How to preserve food nutrients?

Each food has nutrients, but does not mean that you will be able to eat the food intake of the nutrients contained in the original number, as in the purchase, storage, processing and quietly when they lose.
Grain, for example, you may be fine food to buy rice and flour, and grain of the B vitamins, minerals and dietary fiber, mainly in the shell and the germ of grain, after finishing, the polished rice than ordinary rice 65% reduction of fat, protein 16%, Vitamin B177%, Vitamin B280%, niacin (vitamin B3) 81%, Vitamin B671%, Vitamin E86%, pantothenic acid 50%, 67% folic acid, iron, calcium and minerals almost "annihilated." Refined white flour with whole wheat flour compared to 60% loss of calcium, iron 76%, 78% zinc, magnesium 85%, copper 68%, involved in the synthesis of the chromium ions of insulin decreased by 98%! Fine white powder of dietary fiber and only 25% of the standard powder. From the above data shows, eat white rice and white flour is easy to lack of nutrients, and eat more whole grains can be avoided.
Outer leaves discarded food tastes better than cabbage leaves, and the outer leaves, and most people do not eat the lettuce leaves, celery leaves much higher than the nutrient content of cabbage, lettuce leaves, such as the carotenoids is much higher than the lettuce stem.