Controversial Aspects of the Gluten-Free Diet: Can I Eat Oats?

Background Information on Oats and the Gluten-Free Diet

To understand the controversy about oats, you need to be familiar with the history of oats and the gluten-free diet. Dicke's classic feeding studies were the basis for the gluten-free diet as we know it today. The studies suggested that wheat flour, rye flour, and oats are harmful (barley was later added to this list). Corn flour, cornstarch, rice flour, peeled boiled potatoes, and wheat starch were determined to be harmless.

Historical Nugget

Information contained in their scientific publications suggests that Dicke and colleagues concluded that oats are harmful to patients with celiac disease based on the response to oats of one patient. Today, researchers require an abundance of evidence in order to draw a definitive conclusion as to the safety of a product. In recent times, numerous persons with celiac disease have been studied to try to determine the safety of oats. And we still don't have a definitive conclusion.

However, almost as soon as the gluten-free diet became the treatment for celiac disease, some physicians and researchers questioned whether oats should be included on the list of grains to avoid. Early studies that further assessed the safety of oats had findings that were contradictory—some concluding that oats are safe, others that they are harmful. However, many of these studies were not of the quality we expect from scientific studies conducted today. Most of them had to rely on now-outdated assessment procedures to determine safety.

Recent Research on the Safety of Oats

Since 1995, several studies investigating the safety of oats have used the intestinal biopsy as their method of investigation. The intestinal biopsy is considered the gold standard or best available test for diagnosing celiac disease. Participants in these studies were either newly diagnosed with celiac disease or in remission. In general, they underwent an intestinal biopsy before the start of the study and then consumed daily amounts of oats for the length of the study period. At the end of the study period, they underwent another biopsy. Biopsies from before and after the study period were compared to determine whether oat consumption had either affected recovery of the intestinal mucosa (among newly diagnosed persons with celiac disease) or adversely affected the intestinal mucosa of persons with celiac disease in remission. For the most part, these recent studies have concluded that moderate amounts of uncontaminated oats are safe for consumption by most people with celiac disease.

Evidence Suggesting Oat Consumption May Be Harmful

One recent study found that while the moderate consumption of oats did not shorten or blunt the villi of the small intestine, it did result in a significant increase in intraepithelial lymphocytes, which are white blood cells found inside the lining of the small intestine. Lymphocytes are present wherever and whenever there is inflammation in the body, so the increase indicated a possible immune system reaction. An increase in intraepithelial lymphocytes is considered one of the first signs of mucosal damage in celiac disease.

Another study found that oats did not harm the intestinal mucosa of most—but not all—study participants. One study participant out of nineteen developed villous atrophy (blunting of the intestinal villi) and rash (the patient had dermatitis herpetiformis) while consuming oats. When oats were removed from the patient's diet, the rash resolved, and villi returned to a near-normal appearance. When oats were reintroduced, the patient again developed a rash and villous atrophy.

This finding, that one study participant appeared to be negatively affected by oats, prompted a group of researchers to further investigate the possibility of oat intolerance among some persons with celiac disease. They studied the intestinal mucosa of three patients who had previously developed mucosal inflammation while consuming oats. When biopsy tissue of the intestinal mucosa of these patients was exposed to avenin—the prolamin protein found in oats—in a test tube, researchers were able to identify lymphocytes made specifically in response to avenin. The investigators concluded that some persons with celiac disease have lymphocytes in their mucosa that can react with this oat protein and cause mucosal inflammation.

It is important to keep in mind that the number of people harmed by oats appears to be very small. Nonetheless, if you wish to add uncontaminated oats to your diet, it is important to monitor yourself for any new symptoms. (But keep in mind that oats are high in fiber, and fiber may cause gastrointestinal symptoms unrelated to celiac disease.) You also may want to discuss with your physician whether periodic serological testing would be useful. Additionally, if you are newly diagnosed with celiac disease, you may want to wait to add oats to your diet until after you are stabilized on a gluten-free diet.

