Though osteoporosis is a very real problem for a large population of aging men and women, the effects of spaceflight travel on astronauts make them even more susceptible to bone breakdown. For decades, NASA has studied ways to mitigate the inevitable bone density loss of its astronauts but its latest research has found that omega 3 fatty acids in fish oil offer benefits—a solution that would surely have beneficial implications for those with bone health issues here on Earth.

Why do astronauts’ bones suffer more pronounced bone density issues? According to Sara Zwart, PhD, deputy manager for nutritional biochemistry, Universities Space Research Association, NASA Johnson Space Center’s Human Adaptation and Countermeasures Division in Houston, TX, it all boils down to gravity.

“Bone breaks down in microgravity because the additional loading normally imparted by gravity is not present,” she explained. “Basically, the body doesn’t think it needs the same amount of bone as it did on Earth. While this is fine during flight, this poses a problem when the crew returns to Earth (or could be a problem once they reach 1/3 or 1/6 x g on Mars or the Moon) when the body needs the extra bone for support in a gravitational field.”

The observational research compiled by Dr. Zwart, et al, was published in the May issue of the Journal of Bone and Mineral Research and reported on four types of studies using cell culture, ground-based bed rest and data from both space shuttle and International Space Station crew members.

In a series of cell-based studies, scientists documented that adding a specific omega 3 fatty acid to cells would inhibit the activation of factors that lead to bone breakdown. This was true in both typical cell cultures and those designed to mimic weightlessness. The inhibited factor is known as “nuclear factor kappa B” or NFKB. NFKB is involved in immune system behavior and the inflammation process. The activation of NFKB in different tissues can lead to bone and muscle loss.

In a study of astronauts returning from short-duration shuttle missions, researchers found that NFKB activation was increased in blood cells collected at landing, and remained elevated for two weeks. These data provide evidence that inflammatory processes may be involved in some of the adaptation to microgravity and suggest that reducing NFKB activation could serve as a countermeasure to bone loss.

A ground-based bed rest study was conducted on 16 subjects with the evaluations performed after 60 days. Bed rest simulates some of the effects of weightlessness, including muscle and bone loss. During the study, higher intake of omega 3 fatty acids was associated with less bone loss.

Based on these studies, the investigators evaluated bone loss in astronauts and compared their findings to reported fish intake during spaceflight. Researchers found that astronauts who ate more fish lost less bone mineral after four-to-six-month spaceflights. Tracking fish consumption is not as accurate as determining exact diet and omega 3 fatty acid intake, but these data were not available.

To be clear, the omega 3 consumed by study subjects was derived from fish, not omega 3 supplements. “As a crude estimate of omega 3 fatty acid intake, we found that crewmembers who consumed the most fish servings per week lost the least amount of bone,” reported Dr. Zwart. “In our studies, the maximum number of fish servings per week consumed by a crewmember was about ­­­4.5 servings/week. In the bed rest studies, subjects that consumed the most total omega 3 fatty acids (not only from fish) had less bone breakdown.”

When asked if the notion of omega 3 supplementation could be a future consideration for improving the bone health of space travelers, Dr. Zwart said more research was warranted but for now, food-sourced omega 3 trumped supplements. “Whenever possible, on Earth and in space, it’s usually best to get nutrients from food sources. Besides fish, some nuts and other foods provide natural sources of omega 3 fatty acids,” she said. “Before providing recommendations on the benefits of omega 3 fatty acids in space, intervention studies need to be performed to document our findings in controlled treatment studies, and to further test the efficacy of food sources versus supplements."

“These results are very exciting, and provide initial evidence that nutrition may be a key factor in mitigating bone loss in astronauts,” concluded Dr. Zwart’s colleague, ­Scott Smith, a nutritionist at NASA's Johnson Space Center in Houston and one of the paper's authors.

The studies were conducted by a team of scientists across multiple disciplines at Johnson. Smith and Dr. Zwart lead the center's Nutritional Biochemistry Laboratory. Duane Pierson and Satish Mehta work for the Microbiology Laboratory and led the shuttle-based studies. Steve Gonda, a NASA scientist and a co-author, died prior to the publication of the studies.