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Omega-3 fatty acids may play a protective role in long-term lung health, according to longitudinal and Mendelian randomization analyses.

Higher plasma levels of omega-3 fatty acid were associated with attenuated lung function decline in 15,063 patients with repeated measures of forced expiratory volume in the first second (FEV₁) and forced vital capacity (FVC), reported Patricia A. Cassano, PhD, of Cornell University in Ithaca, New York, and coauthors.

Similarly, a single percent increase in the proportion of docosahexaenoic acid (DHA) within total fatty acids was associated with an attenuation of FEV₁ and FVC at a rate of 1.4 mL/year and 2.0 mL/year, respectively, according to the study published in the .

A single percent increase in DHA was also associated with a 7% decreased incidence of spirometry-defined airway obstruction.

"We know a lot about the role of diet in cancer and cardiovascular diseases, but the role of diet in chronic lung disease is somewhat understudied," said Cassano in a press release. "This study adds to growing evidence that omega-3 fatty acids, which are part of a healthy diet, may be important for lung health too."

Omega-3 fatty acids, common in fish and plant oils, have been suggested to have numerous health benefits, playing a role in potentially preventing or controlling conditions like heart disease, eczema, and stroke, among others -- though the evidence is controversial in some cases.

"Metabolites of these fatty acids help resolve inflammation by blocking recruitment and inducing clearance of immune cells from sites of inflammation and by downregulating the expression of transcriptional factors like NF-κB that increase expression of inflammatory cytokines," the study authors noted.

Of the acids in that family, alpha-linolenic acid (ALA) cannot be produced in the body and is obtained through dietary measures. In contrast, DHA, docosapentaenoic acid (DPA), and eicosapentaenoic acid (EPA) can be derived from ALA in the body on a small scale, and can be consumed.

Cassano's group reported that raising the AHA, EPA, or DHA by one standard deviation was associated with an FEV₁ attenuation of 0.77, 0.62, and 1.77 mL per year, respectively. For FVC, attenuations were 1.30, 0.84, and 2.43 mL/year (P<0.005 for all).

Associations regarding DHA levels and health outcomes were largely consistent across Black, Hispanic, and white patients, and regardless of sex or smoking history.

However, when accounting for race and ethnicity, smoking history, and sex, associations between ALA and FEV₁ attenuation as well as EPA with attenuations of either outcome were determined to not be significant.

Data for the longitudinal study were taken from the National Heart, Lung, and Blood Institute (NHLBI) Pooled Cohorts Study covering Atherosclerosis Risk in Communities Study, the Coronary Artery Risk Development in Young Adults Study, the Cardiovascular Health Study, and the Multi-Ethnic Study of Atherosclerosis, all of which included omega-3 fatty acids measurements in plasma phospholipids.

Of the participants included in the NHLBI Pooled Cohorts Study, 55% were women and the average age was 56 years old. More than two-thirds were white, one-fifth were Black, 7% were Hispanic, and 4% were Asian. Patients were generally healthy, and the majority did not have chronic lung disease. A little over a third (36%) were former smokers, and 16% were current smokers. They were followed for 7 years on average.

Of total plasma phospholipid fatty acids, the average relative AHA level was at 0.2%, EPA was at 0.7%, DPA was at 0.9%, and DHA was at 3.3%.

The average decline of lung function was 36.8 mL each year for FEV₁ and 35.8 mL each year for FVC.

A complementary two-sample Mendelian randomization study, based on a publicly available genome-wide association study, also supported positive associations of genetically predicted downstream omega-3 fatty acids with FEV₁ and FVC.

Some limitations of the longitudinal arm of the study include plasma phospholipids being measured only once per cohort at varying times. The number of spirometry measurements per cohort also varied, with most participants receiving at least two.

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