The study … examined 402 people with mild to moderate Alzheimer’s. They were randomly assigned to take 2 grams a day of omega‑3 capsules containing docosahexaenoic acid (or DHA) or a placebo capsule. The participants were followed for 18 months, and their cognitive and functional abilities were reassessed. They also underwent MRI to look at the brain.
There was no benefit seen in the patients taking omega‑3 fatty-acid supplements in either brain volume or cognitive function.
Comments: Does this study mean that DHA or omega‑3 in general are not good for the brain? No! This study suggests that taking DHA supplements after Alzheimer’s diagnosis is not helpful. Prior evidence shows that omega‑3 consumption (especially DHA) long before the onset of Alzheimer’s symptoms reduces the risk of developing the disease. Indeed, several studies have shown that eating fish (the primary source in our diet of omega‑3 fatty acids) is associated with a reduced risk of cognitive decline or dementia.
The authors of the JAMA study also speculate that DHA supplements could be used as a treatment for people who have not yet been diagnosed with Alzheimer’s but are already developing dementia pathology in their brain: “Individuals intermediate between healthy aging and dementia, such as those with mild cognitive impairment, might derive benefit from DHA supplementation, although further study will be necessary to test this hypothesis.”