Geologists determine early Earth was a 'water world' by studying exposed ocean crust

Ocean panorama (stock image).

The Earth of 3.2 billion years ago was a "water world" of submerged continents, geologists say after analyzing oxygen isotope data from ancient ocean crust that's now exposed on land in Australia.

And that could have major implications on the origin of life.

"An early Earth without emergent continents may have resembled a 'water world,' providing an important environmental constraint on the origin and evolution of life on Earth as well as its possible existence elsewhere," geologists Benjamin Johnson and Boswell Wing wrote in a paper just published online by the journal Nature Geoscience.

Johnson is an assistant professor of geological and atmospheric sciences at Iowa State University and a recent postdoctoral research associate at the University of Colorado Boulder. Wing is an associate professor of geological sciences at Colorado. Grants from the National Science Foundation supported their study and a Lewis and Clark Grant from the American Philosophical Society supported Johnson's fieldwork in Australia.

Johnson said his work on the project started when he talked with Wing at conferences and learned about the well-preserved, 3.2-billion-year-old ocean crust from the Archaean eon (4 billion to 2.5 billion years ago) in a remote part of the state of Western Australia. Previous studies meant there was already a big library of geochemical data from the site.

Johnson joined Wing's research group and went to see ocean crust for himself -- a 2018 trip involving a flight to Perth and a 17-hour drive north to the coastal region near Port Hedland.

After taking his own rock samples and digging into the library of existing data, Johnson created a cross-section grid of the oxygen isotope and temperature values found in the rock.

(Isotopes are atoms of a chemical element with the same number of protons within the nucleus, but differing numbers of neutrons. In this case, differences in oxygen isotopes preserved with the ancient rock provide clues about the interaction of rock and water billions of years ago.)

Once he had two-dimensional grids based on whole-rock data, Johnson created an inverse model to come up with estimates of the oxygen isotopes within the ancient oceans. The result: Ancient seawater was enriched with about 4 parts per thousand more of a heavy isotope of oxygen (oxygen with eight protons and 10 neutrons, written as 18O) than an ice-free ocean of today.

How to explain that decrease in heavy isotopes over time?

Johnson and Wing suggest two possible ways: Water cycling through the ancient ocean crust was different than today's seawater with a lot more high-temperature interactions that could have enriched the ocean with the heavy isotopes of oxygen. Or, water cycling from continental rock could have reduced the percentage of heavy isotopes in ocean water.

"Our preferred hypothesis -- and in some ways the simplest -- is that continental weathering from land began sometime after 3.2 billion years ago and began to draw down the amount of heavy isotopes in the ocean," Johnson said.

The idea that water cycling through ocean crust in a way distinct from how it happens today, causing the difference in isotope composition "is not supported by the rocks," Johnson said. "The 3.2-billion-year-old section of ocean crust we studied looks exactly like much, much younger ocean crust."

Johnson said the study demonstrates that geologists can build models and find new, quantitative ways to solve a problem -- even when that problem involves seawater from 3.2 billion years ago that they'll never see or sample.

And, Johnson said these models inform us about the environment where life originated and evolved: "Without continents and land above sea level, the only place for the very first ecosystems to evolve would have been in the ocean."

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Materials provided by Iowa State University. Note: Content may be edited for style and length.

Geologists determine early Earth was a 'water world' by studying exposed ocean crust

Ocean panorama (stock image).

The Earth of 3.2 billion years ago was a "water world" of submerged continents, geologists say after analyzing oxygen isotope data from ancient ocean crust that's now exposed on land in Australia.

And that could have major implications on the origin of life.

"An early Earth without emergent continents may have resembled a 'water world,' providing an important environmental constraint on the origin and evolution of life on Earth as well as its possible existence elsewhere," geologists Benjamin Johnson and Boswell Wing wrote in a paper just published online by the journal Nature Geoscience.

Johnson is an assistant professor of geological and atmospheric sciences at Iowa State University and a recent postdoctoral research associate at the University of Colorado Boulder. Wing is an associate professor of geological sciences at Colorado. Grants from the National Science Foundation supported their study and a Lewis and Clark Grant from the American Philosophical Society supported Johnson's fieldwork in Australia.

Johnson said his work on the project started when he talked with Wing at conferences and learned about the well-preserved, 3.2-billion-year-old ocean crust from the Archaean eon (4 billion to 2.5 billion years ago) in a remote part of the state of Western Australia. Previous studies meant there was already a big library of geochemical data from the site.

