I did some research thanks to google and found in many articles they shared the same 4 types of foods. The following are resources for Food Journal and BBC.
Fish. Whole Grains. Green Leafy Vegetables. Berries.
My mother always told me to make sure I ate my fish because it will fuel my brain. I want to qualify that by broiled or baked fish that is not breaded is good for you. Not only do you get a healthy serving of protein but you also get a healthy type of fat called Omega 3, it boosts your cardio health which in turn boosts all your other systems including your brain. It keeps your vessels clean and free of that bad cholesterol building up in your arteries.
Whole Grains offer nutrients, protein and healthy carbs that your body turns into energy. Keeping a healthy intake of this food group will help you stay fuller longer and help maintain your stamina through the late night studies.
Green Leafy Vegetables are no secret when it comes to the good they provide for your body. Eating deep green vegetables that are fresh brings more water, vitamins and minerals to your body as well as fiber. Stay away from canned vegetables, fruits or canned anything. The process of canning impregnates the contents with enough sodium and preservatives to make them last years which by nature is not normal for natural food and essentially the nutritional value plummets.
Finally my personal favorite, berries. Again no secrets here, they are loaded with antioxidants, fiber, healthy sugar, and sweetness to help you study better.