Part 4 (1/2)
Another support for the cancer-preventing effects of exercise can be found in studies of diabetes. Insulin produced in the pancreas is needed by cells so that they can absorb glucose from the blood and store it. The level of insulin must correspond to the bodyas needs, and if this balance is destroyed, the likelihood for developing cancer increases.
Patients suffering from type 2 diabetes have been found to produce higher quant.i.ties of a protein called insulin-like growth factor I (IGF-I), which is thought to trigger cancerous growth. The rates of colon, liver, pancreas, endometrium, and breast cancer are in fact higher among people with type 2 diabetes. 12 That does not sound good at all, but luckily one can do something about it: Physical exercise, as we saw, can reverse the symptoms of diabetes and also appears to lower the IGF-I level.
BMI AND CANCER.
As they continue to explore the causes of cancer, doctors ascribe a greater role to obesity than they once did. British scientists reviewing data pooled from more than 140 studies have just confirmed that the risk of developing a number of common and some less common cancers goes up with increasing BMI.13 An earlier study had already revealed that the risk of obese men for developing an extraordinarily aggressive version of prostate cancer is increased by 80 percent.14 Thomas Hawighorst and Gnter Emons, at the University Hospital Gttingen, Germany, published a review article on the subject painting a very somber but realistic picture. By now, there is asufficiently hard evidence for the connection between adiposity and an elevated risk for cancera of the endometrium, the kidney, the breast, the colon, and esophagus, whereas, aThe prognosis for adipose women with breast cancer is worse, and gaining weight after the diagnosis also has a bad prognostic effect.a15 The American Cancer Society published a particularly extensive survey on the subject.16 The study started more than 20 years ago and included more than 900,000 women and men. Their average age was 57, and none had any tumor-based diseases. In the following 16 years, 6.3 percent of them died because of a condition that was caused by cancer. Then, the researchers a.n.a.lyzed the data to see whether there was a link between the death rate and body weight. In order not to distort their findings, they excluded risk factors and used only data from people who never had smoked.
According to the study, the risk for dying from cancer is approximately 10 percent higher for women with a BMI between 25 and 29.9 and three times higher for women with a BMI between 30 to 40. And extremely obese women have a risk for dying from cancer that is elevated by 88 percent, compared to normal-weight women. The data of the men revealed a similarly gloomy picture.
In total, the researchers figure that obesity causes about 20 percent of all deaths of women related to cancer. Among men, the number is about 14 percent. The experts of the International Agency for Research on Cancer in Lyon, France, estimate that 25 percent of cancer cases worldwide are caused by excess weight or obesity and a sedentary lifestyle.17 Apart from overeating, lack of exercise is in most cases the reason why people balloon and develop a pathological condition. Excess fat on the body impairs the whole metabolism and causes several of the risks mentioned earlier. The biochemistry of the estrogens becomes messed up, and the insulin system gets out of balance. The longer an affected person remains physically inactive, the worse everything getsa”because muscle ma.s.s is incrementally replaced with fat.
Love handles and potbellies are by no means pa.s.sive additions to a body; rather, they actively interfere with some processes in the rest of the organism. Certain messenger substances, so called adipocytokines, are produced by fat tissue and can play a role in the development of cancer. The experts Hawighorst and Emons conclude that in obese people athe metabolic-biochemical effects of overweight can cause the formation of a malignant tumor in a multi-level process.a18 Researchers still speculate whether and if exercise affects an already existing tumor. Physical activity increases the demand for oxygen and nutrientsa”which might starve the tumor of these resources. If the blood is primarily pumped into the muscles, one could reason that there is not much left to feed the tumor.
Although evidence continues to acc.u.mulate that being physically active reduces a personas risk for developing certain cancers, to date, the many details of the mechanism remain unknown. Many factors may act together and might vary from individual to individual. However, even though the ideal amount of exercise to prevent cancer has yet to be determined, doctors and physiologists working in the field are convinced that becoming active is worthwhile anyhow. As Kim Westerlind of the AMC Cancer Research Center in Denver, Colorado, concludes, aIt would appear reasonable to suggest that regular moderate physical activity be incorporated into [a] healthy lifestyle for all its already well-established benefits, as well as to potentially reduce cancer risk.a19 EXERCISE AND QUALITY OF LIFE IN CANCER PATIENTS.