Johnson joined Wing's research group and went to see ocean crust for himself -- a 2018 trip involving a flight to Perth and a 17-hour drive north to the coastal region near Port Hedland.

After taking his own rock samples and digging into the library of existing data, Johnson created a cross-section grid of the oxygen isotope and temperature values found in the rock.

(Isotopes are atoms of a chemical element with the same number of protons within the nucleus, but differing numbers of neutrons. In this case, differences in oxygen isotopes preserved with the ancient rock provide clues about the interaction of rock and water billions of years ago.)

Once he had two-dimensional grids based on whole-rock data, Johnson created an inverse model to come up with estimates of the oxygen isotopes within the ancient oceans. The result: Ancient seawater was enriched with about 4 parts per thousand more of a heavy isotope of oxygen (oxygen with eight protons and 10 neutrons, written as 18O) than an ice-free ocean of today.

How to explain that decrease in heavy isotopes over time?

Johnson and Wing suggest two possible ways: Water cycling through the ancient ocean crust was different than today's seawater with a lot more high-temperature interactions that could have enriched the ocean with the heavy isotopes of oxygen. Or, water cycling from continental rock could have reduced the percentage of heavy isotopes in ocean water.

"Our preferred hypothesis -- and in some ways the simplest -- is that continental weathering from land began sometime after 3.2 billion years ago and began to draw down the amount of heavy isotopes in the ocean," Johnson said.

The idea that water cycling through ocean crust in a way distinct from how it happens today, causing the difference in isotope composition "is not supported by the rocks," Johnson said. "The 3.2-billion-year-old section of ocean crust we studied looks exactly like much, much younger ocean crust."

Johnson said the study demonstrates that geologists can build models and find new, quantitative ways to solve a problem -- even when that problem involves seawater from 3.2 billion years ago that they'll never see or sample.

And, Johnson said these models inform us about the environment where life originated and evolved: "Without continents and land above sea level, the only place for the very first ecosystems to evolve would have been in the ocean."

---

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Materials provided by Iowa State University. Note: Content may be edited for style and length.

Vitamin D at High Dose Can Worsen MS, Early Study Says

High-dose vitamin D supplements appear to aggravate inflammation and myelin loss in the brain and spinal cord, and worsen the disability associated with multiple sclerosis (MS), a study in a mouse disease model reported.

Excessive use of vitamin D causes calcium levels to spike, which directly increase the inflammatory state of immune cells and their capacity to infiltrate the central nervous system (CNS; the brain and spinal cord), the researchers observed.

Supplements given in moderation, however, may help to ease disease symptoms.

The findings were presented at the Americas Committee for Treatment and Research in Multiple Sclerosis (ACTRIMS) Forum 2020, held Feb. 27–29 in Florida, in the poster “High Dose Vitamin D Worsens Experimental CNS Autoimmune Disease By Raising T Cell-excitatory Calcium.” The presenter was Sebastian Torke, PhD, with the Institute of Neuropathology, University Medical Center in Göttingen, Germany.

A large body of data suggests that low vitamin D levels raise a person’s risk of developing MS. But whether or not vitamin supplements should be given to people who already have the disease is under debate.

In general, MS patients have relatively low levels of vitamin D. Based on studies showing an association between low levels of this vitamin and a higher risk of relapses and earlier disability, doctors often recommend oral vitamin D3 (cholecalciferol) supplements to their patients.

Yet, it is unclear whether such supplements offer therapeutic benefits to MS patients, and if they do, what doses should be advised. While relatively low doses of vitamin D appear to be safe, high doses are likely toxic and potentially harmful.

Researchers set out to model the consequences of this common practice by investigating the effects of long-term vitamin D supplements given to mice.

They fed mice a diet containing either a low concentration (less than 5 IU of vitamin D3/kg of food), a standard amount (1,500 IU/kg), or a high dose (75,000 IU/kg) of vitamin D3 for 15 weeks (about three and a half months).

These three doses were chosen to generate serum levels of 25-hydroxyvitamin D [25(OH)D] — the molecule measured in a vitamin D blood test — reflective of what is typically seen in patients with vitamin D deficiency (less than 30 nmol/l), in those taking modest supplements and achieving normal vitamin D levels (100 nmol/l), and in those with disproportionally high supplements (250 nmol/l).

