The new study, published in the Journal of Bone and Mineral Research, analysed blood samples from women with and without a history of having a broken hip – finding that those with higher levels of omega-3 fatty acids from both plant and fish sources in their blood were associated with a lower likelihood of having fractured a hip.
In addition to simply looking at omega-3s levels, the researchers also looked at omega-6 fatty acids – which are generally plentiful in a Western diet – finding that as the ratio of omega-6 fatty acids to omega-3s increased, so did the risk for hip fracture.
“These results suggest that higher red blood cell (RBC) alpha-linolenic acid, as well as eicosapentaenoic acid and total n-3 PUFAs, may predict lower hip fracture risk. Contrastingly, a higher RBC omega-6/omega-3 ratio may predict higher hip fracture risk in postmenopausal women,” said the authors – led by Tonya Orchard of The Ohio State University, USA.
"One thing that was critically important was that we didn't use self-report of food intake, because there can be errors with that,” explained Professor Rebecca Jackson, senior author of the study. “We looked directly at the exposure of the bone cell to the fatty acids, which is at the red blood cell level."
"Red blood cell levels also give an indication of long-term exposure to these fatty acids, which we took into account in looking for a preventive effect," she added.
The team examined red blood cell PUFAs as predictors of hip fracture risk in postmenopausal women using a nested case-control study of 400 pairs of women.
Jackson and her colleagues used 201 incidents of hip fracture cases from the Bone Mineral Density (BMD) cohort, along with 199 additional incident hip fracture cases randomly selected from the WHI Observational Study – these cases were 1:1 matched on age, race, and hormone use with non–hip fracture controls before RBCs were analysed for omega-3 and omega-6 content.
The analysis showed that higher levels of total omega-3 fatty acids and levels of alpha-linolenic acid (ALA) and eicosapentaenoic acid (EPA) were associated with a lower risk of hip breaks in the study sample.
On the other hand, women who had the highest ratio of omega-6 to omega-3 fatty acids had nearly twice the risk of hip fractures compared to women with the lowest ratios, the team found.
Jackson noted, however, that their study findings are from an observational study, and so did not measure cause and effect – adding that because of this the findings are not definitive enough to suggest that taking omega-3 supplements would prevent hip fractures in postmenopausal women.
"We don't yet know whether omega-3 supplementation would affect results for bone health or other outcomes," said Orchard.
"Though it's premature to make a nutrition recommendation based on this work, I do think this study adds a little more strength to current recommendations to include more omega-3s in the diet in the form of fish, and suggests that plant sources of omega-3 may be just as important for preventing hip fractures in women,” she added.