A gluten-free diet (GFD) is a diet that strictly excludes gluten, a mixture of proteins found in wheat and related grains, including barley, rye, oat, and all their species and hybrids (such as spelt, kamut, and triticale). The inclusion of oats in a gluten-free diet remains controversial. Oat toxicity in people with gluten-related disorders depends on the oat cultivar consumed because the immunoreactivities of toxic prolamins are different among oat varieties. Furthermore, oats are frequently cross-contaminated with other gluten-containing cereals. The long-term effects of consumption of uncontaminated oats (labeled as “pure oat” or “gluten-free oat” are still unclear and further studies identifying the cultivars used are needed before making final recommendations.
Gluten causes health problems for those with gluten-related disorders, including celiac disease (CD), non-celiac gluten sensitivity (NCGS), gluten ataxia, dermatitis herpetiformis (DH) and wheat allergy. In these people, the gluten-free diet is demonstrated as an effective treatment, but several studies show that about 79% of the people with coeliac disease have an incomplete recovery of the small bowel, despite a strict gluten-free diet. This is mainly caused by inadvertent ingestion of gluten. People with poor basic education and understanding of gluten-free diet often believe that they are strictly following the diet, but are making regular errors.
In addition, a gluten-free diet may, in at least some cases, improve gastrointestinal or systemic symptoms in diseases like irritable bowel syndrome, rheumatoid arthritis, multiple sclerosis or HIV enteropathy, among others. Gluten-free diets have also been promoted as an alternative treatment of people with autism, but the current evidence for their efficacy in making any change in the symptoms of autism is limited and weak.
Gluten proteins have low nutritional and biological value, and the grains that contain gluten are not essential in the human diet. However, an unbalanced selection of food and an incorrect choice of gluten-free replacement products may lead to nutritional deficiencies. Replacing flour from wheat or other gluten-containing cereals with gluten-free flours in commercial products may lead to a lower intake of important nutrients, such as iron and B vitamins. Some gluten-free commercial replacement products are not enriched or fortified as their gluten-containing counterparts, and often have greater lipid/carbohydrate content. Children especially often over-consume these products, such as snacks and biscuits. Nutritional complications can be prevented by a correct dietary education.
A gluten-free diet should be mainly based on naturally gluten-free foods with a good balance of micro and macro nutrients: meat, fish, eggs, milk and dairy products, legumes, nuts, fruits, vegetables, potatoes, rice, and maize are all appropriate components of such a diet. If commercially prepared, gluten-free replacement products are used, choosing those that are enriched or fortified with vitamins and minerals is preferable. Pseudocereals (quinoa, amaranth, and buckwheat) and some minor cereals are healthy alternatives to these prepared products and have high biological and nutritional value.