. "Eating foods that cause gas is the only way for the microbes in the gut to get nutrients," he says. "If we didn't feed them carbohydrates, it would be harder for them to live in our gut."

And we need to keep these colon-dwelling critters content, Kashyap says. When they gobble up food — and create gas — they also make molecules that boost the immune system, protect the lining of the intestine and prevent infections.

"A healthy individual can have up to 18 flatulences per day and be perfectly normal," he adds.

Gas gets into the digestive tract primarily through  two routes: Swallowing air (which we all do when we eat and chew gum) and your microbiome. That's the collection of organisms in the GI tract that scientists and doctors are currently all fired up about. (Check our colleague Rob Stein's recent series on it.) That microbiome includes hundreds of different bacteria. But there are also organisms from another kingdom shacking up with them: the archaea.

All these microbes are gas-making fools. They eat up unused food in your large intestine, like fiber and other carbohydrates we don't digest, and churn out a bunch of gases as waste. But that's not all they make. They also produce a slew of molecules (called short chain fatty acids) that may promote the growth of other beneficial bacteria and archaea.

And the more fiber you feed these friendly inhabitants, the more types of species appear, studies have found. "Undigested carbohydrates allow the whole ecosystem to thrive and flourish," Kashyap says. Most gas made by the microbiome is odorless. It's simply carbon dioxide, hydrogen or methane. But sometimes a little sulfur slips in there."That's when it gets smelly," Kashyap says.

But here's the hitch: Many of the smelly sulfur compounds in vegetables have healthful properties. Take for instance, the broccoli, mustard and cabbage family. These Brassica vegetables are packed with a sulfur compound, called sulforaphane, that is strongly associated with a reduced risk of cancer. Another possible benefit of a little smelly gas? It may reduce the total volume of air in the gut, Kashyap says. 

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This study suggests another reason to avoid Triclosan. From Science Daily:

In lab tests, the antimicrobial ingredient triclosan spurs growth of breast cancer cells

Some manufacturers are turning away from using triclosan as an antimicrobial ingredient in soaps, toothpastes and other products over health concerns. And now scientists are reporting new evidence that appears to support these worries. Their study, published in the ACS journal Chemical Research in Toxicology, found that triclosan, as well as another commercial substance called octylphenol, promoted the growth of human breast cancer cells in lab dishes and breast cancer tumors in mice.

Kyung-Chul Choi and colleagues note that hormonal imbalances seem to play a role in the development of breast cancer. Given that link, researchers are investigating whether endocrine-disrupting chemicals (EDCs), which are compounds that act like hormones, might spur cancer cell growth. EDCs have become ubiquitous in products, in the environment and even in our bodies. Research has found that two EDCs -- triclosan, an antimicrobial ingredient in many products, including soaps, cosmetics and cutting boards; and octylphenol, which is in some paints, pesticides and plastics -- have accumulated in the environment. Additionally, triclosan is reportedly in the urine of an estimated 75 percent of Americans. Choi's team wanted to see what effect the two compounds have on breast cancer cells.

In tests on human breast cancer cells and in special immunodeficient mice with tissue grafts, the scientists found that both agents interfered with genes involved with breast cancer cell growth, resulting in more cancer cells. Mice that were exposed to the two compounds had larger and denser breast cancer tumors than the control group. "Although the doses of EDCs were somewhat high, we did this to simulate their effects of daily exposure, as well as body accumulation due to long-term exposure, simultaneously in animal experiments," said Choi. "Thus, exposure to EDCs may significantly increase the risk of breast cancer development and adversely affect human health," the researchers state in the paper.

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Excerpts from a very interesting NPR interview with Dr. Martin Blaser and his views on the human microbiome. The big take-away: our modern life-style is not good for the gut microbiome. His recently published book is Missing Microbes: How the Overuse of Antibiotics is Fueling Our Modern Plagues.

From NPR News: Modern Medicine May Not Be Doing Your Microbiome Any Favors

There are lots of theories about why food allergies, asthma, celiac disease and intestinal disorders like Crohn's disease have been on the rise. Dr. Martin Blaser speculates that it may be connected to the overuse of antibiotics, which has resulted in killing off strains of bacteria that typically live in the gut.

Blaser is an expert on the human microbiome, which is the collection of bacteria, viruses, fungi and other microbes that live in and on the body. In fact, up to 90 percent of all the cells in the human body aren't human at all — they're micro-organisms. Blaser is the director of NYU's Human Microbiome Program and a former chairman of medicine there. His new book is called Missing Microbes: How the Overuse of Antibiotics Is Fueling Our Modern Plagues.

