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Published on Leave a comment on Lifestyle Linked to One Third of Cancer Deaths

For those who need convincing that lifestyle can contribute to development of cancer or its prevention, new medical research has once again supported the importance of lifestyle choices. A report from Australian researchers (with similar findings as a study in the US) stated: an estimated 38% of cancer deaths and 33% of cancer diagnoses could have been prevented with healthy lifestyle choices.

And what were the lifestyle choices that are linked to cancer?  The researchers list 20 separate things (in 8 broad groups) that are known to cause or are linked to cancer. They are: tobacco smoke (smoking or second-hand smoke), dietary factors (low-intake of fruit, non-starchy vegetables, and dietary fiber; and high intake of red and processed meat), overweight/obesity, alcohol, physical inactivity, solar ultraviolet radiation, certain infections (they list 7 infections, such as human papillomavirus, hepatitis B, hepatitis C), and reproductive factors (lack of breastfeeding, menopausal hormone therapy use, combined oral contraceptive use). Note that they found that the #1 most important lifestyle factor is tobacco smoke - and it accounted for about 23% of all preventable cancer deaths in Australia. From Medscape:

One Third of Cancer Deaths Could Be Prevented by Lifestyle

As we head into the festive season, many are looking forward to the tradition of "Eat, drink, and be merry." But as another research paper shows that more than a third of cancer deaths could be prevented by lifestyle, maybe a qualifier should be added:"celebration in moderation." The latest statistics come from Australia, where researchers note that 44,004 cancer deaths occurred in 2013. But an estimated 38% of these deaths and 33% of cancer diagnoses could have been prevented with healthy lifestyle choices, says a research team led by Louise Wilson, MEpi, at the QIMR Berghofer Medical Research Institute and the University of Queensland, Brisbane.

These cancer diagnoses and deaths were seen in Australians of all ages and are directly attributable to 20 known modifiable risk factors within eight categories that are established causes of cancer, the study authors say. The report is published in the February 2018 issue of the International Journal of Cancer.

Smoking was the leading cause of preventable cancer death in Australia in 2013 and accounted for 23% of all cancer deaths. ...Three other categories of modifiable risk factors — poor diet, overweight/obesity, and infections — accounted for 5% of cancer deaths each. In a fifth category, alcohol-related cancer accounted for 2.4% of deaths. Physical inactivity factors were responsible for 0.8% of cancer deaths, overexposure to ultraviolet radiation for 3.2% of cancer deaths, and, in the eighth category, reproductive or hormonal factors were linked to 0.4% of cancer deaths.

In the diet category, risk factors include low intake of fruit, nonstarchy vegetables, and dietary fiber and high intake of red and processed meat. In the infection category, seven cancer-causing agents, including human papillomavirus (associated with cancer of the vulva, vagina, penis, anus, oral cavity, and oropharynx) and Helicobacter pylori (noncardia stomach cancer), are included. Lack of breastfeeding, use of menopausal hormone therapy, and use of combined oral contraceptive use (breast and cervical cancer) are listed as preventable risk factors in the reproductive category.

These findings are in keeping with other research on the role of modifiable lifestyle-related risk factors in cancer prevention. As previously reported by Medscape Medical News, results from a large cohort study in the United States led researchers to conclude that 20% to 40% of cancer cases and related mortality could be prevented by not smoking, maintaining a healthy weight, and exercising regularly. In another report, results from a national online survey undertaken by the American Society of Clinical Oncology showed that, like their Australian counterparts, most US adults don't know alcohol and obesity are major risk factors for cancer. [Original study.]

A dividing lung cancer cell. Lung cancer is associated with smoking. Credit: National Institute of Health (NIH). 

 

Published on Leave a comment on Vigorous Physical Activity Linked To Lower Death Risk In Older Women

The message is clear from a recent study: older adults should get out and move, move , move (brisk walking is fine) - to lower the risk of early death. The older women engaging in the most moderate to vigorous activity had a 65% lower risk of early death during an average follow-up period of 2.3 years (when compared to the women with the least exercise).

