Well: How Exercise May Protect Against Depression

Photo Credit Getty Images

Phys Ed

Gretchen Reynolds on the science of fitness.

Exercise may help to safeguard the mind against depression through previously unknown effects on working muscles, according to a new study involving mice. The findings may have broad implications for anyone whose stress levels threaten to become emotionally overwhelming.

Mental health experts have long been aware that even mild, repeated stress can contribute to the development of depression and other mood disorders in animals and people.

Scientists have also known that exercise seems to cushion against depression. Working out somehow makes people and animals emotionally resilient, studies have shown.

But precisely how exercise, a physical activity, can lessen someone's risk for depression, a mood state, has been mysterious.

So for the new study, which was published last week in Cell, researchers at the Karolinska Institute in Stockholm delved into the brains and behavior of mice in an intricate and novel fashion.

Mouse emotions are, of course, opaque to us. We can't ask mice if they are feeling cheerful or full of woe. Instead, researchers have delineated certain behaviors that indicate depression in mice. If animals lose weight, stop seeking out a sugar solution when it's available — because, presumably, they no longer experience normal pleasures — or give up trying to escape from a cold-water maze and just freeze in place, they are categorized as depressed.

And in the new experiment, after five weeks of frequent but intermittent, low-level stress, such as being restrained or lightly shocked, mice displayed exactly those behaviors. They became depressed.

The scientists could then have tested whether exercise blunts the risk of developing depression after stress by having mice run first. But, frankly, from earlier research, they knew it would. They wanted to parse how.

So they bred pre-exercised mice.

A wealth of earlier research by these scientists and others had shown that aerobic exercise, in both mice and people, increases the production within muscles of an enzyme called PGC-1alpha. In particular, exercise raises levels of a specific subtype of the enzyme known unimaginatively as PGC-1alpha1. The Karolinska scientists suspected that this enzyme somehow creates conditions within the body that protect the brain against depression.

But to determine if that theory was true, they had to isolate the PGC-1alpha1 from all the other substances pumped out by the muscles during and after exercise. So they created mice that, even without exercising, were awash in high levels of PGC-1alpha1. Their muscles produced lots of it, even when they were lazing around.

The scientists then exposed these animals to five weeks of mild stress. The mice responded with slight symptoms of worry. They lost weight. But they did not develop full-blown rodent depression. They continued to seek out sugar and fought to get out of the cold-water maze. Their high levels of PGC-1alpha1 appeared to render them depression-resistant.

But the scientists knew that the PGC-1alpha1 was almost certainly not directly protecting the animals' brains. It doesn't work that way, acting directly on cells. Rather it is what's known as a promoter, sparking activity in genes, which in turn express proteins that then affect various physiological processes throughout the body.

So the scientists looked for which processes were being most notably intensified in their PGC-1alpha1-rich mice. They found one in particular, involving a substance called kynurenine that accumulates in human and animal bloodstreams after stress. Kynurenine can pass the blood-brain barrier and, in animal studies, has been shown to cause damaging inflammation in the brain, leading, it is thought, to depression.

But in the mice with high levels of PGC-1alpha1, the kynurenine produced by stress was set upon almost immediately by another protein expressed in response to signals from the PGC-1alpha1. This protein changed the kynurenine, breaking it into its component parts, which, interestingly, could not pass the blood-brain barrier. In effect, the extra PGC-1alpha1 had called up guards that defused the threat to the animals' brains and mood from frequent stress.

Finally, to ensure that these findings are relevant to people, the researchers had a group of adult volunteers complete three weeks of frequent endurance training, consisting of 40 to 50 minutes of moderate cycling or jogging. The scientists conducted muscle biopsies before and after the program and found that by the end of the three weeks, the volunteers' muscle cells contained substantially more PGC-1alpha1 and the substance that breaks down kynurenine than at the study's start.

The upshot of these results, in the simplest terms, is that "you reduce the risk of getting depression when you exercise," said Maria Lindskog, a researcher in the department of neuroscience at the Karolinska Institute and a study co-author.