"Since World War II, we've seen big rises in a number of diseases: asthma, allergies, food allergies, wheat allergy, juvenile diabetes, obesity. ... These are all diseases that have gone up dramatically in the last 50 or 70 years. One of the questions is: Why are they going up? Are they going up for 10 different reasons, or perhaps there is one reason that is fueling all of them."

"My theory is that the one reason is the changing microbiome; that we evolved a certain stable situation with our microbiome and with the modern advances of modern life, including modern medical practices, we have been disrupting the microbiome. And there's evidence for that, especially early in life, and it's changing how our children develop."

"There's a choreography; there's a normal developmental cycle of the microbiome from birth over the first few years of life, especially the first three years, [that] appear[s] to be the most important. And that's how nature has, how we have, evolved together so that we can maximize health and create a new generation, which is nature's great purpose. And because of modern practices, we have disrupted that. And then the question is: Does that have consequence[s]?"

"As far as we know, when the baby is inside the womb it is apparently sterile. ... The big moment of truth is when the membranes rupture, the water breaks, and the baby starts coming out. And that's where they first get exposed to the bacteria of the world, and the first bacteria they're exposed to is their mother's bacteria in the birth canal. So as labor proceeds, the babies are in contact with the microbes lining their mother's vagina and, as they're going out, they're covered by these bacteria. They swallow the bacteria; it's on their skin. ..."

"That's their initial exposure to the world of bacteria. That's how mammals have been doing it for the last 150 million years, whether they're dolphins or elephants or humans. ... And we know a little about what those bacteria are. The most common bacteria are lactobacillus and there's evidence that over the course of pregnancy the microbiome in the vagina changes, just as many other parts of the body are changing. The microbiome is changing in its composition in terms of maximizing lactobacilli, and these are bacteria that eat lactose, which is the main component of milk. So the baby's mouth is filled with lactobacilli. The first thing that happens is they go up against their mom's breast and they inoculate the nipple with lactobacilli and now milk and lactobacilli go into the new baby and that's the foundation for their microbiome and that's how they start their life. ..."

"You could project that if they didn't acquire these organisms or they didn't acquire them normally or at the normal time, then the foundations might be a little shaky."

"Shortly after birth, they compared the microbiomes in the babies that came out. The babies that were born vaginally, their microbiome, not surprisingly, looked like the mom's vagina everywhere in the body — in their GI tract, on their skin, in their mouth. But the babies born by C-section, their microbiome looked like skin and it didn't even necessarily look like the mom's skin, maybe it was somebody else in the operating room. So it's clear that the microbiome is different immediately depending on the kind of birth."

"What I can tell you is that our immune system is quite complex. There are many kinds of immune cells. There are cells that strongly recognize foreign substances, there are ones that try to damp [the immune system] and down-regulate it. There's what we call innate immunity, which is the immunity we're all born with, and then there's adaptive immunity — the immunity that develops when we experience different kinds of exposures. So it's very complex."

"There are many different probiotics.  I think I can say three things: The first is that they're almost completely unregulated; second is that they seem to be generally safe; and third is that they're mostly untested. ... I'm actually a big believer in probiotics; I think that's going to be part of the future of medicine, that we're going to understand the science of the microbiome well enough so that we can look at a sample from a child and say this child is lacking such-and-such an organism and now we're going to take it off the shelf and we're going to give it back to that child. ... "

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An argument for the need for human exposure to the microbes in rural environments. However, the role of diesel exhaust and other urban air pollutants is not discussed here (for example, diesel exhaust is linked to asthma). From Science Daily:

Rural microbes could boost city dwellers' health, study finds

The greater prevalence of asthma, allergies and other chronic inflammatory disorders among people of lower socioeconomic status might be due in part to their reduced exposure to the microbes that thrive in rural environments, according to a new scientific paper co-authored by a University of Colorado Boulder researcher.

The article, published in the journal Clinical & Experimental Immunology, argues that people living in urban centers who have less access to green spaces may be more apt to have chronic inflammation, a condition caused by immune system dysfunction.

When our immune systems are working properly, they trigger inflammation to fight off dangerous infections, but the inflammation disappears when the infection is gone. However, a breakdown in immune system function can cause a low level of inflammation to persist indefinitely. Such chronic inflammation can cause a host of health disorders.

