Tuesday, August 28, 2012

How to keep your bones safe in the Space through diet and exercise


Eating the right diet and exercising hard in space helps
protect International Space Station astronauts' bones, a finding that
may help solve one of the key problems facing future explorers
heading beyond low Earth orbit.

A new study, published this month in the Journal of Bone and Mineral
Research, evaluated the mineral density of specific bones as well as
the entire skeleton of astronauts who used the Advanced Resistive
Exercise Device (ARED), a 2008 addition to the space station that can
produce resistance of as much as 600 pounds in microgravity.
Resistance exercise allows astronauts to "lift weights" in

Researchers compared data measured from 2006 until the new device
arrived, when astronauts used an interim workout that offered about
half the total resistance of the ARED. The researchers found
astronauts using the advanced exercise system returned to Earth with
more lean muscle and less fat, and maintained their whole body and
regional bone mineral density compared to when they launched. Crew
members using ARED also consumed sufficient calories and vitamin D,
among other nutrients. These factors are known to support bone health
and likely played a contributing role.

"After 51 years of human spaceflight, these data mark the first
significant progress in protecting bone through diet and exercise,"
said Scott M. Smith, NASA nutritionist at the agency's Johnson Space
Center in Houston and lead author of the publication.

Since the 1990s, resistance exercise has been thought to be a key
method of protecting astronauts' bones. Normal, healthy bone
constantly breaks down and renews itself, a process called
remodeling. As long as these processes are in balance, bone mass and
density stay the same. Earlier studies of Russian Mir space station
residents found an increased rate of breakdown, but little change in
the rate of regrowth that resulted in an overall loss in bone
density. In the new study, researchers looked at preflight and
postflight images of bone using X-ray densitometry, as well as
in-flight blood and urine measurements of chemicals that reflect bone
metabolism. In crew members who used the ARED device during
spaceflight, bone breakdown still increased, but bone formation also
tended to increase, likely resulting in the maintenance of whole bone
mineral density.

"The increase in both bone breakdown and formation suggests that the
bone is being remodeled, but a key question remains as to whether
this remodeled bone is as strong as the bone before flight," said Dr.
Jean Sibonga, bone discipline lead at Johnson and coauthor of the
Studies to evaluate bone strength before and after flight are
currently under way.

Beyond bone strength, further study is required to determine the best
possible combination of exercise and diet for long-duration crews.
Dietary effects on bone are being studied on the space station right
now, with one experiment evaluating different ratios of animal
protein and potassium in the diet on bone health. Another is looking
at the benefits for bone of lowering sodium intake.

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