Gluten Contamination of Oats

Another area of concern with oats is contamination with wheat, barley, or rye. According to oat millers, oats may be contaminated with one or more of these grains when they arrive at the mill. Oats are frequently grown in rotation with wheat and other grains—one year wheat is grown, the next year oats are grown, and so on. Depending upon the previous year's crop, there will likely be some foreign grain growing in the oat field, which will then be harvested along with the oats. In addition, oats may become contaminated with other grains during transport from field to mill, because shippers use railcars or trailers that may contain foreign grain from a prior load. While oats may undergo thorough cleaning at the mill and pass through sizing equipment to remove foreign grain, they nonetheless may still contain small amounts of wheat or other gluten-containing grains particularly if the grains have similar sizes.

Research on the Gluten Contamination of Commercial Oats.

Relatively little information is available on the gluten contamination of commercial oats in the United States. In a study I conducted and published in 2004, twelve containers of oats (four lots taken from each of three brands—Quaker, Country Choice, and McCann's) were assessed for contamination with wheat, barley, or rye. Gluten contamination ranged from less than 3 parts per million of gluten to 1,807 parts per million. Under the Food and Drug Administration's proposed ruling for use of the term gluten free on food labels, gluten-free foods, including oats, must contain less than 20 parts per million of gluten. Only three of the twelve containers analyzed would be considered gluten free under this ruling and under the Draft Revised Codex Standard for Foods for Special Dietary Use for Persons Intolerant to Gluten.

In another study, published in 2006, 108 oat samples from Europe, Canada, and the United States were assessed for contamination with wheat, barley, and rye. Again, gluten contamination was substantial, with 61 percent having gluten contamination over 200 parts per million.

Gluten-Free Oats

At least five manufacturers in North America (Gluten Free Oats, Cream Hill Estates, Gifts of Nature, Bob's Red Mill, and Only Oats) produce gluten-free oats as determined through independent testing conducted by the Gluten Free Certification Organization and the Food Allergy Research and Resource Program. These manufacturers are doing this through carefully monitored growing, harvesting, and processing procedures. For more information on these oat companies, see their websites: glutenfreeoats.com, pureoats.com, giftsofnature.net, bobsredmill.com, and onlyoats.com.

Recommendations for Oat Consumption

The question of whether oats should be consumed is not as easy to answer as many persons with celiac disease would like. Persons with celiac disease may want to consider the following points when deciding about oat consumption:

• For most adults and children with celiac disease, uncontaminated oats appear safe to consume in moderation (approximately ½ cup of dry rolled oats or ¼ cup of dry steel-cut oats per day).
• Some with celiac disease appear unable to tolerate even uncontaminated oats.
• Cross-contamination of oats with wheat, barley, or rye is a concern.
• Small amounts of gluten contamination in gluten-free processed foods may be inevitable. However, the question is one of degree—what amount of contamination is acceptable.
• The Draft Revised Codex Standard for Foods for Special Dietary Use for Persons Intolerant to Gluten of the Codex Alimentarius Commission states that gluten-free foods may contain no more than 20 milligrams per kilogram of gluten (20 parts per million).
• According to the FDA's proposed rule on use of the term gluten free on food labels, oats may bear a "gluten-free" claim as long as they contain less than 20 parts per million of gluten. However, this amount may be changed before this rule is finalized.
• Brands of oats are now on the market that have been tested and consistently found to be gluten free as defined by both Codex and FDA.

When assessing whether or not to include a particular oat product in your diet, it is important to understand what tests were used to determine its gluten-free status. Tests for gluten contamination are not created equal; some are better than others. At present, the best available test for gluten contamination of oats is the R5 ELISA. This assay has a limit of detection of 3 parts per million of gluten and a limit of quantification of 5 parts per million of gluten. It has been endorsed by Codex as the method for determining gluten content of gluten-free foods and is tentatively being considered by the FDA to help enforce its regulations on "gluten-free" labeling.

To find out how a particular product was tested, call the company's customer service number or visit its website.

In My Opinion

In my opinion, oats containing less than 20 parts per million of gluten—the limit proposed by the FDA—are safe for almost all persons with celiac disease to eat. At the present time, I recommend purchasing oats only from manufacturers that document through R5 ELISA testing the level of gluten in their products. Be forewarned, however, that ordering products from these companies is expensive, and the products are not yet widely available in retail stores. However, if you miss your oats, the cost of these products may be worth it. As an added bonus, oats are quite nutritious, containing 4 grams of dietary fiber per half cup of dry rolled oats.