It's too simple to single out our particular food (or foods) as being "best" for memory. Memory is too complicated a process, and it requires a greater variety of nutrients than any single food can provide.
Since remembering involves a good bit of brain activity, and brain activity puts special emphasis on a healthy nervous system and healthy blood flow, all steps you can take to improve your blood flow, circulation, and nervous system function may end up contributing to better memory. Because we feel that the answer to your question about memory is more inclusive than just fruits and vegetables, we are going to answer it from that perspective.
A first important step would be upgrading the overall fat quality in your meal plan. You'll want to focus on plant foods like walnuts, flaxseeds, cold water fish like salmon, and oils like extra virgin olive oil, because the types of fat contained in these foods help keep your blood vessels and nerve wrappings healthy. (Among these fats is a group called omega-3 fat. It's impossible to overestimate the importance of certain omega-3 fatty acids&mdashespecially the fatty acid called DHA, or docosahexaenoic acid-in brain and nervous system function). What you are not going to want are hydrogenated oils that contain trans fatty acids, fried foods, large amounts of beef fat, pork fat, or chicken fat, or other high-fat, processed foods.
You're also going to want plenty of antioxidant nutrients like vitamins C, E, beta-carotene, colorful plant flavonoid and carotenoid pigments, and minerals like zinc and manganese. Vegetables and fruits that are richly colored are usually your best bet here. We do not know where you live and therefore which fruits and vegetables you have available so we would just say that it would be good to look for ones that are deep in color…such as deep green (like leafy greens such as mustard greens, kale, broccoli, etc.), deep orange (papaya, sweet potato, winter squash, etc.), dark blue (berries, eggplant, purple cabbage, etc.) and deep red (berries, cherries, tomatoes, peppers, etc).
B-complex vitamins are another particularly important category of nutrient when it comes to brain function and memory. Many of the nervous system messengers that send signals back and forth between our nerves (called neurotransmitters) cannot be synthesized without the presence of B vitamins. Vitamins B6, folate, and choline would be especially important here, even though all of the B-complex vitamins would play a supportive role.
Choline is readily available from common foods. Liver, egg yolk, soybeans, and to a lesser extent cow's milk, most fish, and whole grains are significant sources of choline. Lecithin (another name for phosphatidylcholine) is another beneficial form of choline found in both eggs and soybeans.
Serine and carnitine are amino acids that you can also obtain from food, especially animal foods. We like the fish listed on our website and our lean, low-fat meats as sources of these two nutrients.
Overall, we would emphasize the importance of your overall diet in providing a very wide range of nutrients as a way of supporting your memory processes rather than any individual food or particular dietary supplement. We would also remind you that when it comes to healthy nervous and cardiovascular systems, exercise is just as important as food and cannot be ignored.
For more information on this topic see:
Khalsa DS. Integrated Medicine and the Prevention and Reversal of Memory Loss. Altern Ther Health Med. 1998;4(6):38-43.
McDaniel MA, Maier SF, Einstein GO. "Brain-Specific" Nutrients: a Memory Cure? Nutrition. 2003;19(11-12):957-75.