The effect of vitamin C on upper respiratory infections in adolescent swimmers: a randomized trial

Vitamin C reduces the severity of common colds: a meta-analysis

BACKGROUND

Randomized trials have shown that vitamin C shortens the duration of common colds. Some trials reported greater effects on severe cold symptoms compared with mild symptoms. This review systematically compares the effects of vitamin C on severe and mild common cold symptoms.

METHODS

We included all placebo-controlled trials of orally administered vitamin C in doses of at least 1 g/day for the common cold for people in good health at baseline. The analysis was restricted to trials which reported both the total duration of the common cold, and the severity of the common cold measured using severity scales, the duration of more severe stages of the cold, or proxies for severe colds such as days indoors. Findings were pooled using the inverse variance, fixed effect options of the metacont function of the R package meta to calculate the ratio of means estimate.

RESULTS

Fifteen comparisons from 10 trials which reported both mild and severe symptoms were identified. All trials were randomized and double-blind. Compared to placebo, vitamin C significantly decreased the severity of the common cold by 15% (95% CI 9-21%). The direct comparison of the effect of vitamin C on mild and severe symptoms was limited to five comparisons which found that vitamin C had a significant benefit on the duration of severe symptoms. In this subset, there was a significant difference in the size of the effect of vitamin C on the overall duration of colds versus the duration of severe colds (P = 0.002), and vitamin C had no significant effect on the duration of mild symptoms.

CONCLUSIONS

The common cold is the leading cause of acute morbidity and a major cause of absenteeism from work and school. However, absenteeism is dependent on the severity of symptoms. The finding that vitamin C may have a greater effect on more severe measures of the common cold is therefore important. Further research on the therapeutic effects of vitamin C on the common cold should measure outcomes of differing levels of severity.

Enhancement of Antiviral T-Cell Responses by Vitamin C Suggests New Strategies to Improve Manufacturing of Virus-Specific T Cells for Adoptive Immunotherapy

Allogeneic and autologous transplantation of hematopoietic stem cells (HSCT) are being routinely used to treat patients with leukemia and lymphoma. Due to the required immunosuppression after stem cell transplantation, infection and reactivation by viruses are life-threatening complications. In recent years, adoptive transfer using virus-specific T cells (VSTs) has emerged as alternative to conventional therapies. Since vitamins are described to influence the immune system and its cellular components, the aim of this study was to examine whether vitamins modulate VST function and thereby enable an improvement of therapy. For that, we investigated the impact of vitamin C and D on the functionality of cytomegalovirus (CMV)-specific T cells isolated from CMV-seropositive healthy donors. We were able to show that vitamin C increases the expansion and activation state of CMV-specific T cells, and an increased influence of vitamin C was observed on cells isolated from male donors and donors above 40 years of age. A higher frequency of the terminally differentiated effector memory CD8+ T-cell population in these donors indicates a connection between these cells and the enhanced response to vitamin C. Thus, here we provide insights into the impact of vitamin C on cytotoxic T cells as well as possible additional selection criteria and strategies to improve VST functionality.

The Role of Micronutrients in Support of the Immune Response against Viral Infections

Viral infections are a leading cause of morbidity and mortality worldwide, and the importance of public health practices including handwashing and vaccinations in reducing their spread is well established. Furthermore, it is well known that proper nutrition can help support optimal immune function, reducing the impact of infections. Several vitamins and trace elements play an important role in supporting the cells of the immune system, thus increasing the resistance to infections. Other nutrients, such as omega-3 fatty acids, help sustain optimal function of the immune system. The main aim of this manuscript is to discuss of the potential role of micronutrients supplementation in supporting immunity, particularly against respiratory virus infections. Literature analysis showed that in vitro and observational studies, and clinical trials, highlight the important role of vitamins A, C, and D, omega-3 fatty acids, and zinc in modulating the immune response. Supplementation with vitamins, omega 3 fatty acids and zinc appears to be a safe and low-cost way to support optimal function of the immune system, with the potential to reduce the risk and consequences of infection, including viral respiratory infections. Supplementation should be in addition to a healthy diet and fall within recommended upper safety limits set by scientific expert bodies. Therefore, implementing an optimal nutrition, with micronutrients and omega-3 fatty acids supplementation, might be a cost-effective, underestimated strategy to help reduce the burden of infectious diseases worldwide, including coronavirus disease 2019 (COVID-19).

