Blocking effect of vitamin C in exercise-induced asthma. The attenuation of exercise-induced bronchospasm by ascorbic acid. Ascorbic acid supplementation attenuates exercise-induced bronchoconstriction in patients with asthma. Lack of acute effects of ascorbic acid on spirometry and airway responsiveness to histamine in subjects with asthma. The effect of vitamin C on antigen-induced bronchospasm. Ascorbic acid in bronchial asthma. High dose ascorbic acid in Nigerian asthmatics. Oral magnesium and vitamin C supplements in asthma: a parallel group randomized placebo-controlled trial.
To determine if vitamin C (ascorbic acid) has a protective effect on the hyperreactive airways of patients with exercise-induced asthma (EIA).
                All the patients underwent pulmonary function tests at rest, before and 1 hour after receiving 2 g of oral ascorbic acid. They were then randomly assigned in a double-blind manner to receive 2 g of ascorbic acid or a placebo 1 hour before a 7-minute exercise session on a treadmill. Pulmonary function tests were performed after an 8-minute rest. This procedure was repeated 1 week later, with each patient receiving the alternative medication.
                A university hospital.
                Twenty patients with asthma (13 males and 7 females), with ages ranging from 7 to 28 years (mean, 13.8 years). All patients who had a decline of at least 15% in their forced expiratory volume in 1 second after a standard exercise test on a motorized treadmill received a diagnosis of EIA. MAIN-OUTCOME MEASURES: All patients were advised to stop using their regular asthma medication or bronchodilator 12 hours before the test. Pulmonary function tests were performed in the same ambient conditions on all patients.
                All patients received a diagnosis of EIA. Ascorbic acid administration did not change the results of pulmonary functions at rest after 1 hour. In 9 patients, a protective effect on exercise-induced hyperreactive airways was documented. Four of 5 patients who received ascorbic acid and documented a protective effect on EIA continued to receive ascorbic acid, 0.5 g/d, for 2 more weeks with the same protective effect.
                The efficacy of vitamin C in preventing EIA cannot be predicted. However, vitamin C may have a protective effect on airway hyperreactivity in some patients with EIA. In order to study the potential benefit of ascorbic acid in asthma we investigated its role in exercise-induced bronchospasm (EIB). Twelve asthmatic subjects were recruited on the basis of findings compatible with EIB. On two subsequent days the subjects ingested 500 mg. of ascorbic acid or a placebo. The study was performed in a double-blind randomized fashion. Partial and maximal expiratory flow volume (PEFV and MEFV) curves were used to determine pulmonary function changes. Pretreatment with ascorbic acid led to a significant attenuation of the bronchospasm seen five minutes after exercise compared to placebo, as measured by FVC (0.23 +/- 0.08 L decrease after ascorbic acid, 0.48 +/- 0.14 L decrease after placebo) and by FEV1 (0.24 +/- 0.06 decrease after ascorbic acid, 0.44 +/- 0.14 decrease after placebo) Mean +/- SE). These results suggest a mild antibronchospastic action of ascorbic acid in subjects with EIB. Previous research has shown that diet can modify the bronchoconstrictor response to exercise in asthmatic subjects.
                Determine the effect of ascorbic acid supplementation on pulmonary function and several urinary markers of airway inflammation in asthmatic subjects with exercise-induced bronchoconstriction (EIB).
                Eight asthmatic subjects with documented EIB participated in a randomized, placebo controlled double-blind crossover trial. Subjects entered the study on their usual diet and were placed on either 2 weeks of ascorbic acid supplementation (1500 mg/day) or placebo, followed by a 1-week washout period, before crossing over to the alternative diet. Pre- and post-exercise pulmonary function, asthma symptom scores, fraction of exhaled nitric oxide (FENO), and urinary leukotriene (LT) C4-E4 and 9alpha, 11beta-prostagladin (PG) F2] were assessed at the beginning of the trial (usual diet) and at the end of each treatment period. Results: The ascorbic acid diet significantly reduced (p < 0.05) the maximum fall in post-exercise FEV1 (-6.4 +/- 2.4%) compared to usual (-14.3 +/- 1.6%) and placebo diet (-12.9 +/- 2.4%). Asthma symptoms scores significantly improved (p<0.05) on the ascorbic acid diet compared to the placebo and usual diet. Post-exercise FENO, LTC4-E4 and 9alpha, 11beta-PGF2 concentration was significantly lower (p<0.05) on the ascorbic acid diet compared to the placebo and usual diet.
