Correspondence Address:
Shailendra Nath Gaur
Department of Pulmonary Medicine, Vallabhbhai Patel Chest Institute, University of Delhi, Delhi
India

Full Text

Asthma is a common chronic inflammatory disease of the airway manifesting as airway hyper-responsiveness that leads to recurrent episodes of wheezing, breathlessness, chest tightness and coughing. [1] There is widespread, variable and often reversible airflow limitation. Most of the newer therapeutics are aimed at decreasing the airway inflammation. The nutritional aspect of bronchial asthma has focused attention recently as non-pharmacologic adjuncts in management of asthma. Following review focuses on current knowledge about nutritional supplementation in bronchial asthma.

Benefits of vegetarian diet

Animal products have arachidonic acid which lead to formation of leukotrienes. They contribute to allergic reaction observed in airways of asthmatics. Absence of arachidonic acid in vegetarian diet is therefore helpful in asthmatics. Certain vegetables like onion and garlic contain flavinoids which have been shown to inhibit inflammatory response. Observed Vitamin C deficiency in asthma can be corrected by intake of fruits and vegetables rich in it like pepper, strawberries, green leafy vegetables, broccoli and citrus fruits etc. It has been shown that diet rich in Vitamin C leads to significantly less wheezing in childhood asthma. [2] A vegetarian diet given for 1 year in conjunction with many specific dietary changes such as avoidance of caffeine, sugar, salt, and chlorinated tap water and combined with a variety of herbs and supplements led to significant improvement in one group of asthmatics. [3]

Salt intake

High salt intake has been linked with adverse effect on asthma. Several trials have shown benefit of salt restriction in diet with evidence of clinical improvement in asthma. [4] A vegetarian diet also helps to maintain body's sodium and potassium balance leading to theoretical advantage in asthma.

Role of antioxidants

Asthma is a state of increased oxidative stress in airways. Oxidant stress has been linked to increased inflammation and hence represents a risk factor for development of bronchial asthma. [5] Increased production of reactive oxygen species (ROS) also leads to direct tissue damage by oxidation of proteins, DNA and lipids. So a potential role of antioxidants in mangement of asthma has been suggested. Low intake of antioxidant vitamins A, C and E have been shown to be associated with worse spirometric parameters in children. [6] Their low level appears to increase risk of asthma. Dietary selenium (Se) deficiency lowers erythrocyte glutathione peroxidase activity which again leads to increased oxidative stress and increased risk of asthma. In studies Se supplementation has been shown to cause clinical improvement, though pulmonary function tests do not appear to be improved. [7] Another antioxidant that has been of some role in excercise-induced asthma is lycopene. [8] Lycopene is related to beta-carotene and found in tomatoes.

Magnesium

Magnesium deficiency is often found in asthmatics. [9] Magnesium helps to prevent and stop bronchial muscle spasms. Magnesium competitively inhibits ionized calcium and relaxes bronchial smooth muscle tissue. Intravenous administration of magnesium ends an asthma attack within minutes. [10] Oral route has not been proven to be beneficial, but it probably is.

Vitamin B6 and B12

Vitamin B6 deficiency has been observed in asthma patients. [11] It may be because of asthma itself or due to its depletion by theophylline given for treatment of asthma. B6 is a critical coenzyme for formation of adenosine triphosphate (ATP) and cyclic adenosine monophosphate. In one trial there was a dramatic decrease in frequency and severity of asthma attacks when Vitamin B6 supplementation was given. [12] Some asthmatics react to food additives, such as sulfites, tartrazine and sodium benzoate. In a study by Anibarro B et al., it was concluded that Vitamin B12, taken in large doses, can decrease likelihood that asthmatics react to foods with sulfites. [13]

Omega-3 fatty acids

Animal and clinical experiments have confirmed the anti-inflammatory activity of omega-3 fatty acids [the essential fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] and point to the potential for therapeutic use in the management of inflammatory and autoimmune diseases. Their richest source is fish oil. They are beneficial in asthma because they block production of leukotrienes and hence blocking the inflammatory cascade. Double-blind research shows that fish oil reduces reactions to allergens that can trigger attacks in some asthmatics. [14]

Herbal remedies

Ginkgo has been shown to have potential use in the treatment of asthma. Studies using extracted ginkgolides have shown reduction of asthma symptoms. [15] Another herbal remedy suggested for asthma is Indian lobelia (Typhora indica). Chewing its leaves have shown relief of asthma symptoms in one placebo controlled trial. [16] Alkaloid lobeline, extracted from Indian tobacco (Lobelia inflata), is an effective expectorant as well as bronchodilator with suggested benefits in asthma. Inhaled forskolin powder has been shown to decrease bronchial spasms in asthmatics. [17] Forskolin is the active ingredient of herb Coleus forskolii.

Betaine hydrochloride

Betaine hydrochloride is a source of hydrochloric acid which can be supplemented for hypochlorhydia. Hypochlorhydia is significantly associated with childhood asthmatics and supplementation by betaine hydrochloride in combination with avoidance of known food allergens have led to clinical improvement. [18]

Quercetin

Quercetin is a flavonoid found in fruits, vegetables, leaves and grains. Experimental studies have demonstrated it to be an effective bronchodilator by reducing release of histamine and have also shown significant anti-inflammatory activity. [19]

 CONCLUSION

References