The doctrines of few medical fields have been as drastically turned around as they have in cancer medicine. Generations of doctors had been taught that people diagnosed with cancer primarily needed rest. Patients were discouraged from exercising, out of the erroneous belief that this would worsen their health. When the physician Klaus Schle established the worldas first training group for cancer patients in Cologne, Germany, many of his colleagues were outraged. A radiologist warned him: aCan you guarantee you are not going to trigger metastases?a Schle replied: aCan you guarantee that your rays donat trigger growth of new tumors?a20 By rejecting exercise for their cancer patients, medical doctors did more harm than good, says Fernando Dimeo of the Hospital Charit in Berlin. aDuring chemotherapy and the weeks and months to follow patients were put in a pa.s.sive role. Doctors were afraid of overburdening them and advised many of the patients not to partic.i.p.ate in sports and demanding activity even in the long term.a21 But recommending cancer patients to take it easy has severe consequences. At first, people are shocked to learn they have cancer. Then, they are told not to use their bodies much any longera”which makes the situation even more devastating because they now feel completely at the mercy of their illness. On top of this, being confined to rest worsens the impact of chemotherapy and of the cancer drugs, which can cause anemia and heart problems and loss of strength as well as vitality. As a result they are tired, and they become short of breath. aThese symptoms can be worsened by lack of exercise and the subsequent loss of endurance,a warns Dimeo.
In no time the patient is caught in a vicious circle of declining activity and decreasing resilience. Recovery is slowed after each stage of cancer treatment, thereby causing even more inactivity. After a while, a patient enters a phase regarded as a disease in its own right, the so-called fatigue syndrome. Once the cancer treatment is completed, this condition is the biggest problem many patients facea”and can be a direct consequence of medically prescribed lack of exercise.
Too much rest can also worsen the primary disease. As we saw, women diagnosed with cancer have a worse prognosis when they put on five kilograms or more during their cancer treatments. Intriguingly, many patients themselves have intuitively sensed that rest was not good at all for thema”and decided to do something about it. In the United States many people diagnosed with cancer began exercising hard because they hoped this might improve their quality of life and survival chances. One of the pioneers of this movement is Anna Schwartz. When she fell sick with non-Hodgkinas lymphoma, she reminded herself of what had often struck her when she worked as a nurse in an oncology clinic. Those patients who, despite the exhausting treatment, regularly left their rooms and stayed physically active awere in a better mood,a Schwartz recalls. And when she had to go through chemotherapy, she forced herself to exercise. She went jogging and played tennisa”despite a catheter for the cancer drugs in her body.
Since then, this thoroughly fit woman, who is considered as good as cured, has turned her story into a job. Research grants from the National Inst.i.tutes of Health enabled her to carry out scientific studies on the subject. In the resulting publications Schwartz has shown that exercise indeed ameliorates the fatigue syndrome and makes patients stronger again.22 Since then, Schwartz has been offering horse riding for cancer patients in Cave Creek, Arizona, has been giving talks, and has written a book about fitness and cancer.23 The preface was penned by Lance Armstrong who, after overcoming testicular cancer, won the Tour de France seven times. Armstrong himself has declared that he was better and stronger after his illness than before. aWhen people are diagnosed, their first impression is aOh my G.o.d, I am going to die,aa he once said. aOver time, they lose that impression. They get the confidence back, they know they are going to live, they get back to life, they get back to work and they get back to exercise.a24 Encouraged by Armstrongas incredible story, cancer patients began improving their odds and their lives by exercisinga”although many oncologists still dismissed sports, thinking its strain and stress would only weaken patientsa immune systems. By now, however, this patientsa movement has led to a change of thinking among many doctors, says Julia Rowland of the National Cancer Inst.i.tute in Bethesda, Maryland. Many new studies have been initiated to reveal the impact of exercise on cancer patients.