How much exercise did the groups get? The least active had 6.8 minutes per day of moderate to vigorous exercise, and the most active had about 68 minutes/day of moderate to vigorous physical activity. The women wore a Fitbit type of device (an accelerometer) that measured their movements. Moderate to vigorous exercise was any movement that got the heart rate up a bit, made them sweat a little - and which could be brisk walking.

The study was done with older women (in their 70s), but one would think it also applies to men. Note: all-cause mortality means death from any cause (death in general). From Medscape:

Intense Exercise Tied to 65% Lower Death Risk in Older Women

Older women who engaged in the greatest amount of moderate to vigorous physical activity, such as brisk walking, were found to have a 65% lower risk of all-cause mortality compared with women who performed the least amount of such exercise, a new study reports. The researchers examined women in their early 70s in the Women's Health Study (WHS) who wore a triaxial accelerometer for 7 days to measure physical activity. The findings, by Dr I-Min Lee (Brigham and Women's Hospital, Boston, MA) and colleagues, were published November 6, 2017 in Circulation.

It's been known for a long time that physical activity is associated with lower mortality rates, Dr Lee told theheart.org | Medscape Cardiology.... Now that physical activity can be better measured using a research-grade triaxial accelerometer, the magnitude of the reduced risk of short-term death with recommended amounts of moderate to vigorous physical activity can be seen to be as strong as not smoking, Lee said. ... This study "reinforces the message that adults should strive to meet physical activity guidelines of 150 minutes of moderate or 75 minutes of vigorous exercise per week," Dr Alpa Patel (American Cancer Society, Atlanta, Georgia) who recently published a related article that showed benefits from walking told theheart.org | Medscape Cardiology.

From 2011 to 2015, 18,289 of 29,494 living women (63%) in the Women's Health Study agreed to participate in the current study.... The remaining 17,708 women were mailed a research-grade triaxial accelerometer (ActiGraph GT3X+, ActiGraph Corp) and asked to wear it on their hips for 7 days (but to take it off when sleeping or swimming) and then mail it back. 

The women spent a median of 8.4, 5.8, and 0.5 hours/day being sedentary, doing light physical activity, and doing moderate to vigorous physical activity, respectively. "The least active quartile were doing 8 minutes a day of moderate to vigorous . . . physical activity," Lee said, which was typically "brisk walking, anything that gets your heart rate up a little bit, gets you to sweat a little bit." The most active quartile did about 68 minutes/day of moderate to vigorous physical activity. During an average follow-up of 2.3 years, 207 women died. The total amount of physical activity was inversely related to the risk of all-cause mortality during follow-up, after adjustment for age and time spent wearing the device. 

Published on Leave a comment on Exercise Alters Gut Microbes In A Beneficial Way

Two studies (one in mice and one in humans) by researchers at the University of Illinois found that no matter what your diet - exercise changes the gut bacteria in a beneficial way. And when you go back to a sedentary lifestyle, your gut microbes change again and beneficial microbes such as short chain fatty acids (SCFAs), especially butyrates, decline. The effect was more pronounced in lean sedentary adults (as compared to obese sedentary adults).

Beneficial microbes that increased with exercise in humans were species of Faecalibacterium, Roseburia, Lachnospira, Lachnospiraceae, and Clostridiales. Faecalibacterium prausnitzii has been discussed in earlier posts as a beneficial keystone species in the gut (here, here, and here).

What kind of exercises did they do? They did three supervised 30 to 60 minute moderate to vigorous intensity aerobic/endurance exercise sessions per week for 6 weeks, and they could use a cycle ergometer (stationary bicycle) or treadmill each session.

Besides beneficial microbial changes, 6 weeks of exercising resulted in improved body composition (total lean body mass, decreased body fat, increased bone mineral density), and an improvement in cardiorespiratory fitness. These changes reversed in everyone when they went back to 6 weeks of a sedentary lifestyle.

Bottom line: get out and move, move, move. Your gut microbes and your body will thank you.

From Science Daily: Exercise changes gut microbial composition independent of diet, team reports

Two studies -- one in mice and the other in human subjects -- offer the first definitive evidence that exercise alone can change the composition of microbes in the gut. The studies were designed to isolate exercise-induced changes from other factors -- such as diet or antibiotic use -- that might alter the intestinal microbiota.

