Vitamins A, D, E and K
These vitamins appear to be unchanged by cooking. “Fiber, carbohydrates, protein, fat, minerals, trace minerals, and all of vitamins A, D, E and K, remain when vegetables are cooked,” explains Hartley.
Like vitamin C, B vitamins can be lost through boiling because they are water soluble. To decrease the loss of water soluble vitamins, choose cooking methods that minimize the use of water, such as grilling, roasting and microwaving. Making soups and stews will preserve some of these vitamins in the broth. Raw sources of vitamin B include bananas, oysters, tuna and caviar. Liver is also a rich source of B vitamins, but I don’t recommend it raw!
“It is important to differentiate between enzymes that are needed for digestion and enzymes that naturally occur in foods,” points out Hartley. She says that the enzymes found in food have no bearing on digestion. However, enzymes can have other effects on the body. “For instance, the myrosinase enzyme family and indoles found in cruciferous vegetables contain anti-cancer compounds that are destroyed by heat,” says Hartley. Bok choy, broccoli, Brussel sprouts, kale, cauliflower, cabbage, cress, kohlrabi, mustard, rutabaga and turnips are all cruciferous vegetables. Cooking these vegetables also destroys goitrogenic enzymes that interfere with the formation of thyroid hormone. “It’s always a tradeoff,” Hartley reminds us. “With some nutrients becoming more available and others becoming less available, when food is cooked.”
Although some may swear by the raw food diet, Hartley and I agree that it takes a lot of work and careful planning, not to mention the difficulty of giving up foods like cheese and bread. The bottom line is that it’s good to eat plenty of fruits and vegetables, no matter how they are prepared. Garlic and nuts are also best when eaten raw, along with fruits that are high in vitamin C. Consuming a diet that’s high in raw fruits and vegetables can also help you lose weight, because the fiber can help you feel full while consuming fewer calories.
Not only does cooking make many foods more appealing and enhances some nutrients, it also kills off bacteria, which is particularly important when it comes to meat and animal products. “Cooking (and careful chewing!) generally makes food more digestible by softening the fibers,” says Hartley. She recommends a diet that consists of a variety of cooked and raw foods, with a raw source of vitamin C eaten every day.”