The results, says Rowland, have shown that the oncologistsa worries have been unfounded. In many cases exercise actually does improve the mood of the patients and their strength, while lowering the side effects of radiation and chemotherapy.25 When breast cancer patients try strength training two days per week, both physical and mental strength improve significantly.26 Yet exercise does not need to be a daunting activity or even an organized outing to produce significant rewards for breast cancer survivors, researchers at the University of Texas M. D. Anderson Cancer Center, in Houston, have found. Over the course of six months, they regularly met with women who had gone through breast cancer treatment and led sedentary lives. At the meetings the women were encouraged to integrate physical activities like brisk walking and climbing stairs into their lives, five days per week, at least 30 minutes at a time.
After six months, the mobilized women showed many improvements. In contrast with inactive patients, they felt much healthier and had less pain and fewer handicaps. Their const.i.tutions were substantially strengthened, which was doc.u.mented by a small compet.i.tion at the end of the study: the active women were able to walk faster than the inactive ones. aThe wonderful take-away message from this study is that simple exercises, such as walking during coffee breaks or parking farther away from work, can have beneficial effects on physical health and functioning,a says the studyas princ.i.p.al investigator, Karen Basen-Engquist.27 By now, some doctors prescribe exercise even when chemotherapy is still under way or right afterward. Most patients, it is true, do not feel like working out at all. Chemotherapy and radiation therapy not only destroy cancer cells, but also kill stem cells, which give rise, among other things, to cells of the immune system. Thus, immediately after treatment patients have few bodily defenses and are isolated in separate rooms to protect them from potentially deadly viruses and bacteria.
However, this well-intentioned isolation comes with a price, says the sports physician Klaus Schle. In his pioneering work, he has found that bed rest significantly lowered the physical resilience of these individuals. The more rounds of cancer treatment they receive, the harder it is for them to recover. To change that, Schle and three colleagues did something unheard of: they placed stationary bikes in the rooms of 32 patients and encouraged them to pedal for 10 to 20 minutes once or twice a day. Unlike 32 patients that had been isolated the old, sedentary way, these exercising patients recovered faster and more thoroughly from the side effects of cancer treatment. Even very sick patients actually do profit from exercise. They gain muscle strength and endurance without worsening the primary disease.28 EXERCISE AND SURVIVAL.
Even the most optimistic physicians never seriously expected that physical exercise might prolong the life of cancer patients.
But in recent years data have started to emerge indicating that exercise indeed improves survival rates. The effects seen so far are modest in absolute numbers but relate to two of the most widespread and dangerous cancers. Two of the trials involve patients with colon cancer. One included 823 patients with early-stage or slightly advanced tumors that had surgery and adjuvant chemotherapy.29 Six months after the completion of the therapy, Jeffrey Meyerhardt at Dana-Farber Cancer Inst.i.tute in Boston asked them to report how much physical activity they had engaged in. The data show that exercise corresponding to walking for 60 minutes, six days per week aappears to reduce the risk of cancer recurrence and mortality.a Meyerhardt has produced similar results in another study in which he and his colleagues observed 573 women who had been treated for colon cancer.30 Patients who started exercising after their diagnosis lived longer than sedentary ones; the survival rate was increased by 50 percent. Since that study, Jeffrey Meyerhardt tells his patients that aexercise might be advantageous for them.a Finally, the epidemiologist Mich.e.l.le Holmes of Brigham & Womenas Hospital in Boston has found a similar effect for breast cancer.31 She and her colleagues a.n.a.lyzed the cancer progressions of nearly 3,000 women and found a significant correlation between the level of activity and survival. If a woman walks three to four hours per week, the risk of breast cancer death is lowered by 50 percent.
When an effect in a similar range is seen using a conventional cancer drug, leading doctors are quick to talk about a amajor advancea or a amajor turning point.a32 Meyerhardt and Holmes are much more cautious and say that their findings are not proof at this point. A correlation between cancer survival and exercise level does not prove that exercise was the cause. There is no study yet that would say a person can literally run away from cancer. However, more and more data point to the benefits of physical activity.