In the first study, scientists transplanted fecal material from exercised and sedentary mice into the colons of sedentary germ-free mice, which had been raised in a sterile facility and had no microbiota of their own. In the second study, the team tracked changes in the composition of gut microbiota in human participants as they transitioned from a sedentary lifestyle to a more active one -- and back again.

Recipients of the exercised mouse microbiota also had a higher proportion of microbes that produce butyrate, a short-chain fatty acid that promotes healthy intestinal cells, reduces inflammation and generates energy for the host. They also appeared to be more resistant to experimental ulcerative colitis, an inflammatory bowel disease.

In the human study, the team recruited 18 lean and 14 obese sedentary adults, sampled their gut microbiomes, and started them on an exercise program during which they performed supervised cardiovascular exercise for 30-60 minutes three times a week for six weeks. The researchers sampled participants' gut microbiomes again at the end of the exercise program and after another six weeks of sedentary behavior. Participants maintained their usual diets throughout the course of the study. Fecal concentrations of SCFAs, in particular butyrate, went up in the human gut as a result of exercise. These levels declined again after the participants reverted to a sedentary lifestyle.

The most dramatic increases were seen in lean participants, who had significantly lower levels of SCFA-producing microbes in their guts to begin with. Obese participants saw only modest increases in the proportion of SCFA-producing microbes. The ratios of different microbes in the gut also differed between lean and obese participants at every stage of the study, the researchers said. "The bottom line is that there are clear differences in how the microbiome of somebody who is obese versus somebody who is lean responds to exercise," Woods said. " [Original study in humans.]

Published on Leave a comment on Exercise Is a Maintenance Program For the Brain?

It's reassuring to see that there are positive things one can do to maintain brain health as one ages. With normal aging, the brain typically shrinks a little with each passing decade  - starting from about the age of 40. But one recent Australian study, which reviewed the results of many other studies, found that exercise slows down this shrinkage in humans, specifically in the left hippocampus. That is, that aerobic exercise had a significant positive effect on the volume of the left hippocampus. This matches the result of animal studies.

The researchers pointed out that some studies found increases also in other parts of the human brain from exercise (e.g. in the white matter), but that they did not look at and review those studies. [See posts on research.] The good news is that positive effects were from exercise programs generally lasting less than 12 months. But it is unknown which type of exercise is best, or whether it is general "activity level and movement" that is most important. Bottom line: Get out there and move, move, move for brain health. And for cardiorespiratory fitness. It's all linked and it's all good. From Medical Xpress:

Exercise maintains brain size, new research finds

Aerobic exercise can improve memory function and maintain brain health as we age, a new Australian-led study has found. In a first of its kind international collaboration, researchers from Australia's National Institute of Complementary Medicine at Western Sydney University and the Division of Psychology and Mental Health at the University of Manchester in the UK examined the effects of aerobic exercise on a region of the brain called the hippocampus, which is critical for memory and other brain functions.

Brain health decreases with age, with the average brain shrinking by approximately five per cent per decade after the age of 40. Studies in mice and rats have consistently shown that physical exercise increases the size of the hippocampus but until now evidence in humans has been inconsistent.

The researchers systematically reviewed 14 clinical trials which examined the brain scans of 737 people before and after aerobic exercise programs or in control conditions. The participants included a mix of healthy adults, people with mild cognitive impairment such as Alzheimer's and people with a clinical diagnosis of mental illness including depression and schizophrenia. Ages ranged from 24 to 76 years with an average age of 66. The researchers examined effects of aerobic exercise, including stationary cycling, walking, and treadmill running. The length of the interventions ranged from three to 24 months with a range of 2-5 sessions per week.

Overall, the results – published in the journal NeuroImage– showed that, while exercise had no effect on total hippocampal volume, it did significantly increase the size of the left region of the hippocampus in humans.