Whether the same biochemical processes likewise combat depression that already exists is less certain, said Jorge Ruas, a principal investigator at the Karolinska Institute and the study's senior author. But he is hopeful. "We think that this mechanism would be efficient if activated after depression has begun," he said. He and his colleagues hoped to test that possibility in mice soon.

In the meantime, if work and other pressures mount, it may be a good idea to go for a jog. It may just keep your kynurenine in check.

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Well: Ask Well: Weights Before Cardio?

Photo Credit Ariel Zambelich

A

Many dedicated gym-goers have heard that aerobic and resistance-style exercise should not be combined in a single workout; or if they are, that one or the other must come first. The theory behind these claims is that each form of exercise interferes, physiologically, with the other, potentially blunting the desired training effects.

But the best available science disagrees. In an interesting study published in March in the Journal of Applied Physiology, healthy young volunteers vigorously rode a stationary bicycle using one leg and then completed resistance exercises with both legs, meaning that one limb did both types of exercise; the other only weights. After five weeks, both legs had grown equally large and strong. Cycling first had not reduced the impacts of weight training.

Similarly, a 2012 study of sedentary, middle-age men found that they developed specific molecular changes in their leg muscles after riding a stationary bicycle that were distinct from those occurring on a separate day after lower-body weight training. But when the men performed both forms of exercise one after the other (doing half as much of each), they robustly developed both types of molecular responses.

"We saw no indications of interference," said Stuart Phillips, a professor of kinesiology at McMaster University in Hamilton, Ontario, who oversaw the study.

Perhaps most telling, the order of the exercises in these studies was immaterial. In the 2014 study, the men rode and then lifted; in Dr. Phillips's study, they lifted and then rode. Muscles, it seems, "can't tell the difference," Dr. Phillips said.

So don't worry overmuch about which exercise comes when. "Just set up a workout regimen that happens to be convenient for you," Dr. Phillips said.

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Well: Vitamin E and Selenium Fail to Prevent Cataracts

Many health supplement companies, and some medical experts, have recommended vitamin E and selenium for reducing the risk for cataracts. But a large new study has found they are unlikely to provide benefit, though selenium might have a small effect.

Researchers randomly assigned 11,267 men over 50 to four groups of about 2,800 each. Members of one group took a daily placebo, those in the second took 400 IU of vitamin E daily, those in a third took 200 micrograms of selenium a day, and those in the fourth group took both vitamin E and selenium.

The five-year study, published in JAMA Ophthalmology, found 389 confirmed cataracts: 98 in those who took vitamin E, 99 in those who took both supplements, 86 in those who took only selenium, and 106 in the placebo group. None of the differences was statistically significant, though selenium showed a trend that suggests it might have a slight benefit; additional research would be needed.

"The results are consistent with earlier trials of vitamin E," said the lead author, William G. Christen, an associate professor of medicine at Brigham and Women's Hospital in Boston. "They show that for cataracts, the effect is nothing."

But, he added, "These are the first data on selenium alone, and we can't rule out a small but still important effect."

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Well: Ask Well: Weights Before Cardio?

Photo Credit Ariel Zambelich

Ask Well

Your health questions answered by Times journalists and experts.

A

Many dedicated gym-goers have heard that aerobic and resistance-style exercise should not be combined in a single workout; or if they are, that one or the other must come first. The theory behind these claims is that each form of exercise interferes, physiologically, with the other, potentially blunting the desired training effects.

But the best available science disagrees. In an interesting study published in March in the Journal of Applied Physiology, healthy young volunteers vigorously rode a stationary bicycle using one leg and then completed resistance exercises with both legs, meaning that one limb did both types of exercise; the other only weights. After five weeks, both legs had grown equally large and strong. Cycling first had not reduced the impacts of weight training.

