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Older adults who eat greater amounts of fish end up preserving their bone density better than people who don't eat as much fish, a new study finds.
The study doesn't prove that such habits strengthen bones, but researchers believe that the combination of different oils in the fish protects bones from losing mass over time.
"We think omega 3 fatty acids from fish help to prevent" bone loss, said lead researcher Dr Katherine Tucker, a professor at North-eastern University.
Preventing bone loss - not simple
But her study finds that preventing bone loss is not as simple as upping the levels of omega 3 fats in people's diet.
Her group looked at surveys, collected in the 1980s and 90s, of the eating habits of more than 600 seniors who lived in Framingham, Massachusetts.
Measurements of the bone density in their hips were taken four years apart.
Women who ate three or more weekly servings of dark fish, such as salmon or mackerel, had smaller amounts of bone loss four years later, compared to women who ate less fish.
Men’s reduced bone loss
Men who ate dark fish or tuna at least three times per week also had less bone loss than other men.
The study was unable to show that fish was the cause of the differences in bone loss, but merely that the two are associated.
Fish are rich in the omega 3 fatty acids, EPA and DHA.
Looking further into what people ate, the researchers broke down how much of both omega 3 and omega 6 fatty acids people were getting in their diet. They found that it's not just the omega 3s that are involved in bone density.
High levels of an omega 6 fatty acid, called arachidonic acid, was linked to less bone loss in women - but only when women also consumed higher levels of omega 3 fats.
Good balance
"It looks like you need to have those in a good balance," Tucker said. "If you have very low levels of arachidonic acid, then you didn't see the benefits of the omega 3s."
"You can't just take a supplement of one and have a good effect," Tucker added. Too much of one fat could actually be harmful.
In men, high arachidonic acid and low omega 3s was tied to greater loss of bone.
Tucker said there's no exact formula yet of omega 3 and omega 6 fats that would be good for bone health.
Fish appears to provide a good balance, Tucker said, because it has the omega 3 fats that tend to be lacking in Western diets. Omega 6 fatty acids are typically abundant.
Recommendations
The American Heart Association recommends that people eat two servings of fish each week.
Tucker's study, published in the American Journal of Clinical Nutrition, was funded by the National Institutes of Health.
Bone loss is a normal part of aging, and less dense bones are at a greater risk of breaking.
This study did not examine whether the differences in bone loss between frequent fish-eaters and others make any difference in the risk of breaking bones. (Reuters Health/ March 2011)
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