Comparable reductions in hyperpnoea-induced bronchoconstriction and markers of airway inflammation after supplementation with 6·2 and 3·1 g/d of long-chain n-3 PUFA in adults with asthma

Sixteen non-smoking, recreationally active adult men were studied: eight had physician-diagnosed asthma with hyperpnea-induced bronchoconstriction and eight were controls without asthma. The active intervention arms were the hyperpnea-induced bronchoconstriction group, with 8 participants per dose arm, and outcomes were assessed before and after each 21-day treatment period using eucapnic voluntary hyperpnea challenge.

Adults with asthma and hyperpnea-induced bronchoconstriction received oral long-chain n-3 PUFA for 21 days per treatment period in a randomized, block-randomized, placebo-controlled crossover design. The active regimens were 6.2 g/day EPA/DHA (3.7 g EPA and 2.5 g DHA) or 3.1 g/day EPA/DHA (1.8 g EPA and 1.3 g DHA), given as eight capsules daily; treatment periods were separated by 14-day washouts.

Both n-3 PUFA doses reduced hyperpnea-induced bronchoconstriction and airway inflammation, and the lower dose was similar to the higher dose. After 21 days, peak fall in FEV1 after EVH improved to -1000 (SD 460) ml, -29 (SD 17)% with 6.2 g/day and to -700 (SD 420) ml, -21 (SD 15)% with 3.1 g/day, versus placebo; both active treatments differed from placebo, with P < 0.001 and no meaningful difference between doses for key EVH outcomes. The AUC 0-30 for % fall in FEV1 was -415 (SD 382) for 6.2 g/day and -398 (SD 399) for 3.1 g/day versus -595 (SD 424) for placebo (P = 0.004 for treatment × day interaction). Fractional exhaled nitric oxide fell by 24% with 6.2 g/day and 31% with 3.1 g/day, and urinary 9alpha,11beta-PGF2 increases after EVH were reduced by 65% and 56%, respectively. Overall, 3.1 g/day appeared to provide similar benefit to 6.2 g/day, with fewer gastrointestinal withdrawals.

The active-arm sample size was small, with only 8 participants per dose arm, limiting precision and generalizability. The intervention periods were short at 21 days, so durability of benefit is unknown. Two withdrawals occurred in the 6.2 g/day arm because of gastrointestinal distress, which may affect tolerability at the higher dose.