This issue is very important to several people here, and the many others that have Celiac Disease (gluten intolerance) - it is estimated that about 1 in a 100 people have it, but only two and a half percent of them are aware of it. That's millions of people in the U.S. alone.

From the same book as above, Celiac Disease: A Hidden Epidemic:

"How Much Is Too Much?

Anne Lee, nutritionist at the Celiac Disease Center at Columbia University explains:

Everyone always asks me: â??How much gluten can I safely eat?â?ť

I tell patients to think of it this way: eating gluten is like falling down and scraping your knee. You damage the knee, but in time it heals. If youâ??re falling and injuring your knee every day, itâ??s never going to heal.

We know that ingesting an eight of a teaspoon of flour causes visible intestinal damage. We do not know what happens to the intestine with smaller amounts such as the chronic ingestion of bread crumbs on a butter dish.

We do not know how much gluten you must eat - or how often - for that damage to accumulate. We donâ??t know if that crumb in the dish is a scrape, a bruise, or continual damage. So you must be diligent on the issues of cross-contamination and â??cheatingâ?ť.

Living gluten-free (GF) means eliminating all foods containing even a trace amount of the grains containing gluten. That includes foods made with derivatives of those grains or additives and stabilizers containing these grains."