Similarly, a 2012 study of sedentary, middle-age men found that they developed specific molecular changes in their leg muscles after riding a stationary bicycle that were distinct from those occurring on a separate day after lower-body weight training. But when the men performed both forms of exercise one after the other (doing half as much of each), they robustly developed both types of molecular responses.

"We saw no indications of interference," said Stuart Phillips, a professor of kinesiology at McMaster University in Hamilton, Ontario, who oversaw the study.

Perhaps most telling, the order of the exercises in these studies was immaterial. In the 2014 study, the men rode and then lifted; in Dr. Phillips's study, they lifted and then rode. Muscles, it seems, "can't tell the difference," Dr. Phillips said.

So don't worry overmuch about which exercise comes when. "Just set up a workout regimen that happens to be convenient for you," Dr. Phillips said.

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Well: A Doctor, a Rabbi and a Chicken

Photo Credit Keith Negley

"Doctor, is it O.K. for our rabbi to visit my father?"

I was an intern on call in one of the internal medicine wards in an Israeli hospital just south of Tel Aviv. The first day of the Jewish holiday of Sukkot had just ended, and the ward was beginning to fill up with visitors who had been unable to drive until after sunset.

Looking up from what I was doing, I saw the son of one of my patients standing at the counter of the nursing station. He and I had already spoken several times that day about his 75-year-old father, who had been admitted the night before because of a stroke.

The father's CT scan from the night before had been unremarkable, not unusual in patients whose strokes are caused by an interruption of blood flow to portions of the brain. I had explained this to the son, as well as what to expect over the next few days as his father would undergo further testing and then discharge to a rehabilitation facility. I told him that it was impossible at this early stage to predict how much function his father might recover, and cautioned against giving him anything to eat or drink until we were certain that his ability to swallow had not been affected. All of the son's questions had been very appropriate and focused.

"Of course," I responded, smiling and a little surprised that he had asked my permission. No one else had that evening.

Thanking me, he turned around towards the main door of the ward, located just beyond behind the nurses' station. Bowing to the rabbi who was just out of sight, the son addressed him in the third person: "Please, may the honorable rabbi enter." After kissing the rabbi's hand, he straightened up and led the guest to his father's room.

I followed them down the hall with my eyes. It was only as they were about to enter the room that I noticed that the rabbi was carrying a white chicken in his arms. Although quiet, the chicken was very much alive.

Amazed, I stood up and followed them into the room. Inside, there were perhaps 20 people, the men standing in a tight circle around my patient's bed, the women sitting off to the side. The rabbi, who I suspected would be visiting other patients that evening, had already begun to chant the prayer for the recovery of the sick, one that I recognized. Totally new for me, however, was the role of the chicken. Clasped snugly in the rabbi's hands, the bird was being waved in tight circles about 12 inches above the patient's head as the prayer was being chanted. I was familiar with the practice of kaparot, in which observant Jews swing a live chicken over their heads on the day before Yom Kippur to symbolize the casting away of sin. I had never, however, seen or heard of this being done as part of a Jewish healing ceremony.

My patient's eyes were partially closed, but the rest of the men by the bedside were fully engaged in ritual. Swaying back and forth, some chanted along with the rabbi. Only one person seemed to notice me as I entered the room. He glanced at me in a stern way, as if warning me not to interfere. I stayed there for a minute until one of the nurses called me away to see another patient.

A couple days later, I asked the son about the ritual I had witnessed. They were members of the local Persian-Jewish community, he explained, and this particular way of reciting the prayer for the sick — with the chicken — was their custom. Be'ezrat hashem (with God's help), his father would make a full recovery.

I was very impressed by how deftly the son was able to maneuver between two very different belief systems explaining his father's disease and paths towards possible recovery: biomedical and religious. As evidenced from our repeated discussions about tests and treatment plans for his father, he clearly understood — and valued — what modern medicine could offer. And yet, his belief in Divine mercy and intercession was unshakeable.

