Why are gluten and casein considered "bad"?

Answer 1

They are common allergens. If you are not allergic to them, then they are fine. Actually gluten sensitivity and milk intolerance are not technically allergies, but the point is that many people do have a bad reaction to these foods. The majority, however, can eat both with no trouble. You should learn to notice how your body reacts to different foods and avoid the ones that give you trouble. Other problem foods can be peanuts, tree nuts, eggs, shellfish, tomatoes, or almost any other food. Eat what agrees with YOU.

Answer 2

It could thicken blood.