Some scientists have hypothesized that the increase of chronic inflammation in wealthier Western countries is connected to lifestyles that have essentially become too clean. The so-called "hygiene hypothesis" is based on the notion that some microbes and infections interact with the immune system to suppress inflammation and that eliminating exposure to those things could compromise your health.

The authors agree that microbes and some types of infections are important because they can keep the immune system from triggering inflammation when it's not necessary, as happens with asthma attacks and allergic reactions.

But they say the infections that were historically important to immune system development have largely been eliminated in developed countries. The modern diseases we pick up from school, work and other crowded areas today do not actually lead to lower instances of inflammatory disorders.

During our evolutionary history, the human immune system was exposed to microbes and infections in three important ways: commensal microbes were passed to infants from their mothers and other family members; people came into contact with nonpathogenic microbes in the environment; and people lived with chronic infections, such as helminths, which are parasitic worms found in the gut and blood.

In order for those "old infections" to be tolerated in the body for long periods of time, they evolved a mechanism to keep the human immune system from triggering inflammation. Similarly, environmental bacteria, which were abundant and harmless, were tolerated by the immune system. According to Rook, a professor at UCL, "Helminthic parasites need to be tolerated by the immune system because, although not always harmless, once they are established in the host efforts by the immune system to eliminate them are futile, and merely cause tissue damage."

In contrast, relatively modern "crowd infections," such as measles or chicken pox, cause an inflammatory response. The result is that either the sick person dies or the infection is wiped out by the inflammation and the person becomes immune from having the same infection again in the future.

Collectively, the authors refer to the microbes and old infections that had a beneficial impact on the function of our immune systems as "old friends." Exposure to old friends plays an important role in guarding against inflammatory disorders, the authors said. Because the "old infections" are largely absent from the developed world, exposure to environmental microbes -- such as those found in rural environments, like farms and green spaces -- has likely become even more important.

The authors say this would explain why low-income urban residents -- who cannot easily afford to leave the city for rural vacations -- are more likely to suffer from inflammatory disorders. The problem is made worse because people who live in densely populated areas also are more likely to contract crowd infections, which cause more inflammation.

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Good news for those who enjoy drinking a little wine. From Medical Xpress:

A little wine might help kidneys stay healthy

An occasional glass of wine might help keep your kidneys healthy, new research suggests. And for those who already have kidney disease, which puts one at higher risk for cardiovascular problems, moderate wine drinking might help the heart. the researchers added.

"Those [with healthy kidneys] who drank less than one glass of wine a day had a 37 percent lower risk of having chronic kidney disease than those who drank no wine," said study author Dr. Tapan Mehta, a renal fellow at the University of Colorado Anschutz Medical Center, in Aurora.

"Those with chronic kidney disease who drank less than one glass a day had a 29 percent lower risk of cardiovascular events [than those who drank no wine]," he added.

Mehta and his colleagues looked at data from the 2003 to 2006 National Health and Nutrition Examination that included nearly 6,000 people. Of those, about 1,000 had chronic kidney disease.

Having chronic kidney disease increases the risk of cardiovascular disease. About 26 million Americans have chronic kidney disease, often caused by diabetes and high blood pressure, according to the National Kidney Foundation. Previous research has found that moderate drinking is linked to heart benefits.

Exactly why wine might do that is not known for sure, Mehta said. Drinking moderate amounts is linked with lower levels of protein in the urine. In those who have kidney disease, higher protein levels in the urine are linked with an increased risk of progression of kidney disease. The polyphenols found in wine have anti-inflammatory and antioxidant properties, which may help explain the protective heart effects, he said.

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Based on this research, the message stays the same: get out there and exercise for healthy aging. From Medical Xpress:

Midlife occupational and leisure-time physical activity limits mobility in old age

Strenuous occupational physical activity in midlife increases the risk of mobility limitation in old age, whereas leisure-time physical activity decreases the risk. This is found in a study which followed up 5,200 public sector employees for 28 years. The study was conducted at the Gerontology Research Center in Finland and the Finnish Institute of Occupational Health.

Heavy physical labor is often repetitive, wears the body and lasts for several hours a day. On the contrast, leisure-time physical activity is designed to improve fitness and provide recreation and a typical exercise session lasts for one or two hours. Even though both are based on muscle activity and result in energy expenditure, their long-term consequences are different.

"A person doing heavy manual work may compensate for its detrimental effects by participating in brisk leisure-time physical activity," says professor Taina Rantanen, the leader of the research group.

Mobility limitation was assessed five times and was based on a person's ability to maintain and change body positions, carry and handle objects and walk and move. The baseline assessment took place in 1981 and the last assessment in 2009. 