All three diets contained identical calcium (1%) and phosphate (0.7%) concentrations.

Researchers then induced MS-like disease in the mice and followed their clinical symptoms, CNS inflammation and damage, and immune cell behavior.

Results showed that, compared to MS mice not given supplements, a moderate dose of vitamin D eased disease severity, which was linked to an expansion of regulatory T-cells — immune cells that help to keep immune responses in check.

The opposite, however, happened in mice fed a high-dose vitamin D diet.

“High-dose, long-term vitamin D supplementation lead to much worse disease in these mice,” Torke said.

The animals had excessively high levels of the vitamin in the blood (above 200 nmol/l), and developed “fulminant” disease with severe and persistent disability. This was associated with massive CNS inflammation and the infiltration of activated  T helper 1 (Th1) and Th17 cells — immune cells that can cause inflammation and autoimmune disease — as well as demyelination (loss of myelin), a hallmark of MS.

Researchers decided that calcium is likely at fault for what they considered an “unexpected outcome.”

High-dose vitamin D caused calcium levels to rise to excessive amounts (hypercalcemia) throughout the body, triggering the activation, proliferation, and inflammatory behavior of  T-cells.

Supporting these findings, the researchers also found that exposing mice or human T-cells in vitro (in the lab) to various concentrations of calcium (equivalent to those found in vitamin D-fed mice) increased the entry of calcium into cells, and triggered the activation of pro-inflammatory pathways.

“It is not vitamin D that is bad, but too much vitamin D leads to increased calcium [levels] that promote T-cell proliferation and activation,” Torke said.

Calcium also enhances the ability of T-cells to cross the blood-brain barrier — a highly selective membrane that regulates which substances or cells carried in blood can enter the brain or spinal cord — reflecting a greater ability to infiltrate the CNS.

Inducing hypercalcemia in mice was enough to activate T-cells, confirming that this effect can also occur in a living organism (in vivo).

“These findings highlight excessive vitamin D supplementation and resulting hypercalcemia as novel risk factors promoting worsening of CNS demyelinating disease,” Torke said.

“Our data caution that in light of the currently limited information on a direct beneficial effect of vitamin D in MS, MS patients may be at danger of experiencing untoward immunological and/or clinical effects when vitamin D is supplemented excessively,” Torke concluded.

Astronomers discover unusual monster galaxy in the very early universe

W. M. Keck Observatory (stock image).

An international team of astronomers led by scientists at the University of California, Riverside, has found an unusual monster galaxy that existed about 12 billion years ago, when the universe was only 1.8 billion years old.

Dubbed XMM-2599, the galaxy formed stars at a high rate and then died. Why it suddenly stopped forming stars is unclear.

"Even before the universe was 2 billion years old, XMM-2599 had already formed a mass of more than 300 billion suns, making it an ultramassive galaxy," said Benjamin Forrest, a postdoctoral researcher in the UC Riverside Department of Physics and Astronomy and the study's lead author. "More remarkably, we show that XMM-2599 formed most of its stars in a huge frenzy when the universe was less than 1 billion years old, and then became inactive by the time the universe was only 1.8 billion years old."

The team used spectroscopic observations from the W. M. Keck Observatory's powerful Multi-Object Spectrograph for Infrared Exploration, or MOSFIRE, to make detailed measurements of XMM-2599 and precisely quantify its distance.

Study results appear in the Astrophysical Journal.

"In this epoch, very few galaxies have stopped forming stars, and none are as massive as XMM-2599," said Gillian Wilson, a professor of physics and astronomy at UCR in whose lab Forrest works. "The mere existence of ultramassive galaxies like XMM-2599 proves quite a challenge to numerical models. Even though such massive galaxies are incredibly rare at this epoch, the models do predict them. The predicted galaxies, however, are expected to be actively forming stars. What makes XMM-2599 so interesting, unusual, and surprising is that it is no longer forming stars, perhaps because it stopped getting fuel or its black hole began to turn on. Our results call for changes in how models turn off star formation in early galaxies."

The research team found XMM-2599 formed more than 1,000 solar masses a year in stars at its peak of activity -- an extremely high rate of star formation. In contrast, the Milky Way forms about one new star a year.

