Omega-3 Fatty Acids Simply Explained

1. What It Is About

Omega-3 fatty acids are certain fats from the diet. The best known are two representatives from oily fish and algae: EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). The body can only form these two to a limited extent itself. A third, alpha-linolenic acid (ALA), is found in some plant oils. Only little EPA and DHA is formed from ALA in the body.

Researchers measure how much omega-3 is in the blood. This value is called the omega-3 index. It says something about the supply, but not always something about health. How well the body absorbs omega-3 depends on the form in which it is present and whether there is fat in the food at the same time. Natural sources are fish oil, krill oil and algae oil. They act differently, which makes comparisons between studies difficult.

More than 4000 papers were evaluated for this page. These include laboratory studies, animal studies and studies in humans.

2. What Studies Show

The clearest effect is seen with blood lipids. In a study with 26 people with elevated blood lipid levels, these decreased clearly after eight weeks when the participants received a larger amount of omega-3. In this study there was no discernible influence on inflammatory markers and vascular function. 4

In older adults, one study compared omega-3 with a placebo, that is a tablet without active ingredient. The omega-3 group performed better in tasks that require planning, attention and ordering thoughts. 3

In a further study, 90 people with chronic inflammation and joint complaints took krill oil for 30 days. Pain, stiffness and mobility improved, and the inflammatory marker in the blood decreased. However, the preparation also contained other substances, so the success cannot be attributed to omega-3 alone. 6

45 healthy older men received krill oil, sardine oil or a placebo for twelve weeks. During memory and arithmetic tasks, cerebral blood flow was measurably stronger in both omega-3 groups. In the krill oil group the men also reacted more quickly. The group was small. 8

A large study over approximately five years found no difference in cancer incidence between omega-3 and placebo. 1 In autoimmune diseases, which include rheumatoid arthritis and psoriasis, there was an indication of somewhat fewer new cases overall. For individual diseases, however, no clear effect was shown. 2

3. What Remains Unclear

For most applications it is open which amount over which period is useful. Many human studies run for only a few weeks and measure blood values instead of actual diseases. Whether a changed blood value means that someone falls ill less often is therefore not clarified. Observational studies show associations, but they do not prove causation.

In many studies the distinction between EPA and DHA is missing, and the amounts and time periods used vary greatly. Absorption into the body also differs depending on the preparation form. The omega-3 index in the blood therefore does not always say something about the health course.

In people with heart disease and depression, additional omega-3 added to a medication in a ten-week study showed no clear advantage. 7 For memory and cognitive function the results are inconsistent. Some studies report improvements, others do not. 5

4. What This Means in Everyday Life

Omega-3 is not a switch that can simply be flipped. So far the clearest effect is on blood lipids. For cancer and autoimmune diseases no clear benefit was seen in the larger studies. For cognitive function and mood the results are mixed.

Anyone reading reports that omega-3 helps against a particular disease can look more closely. How many people were studied, for how long, and what was measured? A changed blood value is not yet an improved disease.

The next thing to clarify is which amount and which preparation form benefits which group over a longer period. It is also open whether EPA and DHA act differently in this regard. As long as this is unclear, the decisive question is not whether omega-3 works in principle, but for whom and in which form.

All details with study numbers and sources: detailed page on omega-3 fatty acids. For children: omega-3 fatty acids for children.