                Ascorbic acid supplementation provides a protective effect against exercise-induced airway narrowing in asthmatic subjects. Sixteen adult subjects with asthma in a clinical steady state were studied. On day 1, after baseline spirometry, they underwent four histamine inhalation tests with functional recovery between each test. The provocative concentration causing a 20% fall in FEV1 (PC20) was obtained after each test. On days 2, 3, and 4, after baseline spirometry, active and placebo ascorbic acid (2 gm) was administered orally, double-blind, according to a 4.3.1 two-treatment crossover study design. One hour later, spirometry was performed, and PC20 was reassessed. We found no significant changes in FEV1 and FVC after ascorbic acid as compared with placebo administration. There was no difference between PC20 on days 2, 3, and 4 and by standardizing for the four PC20 results obtained on day 1. We conclude that ascorbic acid has no acute bronchodilator effect and does not alter bronchial responsiveness to histamine in subjects with asthma. The effect of vitamin C pretreatment in preventing ragweed-induced bronchospasm was evaluated in 6 ragweed-sensitive asthmatics studied in a double-blind randomized fashion. The patients received either lactose capsules or 500 mg of ascorbic acid and were studied out of season. Antigen dose-response curves were determined prior to the administration of lactose or ascorbic acid in each individual subject and subsequently after administration of ascorbic acid or lactose. Bothe PD20FEV1 (provocation dose necessary for a 20% reduction in forced expiratory volume in 1 second) and PD35SGaw (provocation dose necessary for a 35% reduction in specific airways conductance) were determined. In none of the six patients was there a change in baseline FEV 1 (p greater than 0.70) nor the overall average baseline specific airways conductance (rho greater than 0.90). Additionally, no statistically significant difference (p greater than 0.60) was noted between log PD35SGaw vitamin C day and lactose day. Likewise, no statistically significant difference (p greater than 0.60) was evident when comparing log PD20FEV1 lactose and ascorbic acid days. Vitamin C (500 MG) HAS NO PROTECTIVE EFFECT AGAINST RAGWEED ANTIGEN-INDUCED BRONCHOSPASM. Sixteen White children with bronchial asthma were divided into two groups; one received standard anti-asthma chemoprophylaxis (SAC) and the other SAC supplemented with 1 g ascorbic acid (Redoxon) given as a single daily dose for a 6-month period. In 10 patients the effects of ascorbic acid on exercise-induced bronchoconstriction (EIB) were assessed by comparing the pre-ascorbic acid results with those obtained 2 1/2 hours after the intravenous injection of 1 g ascorbic acid. Immunological investigations performed on the two groups were assessment of polymorphonuclear leucocyte (PMNL) motility, phagocytosis and nitroblue tetrazolium reduction and measurement of secretory IgA, serum immunoglobulin and total haemolytic complement levels and levels of the components C3 and C4, alpha 1-antitrypsin, antistreptolysin O (ASO), C-reactive protein and antibodies to certain respiratory viruses. These investigations were performed before and 1, 3 and 6 months after the commencement of therapy. Radio-allergosorbent testing for sensitivity to four common allergens was carried out at the outset and after 6 months of therapy. Injection of ascorbic acid had no detectable effects on the degree of EIB. Slight but not significant immunological changes were observed in the SAC group over the 6-month study period. However, in the SAC plus ascorbic acid group significantly improved PMNL motility and decreased ASO levels and reduced (although not to a significant extent) IgE levels and titres of antibodies to the respiratory viruses were observed. Forty-one asthmatic patients in remission were randomly allocated to two treatment groups in a double-blind trial. One group took 1 g, of ascorbic acid as one effervescent tablet once daily and the second group took a matching placebo. The asthmatics were selected from those attending the Asthma Clinic. One criterion for selection was the increase in exacerbation during the rainy season. These exacerbations were precipitated by respiratory infection. After 14 weeks, an assessment of the severity and rate of attacks showed that those on ascorbic acid suffered less severe and less frequent attacks of asthma during the study period. Plasma ascorbic acid astimations showed a significant rise in the level in those taking ascorbic acid over those on placebo. (P < 0.01). Cessation of ascorbic acid in the group taking it increased attack rates. It is concluded that high dose ascorbic acid is probably a good prophylaxis in some bronchial asthmatics. Epidemiological studies suggest that higher intakes of dietary vitamin C and magnesium may be associated with a reduced risk of asthma.
                To determine whether vitamin C or magnesium supplements improve the clinical control of asthma in primary care patients.
                A randomized, placebo-controlled, double-blind parallel group trial of 16 weeks supplementation with 1 g/day vitamin C, 450 mg/day magnesium chelate or matched placebo. Three hundred patients aged 18-60 years with physician-diagnosed asthma, controlled with at least one dose of an inhaled corticosteroid daily, were recruited from 24 primary care practices in Nottingham, UK. The main outcome measures were change in forced expiratory volume in 1 s, forced vital capacity, airway responsiveness to methacholine, mean morning and evening peak flow, symptom scores and bronchodilator use, both individually and as a combined summary statistic.
                There was no evidence of any beneficial effect of either supplement on any outcome measure of asthma control in the primary intention-to-treat analysis, or in an analysis restricted to participants who completed the study.
                Regular dietary supplementation with vitamin C or magnesium adds no clinical benefit to current standard therapy of asthma in primary care patients.
At present, evidence from randomised-controlled trials is insufficient to recommend a specific role for vitamin C in the treatment of asthma. Further methodologically strong and large-scale randomised controlled trials are needed in order to address the question of the effectiveness of vitamin C in asthma.