A small clinical trial from USC suggests that higher doses of omega-3 supplements may be needed in order to prevent or slow cognitive decline from Alzheimer’s disease, because dramatic increases in blood levels of omega-3s are accompanied by far smaller increases within the brain. Among participants who carry a specific mutation that heightens risk for Alzheimer’s, taking the supplements raised levels of a key fatty acid far less compared to those without the mutation.
Source: Supplements with potential to prevent Alzheimer’s affect blood, but less so the brain