Impact of sports participation on incidence of bone traumatic fractures and health-care costs among adolescents: ABCD - Growth Study

Objective: To analyze the risk of bone traumatic fractures according to the engagement in sports, as well as to identify the potential impact of sports participation and traumatic fractures on health-care costs among adolescents. Methods: This is a longitudinal 12-month study of 285 adolescents of both sexes in Brazil. We assessed the occurrence of traumatic fractures and health-care services (hospitalizations, medicine use, medical consultations, and exams) by phone contact every month for 12 months. Adolescents were divided into four groups according to sport characteristics: non-sport (n = 104), non-impact sport (swimming [n = 34]), martial arts (n = 49 [judo, karate, kung-Fu]) and impact sports (n = 98 [track-and-field, basketball, gymnastics, tennis, and baseball]). Results: The incidence of new fractures was 2.1%. The overall costs accounted during the 12-month follow-up were U$ 3,259.66. Swimmers (US$ 13.86) had higher health-care costs than non-sport (US$ 1.82), martial arts (US$ 2.23), and impact sports (US$ 2.32). Conclusion: swimming seems to be related to higher health-care costs among adolescents.

A Review of Micronutrients and the Immune System-Working in Harmony to Reduce the Risk of Infection

Immune support by micronutrients is historically based on vitamin C deficiency and supplementation in scurvy in early times. It has since been established that the complex, integrated immune system needs multiple specific micronutrients, including vitamins A, D, C, E, B6, and B12, folate, zinc, iron, copper, and selenium, which play vital, often synergistic roles at every stage of the immune response. Adequate amounts are essential to ensure the proper function of physical barriers and immune cells; however, daily micronutrient intakes necessary to support immune function may be higher than current recommended dietary allowances. Certain populations have inadequate dietary micronutrient intakes, and situations with increased requirements (e.g., infection, stress, and pollution) further decrease stores within the body. Several micronutrients may be deficient, and even marginal deficiency may impair immunity. Although contradictory data exist, available evidence indicates that supplementation with multiple micronutrients with immune-supporting roles may modulate immune function and reduce the risk of infection. Micronutrients with the strongest evidence for immune support are vitamins C and D and zinc. Better design of human clinical studies addressing dosage and combinations of micronutrients in different populations are required to substantiate the benefits of micronutrient supplementation against infection.

Vitamin C Can Shorten the Length of Stay in the ICU: A Meta-Analysis

A number of controlled trials have previously found that in some contexts, vitamin C can have beneficial effects on blood pressure, infections, bronchoconstriction, atrial fibrillation, and acute kidney injury. However, the practical significance of these effects is not clear. The purpose of this meta-analysis was to evaluate whether vitamin C has an effect on the practical outcomes: length of stay in the intensive care unit (ICU) and duration of mechanical ventilation. We identified 18 relevant controlled trials with a total of 2004 patients, 13 of which investigated patients undergoing elective cardiac surgery. We carried out the meta-analysis using the inverse variance, fixed effect options, using the ratio of means scale. In 12 trials with 1766 patients, vitamin C reduced the length of ICU stay on average by 7.8% (95% CI: 4.2% to 11.2%; p = 0.00003). In six trials, orally administered vitamin C in doses of 1⁻3 g/day (weighted mean 2.0 g/day) reduced the length of ICU stay by 8.6% (p = 0.003). In three trials in which patients needed mechanical ventilation for over 24 hours, vitamin C shortened the duration of mechanical ventilation by 18.2% (95% CI 7.7% to 27%; p = 0.001). Given the insignificant cost of vitamin C, even an 8% reduction in ICU stay is worth exploring. The effects of vitamin C on ICU patients should be investigated in more detail.

