Fish oil supplementation does not lower C‐reactive protein or interleukin‐6 levels in healthy adults

Randomized placebo-controlled trial in healthy community-dwelling adults aged 30-54 years from the Pittsburgh, United States area. Participants had relatively low habitual EPA+DHA intake and no inflammatory conditions.

Participants in the fish oil group took two 1000 mg oral fish oil capsules daily for 18 weeks, providing 1000 mg EPA and 400 mg DHA per day, for a total of 1400 mg EPA+DHA daily. The active regimen was compared with placebo.

Eighteen weeks of 1400 mg/day EPA+DHA did not reduce systemic inflammation in healthy adults. Compared with placebo, CRP was not significantly different with imputed data (M diff 0.05 mg L À1, 95% CI À0.24, 0.19; P = 0.21) or without imputed data (M diff 0.04 mg L À1, 95% CI À0.21, 0.29; P = 0.37). IL-6 also did not change significantly (M diff À0.04 pg mL À1, 95% CI À0.27, 0.19; P = 0.59 with imputed data). Fish oil likewise did not alter ex vivo production of IL-6, IL-1β, IL-8, or TNF-α. Mild tolerability issues were reported, including more fishy belch or aftertaste and more loose stool, bloating, or gas pains, but there were no serious adverse events.

The population was healthy with low baseline inflammatory burden, which may limit ability to detect change and reduces generalizability to inflamed or clinical populations. The dose was moderate and treatment lasted only 18 weeks, so larger doses or longer exposure may be required. Arm-level sample size and several baseline characteristics were not reported in the source packet.