Modern day processed foods are usually packed with chemicals and preservative to keep microbes (bacteria, yeast, mold) from eating the food, causing it to go bad. The methods used in processing kill the microbes and prevent them from living on the food. Freezing and heating are generally not harmful ways of processing foods. The processed foods you want to stay away from are the ones that have been "cleaned" (bacteria killed) and preserved through the use of chemicals.
- Sodium Content - Salt is a great preservative, and also gives taste to bland foods. Because of this, most processed goods have an extremely high sodium content (mcvitamins.com). Don't be fooled by the "healthy" frozen meal choices. If most of the fat is cut out of a dish, the best way to make it taste yummy is to add salt. The Meatloaf SmartOne frozen meal has 880 mg of salt - 73% of the recommended daily value! (livestrong.com).
- Lack of Enzymes - "Every metabolic function in our body and every chemical reaction that keeps us healthy is helped by enzymes" (mcvitamins.com). Processing by heating removes most enzymes from food. Enzymes are destroyed when food reaches 114 degrees Fahrenheit. Enzymes are "re-supplied" partly by the body, and partly from raw foods that we eat ()fruit, vegetables, meat). Since 50% of enzymes are used just digesting food, if there aren't enough the body has to start taking them from other organs. For lack of a better way to say it: "Evidence, the high number of indigestion aids sold and the fact that you get sleepy after a meal. The body is stealing energy (enzymes) from other bodily functions. Without these enzymes, due to the lack of them in the food we eat, the average person only digests about 30 to 70% of what they eat" (mcvitamins.com).
- Missing Nutrients - Many of the processes involved in destroying harmful bacteria also destroys the natural nutrients in the food. Heating, drying, sterilization and canning zap the nutrients out of food. Many companies put these nutrients back in, but they aren't as good for you as they are when naturally occurring. (mcvitamins.com)
- Sugar Content - What do Twinkies, candy and soda have in common? Lots and lots of sugar. I myself have a horrible sweet tooth, so this is the hardest part about avoiding processed foods. Bacteria feeds on sugar, so by eating a lot of it, you may be at risk of lowering the defenses of your immune system (doityourself.com). A diet high in sugar can also lead to diabetes because of the glucose found in the sugar molecule (do it yourself.com)
Bottom line - processed foods are (for the most part) bad for you if they are a part of your daily diet. Do your body a favor and save the Twinkies for a treat and the frozen meals for when you don't have time to cook a fresh dinner.