Now, many oncologists are eager to explore the cancer-fighting properties of exercise further and to carry out more studies. Which kind of exercise would be the best? What would be the ideal amount? However, will the drug industry fund such research? aThere is no doubt that the pharmaceutical industry would back an agent with potential to reduce cancer recurrence by at least 50 percent,a says Wendy Demark-Wahnefried of Duke University Medical Center in North Carolina. aBut who will back a trial that evaluates the potential benefit of sneakers and sweatpants?a33
13.
Longevity, Potency, and Resilience.
AT AGE 20 THE IDEA OF GROWING OLD IS SOMETHING TO THINK about later in life. The body is still going strong; injuries and wounds and broken bones heal rapidly, and there is no moaning and groaning to be heard first thing in the morning. At age 40 wrinkles and the first aging marks appear and love handles may have established themselves in the midsection, but there is still no time to think about getting old. At age 60, people may have gone through one or two operations, perhaps after an unfortunate fall while on vacation. Among friends and acquaintances, the first deaths occur. Subtly one starts to get accustomed to the fact that the body may not be in the best shape. Hearts may start to beat out of rhythm, legs may be swollen in the evening, sleep is no longer so predictable.
This scenario is true for many peoplea”but not for everyone. Around us are people who hardly seem to age, who look nearly the same in the course of many years. In the science department of my magazine there is a slim female colleague who, in the ten years Iave known her, has never really changed. People guess that her age is about 48, but she is 61. Not long ago, such a woman would have been marveled at. In 1900, life expectancy at birth in the United States was 47 years,1 but now it is 78 years at birth for the total population in the United States.2 This increase in life span is remarkablea”and unevenly distributed among the people. One person struggles with bad health and dies at age 60, while another lives to be 100. Why is it that some peopleas bodies break down, while others remain radiant with health?
When you pose this question to people who are blessed with long and healthy lives, itas striking to see how frequently they mention physical activity. On a campground in Sequoia National Park, in the Sierra Nevada Mountains in California, I met an 83-year-old man, Alan Buckley, and asked him about his secret as we held sticks with marshmallows into the fire. Even though many men of his age live in old peopleas homes, Buckley camps every summer in the mountains and looks in the evenings at the Milky Way before going to bed. So what is his secret? Buckley says he simply always walks when he moves around on his walnut tree plantation. He shakes his head when he thinks about the aweekend warriors,a as he calls them, who sit in their cars and offices and armchairs during the week and try to make up for the missed exercise on the weekend.
Antonio Pierro also was always in motion. He was born in 1896 in Forenza, Italy, and sailed at a young age on a s.h.i.+p of immigrants from Naples to New York. He fought as a soldier for the United States in the First World War and then settled in New England. During his entire life, he was active, raking leaves and shoveling snow until he died at age 110. Antonio Pierro also said exercise was his secret. He once told a reporter: aIf you donat have exercise, you get stiff, youare not worth anything.a3 There are many such examples. In our family, it was grandfather August. He lived in the country outside Cologne, Germany, and worked as a carpenter at a time when craftsmen took a nap in the hay after lunch. Every day, August took an evening stroll for an hour, and he lived to be 98 years old.
These long and fulfilled lives are more than just chance. Epidemiological studies of thousands of men and women have shown that the regular use of our muscles is the only means capable of prolonging the human life.4 Being fit reduces mortality by 50 percent. People who burn 1000 kilocalories per week by additional exercise increase their probability of surviving by 20 percent. And if people become physically active but also quit smoking, they will live eight years longer, on average.
