Micronutrients and allergies
What have researchers discovered about the link between allergic processes and nutrition? The following is a summary of some of this research. Most of these studies have been done in adults.
- Vitamin C is a major antioxidant substance in the airway surface liquid of the lung where it could be important in protecting against environmental oxidants. A study from the American Journal of Clinical Nutrition showed that a diet low in vitamin C was a risk factor for asthma.
- Patients with asthma who reported a high dietary magnesium intake had better lung function and a reduction in the relative risk of wheezing. Animal studies have shown that magnesium deficiency increases the amount of histamine released into the blood. Histamine is a natural chemical in our bodies that, when released, causes many of the symptoms of allergies.
- Low selenium levels were observed in patients with asthma when compared to a group of patients without asthma.
- In a group of 20 patients with exercise-induced asthma, two grams of vitamin C was administered and lung function was tested. In nine patients, a protective effect on their exercise-induced asthma was documented after vitamin C was given.
- A dietary questionnaire used to determine intakes of different nutrients in patients with asthma and allergic rhinitis, and then in control patients without disease, showed that those with the lowest intakes of vitamin C and manganese were associated with more than five-fold increased risk of asthma. Also those with low intakes of zinc had increased risk of symptoms of seasonal allergies, and those with low magnesium intakes had increased risk of asthma.
- Children who ate fresh oily fish had a significantly reduced risk of asthma. No other food groups or nutrients were significantly associated with either an increased or reduced risk of asthma. This study concluded that consumption of oily fish may protect against childhood asthma.
- A study of 17 adult asthmatics found that when their diets were supplemented with daily dosages of 400 IU of vitamin E and 500 milligrams of vitamin C there was an 18 percent increase in the peak flow capacity (a measure of lung function) over those on regular diets.
- A diet significantly deficient in vitamins A and E and lower in other nutrients was found in the diets of brittle asthmatics compared to non-brittle asthmatics and healthy controls. Brittle asthma is characterized by repeated life-threatening attacks despite appropriate medical treatment. In addition, selenium, magnesium, and vitamin C intake was somewhat lower in brittle asthmatics.
- Proanthocyanidins (found in grape seed extract) have been found to have an antihistaminic effect.