"XMM-2599 may be a descendant of a population of highly star-forming dusty galaxies in the very early universe that new infrared telescopes have recently discovered," said Danilo Marchesini, an associate professor of astronomy at Tufts University and a co-author on the study.

The evolutionary pathway of XMM-2599 is unclear.

"We have caught XMM-2599 in its inactive phase," Wilson said. "We do not know what it will turn into by the present day. We know it cannot lose mass. An interesting question is what happens around it. As time goes by, could it gravitationally attract nearby star-forming galaxies and become a bright city of galaxies?"

Co-author Michael Cooper, a professor of astronomy at UC Irvine, said this outcome is a strong possibility.

"Perhaps during the following 11.7 billion years of cosmic history, XMM-2599 will become the central member of one of the brightest and most massive clusters of galaxies in the local universe," he said. "Alternatively, it could continue to exist in isolation. Or we could have a scenario that lies between these two outcomes."

The team has been awarded more time at the Keck Observatory to follow up on unanswered questions prompted by XMM-2599.

"We identified XMM-2599 as an interesting candidate with imaging alone," said co-author Marianna Annunziatella, a postdoctoral researcher at Tufts University. "We used Keck to better characterize and confirm its nature and help us understand how monster galaxies form and die. MOSFIRE is one of the most efficient and effective instruments in the world for conducting this type of research."

Other researchers taking part include Daniel Lange-Vagle and Theodore Peña of Tufts University; Adam Muzzin and Cemile Marsan of York University, Canada; Ian McConachie and Jeffrey Chan of UCR; Percy Gomez of Keck Observatory; Erin Kado-Fong of Princeton University; Francesco La Barbera of INAF-Osservatorio Astronomico di Capodimonte, Italy; Ivo Labbe of Swinburne University of Technology, Australia; Julie Nantais of Andrés Bello National University, Santiago, Chile; Mario Nonino of Astronomical Observatory of Trieste, Italy; Paolo Saracco of Astronomical Observatory of Brera, Italy; Mauro Stefanon of Leiden University, Netherlands; and Remco F. J. van der Burg of the European Southern Observatory, Germany.

Wilson led the W. M. Keck Observatory data acquisition. Forrest led the processing and analysis.

The study was supported by grants from the National Science Foundation and NASA.

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Materials provided by University of California - Riverside. Original written by Iqbal Pittalwala. Note: Content may be edited for style and length.

Mystery of how early animals survived ice age

Mystery of how early animals survived ice age

How did life survive the most severe ice age? A McGill University-led research team has found the first direct evidence that glacial meltwater provided a crucial lifeline to eukaryotes during Snowball Earth, when the oceans were cut off from life-giving oxygen, answering a question puzzling scientists for years.

In a new study published in the Proceedings of the National Academy of Sciences, researchers studied iron-rich rocks left behind by glacial deposits in Australia, Namibia, and California to get a window into the environmental conditions during the ice age. Using geological maps and clues from locals, they hiked to rock outcrops, navigating challenging trails to track down the rock formations.

By examining the chemistry of the iron formations in these rocks, the researchers were able to estimate the amount of oxygen in the oceans around 700 million years ago and better understand the effects this would have had on all oxygen-dependent marine life, including the earliest animals like simple sponges.

"The evidence suggests that although much of the oceans during the deep freeze would have been uninhabitable due to a lack of oxygen, in areas where the grounded ice sheet begins to float there was a critical supply of oxygenated meltwater. This trend can be explained by what we call a 'glacial oxygen pump'; air bubbles trapped in the glacial ice are released into the water as it melts, enriching it with oxygen," says Maxwell Lechte, a postdoctoral researcher in the Department of Earth and Planetary Sciences under the supervision of Galen Halverson at McGill University.

Around 700 million years ago, the Earth experienced the most severe ice age of its history, threatening the survival of much of the planet's life. Previous research has suggested that oxygen-dependent life may have been restricted to meltwater puddles on the surface of the ice, but this study provides new evidence of oxygenated marine environments.

"The fact that the global freeze occurred before the evolution of complex animals suggests a link between Snowball Earth and animal evolution. These harsh conditions could have stimulated their diversification into more complex forms," says Lechte, who is also the study's lead author.

Lechte points out that while the findings focus on the availability of oxygen, primitive eukaryotes would also have needed food to survive the harsh conditions of the ice age. Further research is needed to explore how these environments might have sustained a food web. A starting point might be modern ice environments that host complex ecosystems today.