In her book "The Spirit Catches You and You Fall Down," Anne Fadiman describes the collision between two radically different belief systems, shamanism and biomedicine, held by the parents of a Hmong girl suffering from epilepsy and the physicians caring for her. The pushback the parents encountered from the medical team when they tried to incorporate shamanistic healing into their daughter's treatment plan led them to reject biomedicine altogether, with tragic consequences.

Although it hadn't occurred to me to disrupt the unfamiliar ceremony with the chicken — mostly because I was so astonished by it — I probably would have been within my rights to do so: bringing live poultry into an inpatient ward is risky from an infection-control perspective, after all.

I'm glad that I didn't. Doing so would have prevented my patient and his caregivers from accessing the healing potential that their religious beliefs provided them, and likely would have provoked antagonism towards — or the outright rejection of — the biomedicine that I represented. And that would have been detrimental to my patient, who so clearly needed the powers of both in order to heal.

Although nearly 19 years have passed since that October evening, hardly a month goes by in which I do not find myself reflecting on this patient, and the chicken. This invariably occurs because of an interaction I'm having with another patient or family with deeply held beliefs that need not only to be recognized and respected, but also integrated into the therapeutic approach in order for treatment to succeed. It is a lesson that has served me well, and which has helped me to serve so many others over the years.

---

Dennis Rosen, a pediatric pulmonologist practicing in Boston, is the author of "Vital Conversations: Improving Communication Between Doctors And Patients" (Columbia University Press).

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Well: Is Exercise Bad for Your Teeth?

Photo Credit Getty Images

Phys Ed

Gretchen Reynolds on the science of fitness.

Vigorous exercise is good for almost all of the body — except perhaps the teeth, according to a surprising new study of athletes. The study, published in The Scandinavian Journal of Medicine & Science in Sports, found that heavy training may contribute to dental problems in unexpected ways.

There have been hints in the past that athletes could have a heightened risk for cavities and other oral issues. In a study published last year in The British Journal of Sports Medicine, dentists who examined 278 athletes at the 2012 Summer Olympics in London reported that a majority displayed "poor oral health," including high levels of tooth decay, often in conjunction with gum disease and erosion of the tooth enamel. The athletes came from the United States and Europe as well as less-developed parts of the world, and most had access to good-quality dentistry, although many had not visited a dentist in the last year.

The study didn't examine why the athletes were at such high risk of dental problems, although many of us might assume that sugary sports drinks and bars would be a primary cause. Other studies, however, have found little if any link between consuming sports drinks and developing cavities.

So to better understand what is going on inside the mouths of athletes, researchers with the dental school at University Hospital Heidelberg in Germany and other institutions recruited 35 competitive triathletes and 35 age- and gender-matched healthy adults who were not athletes.

All of the volunteers visited the hospital's dental lab for a full oral examination, including collection of their saliva after they had been sitting quietly. They also completed questionnaires about their diets, including consumption of sports drinks and other beverages, their normal oral hygiene routines, and their exercise habits, if any.

Fifteen of the athletes also completed an increasingly strenuous run of about 35 minutes on an outdoor track, during which their saliva was collected several times.

Then the researchers compared the groups' teeth and spit, which turned out to be different in telling ways.

Compared with the control group, the athletes showed significantly greater erosion of their tooth enamel. They also tended to have more cavities, with the risk increasing as an athlete's training time grew. Over all, the more hours that an athlete spent working out, the more likely he or she was to have cavities.

The researchers found no correlation, however, between consuming sports drinks or any other elements of the athletes' diets and their oral health.

They also found no differences in the amount or chemical make-up of their volunteers' saliva after the athletes and the non-athletes had been at rest.

But that situation changed when the athletes worked out. During their experimental runs, the amount of saliva that they produced progressively lessened, meaning that their mouths became drier, regardless of whether they consumed water or other beverages during the workout. The saliva's chemical composition also shifted, growing more alkaline as the workout continued. Excess alkalinity in saliva is thought to contribute to the development of tartar plaques on teeth and other problems.

