Vitamin C and Asthma |
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Vitamin
C,
Asthma
and Dose-dependency
Vitamin C studies, on it’s effectiveness against asthmatic conditions, date back to the mid-1930’s.
A study undertaken by GA Goldsmith and colleagues, measured the blood ascorbic levels of twenty-nine asthmatics and found twenty-two to be below .6 mg % (0.7 % is considered the minimal normal level) and in two of their patients, with hay fever only, ascorbic acid was practically absent from their blood (0.07 and 0.08 mg %).
On a regime of 300 milligrams of ascorbic acid daily for 1 week, 200 milligrams daily for the second week, and 50 milligrams daily thereafter, six of seven of their asthmatics were unable to maintain blood levels of 1.0 mg %, which was easily achieved by a healthy control group.
They interpreted this as a sign that asthmatics had a
greater requirement for ascorbic acid. In some of their patients they found a
relationship between the low blood levels of ascorbic acid and the frequency and
severity of asthmatic attacks. 38,39
Researcher NB Silbert reviewed nineteen papers on
vitamin C and asthmatic conditions. Thirteen reported benefit, some to
complete remission of symptoms, while 6 reported little or no benefit.
Silbert suggested that some of these failures may have been due to inadequate
dosages of ascorbic acid.40
S Ruskin reported that sodium ascorbate (a precursor to ascorbic acid) was more effective in asthma and allergy patients than ascorbic acid in doses of 1,200 to 1,500 mg per day. In a further study he and colleagues showed that, of sixty hay fever patients given 1,000 to 2,250 mg of ascorbic acid daily along with a few milligrams of vitamin B3, 50 percent taking the lower dose, and 75 percent taking the higher dose, showed improvements.41,42
W Dawson and colleagues presented a series of papers on the antagonism of ascorbate on bronchospasm and on the action of ascorbate on smooth muscle. They showed that spasmogen induced broncho-constriction could be prevented by ascorbic acid.
More importantly, they showed that this action is dose-dependent; at low levels it may potentiate the effect of spasmogens, such as histamine, and at higher concentrations it inhibits their spastic effects. This dose-related smooth muscle phenomenon may explain some of the conflicting clinical results of the past six decades.43,44
Bieolory L and Gandi R reported in 1994 that since 1973 there have been 11 clinical studies of vitamin C supplementation in asthma.
They analyzed the studies according to their design, inclusion and exclusion criteria, population studied, variables or factors tested, method of intervention or treatment with vitamin C, and results and conclusions.
From their review they found seven of studies showed significant improvements in respiratory measures and asthma symptoms, including positive effects on pulmonary function tests, bronchoprovocation challenges with methacholine or histamine or allergens, improvement in white blood cell function and motility, and a decrease in respiratory infections.
They also found vitamin C appeared to be dose-dependent, and suggested the data indicated supplementing the diet with 1 to 2 grams of vitamin C daily. This dosage recommendation appears extremely wise based on the increasing exposure to inhaled oxidants along with the growing appreciation on the antioxidant function of vitamin C in the respiratory system. High-dose vitamin C therapy may also help asthmatics by lowering histamine levels.45
Since 1994 there have been a number of other studies supporting the preventative role of vitamin C in asthma.
CS Johnston and associates examined the antihistamine effect of vitamin C administration and its effect on white blood cell (neutrophil) function in healthy men and women.
In the chronic study, 10 subjects ingested a placebo during weeks 1,2,5, and 6, and 2 grams per day of vitamin C during weeks 3 and 4. Fasting blood samples were collected after the initial 2-week period (baseline) and at the end of weeks 4 and 6.
Blood vitamin C levels rose significantly following vitamin C administration, while blood histamine levels fell by 38 percent during the weeks vitamin C was given.
The ability of neutrophils to move in response to an infection (chemotaxis) increased by 19 percent during vitamin C administration and fell 30 percent after vitamin C withdrawal.
However, these changes were linked to histamine concentrations. Chemotaxis was greatest when histamine levels were the lowest. In the part of the study looking at the acute effects of vitamin C, blood histamine concentrations and chemotaxis did not change 4 hours following a single dose of vitamin C.
