He doesn't know the proper reason. According to ayurveda there are three types of foods
1. Satvik (Food of the Brahmins) Fruits from upper part of tree, milk and milk by products come under this this type of food is good for scholars as it won't create anxiety or tension in body.
2. Rajasik( Food of the warriors) Intoxicating drinks , nerve stimulating drinks come under this .
3. Tamasik( Food of the lower castes) Meat, food of underground( tubers, onion , garlic),hard drinks these foods bring negative character in humans.