Yes, I do believe that it is important to know the ingredients of all food. A person should at least be given the opportunity to know what kinds of ingredients and chemicals they are putting into their body. Just because someone eats the occasional treat that might be labeled as junk food doesn't mean that they don't care about their health at all.
It is important is to know the ingredients of junk food just it is important to the know the ingredients of healthy foods. Maybe even more important. Junk food contains many things that are unhealthy for the human body. When one knows the ingredients then he or she can make the choice of whether they want to consume the foods.
I think that while most people will ignore what is in junk food there are people out there who are allergic to certain substances or people out there who want to avoid some substances in general and they are the ones checking the labels and making sure they know what it is in the food they are eating.
I think it is good to know the ingredients of junk food if, for no other reason, to be knowledgeable about what it is that you are consuming. You want to know what you are putting into your body. Especially if you are susceptible to allergies and need to eliminate foods.
Yes, I believe that it is important to know the ingredients of junk food, because people should know what they are putting in their body. If someone is going to ruin their health by eating junk food, they should be able to figure out what is in it. Then they have no excuse for their health.
The McDonald's actually uses the worst ingredients possible in the food the company makes: the fries are made with 17 different ingredients: canola oil, soybean oil, safflower oil, 3 natural flavors, dextrose, tetrasodium pyrophosphate, citric acid, dimethylpolysiloxane (an anti-foaming agent) , corn oil, THBQ (another, very dangerous, anti-foaming agent), dimethylpolysiloxane, salt, silicoaluminate and potassium iodide. After this, see the documentary "Super Size Me", where a man must eat, for a month, every day, only food from McDonald's. And look at this, a McDonald's-made file: http://www1.mcdonalds.ca/NutritionCalculator/IngredientFactsEN.pdf . Now say me where I am wrong.