This result suggests that vitamin C lowers blood histamine only if taken over a period of time.46,47
Vitamin
C, Oxidation and Asthma
In 1995, GE Hatch of the Pulmonary Toxicology Branch, Health Effects Research Laboratory, U.S. Environmental Protection Agency, reported that physician-diagnosed asthma increased 437% in the U.S..
He reviewed the literature to evaluate the possible influence of dietary antioxidants, especially vitamin C on the increasing prevalence of asthma.
Symptoms of ongoing asthma in adults appear to be increased by exposure to environmental oxidants and decreased by vitamin C supplementation. He reported that vitamin C intake in the general population appears to correlate with asthma, suggesting a diet low in vitamin C is a risk factor for asthma.
There is evidence that the oxidants produced by overactive inflammatory cells contribute to ongoing asthma. The author suggests that supplementation with 1,000 to 2,000 milligrams of vitamin C may be important in protecting against inhaled oxidants and the oxidants produced by these inflammatory cells.48
Another study, in 1995, by J Britton, et al., at the University of Nottingham, and supported by the British Lung Foundation and the National Asthma Campaign, found support for the hypothesis that lung function in the general population is related to antioxidant vitamins C & E intakes, and that these vitamins may have a role in protecting against the development of chronic obstructive pulmonary disease (COPD).49
Protection
for Exercise Induced Asthma
In 1997, HA Cohen reported that out of 20 patients, with exercise-induced asthma, given 2,000 mg of vitamin C, a protective effect (lung function) was found in nine and lessened severity of attack in 2 others. Researchers hypothesised that vitamin C may prevent lung damage and inflammation from exposure to free radicals, which are produced more abundantly during exercise.50
Low
Vitamin C and Manganese Increases Risk of Asthma by 500%
In 1997, a dietary survey of asthmatics, allergic rhinitis sufferers and a control group indicated those with the lowest intakes of vitamin C and manganese were associated with more than a five-fold increased risk of asthma. 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.51
The outcome measures were: forced expiratory volume in one second (FEV1); forced vital capacity (FVC); and non-fasting plasma vitamin C.
Plasma vitamin C was positively correlated with both FEV1 and FVC in men, following adjustment for age and height; the association in women was weaker and not statistically significant. In men, differences in FEV1 and FVC for a 50micromol/l difference in vitamin C were 0.22 litres and 0.23 litres respectively.
12.1% of men with vitamin C levels less than or equal to 30 micromol/L had an FEV1 of less than 2 litres, whereas only 4.6% of men with vitamin C levels greater than or equal to 60 micromol/L had an FEV1 less than 2 litres.
The researchers concluded that these results are consistent with data from other studies of vitamin C and respiratory function and suggest that vitamin C is protective for lung function through the whole normal range of dietary intake and lung function.52
Vitamin
C and Upper Respiratory Infections
H Hemila of the Department of Public Health, University of Helsinki, Finland writes that various studies have shown an increased risk of respiratory infections in people performing heavy physical exercise.
Since vitamin C has been shown to affect some components of the immune system, it may have effects upon the increased incidence of respiratory infections caused by heavy physical stress.
Results were analyzed from 3 placebo-controlled studies examining the effect of vitamin C supplementation on the incidence of common cold in people under acute physical stress.
In one study, the participants were school children at skiing camp in the Swiss Alps; in the second they were military troops training in Northern Canada; in the third they were participants in a 90 km race.
A significant reduction in common cold incidence in the vitamin C supplemented (0.6—1.0 g/day) group was found in all 3 studies. The pooled rate ratio (RR) of common cold infections was 0.5 for the vitamin C groups.
These results suggest that vitamin C supplementation is beneficial for individuals performing heavy exercise and who suffer with frequent upper respiratory infections.53
Vitamin C and B3 Deficiencies Found in Bronchial Asthma
EM Rozanov and associates studied 124 patients with bronchial asthma. The majority of patients were found to be deficient in vitamins C and PP during exacerbation of the disease, especially in the winter-spring period of the year.
83% were found to be deficient in nicotinic acid (B3), while 96.8% were deficient in vitamin C. Long-term supplementation with vitamin C and B3 intensified the therapy effectiveness and reduced the terms of the inpatient treatment.54