Fish Oil

Fish oil is the most-widely-supplemented source of marine omega-3 fatty acids (EPA and DHA) and has been studied across cardiovascular disease prevention, triglyceride reduction, glycemic control in type 2 diabetes, joint and arthritis outcomes, dry eye disease, and many other applications. Most clinical trials labeled "omega-3" or "EPA/DHA supplementation" use a fish oil product as the intervention, which means the fish oil literature heavily overlaps with the broader marine-omega-3 evidence base. Fish oil products vary widely in concentration, EPA-to-DHA ratio, formulation (ethyl ester vs. triglyceride forms), and oxidation status, all of which complicate direct comparison between products.

The outcome dimensions covered most heavily are cardiovascular disease prevention (including the large updated meta-analyses covering tens of thousands of participants across many trials), triglyceride reduction (one of the most-studied biochemical outcomes across the fish oil literature), glycemic control in type 2 diabetes (where the literature spans decades of accumulated trials), joint and arthritis outcomes, pregnancy outcomes (typically using fish oil as the omega-3 source), and bleeding-risk safety (specifically studied because of a long-standing theoretical concern from platelet-function research).

Demographically, the literature is unusually broad: cardiovascular trials enroll wide adult age ranges with varied baseline risk; the type 2 diabetes literature has decades of accumulated trials; pregnancy literature is well-developed. Concentration matters substantially - standard fish oil capsules typically contain ~30% EPA+DHA, while concentrated formulations contain 60-90%. Form (triglyceride vs. ethyl ester) affects absorption: triglyceride-form fish oil is somewhat better-absorbed, particularly when taken without a fatty meal, though both forms perform adequately in trials.