DECREASED NUTRIENTS
Processed foods lose a good deal of their vitamin content. This also happens with fresh foods unless they're eaten quickly, but freezing, canning or otherwise altering foods so they keep longer results in nutrient losses. Just growing vegetables and fruits in fertilized soil can reduced the vitamin C content in the final product, the Better Health Channel reports. Blanching foods before freezing also removes water-soluble vitamins like B complex and vitamin C. Milling grains removes the husk, which contains most of the vitamins, while peeling fruits and vegetables can also removes vitamins that lie close to the skin's surface.
ADDITIVES
Preservatives and additives that enhance flavor and taste rarely add any nutritive value and in some cases, have been implicated in causing cancer or other diseases. Sodium nitrite, for example, gives processed meats such as hot dogs and lunch meat their characteristic pink color and also prevents growth of bacteria that cause botulism. However, nitrites can also form nitrosamines, chemical that may increase the risk of cancer in animals and humans. Artificial food colorings, added for no other purpose than to make food look more appetizing, also have been implicated as possible cancer-causing agents.
ADDED FATS AND SUGAR
Processed snack foods, dinners and side dishes almost all contain added sugar, sodium and fats to improve the flavor of dehydrated or frozen meals. All three are associated with major health risks: excess sodium can raise your blood pressure, excess sugar can aggravate diabetes and lead to weight gain and excess fats, particularly trans fats, can increase cholesterol levels and increase the risk of heart disease.