Selenium is a trace mineral that has an essential role in ensuring good brain health, particularly as an antioxidant. Studies have found that depleted levels of selenium result in poor memory, bad moods, and decreased cognitive function, while increasing selenium improves mood, clarity of thinking, and energy levels. You need to get at least 55 micrograms daily. Try foods such as whole grain bread, tuna, and Brazil nuts. One great source of zinc is pumpkin seeds. Zinc is helpful for improving brain power, and just a 1/4 cup provides almost 20 percent of your daily value. Other good sources include spinach, beef, and kidney beans.  Try eating a small handful of pumpkin seeds as an afternoon snack, or sprinkle them over salad or oatmeal for added texture. Many of the foods already listed here are high in antioxidants, such as berries and leafy greens. However, certain drinks are high in antioxidants, too, including tea and coffee. Green tea is particularly beneficial for the brain. Try drinking a cup of tea or two a day. Antioxidants help block free radicals, which can destroy brain cells over time. Omega 3 is excellent brain food, providing a good source of EPA and DHA fatty acids and helping to protect your brain from deterioration. Not getting enough of these fatty acids in your diet can increase your chances of getting Alzheimer's or dementia. Oily fish (e.g., salmon, sardines, herring, tuna), fish oil, walnuts, and flax seeds (linseed) are all good sources of omega-3.  Try chia seeds, which are loaded with ALA and EHA omega-3. They are easy to sprinkle over everything from cereal to salads, as they are flavorless.

Summary:
Eat selenium-rich foods. Increase your zinc. Consume foods rich in antioxidants. Improve your omega-3 intake.