Vitamins and Supplements
Vitamins and supplements are often used by integrative medicine practitioners to treat asthma. This approach differs from dietary interventions in so far as nutritional deficiencies are thought not to be correctable alone through food. Strong epidemiologic evidence demonstrates an association between poor dietary intake, low measured levels of specific nutrients, and asthma with noted deficiencies in:
Antioxidants and cofactors (Vitamins A, C, E; zinc, selenium and copper)
Vitamins and Minerals (magnesium, B6, and B12)
Omega-3 fatty acids
Despite these data, specific supplementation of nutrients has yielded mixed results at best. Nonetheless, supplementation with vitamins, minerals, and fatty acids remain a common integrative medicine strategy.
Vitamin C
Vitamin C is one of the key antioxidant vitamins that is abundant in the extracellular fluid lining the lung. Low vitamin C intake is associated with pulmonary dysfunction (Schwartz 1994).
Both adults (Olusi 1979) and children (Aderele 1985) with asthma have been found to have lower concentrations of vitamin C when compared to normal subjects.
Patients with asthma may have low supplies of vitamin C or an increased demand for vitamin C in the face of an oxidant load resulting in depletion.
Exposure to cigarette smoke depletes respiratory Vitamin C levels.
Four reviews have been conducted examining treatment of asthma with Vitamin C in addition to over 71 abstracts. Significant heterogeneity exists regarding the usefulness of Vitamin C in improving outcomes.
Bielory, 1994
Examined only English language literature using MEDLINE
Concluded that the role of vitamin C in asthma was unclear and that current literature did not support its use
Hatch, et al., 1995
Seven out of 11 studies indicated that vitamin C supplementation might reverse or improve asthma symptoms
Monteleone, et al., 1997
Vitamin C provides short term protective effect on airway responsiveness
Less clear impact on other objective lung function measurements
Cochrane, 2004
Eight trials included
Insufficient evidence to recommend
Promising for exercise-induced asthma
Magnesium
Magnesium's role in decreasing bronchospasm has been investigated in both acute and chronic asthma. Magnesium deficiency is common electrolyte disorder in patients with acute severe asthma.
Maintenance of the cells' transmembrane gradient depends on the presence of magnesium, and hypomagnesemia may result in an increase in neuromuscular cell excitability.
Magnesium is a cation modulating the smooth muscle contractility of different tissues: hypomagnesemia causes their contraction and hypermagnesemia their relaxation.
Treatment of asthma with magnesium has been administered both through IV and oral routes. Intravenous magnesium is now commonly used for serious asthma symptoms (status asthmaticus).
Indicated when other treatments have failed
IV and inhaled magnesium sulfate becoming routine
Long term oral magnesium administration show mixed results (Gontijo-Amaral, 2007)
RCT of 72 children, received 300 mg/d x 2 months
Supplementation helped to reduce bronchial reactivity to methacholine, diminish allergen-induced skin responses and provided better symptom control in pediatric patients with moderate persistent asthma treated with inhaled fluticasone
No change in FVC, FEV1, the forced expiratory flow at 25-75 and FEV1/FVC ratio
Shown to decrease symptoms in adults, but not to improve pulmonary function
Fogarty, 2003, 2006
Two RCTs in adults comparing Vitamin C (1 g/d), magnesium (450 mg/d), or placebo
Magnesium showed no effect on the inhaled corticosteroid dose in either study
Vitamin C had modest corticosteroid sparing effects and potential to reduce exposure to side effects
Selenium
Selenium is important in maintaining glutathione pools. Glutathione peroxidase, a selenium dependent metalloenzyme, is important for reducing HPETE (hydroperoxyeicosatetraenoic acids) to HETE during activation of the arachidonic acid cascade, thereby reducing leukotriene formation and resultant bronchial inflammation.
Both low selenium and glutathione levels have been shown in asthma patients.
Only two RCTs exist examining treatment of asthma with selenium:
Hasselmark, 1993
Fourteen-week RCT in 24 patients
Evidence of clinical improvement but no effect on objective markers such as lung function
Shaheen, 2007
RCT of 197 adults receiving selenium 100 mcg daily or placebo for 24 weeks
The primary outcome was asthma-related quality of life (QoL)
Secondary outcomes included lung function, asthma symptom scores, peak flow and bronchodilator usage
48% increase in plasma selenium in the active treatment group but no change in the placebo
Quality of Life scores improved but not significantly
Selenium supplementation was not associated with any significant improvement in secondary outcomes compared with placebo
Vitamin B6
Pyridoxine (vitamin B6) has been reported to largely correct an abnormality of tryptophan metabolism present in patients with bronchial asthma and to reduce the symptoms of asthma in long-term studies.
Sur, 1993
RCT of 31 patients requiring steroids (oral or inhaled) for 9 weeks
Pyridoxine 300 mg per day (13) or placebo (18)
There was no significant difference
Collipp, 1975
RCT with 76 asthmatic children followed for five months
Pyridoxine therapy - 200 mg daily
Significant improvement in asthma symptoms and reduction in dosage of bronchodilators and cortisone
The data suggest that these children with severe bronchial asthma had a metabolic block in tryptophan metabolism, which was benefitted by long-term treatment with large doses of pyridoxine
Omega-3 Fatty Acids
The use of anti-inflammatory medication is now the standard in asthma treatment. Omega-3 fatty acids are found in fish, nuts, and seeds and have potent anti-inflammatory properties. Omega-3 fatty acids limit leukotriene synthesis by blocking arachidonic acid metabolism and reduce inflammation.
Eating cold-water oily fish (mackerel, sardines, herring, salmon, and cod) is not common in most Western diets and diets low in these essential fats are associated with inflammatory disorders such as asthma. Conversely, epidemiological studies in populations that do eat foods high in omega-3 fats have been shown to significantly reduce the risk of asthma and improve pulmonary function. (Fugh-Berman 1997).
While some positive studies exist in the literature, fish oil supplementation has not yielded unequivocal results. Although under certain circumstances, such as exercise induced asthma, treatment with omega three fatty acids is warranted. In general, these substances have proven helpful in many conditions and can safely be recommended as part of an overall nutrition approach. Typical dosing is 1-2 grams per day of combined EPA and DHA, the two active components in fish oil.
Reisman, 2006, Systematic Review of Fish Oils
10 RCTs with significant heterogeneity
No conclusions could be made
Mickleborough, 2006
RCT of fish oil supplementation on exercise-induced bronchoconstriction (EIB) in 16 adult asthmatic patients
Improved pulmonary function to below the diagnostic EIB threshold in post-exercise FEV1
Reduction of a variety of inflammatory mediators
Surette, 2008
RCT with mild-to-moderate asthma in 35 subjects
Low dose (0.75 g Gamma Linoleic Acid + 0.5 g EPA), high dose (1.13 g Gamma Linoleic + 0.75 g EPA) or placebo emulsion daily
Improved patient quality of life and decrease reliance on rescue medication