A group of nutrients found in fish oil, known as omega-3 fatty acids, may help mitigate bone breakdown that occurs during spaceflight and in those who suffer from osteoporosis, a new study suggests.?
As NASA sets its sights on long-duration missions to Mars and an asteroid, scientists are working hard to understand and cope with medical issues, such as bone loss, that accompany and are likely exacerbated by lengthier space travel.
The NASA-sponsored study built upon decades of research that has examined ways to halt bone density loss in astronauts. The study's findings could have significant implications for space travelers, but also for those who are susceptible to bone loss here on Earth.
The space agency has studied bone loss because it is one of the main effects of exposure to weightlessness in space.
"Your body is very smart, and it adapts to whatever environment you're in," study co-author Scott Smith, a nutritionist at NASA's Johnson Space Center in Houston , told SPACE.com. "For instance, if you start carrying around a backpack with 50 pounds in it, your skeleton will adjust to support that weight. The same is true for spaceflight. Your body knows that it is not carrying around the normal amount of weight."
So, if a person is in space for long periods of time, the body is likely to perceive the state of weightlessness to be more permanent, which could put that person at risk of elevated levels of bone deterioration.
Weak bones in space
The actual rate of bone loss for astronauts in space is difficult to quantify, Smith said, because it varies from person to person.
He roughly estimates that about 1 percent of bone mass is lost per month in space. In comparison, a post-menopausal woman with osteoporosis has a rate of bone loss of roughly 1 percent per year, Smith said. ?
The study's findings are detailed in the May issue of the Journal of Bone and Mineral Research. ?
The researchers conducted a series of studies that examined the effect of adding a specific omega-3 fatty acid, called eicosapentaenoic acid (EPA), to regular bone cell cultures and those designed to mimic weightlessness.
Scientists documented that adding EPA inhibited the activation of factors that lead to bone breakdown. This inhibited factor is known as "nuclear factor kappa B" or NFKB.
NFKB is involved in immune system behavior and the inflammation process, and if activated in different tissues, can lead to bone and muscle loss.
How humans adapt to space
In their study of astronauts who returned from short-duration shuttle missions, the researchers found that NFKB activation was increased in blood cells collected at landing, and remained elevated for two weeks. This provided evidence that inflammatory processes could be involved in part of the body's adaptation to microgravity.
The findings also suggested that by reducing NFKB activation, this could serve as a countermeasure to bone density loss.
The researchers also conducted a ground-based bed rest study on 16 subjects with evaluations performed after 60 days. Bed rest is one way to simulate some of the effects of weightlessness, including muscle and bone loss. In this study, less bone loss was correlated with higher intake of omega-3 fatty acids.
"These models on the ground are not perfect," Smith said. "They're not exactly the same as spaceflight, but they allow us to do much more invasive, intense types of studies than you could ever do during flight."
Fish benefits in space
Based on their findings, the scientists evaluated bone loss in astronauts and compared the results to reported fish intake during spaceflight. It was found that astronauts who ate more fish lost less bone mineral after four-to-six month spaceflights.
Measuring fish consumption is not as accurate as determining exact diet and omega-3 fatty acid intake, but these data were not available.
Furthermore, it may be premature to conclude that the solution to the problem is simply a matter of diet, Smith said.
"In the studies that we reported, we found that there was an association between the number of times [astronauts] ate fish in flight, and the amount of bone they lost after flight," he stated. "This begs two obvious questions: is it an effect of omega-3 on bone? Or, is it that when an astronaut was consuming fish, he or she wasn't consuming something else, like meat, that could have a negative effect on bone."
To expand the current study, researchers will perform a controlled experiment that monitors specific food intake in order to determine if it is possible to directly modulate a loss of bone density through diet.
Medical applications on Earth
In the meantime, these findings have important implications for those who are susceptible to bone loss here on Earth as well, Smith said.
"At NASA, we tend to look at very healthy individuals in a very unique environment," he said. "When we find things about physiology and nutrition, what it allows us to do is understand the basic bone physiology without a disease component ? we're purely dealing with an environmental component. This allows us to see what is going on without confounding factors."
So, while they were found under extreme conditions, the crux of the study's findings are applicable to everyday situations too.
"The bone loss we see during spaceflight is accelerated beyond what we see on Earth," Smith said. "That acceleration allows us to see changes that we wouldn?t normally be able to see, or would be much harder to see. So, in space, we can observe changes in six months that would normally take a multiyear feeding study to observe. It's sort of like time-lapse photography."
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