What's the deal with gluten?

I know many people who have issues with gluten. Some just can’t eat it all. Some have to moderate. My nephew has an allergy to it that can stir up his asthma.
Someone with celiac disease can’t eat gluten at all. Someone with intolerance or sensitivity, the science isn’t as clear whether or not their diet should be as strict. But I am gonna bet those with an intolerance or sensitivity feel better when they limit their gluten intake.
A gluten-free diet might even help people with migraines, ADHD, Down syndrome and other conditions.
I have started to notice more and more products at the grocery are now gluten free, including some cereals.
And I recently ate at a restaurant in Berkeley where many of the items on the menu were gluten free.
Gluten shows up in bread and pasta, but apparently can also be in many other foods, such as cold cuts, salad dressings, beer and licorice.
According to this WebMD article, people need a gluten-free diet only if they have celiac disease or gluten sensitivity, says Stefano Guandalini, MD, director of the University of Chicago Celiac Disease Center. … “People think that gluten-free diets are more healthy,” Guandalini says. “This is, of course, not the case.” In fact, the diet is hard to follow and may pose nutritional drawbacks when people have no medical reason to be on it.
A doctor in the WebMD article warns that eating gluten-free can cause deficiencies in iron, vitamin B12, vitamin D, magnesium, fiber, and other nutrients because people are avoiding breads, cereals, and grains that are fortified. In contrast, many gluten-free products are not fortified.