Probably the most important question one could ask in regards to health. There are some amazing writers and scientists that have written volumes on this topic. My perspective is the same logic that applies to my personal training, eat the foods that give you the most benefit and exclude those that do not. What do I mean by benefit? In the context of food: vitamins, minerals, aka nutrients. So, eat nutrient dense food! The closer to nature the food is the better it is, the more processed it is, usually, the less beneficial it is. Eat your wild caught fish. Eat grass fed, pasturized meats. Eat local, organic, in season vegetables and occasional fruit. Eat more fruit and add some sweet potatoes if you are active. Eat sparingly raw, unsalted nuts such as almonnds, cashews, pecans, brazilian nuts, macadamians. If you're into nut butters same principles apply: raw so NOT roasted, unsalted, organic nut butters. Drink water, some tea from time to time. Ask yourself: Is it processed? If yes, try to avoid it!