Does omega-3 (fish oil) have an effect on bone strength?

Daily intake of 1 gram of omega-3 over three years made no measurable difference in bone density of the spine, hip, or femoral neck in healthy 75-year-olds. This is shown by the DO-HEALTH study, a well-designed clinical trial with nearly 1,500 participants. It is currently the strongest direct evidence we have on omega-3 and bones in older adults.

Earlier research gave a more mixed picture. A systematic review of ten smaller trials found that four studies did observe beneficial effects on bone density or bone turnover, but five studies found nothing. None of those trials measured the truly relevant endpoint: bone fractures. The studies also differed too much from one another to draw firm conclusions. One signal that stood out: the effect appeared larger when omega-3 was combined with calcium.

In postmenopausal women, omega-3 slightly lowers one specific bone turnover marker (osteocalcin), but other markers of bone breakdown or bone formation did not change. What that single reduction means in concrete terms for bone strength is unclear.

Animal and mechanistic research suggests that omega-3 influences calcium metabolism and bone breakdown, but this does not automatically translate to humans. The metabolism of animals and humans differs too much for direct comparison.

In short: there are biological indications that omega-3 might support bones, but the best available trial in older adults showed no effect on bone density. Using omega-3 as a means of preventing bone loss is, certainly on its own, not supported by the evidence. For bone health, calcium and vitamin D remain far better proven to date.