Fish oil helps memory only if your blood is low in a certain chemical

Taking omega-3 supplements every day for six months doesn’t seem to help people with mild to moderate Alzheimer’s think better, no matter what their blood homocysteine levels were to begin with.

For people with early-stage Alzheimer’s, taking a specific fish oil supplement for 6 months might help them think a little better and function more normally—but only if their blood has low levels of a chemical called homocysteine before they start.

If you have Alzheimer’s and your blood has high levels of a substance called homocysteine, taking omega-3 fish oil supplements might help your memory and thinking skills a bit—but only if you look at certain tests, not all of them.