Fruits: Suga- r and fruits need little digestion time and pass quickly through the stomach to the intestine for absorption. However, if they are eaten with slower digesting foods such as proteins, starches or fats, they will be held up in the stomach and ferment which will then affect the digestion process on the whole. Melons may ferment even with other fruits sometimes. Being a sweet fruit, it can be eaten along with other sweet fruits but not with acidic/citrus ones.
Milk: It is a totally different protein than other concentrated proteins like meat, eggs, nuts etc. Milk does not digest in the stomach but in the duodenum. Hence in the presence of milk, the stomach does not respond with its secretion. This prevents the digestion of other foods introduced along with the milk.
Due to its fat and protein content, when it enters the stomach, milk coagulates to curd.
This curd sticks around particles of other foods in the stomach insulating them from gastric juices and preventing their digestion.
Liquids: As a law, no liquid should be taken with solids. Liquid tends to pass away immediately into the intestine, taking away all the digestive enzymes thus inhibiting digestion.
Liquids must be taken prior to a meal or one hour after it but not along with it. All toxic beverages like tea, coffee, alcohol, soft drinks are great hindrance to normal digestion. Gastric secretions are severely restricted in their presence. All fruit juices are passed faster than fruits into the intestine. Citrus fruit juices and lemon water brings down starch digestion creating severe gas and fermentation. It is better to have them alone and on an empty stomach.