Does omega-3 from fish oil help against chronic inflammation?

EPA and DHA (the active fatty acids in fish oil) inhibit multiple inflammatory processes at the same time. They reduce the production of pro-inflammatory substances and stimulate compounds that dampen inflammation, such as resolvins. This mechanism is well documented in both animal and human studies. One important detail: you probably need more than 2 grams of EPA+DHA per day to see a measurable effect. A standard capsule often contains less, so check the label for the EPA+DHA content, not just the total fish oil weight.

The strongest clinical evidence concerns rheumatoid arthritis. Multiple placebo-controlled studies and meta-analyses show that fish oil reduces disease activity and can lower the use of anti-inflammatory medication. This is the condition for which omega-3 has most clearly demonstrated its value.

In inflammatory bowel diseases (such as Crohn's disease and ulcerative colitis) and in asthma, the trials contradict one another. Animal research showed favorable effects, but these did not translate consistently to humans. You cannot yet count on fish oil being helpful here.

In people with multiple sclerosis, a systematic review of seven studies saw encouraging signals, namely fewer relapses and better inflammatory markers, but there are still too few studies for firm conclusions. Treat it as a cautiously positive signal, not as a proven therapy.

A special situation is intravenous administration in seriously ill hospital patients. There, a large network meta-analysis of 47 studies showed a substantial reduction in infections and a shorter length of stay. This says little about a daily fish oil capsule at home; it concerns a medical treatment in a very different patient population. Several authors of that analysis also had financial ties to manufacturers, which makes interpretation somewhat more complicated.

Whether it is better to eat oily fish than to take capsules remains unclear. There are indications that omega-3 from real food is better absorbed and offers additional benefits through synergy with other nutrients, but this is based on a subgroup analysis with too many confounders to draw firm conclusions from.