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Important to know about this nasty bacterial strain for those who use contact lenses. From Science Daily:

Bacteria survive longer in contact lens cleaning solution than previously thought, study shows

Each year in the UK, bacterial infections cause around 6,000 cases of a severe eye condition known as microbial keratitis -- an inflammation and ulceration of the cornea that can lead to loss of vision. The use of contact lenses has been identified as a particular risk factor for microbial keratitis. New research, presented today at the Society for General Microbiology Annual Conference in Liverpool, shows that a bacterial strain associated with more severe infections shows enhanced resistance to a common contact lens disinfectant solution.

Researchers from The University of Liverpool and The Royal Liverpool University NHS Trust tested different strains of the keratitis-causing bacterium Pseudomonas aeruginosa for their ability to survive in a commonly used contact lens cleaning solution. The team compared nine clinical strains of P. aeruginosa, taken from hospital patients in the UK, with P. aeruginosa strain 9027, the standard strain used by lens solution manufacturers.

The results showed that the majority of clinical strains tested were killed within 10 minutes of being immersed in the contact lens solution, comparable with the standard reference strain. However, one clinical isolate, P. aeruginosa strain 39016 -- associated with a more severe case of keratitis with a prolonged healing time -- was able to survive for over four hours, much longer than the reference strain.

Professor Craig Winstanley, who led the research, says: "Microbial keratitis can be devastating for a patient -- it is important that the risk of developing this condition is reduced in contact lens wearers by improving contact lens disinfectant solutions."

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The controversy over the safety of BPA (bisphenol A) is still dragging on. However, the new alternatives to BPA may not be any better and may be even worse. To minimize exposure to BPA and other estrogenic chemicals, try to buy and store food in glass bottles, jars, and containers (glass does not contain plastics of any sort). The following two articles discuss this issue. From Nature:

Toxicology: The plastics puzzle

A stroll down the aisles of a US supermarket reveals a modest victory for consumer activism. In the baby-products section, plastic baby bottles, spill-proof cups and miniature cutlery are proudly marked 'BPA-free' — a sign that they no longer contain the compound bisphenol A, found in many plastics.

The partial withdrawal of BPA is the culmination of two decades of research and hundreds of studies linking the compound — which mimics sex hormones called oestrogens — to adverse health effects in rodents and humans.  The decision by regulators in the United States and European Union to ban BPA from baby bottles, combined with industry marketing campaigns, has convinced many consumers that the plastics and other containers currently used to store food are safe.

It is a false sense of security. BPA is still a constituent of many food containers, especially cans. And when companies did abandon BPA, they often adopted compounds — such as the increasingly common bisphenol S (BPS) — that share much of the same chemistry and raise many of the same concerns as BPA. “People use this chemical to replace BPA without sufficient toxicological information,” says Kyungho Choi, an environmental toxicologist at Seoul National University. “That is a problem.”

BPA has formed the chemical backbone of most hard, clear polycarbonate plastic since the 1950s. Over time, studies have linked the chemical — which can leach out of plastics and into food — to a host of adverse health effects, including reductions in fertility and birth weight, male genital abnormalities, altered behavioural development, diabetes, heart disease and obesity1 (see Nature464, 1122–1124; 2010).

A few years ago, mounting evidence and concerned consumers convinced governments to take action. In 2011, the European Union banned BPA from baby bottles; the United States followed suit a year later. But BPA-based linings are still slathered on the insides of most food and beverage cans, and used to coat water-supply pipes in many countries. The compound is also found in dental sealants and in incubators for premature infants.

BPA-based epoxy linings are widely used because they are strong, flexible and cheap. They tolerate the high temperatures needed to sterilize foods during canning, and do not interact with a huge array of foods and beverages, according to the North American Metal Packaging Alliance in Washington DC. The alliance estimates that 95% of all aluminium and steel can coatings are epoxy-type resins: more than 99.9% of these contain BPA.

New options are beginning to surface. BPS was first made in 1869 as a dye. But because it was introduced into consumer goods only recently — into cash-register receipts in 2006, for example — few researchers have studied its toxicity. “The main question, to which we have no answer, is: 'is BPS as toxic as BPA?'” says René Habert, an endocrinologist at Paris Diderot University.