"When you exercise you produce a chemical called brain-derived neurotrophic factor (BDNF), which may help to prevent age-related decline by reducing the deterioration of the brain," Mr Firth said. "Our data showed that, rather than actually increasing the size of the hippocampus per se, the main 'brain benefits' are due to aerobic exercise slowing down the deterioration in brain size. In other words, exercise can be seen as a maintenance program for the brain.".... Interestingly, physical exercise is one of the very few 'proven' methods for maintaining brain size and functioning into older age.

Published on Leave a comment on Exercise, Exercise, Exercise To Keep From Regaining Weight

So you finally lost weight by diligently dieting, but now the issue is how to keep the weight from creeping back up again. Keeping strict watch over what you eat (basically continuing to diet)? Or exercising? Or...? Another issue muddying the waters is that a big weight loss also lowers the metabolism rate - something that occurred to former participants of the reality TV show The Biggest Loser.

They lost enormous amounts of weight during the 30 week competition (over 100 pounds on average), but 6 years later much of the weight was regained, and they were burning hundreds fewer calories each day at rest. So they had become metabolically much slower over time.

A study looking at 14 former participants of The Biggest Loser 6 years after the show found that a large persistent increase in physical activity was essential for long-term maintenance of weight loss. Those who regained the least weight were the most active, and vice versa. On the other hand, food intake (keeping calorie intake low) wasn't the most important.

How much of an increase in physical activity was needed to maintain the weight loss? Researchers found that an increase of about 80 minutes of daily moderate activity (such as brisk walking) or 35 minutes of daily vigorous activity was needed. From Medscape:

The Biggest Loser: Physical Exertion Is Key to Keeping Weight Off

Persistent increased physical activity is likely essential for long-term maintenance of weight loss, new research from participants in the US TV reality show The Biggest Loser suggests.... Using objective measures for both energy intake and physical activity in 14 former Biggest Loser contestants 6 years after they participated in the competition, Dr Kerns and colleagues found that those who had regained the least weight were the most active, and vice versa. Food intake, on the other hand, had very little effect on long-term weight-loss maintenance.

Asked to comment, Eric Ravussin, PhD, Boyd Professor at Louisiana State University, Baton Rouge, and coeditor of Obesity, told Medscape Medical News that the data align with those of follow-ups to major trials — including the Diabetes Prevention Program and the Action for Health Diabetes (Look AHEAD) study as well as with the National Weight Control Registry — of thousands of people who have lost at least 30 pounds and kept them off for at least a year. "The successful losers…all report high levels of physical activity" for weight maintenance, in contrast to weight loss, for which caloric deficit plays a far greater role, Dr Ravussin noted.

The reason for the difference between what works for weight loss vs maintenance, he said, probably has a lot to do with metabolic adaptation. This was the subject of another Biggest Loser paper published in Obesity in 2016, in which a person's metabolism slows down in response to a large drop in weight, making weight-loss maintenance difficult without an extra "push" from exercise, he explained.

The subjects in the new study were 14 participants with class III obesity who participated in a single season of The Biggest Loser, during which they underwent an intensive 30-week diet and exercise program and lost an average of 60 kg. Most regained weight after the program ended, although the degree of regain was highly variable. The median weight loss after 6 years was 13%. Seven subjects above the median weighed 24.9% less than baseline (maintainers) while the seven below the line (regainers) weighed 1.1% above their baseline. The maintainers had significantly greater increases in physical activity from baseline compared with the regainers..... that 35 minutes a day of intensive exercise, or 80 minutes of moderate activity, would roughly approximate the calorie expenditures among the maintainers.

Published on Leave a comment on Exercise and Lower Rates of Depression

A newly published study suggests that exercising an hour or more per week could lower the incidence of depression. The study followed 33,000 adults in Norway  for 11 years, and found that an hour or more of weekly exercise was associated with 12% fewer cases of developing depression. But note that it didn't prevent anxiety.

Interestingly, the researchers found that "regular leisure-time exercise of any intensity" had these positive effects - it doesn't have to be aerobic or incredibly strenuous exercise. Exercise is associated with a number of biological changes that could have an impact on mental health. From Science Daily:

One hour of exercise a week can prevent depression

A landmark study led by the Black Dog Institute has revealed that regular exercise of any intensity can prevent future depression -- and just one hour can help. Published in the American Journal of Psychiatry, the results show even small amounts of exercise can protect against depression, with mental health benefits seen regardless of age or gender.

