Cooking is a process that is adopted to make food easily digestible, destroy the disease causing germs and to enhance its taste and flavour. It has several advantages and disadvantages. Its effect on key nutrients is as follows:

• Carbohydrates: The starch swells during cooking and gets gelatinized. Thus, cooking helps in proper digestion of carbohydrates.
• Proteins: Moderate heat splits protein and shrinks it in size. As a result it becomes easily digestible. However, severe heat such as during roasting, baking and frying reduces the nutritive value of proteins.
• Fats: Deep little adverse effect on the cooking oil.
• Vitamins A and D: Frying and roasting can of the vitamins due to oxidation by air.
• Thiamine: About 20% to 50% thiamine is lost Riboflavin: This vitamin is lost while cooking because of exposure to strong heat, light and discarding water after cooking. It is also lost if you add soda for cooking dals and vegetables.
• Folic acid and Vitamin B₁₂: Both these vitamins are lost during cooking methods such as pressure cooking, roasting or by frying. In addition to the loss due to heat, folic acid and vitamin B₁₂ are also lost when excess water is discarded after cooking.
• Vitamin C: This vitamin is lost by oxidation due to exposureto air and by discarding excess water after cooking. About 10% to 60% vitamin C is lost during cooking depending upon its method and the vegetable cooked.
• Calcium and Phosphorus: These minerals are lost when excess cooking water is discarded.
• Iron: It is lost when excess water is discarded after cooking. Iron percentage of food increases if vegetables are cut with iron knife or are cast iron pans.
• Sodium, Potassium and Magnesium: These minerals are lost when excess water is discarded after cooking. Addition of common salt increases the sodium content of food. Increased sodium decreases potassium levels.