The similarity of BPS's structure to that of BPA is enough to raise suspicions that it may mimic oestrogens, says Cheryl Watson, a biochemist at the University of Texas Medical Branch in Galveston. When combined with levels of oestradiol found in adult women, BPS seemed to over-stimulate the pathway, shutting it down and causing cell suicide. The results, says Watson, were typical of those expected of an oestrogen mimic: inappropriate activation of oestrogen responses, disruption of normal oestrogen-response pathways, and eventual cell death. 

Some manufacturers have left the bisphenol family in search of a replacement. In 2007, the Eastman Chemical Company launched Tritan — a new heat-resistant clear plastic — for infant-care products such as baby bottles. This BPA-free plastic has since replaced the old BPA-containing polycarbonate in many water bottles, food containers and children's cups. 

In 2011, George Bittner, a neurobiologist at the University of Texas at Austin and the chief executive of Austin-based chemical-testing company CertiChem, reported that 92% of 102 commercially available plastic products leached chemicals with oestrogenic activity7. This included plastics advertised as BPA-free. The reason, Bittner says, is that additives in plastics — such as stabilizers and lubricants — can also bind to oestrogen receptors, as can some of the plastic monomers themselves. Tritan resins produced by Eastman were among the polymers that showed oestrogenic activity in Bittner's assays. 

In 2012, the world produced some 280 million tonnes of plastic. According to a model based on the United Nations' Globally Harmonized System of Classification and Labelling of Chemicals, more than 50% of these plastics contain ingredients that can be hazardous (see Nature 494, 169–171; 2013). Some are carcinogenic; others are oestrogenic.

It is not yet clear how many of these chemicals are dangerous at the concentrations found in the plastics. But mixed together, the chemicals could have synergistic effects. 

Ideally, says Watson, the next generation of chemicals would be tested for effects on oestrogen signalling before widespread deployment in food containers.

From Mother Jones:

The Scary New Evidence on BPA-Free Plastics

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This study came out last month, but I think it is something to be concerned about any time you are thinking about getting cosmetic "fillers". Definitely check out the photo. From Science Daily:

Cosmetic treatment can open door to bacteria

Many people have 'fillers' injected into their facial tissue to give them 'bee-stung lips' or to smooth out their wrinkles. Unfortunately, a lot of cosmetic treatment customers experience unpleasant side effects in the form of tender subcutaneous lumps that are difficult to treat and which -- in isolated cases -- have led to lesions that simply will not heal. Research recently published by the University of Copenhagen now supports that, despite the highest levels of hygiene, this unwanted side effect is caused by bacterial infection.

Injections of fillers were previously reserved exclusively for trauma treatment -- when rebuilding a face disfigured in a traffic accident, for example. However, the jelly-like substances are increasingly being used in beauty treatments with the intention of making lips swell up and to erase the effects of ageing from the skin. Side effects in the form of stubborn, tender lumps or even lesions are becoming an increasing problem:

"Previously, most experts believed that the side effects were caused by an auto-immune or allergic reaction to the gel injected. Research involving tissue from patients and mouse models has now shown that the disfiguring lesions are actually due to bacteria injected in connection with the cosmetic procedure. What is more, we have demonstrated that the fillers themselves act as incubators for infection, and all it takes is as few as ten bacteria to create an ugly lesion and a tough film of bacterial material -- known as biofilm -- which is impossible to treat with antibiotics," says Morten Alhede, a postdoc at the Department of International Health, Immunology and Microbiology, University of Copenhagen.

Treatment with fillers is very common. According to the American Society for Aesthetic Plastic Surgery (ASAPS), treatment with products based on hyaluronic acid -- such as Restylane -- constitutes the second-most popular non-surgical cosmetic procedure in the United States. The precise figures for Denmark are not known, but there can be no doubt that the numbers are rising rapidly -- and a rise in the number of treatments will inevitably make the side effects more evident.

"Because a lot of cosmetic practitioners refuse to accept that side effects from filler procedures are caused by bacteria, claiming that such problems are caused by allergic reactions, the usual procedure has been to treat with steroids. This is actually the worst possible treatment because steroid injections exacerbate the condition and give the bacteria free rein. Fortunately, many of the filler producers have now become aware of the risk of bacteria and recognise that the gel can act as a bacterial incubator," says Associate Professor Thomas Bjarnsholt from the Department of International Health, Immunology and Microbiology. He continues:

"The problem will become very serious when the treatment becomes so widespread that people are able to walk in off the street to have their wrinkles smoothed out. Experts recommend keeping facial skin free from make-up for a month before undergoing a treatment involving fillers. Good hygiene is always important. Even when you abide by all the rules and regulations, it is difficult to avoid bacteria completely as they are often buried far below the surface of the skin."