The extent of the changes in the athletes' saliva during a workout were something of a surprise, said Dr. Cornelia Frese, a senior dentist at University Hospital Heidelberg, who led the study.

"We had thought sports drinks and nutrition might have the most detrimental influence on dental decay," she said, "but we saw no direct link" between them. Instead, it was the changes in saliva during exercise that differentiated the athletes' mouths from those of the control group. Since saliva "has a very protective function" for teeth, Dr. Frese said, having less of it or a chemically different version during exercise could be problematic.

But, she cautions, this study was small, short-term and in many ways unrepresentative of the oral risks most of us would likely face from exercise. "The athletes participating in our study had a mean weekly training time of nine hours," she said. They were, in technical parlance, hard-core.

"All we can say" based on the data from this group, she said, "is that prolonged endurance training might be a risk factor for oral health." Whether less frequent or intense exercise would likewise affect oral health is uncertain but unlikely, Dr. Frese said.

Still there are a few precautions that anyone who exercises and has concerns about their oral health might want to take, she said. Drinking water during workouts could be a start, although the connection between hydration and oral health is not scientifically established, Dr. Frese said. More generally, brush and floss, as you know you should. And if you're a serious endurance athlete, consider visiting a dentist with a specialty in sports dentistry, she said. The goal is to ensure that your teeth remain in as good shape as the rest of you.

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Well: A Better Baby I.C.U.

By many measures, a neonatal intensive care unit, or NICU, with single-family rooms produces better results than one with a shared, open-bay arrangement, a new study has found.

Researchers tracked outcomes in an open-bay NICU for 18 months before the unit was moved to a new single-family room facility. Then they tracked successive admissions to the new facility and compared them with the open-bay NICU results.

There were no differences between the 151 infants in either type of intensive care unit in terms of gestational age at birth, race or maternal educational status or ethnicity. But the study, published in Pediatrics, found significant differences in medical outcomes.

Infants in the single-family rooms weighed more at discharge and gained weight more rapidly. They needed fewer medical procedures, had increased attention, less stress, less lethargy and less pain.

"In a room, you have privacy, the lighting you want, nurses who work one-on-one with the moms. It's relaxed, it's calm," said the lead author, Barry M. Lester, director of the Brown Center for the Study of Children at Risk at Women and Infants Hospital of Rhode Island. "There's more maternal involvement than in the open bay and more maternal involvement leads to better behavioral and medical outcomes."

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Well: Artificial Sweeteners May Disrupt Body’s Blood Sugar Controls

Photo Researchers say gut bacteria changed in subjects that consumed artificial sweeteners, leading to glucose intolerance.Credit Weizmann Institute of Science

Artificial sweeteners may disrupt the body's ability to regulate blood sugar, causing metabolic changes that can be a precursor to diabetes, researchers are reporting.

That is "the very same condition that we often aim to prevent" by consuming sweeteners instead of sugar, said Dr. Eran Elinav, an immunologist at the Weizmann Institute of Science in Israel, at a news conference to discuss the findings.

The scientists performed a multitude of experiments, mostly on mice, to back up their assertion that the sweeteners alter the microbiome, the population of bacteria that is in the digestive system.

The different mix of microbes, the researchers contend, changes the metabolism of glucose, causing levels to rise higher after eating and to decline more slowly than they otherwise would.

The findings by Dr. Elinav and his collaborators in Israel, including Eran Segal, a professor of computer science and applied mathematics at Weizmann, are being published Wednesday by the journal Nature.

Cathryn R. Nagler, a professor of pathology at the University of Chicago who was not involved with the research but did write an accompanying commentary in Nature, called the results "very compelling."

She noted that many conditions, including obesity and diabetes, had been linked to changes in the microbiome. "What the study suggests," she said, "is we should step back and reassess our extensive use of artificial sweeteners."

Previous studies on the health effects of artificial sweeteners have come to conflicting and confusing findings. Some found that they were associated with weight loss; others found the exact opposite, that people who drank diet soda actually weighed more.

