Debate continues on whether asthma can be improved by avoiding foods that are thought to be harmful, or by eating more of foods that are considered to be healthier. Into this discussion has been thrown new evidence related to the weight debate: children who are overweight or obese are more likely to have asthma than those children who have normal weight. (Also see Chapter 10.)

In coming years, the impact of a child's diet on his asthma symptoms is likely to become the subject of more study.

Food Sensitivities

A small percentage of children with asthma do have food allergies. When a child has an actual food allergy, he may react to foods such as milk, eggs, wheat, shellfish, soy, or peanuts. To detect these allergies, a child can undergo a medically supervised test in which a particular food is removed from his diet and symptoms are studied.

However, one idea that has been the cause of discussion among many parents is the so-called “hidden food allergies” — that a child has sensitivity to certain foods that can't be detected by health care providers.

This hidden trigger, though, has not been detected by any studies. If anything, health care providers have warned that a diet that eliminates foods suspected of causing allergies — without medically confirming this relationship — could cause more problems for the child. Without certain foods, these children could encounter nutritional deficiencies that could harm their health.

Healthful Diets

For years, advocates of healthy eating have pointed out how many processed or convenience foods — those foods made of refined wheats and sugars and unhealthy fats — were leading to weight gains among children. Those with an interest in asthma and nutrition cited how sugar could impair the immune system for hours, and how poor eating in general could trigger an asthma attack.

This emerging information on asthma and obesity, along with growing research into the impact of nutrients on asthma, has increased interest on the impact of foods — particularly those high in vitamins and minerals, moderate in protein, balanced with healthy fats, and high in fiber.

More research is needed in this area, but some studies of children who had diets that excluded most processed foods have shown interesting results. For instance, 690 Greek children ages 7 to 18 years who adhered to a “traditional Mediterranean diet” demonstrated few asthma symptoms such as wheezing and runny nose.

The children, who lived in rural Crete, had a diet high in fruits, vegetables, and nuts — including grapes, oranges, apples, and fresh tomatoes (the main local produce in Crete) — which contain many nutrients that may help with asthma symptoms.