After all, we are born to run. We evolved the ability to run long distancesa”and this, believes the anthropologist Daniel Lieberman at Harvard University, was crucial for our evolution. When it comes to endurance, we are among the best athletes in the animal kingdom. Leopards, for example, might sprint much faster, but over long distances, the big cats will be worn out before long. Actually, most mammals are not capable of running or trotting for longer than 15 minutes. Chimpanzees, with their bowlegs, come off especially badly. In contrast, humans evolved to become true endurance runners. Thanks to our uncovered skin and our sweat glands, we are able to regulate our body temperature even when we move for an extended time in hot weather. And unlike all the other apes, the human body sports a large gluteal muscle, Musculus gluteus maximus, which in biomechanical terms enables us to run. Because our potential for endurance running is genetically hardwired into our bodies, we can utilize it even in old age. aHumans are astonis.h.i.+ng athletes,a Lieberman says. aThey can keep running.a And yet physicians traditionally thought older people would not have these capabilities. When older runners started attempting marathons, doctors and organizers wondered whether they would need additional care. But these runners did just fine: older athletes can reach the finish line just as comfortably as the younger ones. It is not age that matters but preparation and fitness.5 Bob Matteson of Bennington, Vermont, began his running career at age 69. By now this ancient gazelle is in his 90s and belongs to the fastest people of his age group.6 The course of our lives is often set in middle age. Good strength of grip and normal weight are predictors for an unusually long life. Conversely, the risk of dying because of cancer increases by 29 percent among sedentary women. If a person does not exercise at all, basic strength decreases every year by 1 to 2 percent. At some point, strength falls short of a certain threshold, leaving the muscles unable to fulfill their functiona”until finally one day a person is too weak to get up from a chair. Comparing this loss of 1 or 2 percent of strength per year with the gain of 30 to 40 percent that can be achieved by training makes it clear that the potential for renewal amounts to 15 to 20 years, which beats any antiaging remedy by far.
Any person who was born healthy can reap the good effects of exercise. Contrary to common belief, this is little affected by an individualas genetic makeup. The impact of the genes on the life expectancy is much smaller than most people would imagine. A survey among thousands of twins revealed that the physically active member of the pair has a significantly lower mortality than the sedentary sibling.7 The proverb that one should choose oneas parents carefully in order to have a long, healthy life is becoming less true. Genes may determine the way we age by 30 percent;8 the environment determines the rest. To a large extent, we determine how fast we age. Apart from smoking, it is above all disuse of the body that shortens lives. This weakens the potency of men, makes us vulnerable to stress, steals our healthy sleep, and increases the number of illnesses we get.
WORKING OUT FOR POTENCY.
It was the first day of June 1889 when the neurologist Charles Edouard Brown-Sequard declared at the Biological Society of France in Paris that he had discovered a fountain of youth and had already tested it. The result, the 72-year-old professor claimed, was nothing but a sensation. Brown-Sequard said he felt physically strong and mentally awakened. He had gotten rid of his constipation and urinated again like in his young days, in a high arch. The professor was convinced these improvements were due to an extract he had prepared from the testes of guinea pigs and dogs, and subsequently injected into his own body. As it turned out, this supposed antiaging regimen had, if anything, a placebo effect because its recipe was simply too weak to work. Nevertheless, Brown-Sequard had founded a new field dealing with the production and effects of hormones, today known as endocrinology. Furthermore, his hunch that the testes are an important reloading point for hormones was subsequently proven right.9 By 1935, chemists were able to simulate the work of the glands by synthesizing testosterone in the laboratory. Normally, it is produced in the male body but alsoa”in smaller amountsa”in the female body. It promotes the maturation of the male reproductive organs; helps with the production of new sperm; and, in both s.e.xes, strengthens the libido.
Furthermore, testosterone acts as an anabolic hormone and increases the buildup of proteins in cells, enabling muscle growth, for example. Small wonder that testosterone and the similar hormone DHEA are marketed as antiaging products and consumed by many men. Doctors and public-relations people with ties to pharmaceutical companies even invented a disease, which they have named amale menopause,a to generate more sales. Due to an age-related decline of testosterone, men supposedly become sluggish, s.e.xually slack, and grumpy.