Some found a correlation between artificial sweeteners and diabetes, but those findings were not entirely convincing: Those who switch to the products may already be overweight and prone to the disease.

While acknowledging that it is too early for broad or definitive conclusions, Dr. Elinav said he had already changed his own behavior.

"I've consumed very large amounts of coffee, and extensively used sweeteners, thinking like many other people that they are at least not harmful to me and perhaps even beneficial," he said. "Given the surprising results that we got in our study, I made a personal preference to stop using them.

"We don't think the body of evidence that we present in humans is sufficient to change the current recommendations," he continued. "But I would hope it would provoke a healthy discussion."

In the initial set of experiments, the scientists added saccharin (the sweetener in the pink packets of Sweet'N Low), sucralose (the yellow packets of Splenda) or aspartame (the blue packets of Equal) to the drinking water of 10-week-old mice. Other mice drank plain water or water supplemented with glucose or with ordinary table sugar. After a week, there was little change in the mice that drank water or sugar water, but the group getting artificial sweeteners developed marked intolerance to glucose.

Glucose intolerance, in which the body is less able to cope with large amounts of sugar, can lead to more serious illnesses like metabolic syndrome and Type 2 diabetes.

When the researchers treated the mice with antibiotics, killing much of the bacteria in the digestive system, the glucose intolerance went away.

At present, the scientists cannot explain how the sweeteners affect the bacteria or why the three different molecules of saccharin, aspartame and sucralose result in similar changes in the glucose metabolism.

To further test their hypothesis that the change in glucose metabolism was caused by a change in bacteria, they performed another series of experiments, this time focusing just on saccharin. They took intestinal bacteria from mice who had drank saccharin-laced water and injected them in mice that had never been exposed any saccharin. Those mice developed the same glucose intolerance. And DNA sequencing showed that saccharin had markedly changed the variety of bacteria in the guts of the mice that consumed it.

Next, the researchers turned to a study they were conducting to track the effects of nutrition and gut bacteria on people's long-term health. For 381 nondiabetic participants in the study, the researchers found a correlation between the reported use of any kind of artificial sweeteners and signs of glucose intolerance. In addition, the gut bacteria of those who used artificial sweeteners were different from those who did not.

Finally, they recruited seven volunteers who normally did not use artificial sweeteners and over six days gave them the maximum amount of saccharin recommended by the United States Food and Drug Administration. In four of the seven, blood-sugar levels were disrupted in the same way as in mice.

Further, when they injected the human participants' bacteria into the intestines of mice, the animals again developed glucose intolerance, suggesting that effect was the same in both mice and humans.

"That experiment is compelling to me," Dr. Nagler said.

Intriguingly — "superstriking and interesting to us," Dr. Segal said — the intestinal bacteria of the people who did experience effects were different from those who did not. This suggests that any effects of artificial sweeteners are not universal. It also suggests probiotics — medicines consisting of live bacteria — could be used to shift gut bacteria to a population that reversed the glucose intolerance.

Dr. Frank Hu, a professor of nutrition and epidemiology at the Harvard School of Public Health who did not take part in the study, called it interesting but far from conclusive and added that given the number of participants, "I think the validity of the human study is questionable."

The researchers said future research would examine aspartame and sucralose in detail as well as other alternative sweeteners like stevia.

Correction: September 20, 2014
An article Thursday about the effect of artificial sweeteners on metabolism misstated the title of a researcher who commented on the study. Dr. Frank Hu is a professor of nutrition and epidemiology, not immunology, at the Harvard School of Public Health.

A version of this article appears in print on 09/18/2014, on page A4 of the NewYork edition with the headline: Artificial Sweeteners Alter Metabolism, Study Finds.

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DealBook: Bayer to Spin Off Plastics Group to Focus on Health Care

Photo A Bayer plant in Leverkusen, Germany. Though it started as a chemical company, Bayer now makes nearly half its revenue from its health care business.Credit Ina Fassbender/Reuters

Updated, 7:42 p.m. | The German drug maker Bayer said on Thursday that it planned to spin off its polymer business into a new, publicly listed entity as the company moves to shift its focus primarily to health care.

