HOUSTON -

Gluten-free products are in grocery stores and on billboards. Some restaurants even feature special menus with gluten-free options.

It's a nutrition craze that shows no signs of slowing down. So, on Friday, the Food and Drug Administration took a big step to make sure consumers get the real deal when they buy gluten-free products.

Gluten is a protein found in pasta, breads and grains. For a small number of Americans diagnosed with celiac disease, gluten is public enemy number one.

Dr. Eric Sandberg with Houston's Kelsey-Seybold Clinic said the intestinal symptoms are painful.

"Especially bloating, stomach pain, they often have diarrhea and associated weight loss," Dr. Sandberg explained.

By eliminating gluten, the symptoms usually clear up. But knowing which foods are safe and which ones are not is the biggest battle.

"It's impossible to avoid something if we really don't have confidence in the labeling," said Dr. Sandberg.

Products that comply with the newly released FDA "gluten-free" labeling rule are defined as:

Foods that inherently do not contain gluten (i.e. raw carrots or grapefruit juice) may use the "gluten-free" claim.

Foods with any whole, gluten-containing grains (i.e. spelt wheat) as ingredients may not use the claim.

Foods with ingredients that are gluten-containing grains that are refined but still contain gluten (i.e. wheat flour) may not use the claim.

Foods with ingredients that are gluten-containing grains that have been refined in such a way to remove the gluten may use the claim, so long as the food contains less than 20 parts per million of gluten (i.e. wheat starch).

Foods may not use the claim if they contain 20 parts per million of gluten or more as a result of cross-contact with gluten containing grains.

"Adherence to a gluten-free diet is the key to treating celiac disease, which can be very disruptive to everyday life,” said FDA Commissioner Margaret A. Hamburg, in the release. "The FDA's new 'gluten-free' definition will help people with this condition make food choices with confidence and allow them to better manage their health."

Manufacturers will have until Aug. 5, 2014, to update their labels in compliance with the new requirements. Foods labeled as "without gluten," "free of gluten" or "no gluten" will also be held to the same standard.

"We encourage the food industry to come into compliance with the new definition as soon as possible and help us make it as easy as possible for people with celiac disease to identify foods that meet the federal definition of 'gluten-free,' " said Michael R. Taylor, the FDA's deputy commissioner for foods and veterinary medicine, in the release.

Dr. Sandberg supports the new standards.

"I think better labeling helps consumers make better choices and that's going to be to everyone's advantage," he said.

Along with the true medical need, Dr. Sandberg said eating gluten free foods have become a bit of a food fad that may be hyped.

"People have talked about gluten-free to help with fatigue to help with headaches, to help with weight loss, but there's not strong evidence that gluten avoidance helps with these symptoms."