The Effect of Olive Leaf Extract on Upper Respiratory Illness in High School Athletes: A Randomised Control Trial

Upper respiratory illness (URI) has a major impact on both training and competition in an athletic setting. High school athletes are a sub-category who have reported higher illness rates than professional and sub-elite high school athletes of the same sport. Olive leaf extract (OLE) is an over-the-counter supplement that contains polyphenols, notably oleuropein and hydroxytyrosol, that have antiviral, antibacterial, anti-inflammatory and antioxidant properties that may reduce URI rates. Thirty-two high school students who play sport for the elite team at their school were recruited to a randomised controlled trial and allocated to a daily placebo or OLE (extent equivalent to 20 g of olive leaf, containing 100 mg oleuropein) supplementation for nine weeks during their competitive season. Twice weekly measures of wellbeing, training load and respiratory illness (sporting upper respiratory illness (SUPPRESS) questionnaire) were recorded at trainings, meetings or games. There was no significant difference in illness incidence (odds ratio (OR): 1.02 (95% confidence interval (CI) 0.21–4.44)), but there was a significant 28% reduction in sick days (OR: 0.72 (95% CI 0.56–0.93) p-value = 0.02) when supplemented with OLE. The dietary intakes of the athletes were sub-optimal with regard to immune support. OLE supplementation over a season did not significantly reduce URI incidence, but did decrease duration in high school athletes, potentially aiding return to play.

Efficacy of vitamin C for the prevention and treatment of upper respiratory tract infection. A meta-analysis in children

PURPOSE

Upper respiratory tract infection (URTI) is a common infection in children, generally caused by viral respiratory infection. Vitamin C is currently proposed as prophylaxis for URTI. The purpose of this study was to assess the effectiveness of vitamin C administration in children for the prevention and reduced duration of URTI through a systematic literature review.

METHODS

Review of the literature conducted between October 2017 and January 2018 in the main medical databases (CENTRAL, Medline and Embase) and by a gray literature approach. The selection criteria were: double-blind randomized controlled trials (RCTs) comparing vitamin C use to placebo in children aged 3 months to 18 years without chronic infection. Efficacy was assessed in terms of incidence, duration and severity of symptoms of URTI. A meta-analysis was conducted where possible.

RESULTS

Eight RCTs, including 3135 children aged 3 months to 18 years, were selected. Quantitative analysis showed no difference between vitamin C administration and placebo (odds ratio = 0.75, 95% CI [0.54-1.03], p = 0.07, I² = 74%). Vitamin C administration was found to decrease the duration of URTI by 1.6 days (standardized mean differences = -0.30 [-0.53; -0.08], p = 0.009, I² = 70%). Children under 6 years of age benefit from more effective vitamin C supplementation associated with echinacea. No serious adverse events were reported.

CONCLUSIONS

Although no preventive effects were found, vitamin C intake reduced the duration of URTI. Considering the frequency of URTI, the inappropriate prescription of antibiotics, and the safe nature of vitamin C, its supplementation is justified, especially in children under 6 years of age and those who present a high frequency of URTI. There is a sound rationale for further trials with greater statistical power among children of this age.

Extra Dose of Vitamin C Based on a Daily Supplementation Shortens the Common Cold: A Meta-Analysis of 9 Randomized Controlled Trials

Aim

To investigate whether vitamin C is effective in the treatment of the common cold.

Method

After systematically searching the National Library of Medicine (PubMed), Cochrane Library, Elsevier, China National Knowledge Infrastructure (CNKI), VIP databases, and WANFANG databases, 9 randomized placebo-controlled trials were included in our meta-analysis in RevMan 5.3 software, all of which were in English.