"This study actually solves two mysteries about the Snowball Earth at once. It not only provides explanation for how early animals may have survived global glaciation, but also eloquently explains the return of iron deposits in the geological record after an absence of over a billion years," says Professor Galen Halverson.

About the study

"Subglacial meltwater supported aerobic marine habitats during Snowball Earth" by Maxwell Lechte, Malcolm Wallace, Ashleigh van Smeerdijk Hood, Weiqiang Li, Ganqing Jiang, Galen Halverson, Dan Asael, Stephanie McColl, and Noah Planavsky is published in Proceedings of the National Academy of Sciences of the United States of America. The paper is a collaboration between McGill University, University of Melbourne, Nanjing University, University of Nevada, Las Vegas, and Yale University.

This work received financial support from the Australian Government Research Training Program Scholarship, the Albert Shimmins Award, the Australian Research Council Discovery Grant, the NASA Astrobiology Postdoctoral Fellowship, the Puzey Fellowship, and the Australian Research Council.

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Some stress in early life extends lifespan, research in roundworms shows

Caenorhabditis elegans 

Some stress at a young age could actually lead to a longer life, new research shows.

University of Michigan researchers have discovered that oxidative stress experienced early in life increases subsequent stress resistance later in life.

Oxidative stress happens when cells produce more oxidants and free radicals than they can deal with. It's part of the aging process, but can also arise from stressful conditions such as exercise and calorie restriction.

Examining a type of roundworm called Caenorhabditis elegans, U-M scientists Ursula Jakob and Daphne Bazopoulou found that worms that produced more oxidants during development lived longer than worms that produced fewer oxidants. Their results are published in the journal Nature.

Researchers have long wondered what determines variability in lifespan, says Jakob, a professor of molecular, cellular and developmental biology. One part of that is genetics: If your parents are long-lived, you have a good chance for living longer as well. Environment is another part.

That other stochastic -- or random -- factors might be involved becomes clear in the case of C. elegans. These short-lived organisms are a popular model system among aging researchers in part because every hermaphroditic mother produces hundreds of genetically identical offspring. However, even if kept in the same environment, the lifespan of these offspring varies to a surprising extent, Jakob says.

"If lifespan was determined solely by genes and environment, we would expect that genetically identical worms grown on the same petri dish would all drop dead at about the same time, but this is not at all what happens. Some worms live only three days while others are still happily moving around after 20 days," Jakob said. "The question then is, what is it, apart from genetics and environment, that is causing this big difference in lifespan?"

Jakob and Bazopoulou, a postdoctoral researcher and lead author of the paper, found one part of the answer when they discovered that during development, C. elegans worms varied substantially in the amount of reactive oxygen species they produce.

Reactive oxygen species, or ROS, are oxidants that every air-breathing organism produces. ROS are closely associated with aging: the oxidative damage they elicit are what many anti-aging creams claim to combat. Bazopoulou and Jakob discovered that instead of having a shorter lifespan, worms that produced more ROS during development actually lived longer.

"Experiencing stress at this early point in life may make you better able to fight stress you might encounter later in life," Bazopoulou said.

When the researchers exposed the whole population of juvenile worms to external ROS during development, the average lifespan of the entire population increased. Though the researchers don't know yet what triggers the oxidative stress event during development, they were able to determine what processes enhanced the lifespan of these worms.

To do this, Bazopoulou sorted thousands of C. elegans larvae according to the oxidative stress levels they have during development. By separating worms that produced large amounts of ROS from those that produced little amounts of ROS, she showed that the main difference between the two groups was a histone modifier, whose activity is sensitive to oxidative stress conditions.

The researchers found that the temporary production of ROS during development caused changes in the histone modifier early in the worm's life. How these changes persist throughout life and how they ultimately affect and extend lifespan is still unknown. What is known, however, is that this specific histone modifier is also sensitive to oxidative stress sensitive in mammalian cells. Additionally, early-life interventions have been shown to extend lifespans in mammalian model systems such as mice.

"The general idea that early life events have such profound, positive effects later in life is truly fascinating. Given the strong connection between stress, aging and age-related diseases, it is possible that early events in life might also affect the predisposition for age-associated diseases, such as dementia and Alzheimer's disease," Jakob said.

