Protecting the Nutrients in Cooked Foods

Myth: All raw foods are more nutritious than cooked ones.
Fact: Some foods (such as meat, poultry, and eggs) are positively dangerous
when consumed raw (or undercooked). Other foods are less nutritious raw
because they contain substances that destroy or disarm other nutrients. For
example, raw dried beans contain enzyme inhibitors that interfere with the
work of enzymes that enable your body to digest protein. Heating disarms
the enzyme inhibitor.
But there’s no denying that some nutrients are lost when foods are cooked.
Simple strategies such as steaming food rather than boiling, or broiling rather
than frying, can significantly reduce the loss of nutrients when you’re cooking
food.
Maintaining minerals
Virtually all minerals are unaffected by heat. Cooked or raw, food has the
same amount of calcium, phosphorus, magnesium, iron, zinc, iodine, selenium,
copper, manganese, chromium, and sodium. The single exception to
this rule is potassium, which — although not affected by heat or air —
escapes from foods into the cooking liquid.
Those volatile vitamins
With the exception of vitamin K and the B vitamin niacin, which are very
stable in food, many vitamins are sensitive and are easily destroyed when
exposed to heat, air, water, or fats (cooking oils).
To avoid specific types of vitamin loss, keep in mind the following tips:
Vitamins A, E, and D: To reduce the loss of fat-soluble vitamins A and E,
cook with very little oil. For example, bake or broil vitamin A–rich liver
oil-free instead of frying. Ditto for vitamin D–rich fish.
B vitamins: Strategies that conserve protein in meat and poultry during
cooking also work to conserve the B vitamins that leak out into cooking
liquid or drippings: Use the cooking liquid in soup or sauce. Caution: Do
not shorten cooking times or use lower temperatures to lessen the loss
of heat-sensitive vitamin B12 from meat, fish, or poultry. These foods
and their drippings must be thoroughly cooked to ensure that they’re
safe to eat.
Do not rinse grains (rice) before cooking unless the package advises you
to do so (some rice does need to be rinsed). Washing rice once may take
away as much as 25 percent of the thiamin (vitamin B1). Toast or bake
cakes and breads only until the crust is light brown to preserve heatsensitive
Bs.
Vitamin C: To reduce the loss of water-soluble, oxygen-sensitive vitamin
C, cook fruits and vegetables in the least possible amount of water. For
example, when you cook 1 cup of cabbage in 4 cups of water, the leaves
lose as much as 90 percent of their vitamin C. Reverse the ratio — one
cup water to 4 cups cabbage — and you hold on to more than 50 percent
of the vitamin C.
Serve cooked vegetables quickly: After 24 hours in the fridge, vegetables
lose one-fourth of their vitamin C; after two days, nearly half.
Root vegetables (carrots, potatoes, sweet potatoes) baked or boiled
whole, in their skins, retain about 65 percent of their vitamin C.