There are many potential risks to withdrawing normal or regular foods, especially from young children. For example, according to Mari-Bauset et al (2015), “The combination of food selectivity and restrictive diets can make it difficult to achieve an adequate diet, consequently resulting in an excessive intake of certain foods and/or deficiencies and malnutrition due to insufficient amounts of other foods. In turn, inadequate intakes may lead to the development of chronic and degenerative conditions that tend to appear in the third or fourth decade of life (cardiovascular disease, high blood pressure, diabetes, dyslipidaemia, and osteoporosis, among others) or even earlier, in the case of menstrual disturbances, sleep apnoea, and psychosocial disorders”.
There are no known contraindications (something which makes a particular treatment or procedure potentially inadvisable) for the Feingold diet.
However, some people on the autism spectrum eat only a limited range of food. They already have a less healthy and less varied diet than other people. Restricting what they eat even further may reinforce those rigid eating patterns. It may also increase their social isolation (because they can’t eat the same food as their peers at parties or restaurants).
If you have concerns about your own diet or your child's diet you should seek advice from a responsible health professional such as a health visitor or GP. This may lead to a referral to a dietitian – in particular one with experience of working with individuals on the autism spectrum.