In the largest and most extensive study of its kind, the analysis involved 33,908 Norwegian adults who had their levels of exercise and symptoms of depression and anxiety monitored over 11 years. The international research team found that 12 percent of cases of depression could have been prevented if participants undertook just one hour of physical activity each week.

A healthy cohort of participants was asked at baseline to report the frequency of exercise they participated in and at what intensity: without becoming breathless or sweating, becoming breathless and sweating, or exhausting themselves. At follow-up stage, they completed a self-report questionnaire (the Hospital Anxiety and Depression Scale) to indicate any emerging anxiety or depression.

Results showed that people who reported doing no exercise at all at baseline had a 44% increased chance of developing depression compared to those who were exercising one to two hours a week. However, these benefits did not carry through to protecting against anxiety, with no association identified between level and intensity of exercise and the chances of developing the disorder. [Original article.]

Published on Leave a comment on Don’t Just Sit For Long Periods – Move Every Half Hour

OK everyone - even if you sit all day at a desk job, the research is clear: try to get up and stretch or move a little every 30 minutes. Researchers followed middle-aged and older adults over a 5 1/2 year period and found that total sitting time (sedentary behavior) and prolonged, uninterrupted sedentary behavior were associated with in increased risk for death from any cause (all-cause mortality). But..adults who kept most of their sitting bouts to less than 30 minutes had the lowest risk of death. The researchers felt that getting up and moving every half hour seems to protect against the health risks (cardiometabolic effects) from just sitting and sitting and sitting. Are you moving yet?

From Science Daily: Long sitting periods may be just as harmful as daily total

A new study finds that it isn't just the amount of time spent sitting, but also the way in which sitting time is accumulated during the day, that can affect risk of early death. The study, published online today in Annals of Internal Medicine, found that adults who sit for one to two hours at a time without moving have a higher mortality rate than adults who accrue the same amount of sedentary time in shorter bouts.

The researchers used hip-mounted activity monitors to objectively measure inactivity during waking time over a period of seven days in 7,985 black and white adults over age 45. (The participants were taking part in the REGARDS study, a national investigation of racial and regional disparities in stroke.)

On average, sedentary behavior accounted for 77 percent of the participants' waking hours, equivalent to more than 12 hours per day. Over a median follow-up period of four years, 340 of the participants died. Mortality risk was calculated for those with various amounts of total sedentary time and various sedentary patterns. Those with the greatest amount of sedentary time -- more than 13 hours per day -- and who frequently had sedentary bouts of at least 60 to 90 consecutive minutes had a nearly two-fold increase in death risk compared with those who had the least total sedentary time and the shortest sedentary bouts.

The researchers also found that participants who kept most of their sitting bouts to less than 30 minutes had the lowest risk of death. "So if you have a job or lifestyle where you have to sit for prolonged periods of time, we suggest taking a movement break every half hour. This one behavior change could reduce your risk of death, although we don't yet know precisely how much activity is optimal," Dr. Diaz said. [Original study.]

Published on Leave a comment on Physical Activity In Midlife Not Linked to Later Cognitive Health

Surprised...is how I felt after reading this study. According to the study, activity levels and exercise in mid-life are not linked to cognitive fitness and dementia later on in life. Instead, higher levels of physical activity and exercise has a beneficial effect on the brain in the short term (e.g., within 2 years or so). This finding of no long-term benefits, but only short-term benefits to the brain from exercise, is contrary to some other (cross-sectional) studies, but is supported by another recent study ("no evidence of a neuroprotective effect of physical activity").