Results

In the evaluation of vitamin C, administration of extra therapeutic doses at the onset of cold despite routine supplementation was found to help reduce its duration (mean difference (MD) = -0.56, 95% confidence interval (CI) [-1.03, -0.10], and P = 0.02), shorten the time of confinement indoors (MD = -0.41, 95% CI [-0.62, -0.19], and P = 0.0002), and relieve the symptoms associated with it, including chest pain (MD = -0.40, 95% CI [-0.77, -0.03], and P = 0.03), fever (MD = -0.45, 95% CI [-0.78, -0.11], and P = 0.009), and chills (MD = -0.36, 95% CI [-0.65, -0.07], and P = 0.01).

Conclusions

Extra doses of vitamin C could benefit some patients who contract the common cold despite taking daily vitamin C supplements.

Vitamin C and Infections

In the early literature, vitamin C deficiency was associated with pneumonia. After its identification, a number of studies investigated the effects of vitamin C on diverse infections. A total of 148 animal studies indicated that vitamin C may alleviate or prevent infections caused by bacteria, viruses, and protozoa. The most extensively studied human infection is the common cold. Vitamin C administration does not decrease the average incidence of colds in the general population, yet it halved the number of colds in physically active people. Regularly administered vitamin C has shortened the duration of colds, indicating a biological effect. However, the role of vitamin C in common cold treatment is unclear. Two controlled trials found a statistically significant dose-response, for the duration of common cold symptoms, with up to 6-8 g/day of vitamin C. Thus, the negative findings of some therapeutic common cold studies might be explained by the low doses of 3-4 g/day of vitamin C. Three controlled trials found that vitamin C prevented pneumonia. Two controlled trials found a treatment benefit of vitamin C for pneumonia patients. One controlled trial reported treatment benefits for tetanus patients. The effects of vitamin C against infections should be investigated further.

Intake of Dietary Fibre and Its Sources Related to Adolescents' Age and Gender, but Not to Their Weight

AIM

The aim of this observational study was to investigate the intake of dietary fibre and its sources among Polish adolescents according to prevalence of overweight after adjustment for age and gender.

METHODS

The study sample consisted of 1,565 students, including 48% boys and 52% girls aged 13-18 with normal weight, overweight and obesity. Dietary information was reported using the Block Screening Questionnaire for Fruit/Vegetable/Fibre Intake. The nutritional status was assessed on the basis of body mass and height measurements. The statistical analysis used one-factor logistic regression, multiple linear regression, trend estimation and a comparison of mean values.

RESULTS

Adolescents consuming white bread and rolls with a frequency ≥4 times/week had OR=0.74 (95% CI 0.56-0.97) for overweight and obesity compared to adolescents with less frequent consumption. For other fibre sources and overall dietary fibre no significant differences were noted in consumption frequency between adolescents with normal weight and overweight/obesity. Overall, boys were more often overweight and obese than girls. Girls had a higher intake of dietary fibre, fruit, fresh vegetables, dark bread and rolls, and lower intake of potatoes, beans and white bread and rolls than boys. Older age was associated with a decrease in the consumption of fruit juices, fruit, potatoes, white bread and rolls, and dietary fibre in girls and a decrease in fruit and fresh vegetable consumption in boys.

CONCLUSION

The intake of dietary fibre was not associated with the prevalence of overweight. As to the fibre sources, only a higher consumption of white bread and rolls decreased the chance of the occurrence of adolescent overweight. The consumption of dietary fibre and its sources was related to the age and gender of adolescents.

Exercise versus no exercise for the occurrence, severity and duration of acute respiratory infections

BACKGROUND

Acute respiratory infections (ARIs) last for less than 30 days and are the most common acute diseases affecting people worldwide. Exercise has been shown to improve health generally and may be effective in reducing the occurrence, severity and duration of acute respiratory infections.

OBJECTIVES

To evaluate the effectiveness of exercise for altering the occurrence, severity or duration of acute respiratory infections.

