Fish oil equals better mental function? Not really, concludes a two-year British study. Earlier studies showed that people who eat more fish have better mental function, and are less likely to develop dementia. But, after studying 748 men and women aged in their 70s, researchers from the London School of Hygiene and Tropical Medicine have cast some doubts on the age-old link. "This is an important finding as a lot of people think fish oil is good for their cognitive function," says researcher Dr. Alan D. Dangour.