Could fish oil supplements protect against fractures?
An estimated 22% of U.S. adults aged 60 and older take omega-3 fatty acid supplements, Dr. LeBoff noted.
Preclinical studies have shown that omega-3 fatty acids reduce bone resorption and have anti-inflammatory effects, but observational studies have reported conflicting findings.
The researchers conducted this ancillary study of VITAL to fill these knowledge gaps.
VITAL enrolled a national sample of 25,871 U.S. men and women, including 5,106 Black participants, with a mean age of 67 and a mean BMI of 28 kg/m2.
Importantly, participants were not recruited by low bone density, fractures, or vitamin D deficiency. Prior to entry, participants were required to stop taking omega-3 supplements and limit nonstudy vitamin D and calcium supplements.
The omega-3 fatty acid supplements used in the study contained eicosapentaenoic acid and docosahexaenoic acid in a 1.2:1 ratio.
VITAL had a 2x2 factorial design whereby 6,463 participants were randomized to receive the omega-3 fatty acid supplement and 6,474 were randomized to placebo. (Remaining participants were randomized to receive vitamin D or placebo.)
Participants in the omega-3 fatty acid and placebo groups had similar baseline characteristics. For example, about half (50.5%) were women, and on average, they ate 1.1 servings of dark-meat fish (such as salmon) per week.
Participants completed detailed questionnaires at baseline and each year.
Plasma omega-3 levels were measured at baseline and, in 1,583 participants, at 1 year of follow-up. The mean omega-3 index rose 54.7% in the omega-3 fatty acid group and changed less than 2% in the placebo group at 1 year.
Study pill adherence was 87.0% at 2 years and 85.7% at 5 years.
Fractures were self-reported on annual questionnaires and centrally adjudicated in medical record review.
No clinically meaningful effect of omega-3 fatty acids on fractures
During a median 5.3-year follow-up, researchers adjudicated 2,133 total fractures and confirmed 1,991 fractures (93%) in 1551 participants.
Incidences of total, nonvertebral, and hip fractures were similar in both groups.
Compared with placebo, omega-3 fatty acid supplements had no significant effect on risk of total fractures (hazard ratio, 1.02; 95% confidence interval, 0.92-1.13), nonvertebral fractures (HR, 1.01; 95% CI, 0.91-1.12), or hip fractures (HR, 0.89; 95% CI, 0.61-1.30), all adjusted for age, sex, and race.
The “confidence intervals were narrow, likely excluding a clinically meaningful effect,” Dr. LeBoff noted.
Among men, those who received fish oil supplements had a greater risk of fracture than those who received placebo (HR, 1.27; 95% CI, 1.07-1.51), but this result “was not corrected for multiple hypothesis testing,” Dr. LeBoff cautioned.
In the overall population, participants with a BMI less than 25 who received fish oil versus placebo had an increased risk of fracture, and those with a BMI of at least 30 who received fish oil versus placebo had a decreased risk of fracture, but the limits of the confidence intervals crossed 1.00.
After excluding digit, skull, and pathologic fractures, there was no significant reduction in total fractures (HR, 1.02; 95% CI, 0.92-1.14), nonvertebral fractures (HR, 1.02; 95% CI, 0.92-1.14), or hip fractures (HR, 0.90; 95% CI, 0.61-1.33), with omega-3 supplements versus placebo.
Similarly, there was no significant reduction in risk of major osteoporotic fractures (hip, wrist, humerus, and clinical spine fractures) or wrist fractures with omega-3 supplements versus placebo.
VITAL only studied one dose of omega-3 fatty acid supplements, and results may not be generalizable to younger adults, or older adults living in residential communities, Dr. LeBoff noted.
The study was supported by grants from the National Institute of Arthritis Musculoskeletal and Skin Diseases. VITAL was funded by the National Cancer Institute and the National Heart, Lung, and Blood Institute. Dr. LeBoff and Dr. Langdahl have reported no relevant financial relationships.
A version of this article first appeared on Medscape.com.