First, the not-so-good news in neuroscience: According to a recent study, cognitive decline may set in as early as age 45, much sooner than previously thought. But before you start to panic, there's also reason for hope: Researchers around the globe are learning that we can build up our brains—making them bigger and sharper—simply by feeding them the right nutrients. Here, six smart foods to add to your shopping cart.

　　Sunflower SeedsA handful provides a good dose of vitamin E, a nutrient that appears to shield neurons from cell-damaging free radicals. After analyzing data from subjects ages 55 and older, Harvard researchers discovered that people who consumed the most vitamin E were 25 percent less likely to develop dementia than those who consumed the least.

　　YogurtHead to the dairy aisle for this plentiful source of vitamin B12. In 2011 scientists found that people with indications of a B12 deficit performed worse on tests of long-term memory. Study author Christy Tangney, PhD, says too little B12 can lead to the degeneration of myelin sheaths—the protective layer around our nerves that allow impulses to travel quickly through the brain.

　　Total Whole GrainIt's high in B, C, D, and E—a medley that may prevent brain shrinkage linked to Alzheimer's. In a 2012 study, subjects with high levels of those vitamins had significantly larger brains and scored better on visual-spatial tests. "The right nutrient combination may be a recipe for Alzheimer's prevention," says lead author Gene Bowman.

　　SalmonFatty fish are full of omega-3s, and new research suggests these nutrients may be essential to maintaining a youthful mind. The study, which involved MRI scans of subjects with an average age of 65, noted that the brains of those with the lowest omega-3 levels in their red blood cells appeared two years older than the brains of those with higher levels.

　　EggsTheir yolks are loaded with D, which helps break down the insoluble plaques that characterize Alzheimer's. Researchers at the UK's University of Exeter examined 858 people and found that those who were deficient in the vitamin were 60 percent more likely to experience cognitive decline during a six-year period.

　　EdamameThe beans are rich in choline, a building block for a neurotransmitter that helps relay information throughout the nervous system. Boston University researchers showed that higher choline intake is linked to better scores on verbal and visual memory tests, and MRI scans revealed that the participants who ate choline-rich foods also had fewer white matter hyperintensities, spots on the brain that are considered possible indicators of increased risk for Alzheimer's.