Gluten only affects those with celiac disease or gluten sensitivity. If a person with any of these conditions ingests gluten, their intestines are unable to digest it and instead become damaged, thus affecting their ability to absorb nutrients, resulting in malnutrition. In otherwise healthy individuals, gluten can be digested without problems. For a more detailed explanation on how gluten affects those with celiac disease, you can read here: http://www.netdoctor.co.uk/diseases/facts/glutenallergy.htm
Gluten is a protein that comes from wheat and wheat products. Because it is a protein, it is good for the body in small doses. Gluten does affect a small percentage of people similar to the affects of lactose intolerance. Celiac disease is the name of the disease for people that are allergic to or have an intolerance to the gluten protein. Gluten does not have any affects on the body if the person does not have Celiac disease.