The beauty of this study is that it followed 646 people for 30 years (from a median age of 46 years in 1978 and 77 years in 2008). The negative is that according to this study, physical exercise in mid-life does not seem to delay or prevent the onset of dementia and Alzheimer's later on in life. Eh... From Medical Xpress:

Physical activity in midlife not linked to cognitive fitness in later years, long-term study shows

A study led by Johns Hopkins Bloomberg School of Public Health researchers that tracked activity levels of 646 adults over 30 years found that, contrary to previous research, exercise in mid-life was not linked to cognitive fitness in later years. The finding suggests that physical activity may not help maintain cognitive function, or help avoid or delay the onset of the debilitating conditions like dementia and Alzheimer's. 

The study, which appears online in the Journal of Alzheimer's Disease, did find that activity levels among study participants in the later years were associated with high cognitive function two years later. This supports earlier research findings that exercise may help to maintain cognitive fitness in the short term.

There is no known treatment or cure for Alzheimer's or dementia, syndromes that involves declining memory, confusion and eventually limited ability to perform daily tasks. To date, there are no preventive measures, such as physical exercise, brain games or a diet regimen, that have been proven to help delay or altogether prevent its onset. The researchers undertook the study because of a growing consensus that physical activity levels helps prevent Alzheimer's, however much of the evidence for this thinking is based on cross-sectional studies that compare responses from one group of participants with another at a given point in time or within a very short duration, typically several years..... That's where longitudinal studies, which look at the same group of participants over a long time, are more helpful.

The researchers used data from the Johns Hopkins Precursors study.... The researchers used responses from 1978 through 2008 from 646 participants (598 men, 48 women) to calculate so-called metabolic equivalents, which quantify physical activity levels. Participants were also asked whether they regularly exercise to a sweat. The team administered cognitive tests in 2008, and, using participants' medical records, scored for dementia through 2011. The researchers identified 28, or 4.5 percent of the cohort, to have Alzheimer's.

No physical activity measure in mid-life was associated with late-life cognitive fitness or onset of dementia. The study confirmed findings of other cross-sectional studies, that higher levels of physical activity and exercise measured close in time to the cognitive testing were associated with better cognitive functioning. The authors also looked at whether patterns of change in physical activity levels over the life span were associated with cognitive health and found no relationships.

The idea that exercise might play a role in preventing or limiting Alzheimer's makes sense, the researchers say, because physical activity, at least in mouse models, has shown less accumulation of B-amyloid plaques, which are thought to play a role in dementia, including Alzheimer's. In addition, physical activity improves blood flow to the brain, which is linked to better cognitive performance. This may explain why studies find that exercise may contribute to cognitive fitness in the short term.

Published on Leave a comment on Exercise Linked To Lower Mortality After Prostate Cancer Diagnosis

Another reason exercise is good for you: A large study found that men who exercise after a diagnosis of prostate cancer (but which is not metastatic) had a lower risk of dying from prostate cancer - as compared to those men who don't exercise.

So get out there and do something that gets you moving - and yes, walking is an exercise (Note: 1 mile = 20 minutes of walking, thus 3 miles = 1 hour).

In this study the average age at diagnosis was 71, but studies find that exercise has numerous benefits at all ages. Some doctors even think of exercise as "anticancer therapy" (here, here). Also, exercise has anti-inflammatory benefits, and current thinking is that chronic inflammation is linked to cancer.

The American Cancer Society in its cancer prevention guidelines recommends that adults should be physically active, and get at least 150 minutes of moderate physical activity or 75 minutes of vigorous intensity activity each week (or a combination of these), preferably spread throughout the week.

From Medscape: Exercise Linked to Lower Mortality With Early Prostate Cancer

Men with nonmetastatic prostate cancer may have longer survival the more they exercise, a recent study suggests. For these men, regular moderate or vigorous physical activity was associated with 31 percent to 37 percent lower likelihood of death during the study, compared to more modest amounts of exercise.

“This confirms and expands on previous work that shows an inverse association between recreational physical activity after diagnosis and risk of prostate cancer-specific mortality,” said lead study author Ying Wang of the American Cancer Society in Atlanta, Georgia, in email to Reuters Health.

Wang and colleagues pulled data from a large, long-term study group established by the American Cancer Society in 1992, focusing on 7,000 men who were diagnosed with prostate cancer between 1992 and 2011. The average age at cancer diagnosis was 71, and there were 2,700 deaths through 2012, including 450 due to prostate cancer and 750 due to heart disease. The average time from diagnosis to death was about eight years for those who died from cancer and 10 years for those who died from other causes.