Next, the researchers want to figure out what key changes are triggered by these early-life events. Understanding this might allow scientists to develop lifespan-extending interventions that work at later stages in life.

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Any amount of running linked to significantly lower risk of early death

Woman running

Any amount of running is linked to a significantly lower risk of death from any cause, finds a pooled analysis of the available evidence, published online in the British Journal of Sports Medicine.

If more people took up running -- and they wouldn't have to run far or fast -- there would likely be substantial improvements in population health and longevity, conclude the researchers.

It's not clear how good running is for staving off the risk of death from any cause and particularly from cardiovascular disease and cancer, say the researchers.

Nor is it clear how much running a person needs to do to reap these potential benefits, nor whether upping the frequency, duration, and pace -- in other words, increasing the 'dose' -- might be even more advantageous.

To try and find out, the researchers systematically reviewed relevant published research, conference presentations, and doctoral theses and dissertations in a broad range of academic databases.

They looked for studies on the association between running/jogging and the risk of death from all causes, cardiovascular disease, and cancer.

They found 14 suitable studies, involving 232,149 people, whose health had been tracked for between 5.5 and 35 years. During this time, 25,951 of the study participants died.

When the study data were pooled, any amount of running was associated with a 27% lower risk of death from all causes for both sexes, compared with no running.

And it was associated with a 30% lower risk of death from cardiovascular disease, and a 23% lower risk of death from cancer.

Even small 'doses' -- for example, once weekly or less, lasting less than 50 minutes each time, and at a speed below 6 miles (8 km) an hour, still seemed to be associated with significant health/longevity benefits.

So running for 25 minutes less than the recommended weekly duration of vigorous physical activity could reduce the risk of death. This makes running a potentially good option for those whose main obstacle to doing enough exercise is lack of time, suggest the researchers.

But upping 'the dose' wasn't associated with a further lowering of the risk of death from any cause, the analysis showed.

This is an observational study, and as such, can't establish cause. And the researchers caution that the number of included studies was small and their methods varied considerably, which may have influenced the results.

Nevertheless, they suggest that any amount of running is better than none, concluding: "Increased rates of participation in running, regardless of its dose, would probably lead to substantial improvements in population health and longevity."

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Materials provided by BMJ. Note: Content may be edited for style and length.

Any amount of running linked to significantly lower risk of early death

Woman running

Any amount of running is linked to a significantly lower risk of death from any cause, finds a pooled analysis of the available evidence, published online in the British Journal of Sports Medicine.

If more people took up running -- and they wouldn't have to run far or fast -- there would likely be substantial improvements in population health and longevity, conclude the researchers.

It's not clear how good running is for staving off the risk of death from any cause and particularly from cardiovascular disease and cancer, say the researchers.

Nor is it clear how much running a person needs to do to reap these potential benefits, nor whether upping the frequency, duration, and pace -- in other words, increasing the 'dose' -- might be even more advantageous.

To try and find out, the researchers systematically reviewed relevant published research, conference presentations, and doctoral theses and dissertations in a broad range of academic databases.

They looked for studies on the association between running/jogging and the risk of death from all causes, cardiovascular disease, and cancer.

They found 14 suitable studies, involving 232,149 people, whose health had been tracked for between 5.5 and 35 years. During this time, 25,951 of the study participants died.

When the study data were pooled, any amount of running was associated with a 27% lower risk of death from all causes for both sexes, compared with no running.

And it was associated with a 30% lower risk of death from cardiovascular disease, and a 23% lower risk of death from cancer.

Even small 'doses' -- for example, once weekly or less, lasting less than 50 minutes each time, and at a speed below 6 miles (8 km) an hour, still seemed to be associated with significant health/longevity benefits.

So running for 25 minutes less than the recommended weekly duration of vigorous physical activity could reduce the risk of death. This makes running a potentially good option for those whose main obstacle to doing enough exercise is lack of time, suggest the researchers.

But upping 'the dose' wasn't associated with a further lowering of the risk of death from any cause, the analysis showed.

This is an observational study, and as such, can't establish cause. And the researchers caution that the number of included studies was small and their methods varied considerably, which may have influenced the results.

Nevertheless, they suggest that any amount of running is better than none, concluding: "Increased rates of participation in running, regardless of its dose, would probably lead to substantial improvements in population health and longevity."

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Story Source:

Materials provided by BMJ. Note: Content may be edited for style and length.