Bayer started in Germany in 1863 as a chemical company making dyes for the textile industry, but now generates nearly half of its sales from its health care business. Among the company's best-known products is its aspirin.

The plan to spin off the polymer business, known as Bayer MaterialScience, was approved by Bayer's management board early this month and by its supervisory board in a unanimous vote on Thursday. Bayer's health care products are part of its life sciences group, which also includes its crop science division. The crop unit, which Bayer will be retaining, focuses on chemical and biological products like insecticides and plant seeds.

"Our intention is to create two top global corporations: Bayer as a world-class innovation company in the life science businesses, and MaterialScience as a leading player in polymers," Marijn Dekkers, the Bayer chief executive, said in a statement on Thursday.

Credit Oliver Berg/European Pressphoto Agency

Bayer said it planned to list the material science business as a separate company in the next 12 to 18 months.

"A major reason for this move is to give MaterialScience direct access to capital for its future development," Bayer said in its statement. "This access can no longer be adequately ensured within the Bayer Group due to the substantial investment needs of the life science businesses for both organic and external growth."

The separation also will allow the polymer business to better align its organization and structure for the industries it serves, the company said.

In recent years, Bayer has been shifting more of its focus and resources to its life science group, which accounted for over 70 percent of its sales last year. In May, Bayer agreed to pay $14.2 billion for Merck's consumer care business, which will bring it the allergy medicine Claritin, the foot care brand Dr. Scholl's and Coppertone sunscreen. The deal will make Bayer one of the largest providers of over-the-counter health care products.

Bayer's core health care business alone generated 18.9 billion euros, or about $24.5 billion, in sales in 2013. It employs 56,000 people, nearly half of the company's work force. Over all, Bayer posted sales of about €40.2 billion in 2013 and had about 113,200 employees.

Photo Marijn Dekkers, C.E.O., said both units would remain industry leaders.Credit Rolf Vennenbernd/European Pressphoto Agency

The life science businesses together had sales of about €29 billion last year and employ nearly 99,000 people, about 29,500 of them in Germany. Bayer and the spun-off plastics business will continue to be based in Leverkusen, Germany. The spinoff will adopt a new name.

The material science business was split off as its own division within Bayer in 2004, but traces its roots to the beginning of the 20th century. One of its scientists, Fritz Hofmann, helped create the first synthetic rubber. Its plastics and coatings are used in passenger and commercial vehicles, CDs and DVDs and in the construction industry.

The material science business had sales of €11.2 billion in 2013, accounting for just under a third of Bayer's sales. After the split, it will employ about 16,800 people worldwide, including about 6,500 in Germany.

The Wall Street Journal, citing sources, reported on Wednesday that Bayer planned to spin off the polymers unit.

A version of this article appears in print on 09/19/2014, on page B5 of the NewYork edition with the headline: Bayer Will Spin Off Plastics Group to Focus on Health Care .

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Well: Artificial Sweeteners May Disrupt Body’s Blood Sugar Controls

Photo Sweeteners alter the microbiome, the population of bacteria that is in the digestive system.Credit Weizmann Institute of Science

Artificial sweeteners may disrupt the body's ability to regulate blood sugar, causing metabolic changes that can be a precursor to diabetes, researchers are reporting.

That is "the very same condition that we often aim to prevent" by consuming sweeteners instead of sugar, said Dr. Eran Elinav, an immunologist at the Weizmann Institute of Science in Israel, at a news conference to discuss the findings.

The scientists performed a multitude of experiments, mostly on mice, to back up their assertion that the sweeteners alter the microbiome, the population of bacteria that is in the digestive system.

The different mix of microbes, the researchers contend, changes the metabolism of glucose, causing levels to rise higher after eating and to decline more slowly than they otherwise would.

