Latin name: Avena sativa
Source material: Untreated planting seeds
Family: Graminae (Poaceae)
Common names: Oats, Oat, Oatmeal, Oat groats
Oats, from an erect, tufted annual grass growing to 1.2 m, are of uncertain origin, but probably arose in Europe from 2 species, Wild oats (A. fatua L.) and Wild red oats (A. sterilis L.). Oats are now cultivated throughout the temperate zones of the world. The major growing areas are the USA, southern Canada, the USSR and Europe, particularly near the Mediterranean. Oats serve as food for humans, animal fodder and bedding, and - especially in the form of extracts - in a variety of industrial uses. There are many named varieties, with new forms being developed each year.
Oats are available as whole Oat grains when only the husks are removed; Oatmeal from cut or ground Oats; and rolled Oats when grains are cut in slices and then steamed and rolled. Oats are by far the most nutritious of the cereal grasses. They are high in vitamin B-1 and contain vitamins B-2 and E. Eaten as a cereal, they are probably best known as the breakfast cereal "porridge" or "oatmeal", but can also be used in many other ways. The seed can be sprouted and served in salads. The grain can be ground into flour and used in making biscuits, sourdough, etc. Oats are fairly low in gluten and so not suitable for making bread. Oat flour inhibits rancidity and, as an additive, increases the length of shelf-stability of fatty foods such as vegetable oils. Oats are also one of the basic ingredients of whisky. The roasted seed is a coffee substitute. Edible oil is obtained from the seed and used in the manufacture of breakfast cereals. Oats are often a major ingredient in cosmetics, creams and skin cleansers.
Oats are widely thought to have medicinal actions. Oat straw and the grain are prescribed to treat general debility and a wide range of nervous conditions.
See under Environment.
No allergens from this food have yet been characterised.
Allergens of 46 and 66 kDa have been isolated from Oats and have been classified as major IgE binding proteins in children with atopic dermatitis (1). The 66 kDa protein was found to bind to IgE antibodies in serum of 28 of 33 (84%) adult patients with atopic dermatitis. Non-specific binding to a region of this protein occurred, which the authors suggest may also represent lectin-like binding (2).
Oats has been shown to contain the panallergen profilin, but at very low levels compared to other foods, e.g., a profilin IgE antibody level of 0.9 vs. 27.3 kUA/l for Celery (3).
Three proteins of 25, 27 and 32 kDa have been identified, by immunoblotting using sera from patients with coeliac disease, as the major coeliac serum IgA-binding components of Oat endosperm. These corresponded to alpha 2, gamma 4, and gamma 3 avenins, respectively (4). These gluten-like allergens are in very low concentration in Oats, and recent studies have reported no adverse effect in patients with coeliac disease, even after long-term consumption of Oats.
An extensive cross-reactivity among the different individual species of the genus Poaceae could be expected (5). By RAST inhibition tests, cross-antigenicity was shown to exist among the cereal grains Rye, Wheat, Triticale, Barley, Oat, Maize and Rice. The degree of cross-reactivity closely paralleled taxonomic relationship and appeared to be in the following order of decreasing closeness: Wheat, Triticale, Rye, Barley, Oat, Rice and Maize. The allergenic activity in the Rye and Wheat extracts was found to be distributed among various fractions of different molecular weights (6). These results were supported by other studies reporting that in subjects sensitised to Wheat and Rye flour, there is significant cross-reactivity among the seed extracts of 12 cereals: Wheat, Durum Wheat, Triticale, Cereal rye, Barley, Rye grass, Oats, Canary grass, Rice, Maize, Sorghum and Johnson grass. Results of the study suggested that the bran layers of cereal grains are at least as allergenic as the flour (7). Sixteen proteins have been reported to be common among Wheat, Rye and Barley extracts, suggesting cross-reactivity among these cereals (2). However, in a study with challenges to the common cereals, 80% reacted to only 1 grain (8).
Wheat gliadin and the corresponding proteins of Rye, Barley and Oats were found to be the allergens in cereal-dependent exercise-induced anaphylaxis (9). Barley contains less gliadin than the other cereals.
A 51-year-old woman developed anaphylaxis following Millet ingestion; cross-reactivity to cereals could be demonstrated by positive SPT and/or IgE antibody measurements. However, these were not clinically relevant (10).
Cross-reactivity among Wheat, Rye, Barley, Oats, Maize, Rice, and the corresponding grass pollens has been reported (11).
Oats may uncommonly induce symptoms of food allergy in sensitised individuals (12). Symptoms may include angioedema, urticaria, atopic dermatitis, asthma, rhinitis, and gastrointestinal symptoms such as nausea, vomiting and abdominal pain. Although IgE antibodies may be detected in patients, this may indicate only latent sensitisation (13-14).
On oral provocation studies in a group of children with cereal allergy, 18 exhibited a positive response to Wheat, 3 to Rye, 1 to Barley, and 1 to Oats. Symptoms involved the skin and the gastrointestinal and oropharyngeal regions. Onset was immediate in 8 children, delayed in 14, and both immediate and delayed in 1 (9).
Wheat gliadin and the corresponding ethanol-soluble proteins of taxonomically closely related cereals, including Oats, were found to be the allergens in cereal-dependent exercise-induced anaphylaxis. Five patients with positive SPT to a Wheat suspension had IgE antibodies to Wheat, Rye, Barley and Oats. The IgE antibodies were in particular directed against the ethanol-soluble protein fractions. The patients had been unaware of any cereal allergy, since anaphylaxis occurred only in association with exercise postprandially.
Oats may be a more relevant allergen in children with atopic dermatitis. In a study of 34 children with this condition, 33 were SPT positive to Wheat and 18 to Oats. IgE antibodies to Wheat was found in 32 children and in 30 to Oats (1). In a study evaluating topical treatments of atopic dermatitis and the role of percutaneous sensitisation to Oats, it was concluded that Oat sensitisation in children with atopic dermatitis seen for allergy testing is higher than expected, and may have resulted from repeated applications of cosmetics with Oats on a predisposed impaired epidermal barrier (15). In a study evaluating the frequency of atopic dermatitis in an unselected German population and the role of food allergy in this condition, 27 selected patients were further evaluated, of whom 19 were shown to have skin reactivity to pollen and/or food allergens. Four were shown to have positive SPT to Oats (16).
Allergy to Oats may also result from occupational exposure, in particular in animal, bakery and mill workers. Baker's asthma has been reported (5).
Cough, wheezing, shortness of breath, fever, stuffy nose, and skin itching/rash on exposure to grain dust have been documented. The condition “grain fever” may also occur (17). Whether these symptoms result from antibody response or physical irritation has not been fully elucidated.
Allergic contact dermatitis to an Avena extract has been reported (18).
Infantile food protein-induced enterocolitis syndrome (FPIES) is a severe, cell-mediated gastrointestinal food hypersensitivity typically provoked by Cow's milk or Soy; it may also be provoked by Oats. Symptoms of typical FPIES are delayed and include vomiting, diarrhoea, lethargy and dehydration. Initial presentation may be severe, resulting in a suspicion of sepsis (19-20).
Oats were previously implicated as a cereal affecting individuals with coeliac disease. Recent studies have shown that the regular consumption of moderate amounts of Oats is safe and well tolerated by adults with coeliac disease and dermatitis herpetiformis (21). However, there are concerns that even if Oats themselves are safe, they nonetheless may be contaminated with Wheat, Rye, or Barley (22). Recent evidence suggests that oats that are pure and uncontaminated with other gluten-containing grains, if taken in limited quantities, are safe for most individuals with coeliac disease (23).
Compiled by Dr Harris Steinman, email@example.com
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