Cooking can limit the availability of some nutrients, such as vitamin C and several B vitamins, but cooking increases the availability of others, such as lycopene in tomatoes and beta-carotene in carrots. The degree to which each nutrient is affected depends on the particular ingredient being cooked.
After cooking, the amount of many nutrients in food decreases. This is especially true for vitamin C, thiamin (vitamin B1), niacin (vitamin B3), folate (vitamin B9), iron, and zinc. The loss of vitamin C occurs primarily during boiling, frying, or smoking; that of other B vitamins during boiling; and that of iron and zinc during cooking generally. Fluoride, added to drinking water to prevent tooth decay, can bind to calcium ions present in foods such as milk and ice cream and prevent them from binding to phosphate molecules present in teeth. As a result, less of the mineral calcium is available for building bones and teeth. Cooking food reduces the amount of fluoride required because much of it is lost during processing.
The body cannot use colorless compounds such as vitamin C for growth or repair of tissues. Instead, they must be converted into colored forms before they can do any good. The body can only use the colored forms of these substances.
The longer a dish is cooked, the more nutrients it loses (9). During the cooking process, several nutrients, notably water-soluble vitamins, are lost. Raw fruits and vegetables may be higher in nutrients such as vitamin C and B vitamins. The more mature the fruit or vegetable, the less nutritious it will be.
As raw fruits and vegetables contain more nutrients than their cooked counterparts, it is important to eat a variety of them to get all the nutrients you need. It is okay to cook some of your food; just make sure to add back in as much as possible. For example, if you roast your vegetables, try not to overcook them and leave them with some bite to them. Add them back into your recipes where they can be used as a base instead of plain roasted vegetables.
Cooking food reduces its nutritional value. This is because certain nutrients are lost during the cooking process. These include most of the fiber, protein, and many of the healthy fats as well. Cooked dishes also tend to have higher levels of sodium and sugar than their uncooked counterparts.
It is best to eat a variety of raw fruits and vegetables. This will help you get all the nutrients you need in a day. It is okay to cook some of them, just make sure to add back in as much as possible.
Cooking Improves the Antioxidant Capacity of Certain Vegetables. Cooking veggies enhances the availability of antioxidants such as beta-carotene and lutein, according to research (19, 20). The antioxidant beta-carotene is converted by the body into vitamin A. Vitamin A is essential for good vision, immune function, reproductive ability, growth, and bone health. Lutein is useful for treating eye diseases such as macular degeneration and cataracts.
Cooking also decreases the amount of toxic substances in vegetables. For example, cooking brussels sprouts reduces the amounts of carcinogens they contain. You may want to cook your vegetables because they're not tasty raw. Or maybe you don't like their texture. Either way, cooking them changes their nature significantly, which means that eating them will offer your body different nutrients and less toxicity than if you ate them raw.
Some studies have shown that people who eat a lot of raw vegetables and fruits are at greater risk of developing certain cancers. Other studies have found no correlation between eating many servings of raw vegetables and fruit and developing cancer. There has been some concern that allium vegetables (such as garlic and onions) might be responsible for causing cancer when eaten in large quantities, but research shows this is not the case.
The American Cancer Society recommends that you should eat at least five servings of fruits and vegetables every day.