SEARCH METHODS

We searched CENTRAL (2014, Issue 6), MEDLINE (1948 to July week 1, 2014), EMBASE (2010 to July 2014), CINAHL (1981 to July 2014), LILACS (1982 to July 2014), SPORTDiscus (1985 to July 2014), PEDro (searched on 11 July 2014), OTseeker (searched on 11 July 2014), the WHO International Clinical Trials Registry Platform (ICTRP) and ClinicalTrials.gov (searched on 11 July 2014).

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs of exercise for ARIs in the general population.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data from the included trials using a standard form. We contacted trial authors to request missing data. One review author entered data and a second review author checked this. There were sufficient differences in the populations trialled and in the nature of the interventions to use the random-effects model (which makes fewer assumptions than the fixed-effect model) in the analysis.

MAIN RESULTS

We included 11 trials involving 904 adults, published between 1990 and 2014. Eight studies were conducted in the USA, and one each in Canada, Spain and Turkey. Sample sizes ranged from 20 to 154 participants aged between 18 and 85 years old. The proportion of female participants varied between 52% and 100%. The duration of follow-up in the studies varied from seven days to 12 months. The exercise type most prescribed for the intervention was aerobic (walking in 70% of the studies, or bicycle riding or treadmill) at least five times a week. Duration was 30 to 45 minutes at moderate intensity. Participants were supervised in 90% of the studies.For four of the primary outcomes the results did not differ significantly and all were low-quality evidence (number of ARI episodes per person per year, rate ratio 0.91 (95% confidence interval (CI) 0.59 to 1.42); proportion of participants who experienced at least one ARI over the study period, risk ratio 0.76 (95% CI 0.57 to 1.01); severity of ARI symptoms, mean difference (MD) -110 (95% CI -324 to 104); and number of symptom days in the follow-up period, MD -2.1 days (95% CI -4.4 to 0.3)). However, one primary outcome, the number of symptom days per episode of illness, was reduced in those participants who exercised (MD -1.1 day, 95% CI -1.7 to -0.5, moderate-quality evidence).We found no significant differences for the secondary outcomes (laboratory parameters (blood lymphocytes, salivary secretory immunoglobulin and neutrophils); quality of life outcomes; cost-effectiveness and exercise-related injuries).There was good adherence to the intervention with no difference between the exercise and non-exercise groups.We rated the quality of evidence for the primary outcomes as low for most outcomes using the GRADE criteria: allocation concealment was not reported and there was a lack of blinding; in addition, there was imprecision (the CI is very wide because of a small number of participants) and inconsistency, which may be due to differences in study design.

AUTHORS' CONCLUSIONS

We cannot determine whether exercise is effective at altering the occurrence, severity or duration of acute respiratory infections. One analysis of four trials suggests that the number of days of illness per episode of infection might be reduced by exercise. The small size of the studies, risk of bias and heterogeneous populations trialled all contribute to the uncertainty. Larger studies, with less risk of bias from patient selection, blinding of outcomes assessors, reporting of all outcomes measured and with registration of study protocols, are required to settle the question.

The effect of vitamin C on bronchoconstriction and respiratory symptoms caused by exercise: a review and statistical analysis

Physical activity increases oxidative stress and therefore the antioxidant effects of vitamin C administration might become evident in people undertaking vigorous exercise. Vitamin C is involved in the metabolism of histamine, prostaglandins, and cysteinyl leukotrienes, all of which appear to be mediators in the pathogenesis of exercise-induced bronchoconstriction (EIB). Three studies assessing the effect of vitamin C on patients with EIB were subjected to a meta-analysis and revealed that vitamin C reduced postexercise FEV1 decline by 48% (95% CI: 33% to 64%). The correlation between postexercise FEV1 decline and respiratory symptoms associated with exercise is poor, yet symptoms are the most relevant to patients. Five other studies examined subjects who were under short-term, heavy physical stress and revealed that vitamin C reduced the incidence of respiratory symptoms by 52% (95% CI: 36% to 65%). Another trial reported that vitamin C halved the duration of the respiratory symptoms in male adolescent competitive swimmers. Although FEV1 is the standard outcome for assessing EIB, other outcomes may provide additional information. In particular, the mean postexercise decline of FEF50 is twice the decline of FEV1. Schachter and Schlesinger (1982) reported the effect of vitamin C on exercise-induced FEF60 levels in 12 patients suffering from EIB and their data are analyzed in this paper. The postexercise FEF60 decline was greater than 60% for five participants and such a dramatic decline indicates that the absolute postexercise FEF60 level becomes an important outcome in its own right. Vitamin C increased postexercise FEF60 levels by 50% to 150% in those five participants, but had no significant effect in the other seven participants. Thus, future research on the effects of vitamin C on EIB should not be restricted to measuring only FEV1. Vitamin C is inexpensive and safe, and further study on those people who have EIB or respiratory symptoms associated with exercise is warranted.

