Oil and Ghee are widely used in Indian cuisine. Milk is commonly used to prepare sweets and puddings. Texts of ayurveda enumerate benefits of cooking with these ingredients.

Benefits of cooking food with ghee:

The foods which are cooked using ghee help to increase body energy and alleviate vata and pitta. Hence ghee is predominantly used in diseases which arise due to vata and pitta.

Benefits of cooking food with oil: 

Consumption of foods cooked with oil alleviates vata. But these foods vitiate pitta , rakta (blood) and increase body heat.

Benefits of cooking with milk:

When cereals like wheat, rice etc are cooked in milk, the preparations help to normalize pitta and kapha.  Consumption of milk cooked preparations increase body strength, quality and quantity of semen and also helps to maintain good health.