|Gliadin in Foods|
(Excerpts and notes on the need for a lifelong GF diet.)
The separation of prolamins in cereal grains is still carried out by classical methods of solvent extraction and the various gliadins are separated by a variety of methods involving chromatography and electrophoresis. Recently methods have been developed in several laboratories (in the U.S. as well as a number of other countries) for the estimation of gliadins in wheat flour as well as various other grain and gluten-free flours.
Ciclitira and Lennox, by using a radio immunoassay for the estimation of alpha- and beta-gliadins in wheat flour, found the content of the two gliadins to vary from 1.2 to 3.3% of the dry matter. The sensitivity of the method was 1mg of alpha- or beta-gliadin. The data suggest that there may be considerable variation in the gluten content of GF flours. Further work suggests that the sensitive radioimmunoassay could be used to define standards for the suitability of GF products based on wheat starch tests for patients wit CD. The authors note that small amount of gliadin found in nominally GF foods may be important in very sensitive patients with CD when consumed on a regular basis.
Meir, et al, using an enzyme-linked immunosorbent assay (ELISA) found that the gliadin content of a crust of crust and crumb was only 0.5-40% of the content of the original flour! McKillop, et al, developed three types of immunoassay. They found that the relative activity in their methods was for wheat flour 5.7, oats 0.047. GF foods, with and without wheat products were similar to oats and corn.
Skerrit and co-workers, in a series of papers, developed a test for promalins based on the used of monoclonal antibodies to cereal proteins. The antibodies detected prolamins in bread wheat, durum wheat, and rye most strongly, followed by barley then oats; detection in rice was weak. The authors state that the selectivity appears suitable for a test for prolamins toxic to patients with CD. The sensitivity (reported to be about 1 in 10,000 parts) seems adequate to assess the gluten content of GF foods. Further development of these methods should aid in clarifying the clinical significance of low levels of prolamins for celiac patients.
Variation in Response. Variations between individuals in their response to a GF diet or to a gluten challenge have been recorded by many workers. In testing the response of children recovered from CD and given daily doses of 2.25g wheat gluten, Hamilton and McNeill found in a series of 12 patients that symptoms of CD reappeared over a period of 1-15 months. Baker and Read reported that 6 to 10 patients challenged with oats developed toxic effects, suggestion that these cereals are not uniformly toxic in all patients. On unrestricted wheat gluten intake, McNicholl, et al, found in a series of 40 children that reversion of the treated mucosa to the flat state may take as long as 35 months and in a few cases 3-4 years. In 36 children, the range was 4 to 35 months.
In testing the effect of various cereals on recovered celiac patients, Anand, et al, found that with barley, although all patients remained symptom-free, there was fall in disaccharidase activity. When rye was given to 2 patients one remained symptom-free but there was mucosal damage and a fall in disaccharidase activity in both patients. They also note that the degree of mucosal damage varied from one patient to another although all were consuming the same amount of the particular cereal. They suggest that there is an inherent variability among celiac subjects which may be responsible for the wide variation in the sensitivity of the illness of the subjects when they consume a diet containing gluten. Variation in patient response may also explain part of the difference on the effect of oats on patients with CS observed by different authors and researchers.
In subjects given a gluten challenge mucosal damage usually appears before intestinal symptoms. Anand, et al, concluded that intestinal symptoms may be a poor guide to the damaging effect of cereals. The same group found histological damage to occur a few hours after challenge. On the other hand, Ciclitira, et al, found no measurable effect on mucosal morphology in 10 patients fed wheat starch flour, but 4 had significant intestinal symptoms. The difference in these findings may be a reflection of variation in response between individuals or of the effect of the amount of gluten in the challenge.
Dose-Time Response. Several attempts have been made to determine the level at which gluten or gliadin is toxic. Dissanayke, et al, made a dietary reassessment of 38 patients with confirmed CD. All had been prescribed a gluten-free diet. Patients were placed in 3 categories according to their assessed gluten intake as gluten-free, small amounts of gluten, or large amounts (0.5g/day) of gluten. Results: patients in the gluten-free group were all symptom-free whereas those consuming large amounts of gluten showed little or no improvement in mucosal structure although most were clinically improved when taken off the regular diet containing about 7g gluten/day.
Hamilton and McNeill gave a slice of bread to 12 children with CD and a GF diet and found that symptoms returned in all patients, but in varying periods of time.
On the basis of the limited data available, it may be concluded that intakes of 1-2mg gliadin per day are toxic. As would be expected, the toxicity of gliadin is related both to the size of dose and length of time administered. Both of these facts need to be taken into consideration in assessing the acceptability of foods and food constituents. Both of these facts need to be considered by the celiac patient when new foods with new combinations of ingredients are introduced into the diet.
GF Diet for Life. The necessity of a lifelong GF diet has been emphasized by many workers. Hamilton and McNeill in a study of 23 children with proven CD failed to detect a single case of CD in which tolerance to wheat gluten was transient. They concluded that the deleterious effect of wheat gluten is long-standing, regardless of the onset or nature of the original disease. Douglas reviewing the work of Mortimer, et al, concluded that a celiac is always a celiac and that the requirement for a GF diet in true CD is lifelong. Similarly, McNeish stated that because there are no means to predict future responses to gluten, the safest advice to patients with CD must be to adhere to a GF diet indefinitely.
CSA Library Series