The findings by Dr. Elinav and his collaborators in Israel, including Eran Segal, a professor of computer science and applied mathematics at Weizmann, are being published Wednesday by the journal Nature.

Cathryn R. Nagler, a professor of pathology at the University of Chicago who was not involved with the research but did write an accompanying commentary in Nature, called the results "very compelling."

She noted that many conditions, including obesity and diabetes, had been linked to changes in the microbiome. "What the study suggests," she said, "is we should step back and reassess our extensive use of artificial sweeteners."

Previous studies on the health effects of artificial sweeteners have come to conflicting and confusing findings. Some found that they were associated with weight loss; others found the exact opposite, that people who drank diet soda actually weighed more.

Some found a correlation between artificial sweeteners and diabetes, but those findings were not entirely convincing: Those who switch to the products may already be overweight and prone to the disease.

While acknowledging that it is too early for broad or definitive conclusions, Dr. Elinav said he had already changed his own behavior.

"I've consumed very large amounts of coffee, and extensively used sweeteners, thinking like many other people that they are at least not harmful to me and perhaps even beneficial," he said. "Given the surprising results that we got in our study, I made a personal preference to stop using them.

"We don't think the body of evidence that we present in humans is sufficient to change the current recommendations," he continued. "But I would hope it would provoke a healthy discussion."

In the initial set of experiments, the scientists added saccharin (the sweetener in the pink packets of Sweet'N Low), sucralose (the yellow packets of Splenda) or aspartame (the blue packets of Equal) to the drinking water of 10-week-old mice. Other mice drank plain water or water supplemented with glucose or with ordinary table sugar. After a week, there was little change in the mice who drank water or sugar water, but the group getting artificial sweeteners developed marked intolerance to glucose.

Glucose intolerance, in which the body is less able to cope with large amounts of sugar, can lead to more serious illnesses like metabolic syndrome and Type 2 diabetes.

When the researchers treated the mice with antibiotics, killing much of the bacteria in the digestive system, the glucose intolerance went away.

At present, the scientists cannot explain how the sweeteners affect the bacteria or why the three different molecules of saccharin, aspartame and sucralose result in similar changes in the glucose metabolism.

To further test their hypothesis that the change in glucose metabolism was caused by a change in bacteria, they performed another series of experiments, this time focusing just on saccharin. They took intestinal bacteria from mice who had drank saccharin-laced water and injected them in mice that had never been exposed any saccharin. Those mice developed the same glucose intolerance. And DNA sequencing showed that saccharin had markedly changed the variety of bacteria in the guts of the mice that consumed it.

Next, the researchers turned to a study they were conducting to track the effects of nutrition and gut bacteria on people's long-term health. For 381 nondiabetic participants in the study, the researchers found a correlation between the reported use of any kind of artificial sweeteners and signs of glucose intolerance. In addition, the gut bacteria of those who used artificial sweeteners were different from those who did not.

Finally, they recruited seven volunteers who normally did not use artificial sweeteners and over six days gave them the maximum amount of saccharin recommended by the United States Food and Drug Administration. In four of the seven, blood-sugar levels were disrupted in the same way as in mice.

Further, when they injected the human participants' bacteria into the intestines of mice, the animals again developed glucose intolerance, suggesting that effect was the same in both mice and humans.

"That experiment is compelling to me," Dr. Nagler said.

Intriguingly — "superstriking and interesting to us," Dr. Segal said — the intestinal bacteria of the people who did experience effects were different from those who did not. This suggests that any effects of artificial sweeteners are not universal. It also suggests probiotics — medicines consisting of live bacteria — could be used to shift gut bacteria to a population that reversed the glucose intolerance.

Dr. Frank Hu, a professor of nutrition and immunology at the Harvard School of Public Health who did not take part in the study, called it interesting but far from conclusive and added that given the number of participants, "I think the validity of the human study is questionable."

The researchers said future research would examine aspartame and sucralose in detail as well as other alternative sweeteners like stevia.

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