Men who were more active before diagnosis were more likely to have lower-risk cancer tumors and a history of prostate screenings. They were also leaner, more likely to be nonsmokers and vitamin users and they ate more fish. Both before and after diagnosis, walking accounted for 73 percent of the physical activity that men did, followed by 10 percent for cycling and 5 percent for aerobic exercise, according to the report online now in European Urology.

Based on exercise levels before diagnosis, moderate to vigorous exercise, including walking, was linked to lower risk of death from prostate cancer, but only for men with lower-risk tumors. But after the diagnosis, the same levels of exercise were linked to lower risk of death from prostate cancer for all men, although the apparent benefit of walking was no longer statistically meaningful. [Original study.]

Published on Leave a comment on Jogging Or Fast Walking May Strengthen Your Back

Guess what? Instead of babying our backs, we may have to be sure to get plenty of running, jogging, or brisk walking to make our backs stronger - specifically, to strengthen the discs in our spines. Once again, a study finds that exercise (here the upright exercise of running, jogging, or fast walking) has benefits.

The authors of the study state that the research results go against conventional medical wisdom - that instead of weakening the spine (conventional view), those people who run or jog  many miles each week may actually be strengthening the discs of the spine. And maybe... the researchers suggest (though it needs to be verified first)... in the future, we may get medical prescriptions to jog or fast walk a certain number of miles each week to strengthen the discs in our spines.

The study found that the ideal speed for the spine health was a slow run or a fast walk (4 miles per hour). Specifically fast walking and slow running at about 2 meters per second (m/s) appeared the most beneficial. However, high impact exercises, or aerobic exercises, slower walking, or no exercise did not have these benefits.

Until now, discs had been considered a "slow tissue," thought to take much longer to respond to exercise than muscle. And that with age and use the discs degenerate, and nothing could really be done to improve them. But the study's findings suggest that exercise can benefit and strengthen the intervertebral disc (IVD) in the spine. As researcher Dr. Belavy said: "It's also important to reduce the amount of time spent in static postures, such as sitting or even standing still. Even going for a walk during a break at work, or choosing to take the stairs rather than the elevator is good for the discs, as well as for overall back health."

From NY Times: Why Running May Be Good for Your Back

People who regularly run or walk briskly appear to have healthier discs in their spines than people who do not exercise, according to one of the first studies to closely examine links between movement and disc health. The findings refute a widely held belief that activities like running might overtax the spine and indicate that, instead, they make it sturdier. The human spine is a complicated mechanism, composed of vertebral bones cushioned between intervertebral discs. These discs, shaped like tiny whoopee cushions, contain a viscous fluid that compresses and absorbs pressure during movement, keeping the back in good working form. With age, disease or injury, spinal discs can degenerate and bulge, resulting in back pain, which can be debilitating.

There were tantalizing hints in animal studies, however, that this idea could be out of date. ....So for the new study, which was published in April in Scientific Reports, researchers at Deakin University in Australia and other institutions decided to examine the backs of people who run and others who do not. Eventually they recruited 79 adult men and women, two-thirds of whom said that they were runners. Some of these told the researchers that they covered more than 30 miles (about 50 kilometers) a week in training. The researchers designated these as the “long-distance” group. The others said that they ran between 12 and 25 miles a week. All had been training for at least five years. The final group rarely exercised at all.

To ensure that people’s reported activity levels were accurate, the researchers asked their volunteers to wear accelerometers for a week. Then they scanned everyone’s spines, using a sophisticated type of M.R.I. that precisely measures the size and liquidity of each disc. And they found differences. In general, the runners’ discs were larger and contained more fluid than the discs of the men and women who did not exercise. Since both greater size and increased levels of internal fluid indicate better disc health, the runners harbored fundamentally healthier spines than the people who were sedentary, says Daniel Belavy, a professor of physical activity at Deakin University who led the study. Interestingly, mileage barely mattered.