Researchers estimate that between 1:100 and 1:1000 -- depending on the type of filler - develops an unfortunate bacterial infection which, in the worst-case scenario, may leave the person in question with a permanently disfigured face.

The biofilm that can develop in the wake of a filler treatment is resistant to antibiotics. "The good news is that infections can be prevented by prophylactic antibiotic treatment, i.e. injecting antibiotics together with the filler itself during the cosmetic treatment process. Our new research emphasises how important it is for all practitioners to follow this procedure to prevent the unwanted complications," explains Morten Alhede.

Injection of fillers: Side effects in the form of stubborn, tender lumps or even lesions are becoming an increasing problem. Photo credit: University of Copenhagen

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Youthful skin (even reversing the effects of aging!) is an excellent reason to exercise. And apparently it's never too late to start. From NY Times:

Younger Skin Through Exercise

Exercise not only appears to keep skin younger, it may also even reverse skin aging in people who start exercising late in life, according to surprising new research.

As many of us know from woeful experience, our skin changes as the years advance, resulting in wrinkles, crow’s feet and sagging skin. This occurs because of changes within our layers of skin. After about age 40, most of us begin to experience a thickening of our stratum corneum, the final, protective, outer layer of the epidermis, itself the top layer of your skin. The stratum corneum is the portion of the skin that you see and feel. Composed mostly of dead skin cells and some collagen, it gets drier, flakier and denser with age.

At the same time, the layer of skin beneath the epidermis, the dermis, begins to thin. It loses cells and elasticity, giving the skin a more translucent and often saggier appearance. These changes are independent of any skin damage from the sun. They are solely the result of the passage of time.

But recently, researchers at McMaster University in Ontario began to wonder if such alterations were inevitable. Earlier studies at McMaster involving mice that were bred to age prematurely had shown that a steady regimen of exercise could stave off or even undo the signs of early aging in these animals. 

Of course, we humans long ago swapped our fur for naked skin. But if exercise could keep animals’ outer layer from changing with age, it might, the researchers speculated, do the same for our skin.

To test that possibility, the scientists first gathered 29 local male and female volunteers ages 20 to 84. About half of the participants were active, performing at least three hours of moderate or vigorous physical activity every week, while the others were resolutely sedentary, exercising for less than an hour per week. Then the researchers asked each volunteer to uncover a buttock. “We wanted to examine skin that had not been frequently exposed to the sun,” said Dr. Mark Tarnopolsky.

The scientists biopsied skin samples from each volunteer and examined them microscopically. When compared strictly by age, the skin samples overall aligned with what would be expected. Older volunteers generally had thicker outer layers of skin and significantly thinner inner layers. But those results shifted noticeably when the researchers further subdivided their samples by exercise habits. They found that after age 40, the men and women who exercised frequently had markedly thinner, healthier stratum corneums and thicker dermis layers in their skin. Their skin was much closer in composition to that of the 20- and 30-year-olds than to that of others of their age, even if they were past age 65.

So the researchers next got skin samples from their buttocks. The volunteers were aged at 65 or older and, at the study’s start, had normal skin for their age. They began a fairly straightforward endurance training program, working out twice a week by jogging or cycling at a moderately strenuous pace, equivalent to at least 65 percent of their maximum aerobic capacity for 30 minutes. This continued for three months. At the end of that time, the researchers again biopsied the volunteers’ skin.

But now the samples looked quite different, with outer and inner layers that looked very similar to those of 20- to 40-year-olds. “I don’t want to over-hype the results, but, really, it was pretty remarkable to see,” said Dr. Tarnopolsky, himself a middle-aged exerciser. Under a microscope, the volunteers’ skin “looked like that of a much younger person, and all that they had done differently was exercise.”

How exercise changes skin composition is not completely clear, but in a separate portion of the study, the researchers checked for alterations in the levels of certain substances created by working muscles. Called myokines, these substances are known to enter the bloodstream and jump-start changes in cells far from the muscles themselves. In this case, the scientists found greatly augmented levels of a myokine called IL-15 in the skin samples of volunteers after exercise. Their skin samples contained almost 50 percent more IL-15 after they had been exercising than at the start of the study.

The researchers suspect that additional myokines and substances are also involved in the skin changes related to exercise, Dr. Tarnopolsky said, making it unlikely that any IL-15 pill, salve or injection will ever replicate the skin benefits of a workout. Nor is there evidence that exercise reverses wrinkling and other damage from the sun, some of which many of us accumulate during outdoor exercise.