Celiac.com 10/07/2008 - Even though nearly 1 out of every 100 people in the world suffers from celiac disease, proper celiac diagnosis can be difficult to diagnose based on symptoms alone, an is often delayed for years. In fact, in the U.S., the average amount of time from first onset of celiac symptoms to a diagnosis for celiac disease is 10 years.
One of the challenges of maintaining a life-long diet free of gluten is that so many foods and food products contain gluten. Examples include dried fruit and fruit pie fillings, cold cuts, sandwich spreads, canned meats, many salad dressings and condiments, prepared soups, flavored yogurt, and even flavored instant coffees and herbal teas.
Following a “strict” gluten-free diet is no guarantee against mucosal damage associated with celiac disease. In two different studies of gluten-free diets, nearly half of the subjects showed villous atrophy. However, the precise level of gluten in each diet was not measured.
The World Health Organization (WHO) defines naturally gluten-free foods as those with 20 parts of gluten per million (PPM) or less, whereas foods that have been artificially rendered gluten-free must have no more than 200 PPM of gluten. Now, this standard is not universally accepted, in part because of the difficulty of precisely determining the amount of gluten present in different foods. Still, it is obvious that a large number of patients with celiac disease can tolerate foods with minimal amounts of gluten.
Researchers A. K. Akobeng, and A. G. Thomas recently set out to examine the threshold for gluten consumption among patients with celiac disease by reviewing the results of a number of previous studies.
In one previous study, researchers examined 4,126 asymptomatic individuals, and found celiac disease in about 1 of 133 of them. The rate for patients with gastrointestinal (GI) symptoms was 1 in 56 subjects. For first-degree relatives of patients with celiac disease, the rate jumped to 1 in 22, while 1 in 39 second-degree relatives tested positive for celiac disease. These figures reflect the existence of a genetic predisposition for the development of celiac disease, as most patients who have celiac disease expressing human leukocyte antigen DQ2 or DQ8 haplotypes.
One population-based study of 1,612 patients with celiac disease that sheds some light on the demographics and symptoms of the disease shows that nearly three times as many women as men develop celiac disease, while about a third of celiac sufferers had seen 2 or more gastroenterologists. In that study, symptoms persisted for an average of 11 years before a diagnosis of celiac disease.
Often, such delays are due to the fact that symptoms of celiac disease are similar to many common GI disorders. In addition to the diarrhea experienced by 85% of celiac sufferers, other common symptoms are abdominal pain and distension, Borborygmi, flatulence, and weight loss. Because celiac disease is tied to numerous medical conditions outside of the GI tract, including osteoporosis, iron-deficiency anemia, neuropathy, asthma, and dermatitis herpetiformis, early and accurate diagnosis is important.
When people with celiac disease eat wheat, rye, or barley, the gluten proteins in these grains sparks inflammation in a part of the small intestine called the lamina propria, which brings about symptoms of the disease.
In 2007, clinicians proposed new diagnostic guidelines to help doctors diagnose celiac disease more accurately. Under these guidelines, the gliadin antibodies previously used to test for celiac disease have been abandoned because of poor sensitivity and specificity. Serologic testing that focuses on immunoglobulin (Ig)A endomysial antibody, or IgA tissue transglutaminase (tTG) antibody, has been shown to have sensitivity and specificity values above 95% for celiac disease.
Researchers examined electronic databases using a broad search strategy that included randomized controlled trials, cohort studies, case control studies, and cross-sectional studies. In all cases, celiac disease was clinically confirmed through small intestinal histology.
Initial research uncovered 35 studies, but only 13 were included for analysis. Most studies were excluded because they were reviews of the diet in celiac disease. Of the studies included in the full analysis, 7 were cross-sectional in design and 3 were randomized controlled trials. The research team gauged the cross-sectional studies to be at moderate risk for bias. Because of the varied nature of the results of the many studies, it was not possible to conduct a pooled statistical analysis of the results. The studies tended to focus more on histologic changes instead of patient symptoms of celiac disease. The review indicated that the total amount of gluten consumed, as opposed to the levels of gluten in individual foods, is the key factor connected with histologic abnormalities in the small intestine. Consumption of gluten at levels of 200 mg/day or more was clearly tied to the development of intestinal abnormalities. Whereas these changes usually show up within a few weeks, one trial that looked at different levels of gluten consumption showed differences in villous height/crypt depth ratio within just one week.
The results of research evaluating consumption of lower levels of gluten have been more uneven. In one study, more than half of subjects consuming only 10 mg of gluten per day experienced worsening of their villous height/crypt ratio. However, another study showed no histologic abnormalities among patients who ingested an average of 34 mg of gluten per day.
The current study basically confirms other recent examinations of the limits of gluten consumption in celiac disease, including one study that recommended a daily gluten consumption limit between 10 mg and 100 mg, and another, based on just 83 subjects, that indicated that the mucosa of the small intestine showed no negative long-term changes when subjects consumed up to 80mg of gluten a day.
While it’s tough to draw specific conclusions from the current study, it seems clear that the standard of 200 PPM or less of gluten in some foods labeled as gluten-free will not protect most celiac disease patients. Instead, the study suggests that a new standard set at a maximum of 20 PPM of gluten will equate to an approximate daily gluten consumption of 6 mg. The body of science suggests that consuming 6mg per day of gluten intake would not promote mucosal abnormalities among most people with celiac disease.
While more conservative, the 6mg per day figure seems to offer the best assurance of avoiding intestinal damage of any kind. Still, the researchers noted the need for more research on the threshold of gluten consumption for people with celiac disease. They specifically noted that standardization of outcomes along with trials to compare particular concentrations of dietary gluten would be helpful.
Until the results of such research, this review offers a reasonable guideline as the threshold gluten consumption for people with celiac disease.
1. Lo W, Sano K, Lebwohl B, Diamond B, Green PH. Changing presentation of adult celiac disease. Dig Dis Sci 2003; 48:395-8.
Aliment Pharmacol Ther. 2008; 27:1044-1052. Epub 2008 February 29.