But in reality, hormone prescriptions help only the drug manufacturer and the prescribing doctor. A study has just shown that neither testosterone nor DHEA enhance well-being when given as drugs. A two-year study of elderly men (using testosterone plaster and DHEA tablets) and women (taking DHEA tablets alone) tested these products. Although this resulted in higher hormone levels, it did not affect muscle strength, aerobic capacity, or quality of life. There was no trace of an antiaging effect.10 Obviously these hormones are helpful and effective only if produced by the body. This natural buildup is stimulated by exercise. This has been shown time and again by researchers like John McKinlay and his colleagues of the New England Research Inst.i.tutes in Watertown, Ma.s.sachusetts. In the 1980s they randomly contacted more than 1,700 men between 40 and 70 years of age. Over time, the researchers a.s.sessed the health of those men via questionnaires and by measuring their hormone levels. On the one hand, the researchers found that the level of male s.e.x hormones incrementally decreases over the course of time; the testosterone level goes down by about 1 percent every year. On the other hand, testosterone level is significantly influenced by lifestyle. Heavy smokers and people who drink a lot of alcohol have lower hormone levels. Inactive, obese men also have a level 10 to 15 percent below that of physically active men of the same age.11 Men suffering from hot flashes often turned out to be sedentary heavyweights. The impact of obesity and other adverse lifestyle factors is roughly as big as the impact of natural aging.12 Thus, McKinlay concludes that male menopause is nothing but a myth, the symptoms more likely to be caused by laziness and an unhealthy lifestyle.
So if men want to boost their testosterone, they simply have to become active. Several studies examined what happened when men at age of 70 began to work out. Unsurprisingly, their strength increased. But their levels of testosterone and growth hormone rose, too. Whereas the hormone production of fit men responds especially strongly to stimuli, formerly inactive men profit, too. Sedentary men aged 66 to 76 training just for one hour on a stationary bike have seen their level of testosterone go up by 23 percent.13 Physical activity also helps men suffering from impotence. The condition, also called erectile dysfunction, is seldom the only problem of the affected men. An individual with an erectile dysfunction usually has quite a few other health issues, such as coronary heart disease, impaired circulation of the legs, and strokesa”all of which are caused by a lack of physical exercise.
So, is a flaccid p.e.n.i.s an indicator for lack of exercise?
Many findings point that way. An elevated body weight is connected with potency problems. The link between impotence and lack of exercise appears to be the endothelium of the blood vessels, which, as we have already seen, is impaired by inactivity. When that happens, the p.e.n.i.s is not properly supplied with blood any longer.
Common sense as well as scientific data thus tell us that impotent men need workouts rather than v.i.a.g.r.a. Whereas the pills are expensive and have side effects, physical exercise is safe and free.
In the Ma.s.sachusetts Male Aging Study, John McKinlay and his colleagues followed more than 590 men.14 At the start of the study, they were middle-aged and all potent. Eight years later, only 83 percent of them had satisfactory erections and, apart from alcohol abuse and smoking, obesity and lack of exercise were the main reasons for the problem. By contrast, some previously sedentary men in the study had adopted an active lifestyle. In comparison to inactive partic.i.p.ants, their likelihood of impotence was reduced by 70 percent. aEarly adoption of healthy lifestyles may be the best approach to reducing the burden of erectile dysfunction on the health and the well-being of older men,a the doctors conclude. Their recommendation? A brisk two-mile walk every day keeps erectile dysfunction away.15 The physician Katherine Esposito has used this effect to help men from southern Italy.16 The 110 partic.i.p.ants in her study were all impotent and overweight (BMI of 30 to 49).
They were randomly a.s.signed into two groups. The control group received information about improving their diets and exercise, but it was kept rather unspecific. Over the next two years they were visited bimonthly by the researchers, but no specific individualized program was provided. The men of the intervention group, however, were asked to lose 10 percent of their body weight and were given concrete tips, namely that they should not eat more than 1,700 kilocalories per day and should begin an active life with swimming, ball games, and many walks. Every four to eight weeks, these partic.i.p.ants were counseled by nutrition experts and physical educators.
Two years later, Esposito compared the two groups. Although there was no difference between the groups with regard to their eating habits, their activity patterns differed profoundly. Among the men only vaguely instructed about physical activity, the amount of exercise went up from 51 to 84 minutes per week. In the other group, however, the increase was from 48 to 195 minutes per week. The program also affected body weight. Whereas the BMI went down from 36.4 to 35.7 in the first group, the men in the training group lost much more fat; the average BMI declined from 36.9 to 31.2.
This lifestyle change was very beneficial for s.e.xual performance. Whereas 5 percent of the men in the control group were able to overcome their impotence, 31 percent of the exercisers were able to do so. This result fits the data from epidemiological studies, which indicate that 79 out of 100 men with erectile dysfunction are overweight or obese.
Many men do actually intuit the potential exercise has for their potency. That was revealed when the Ma.s.sachusetts Male Aging Study examined the course of erectile dysfunction.
More than 300 men were followed for nine years, and during this time impotence problems worsened among 33 percent of them. But in 35 percent of the cases the condition had disappeared. These latter men had apparently adopted healthier lifestyles, with less overeating and more sports, and thus had reversed their illness.
The study has two important messages. First, natural aging impairs potency to a much lesser degree than thought. Second, men can overcome penile problems without pills. This is probably not only because of the physiological improvements, which lead to a better blood supply to the erectile tissue. It might also be that exercise helps men to deal better with stress. With less psychological pressure, l.u.s.t and libido certainly profit. In a true win-win situation, frequent s.e.x enhances fitness and activates the production of hormonesa”which in turn creates even more desire.
STRIKING BACK AT STRESS.
The reason why exercise keeps bodies young and fit is not as evident as it might appear. After all, even moderate use of the muscles leads to an elevated consumption of oxygena”and thereby to an adverse side effect called oxidative stress. In the wake of this stress, highly reactive chemicals are produced, called free radicals, which can damage a cellas DNA.
Fortunately, we are able to protect ourselves against these dangers. As soon as the body is put in motion, a special program is switched on that can neutralize the adverse effects of exercise as well as psychological stress. The gerontologist Suresh Rattan of University Aarhus in Denmark believes that this protection is created by certain proteins (which, for historical reasons, have the confusing name of aheat shock proteinsa). They act as a s.h.i.+eld against stress and thus enhance well-being. In the bodies of Stone Age people, this program was probably switched on most of the time. All humans living today have the same system hardwired into their bodies, but it is usually switched off because modern people hardly use their muscles.17 The problem is, when this stress s.h.i.+eld is turned off, people are still subjected to stress, of a kind that might be even worse than the stress our Stone Age forebears usually had to deal with. Back then, stress always meant that there was an immediate threat and life was in danger. Those situations involve a swift bodily response: energy is released, and the muscles are supplied with glucose. The heart starts beating faster, and blood pressure and breathing frequency increase so that the body can consume more oxygen. Functions that are not needed in life-threatening situations are suppressed: the s.e.x drive, digestion, and the immune system. At the same time, the body is flooded with stress hormones. They ensure that we do not feel pain and sharpen our senses. This system stood the test when our forebears were escaping from mammoths and saber-tooth tigers, and it helps us to this daya”for example, should we have to flee a burning house or run away from other dangers.
So far, so good. But there is a problem: today, even when it is not a matter of life and death, stress waves keep rolling in, due especially to the acceleration of daily life that does not allow us to take any rest periods. Many employees can be reached day and night because of cellular phones, e-mail, and text messages. American companies in particular a.s.sume they can disturb their employees at any time, even vacations. There has never before been more continuous stress than in the technologically connected job world. Absolute silence and peace, on the other hand, can also be bad. Individuals who have no friends and must live in social isolation are often burdened by stress, too.
In past times, stress lasted only a short while: Either the saber-tooth tiger got you, or not. Nowadays, stress persists the whole day. Furthermore, stress and the corresponding response are uncoupled in sedentary people. The released energy is not converted into action but stays inside the body. Rather than actively defending against threats, the author Tara Parker-Pope concludes: aNow youare just a person with unregulated blood sugar, high blood pressure, blood clots, a depressed s.e.x drive and a buckling immune system.a18 Add to that the effects on the brain. An excess of stress hormones (glucocorticoides from the adrenal gland) impairs nerve cells and causes atrophy in certain brain regions.