Probiotics and vitamin C for the prevention of respiratory tract infections in children attending preschool: a randomised controlled pilot study

Background:

This pilot study investigates the efficacy of a probiotic consortium (Lab4) in combination with vitamin C on the prevention of respiratory tract infections in children attending preschool facilities.

Subjects/methods:

In a double-blind, randomised, placebo-controlled pilot study with children aged 3–6 years, 57 received 1.25 × 10¹⁰ colony-forming units of Lactobacillus acidophilus CUL21 (NCIMB 30156), Lactobacillus acidophilus CUL60 (NCIMB 30157), Bifidobacterium bifidum CUL20 (NCIMB 30153) and Bifidobacterium animalis subsp. lactis CUL34 (NCIMB 30172) plus 50 mg vitamin C or a placebo daily for 6 months.

Results:

Significant reductions in the incidence rate of upper respiratory tract infection (URTI; 33%, P=0.002), the number of days with URTI symptoms (mean difference: −21.0, 95% confidence interval (CI):−35.9, −6.0, P=0.006) and the incidence rate of absence from preschool (30%, P=0.007) were observed in the active group compared with the placebo. The number of days of use of antibiotics, painkillers, cough medicine or nasal sprays was lower in the active group and reached significance for use of cough medicine (mean difference: −6.6, 95% CI: −12.9, −0.3, P=0.040). No significant differences were observed in the incidence rate ratio or duration of lower respiratory tract infection or in the levels of plasma cytokines, salivary immunoglobulin A or urinary metabolites.

Conclusions:

Supplementation with a probiotic/vitamin C combination may be beneficial in the prevention and management of URTIs.

Micronutrient supply and health outcomes in children

PURPOSE OF REVIEW

Multiple micronutrient deficiencies are still common worldwide and often occur at an early age, negatively affecting both physical and cognitive development. Even though specific effects of a variety of different micronutrients have been studied extensively, it is understood that a combination of multiple micronutrients may be more beneficial in most instances, as deficiencies usually do not occur in isolation. The aim of this review was to summarize the most recent evidence of the effects of micronutrient interventions on growth, mental, and physical performance as well as morbidity in children.

RECENT FINDINGS

For growth, cognitive or motor function, and morbidity, it appears that providing sufficient amounts of micronutrients especially to the most vulnerable and deficient groups of children can make a difference, but also that the intervention has to be planned carefully. However, findings are still variable, more particularly with reference to morbidity. Two reports of increased diagnoses of infection with micronutrient supplementation are also of concern.

SUMMARY

There are still difficulties in coming to a universal conclusion about benefit in all populations, because reports vary in study design, population, and so on. Although micronutrients have a role in depleted groups, it is also important to not only consider the group of children targeted, but also the regime of administration.

Vitamin C for preventing and treating the common cold

BACKGROUND

Vitamin C (ascorbic acid) for preventing and treating the common cold has been a subject of controversy for 70 years.

OBJECTIVES

To find out whether vitamin C reduces the incidence, the duration or severity of the common cold when used either as a continuous regular supplementation every day or as a therapy at the onset of cold symptoms.

SEARCH METHODS

We searched CENTRAL 2012, Issue 11, MEDLINE (1966 to November week 3, 2012), EMBASE (1990 to November 2012), CINAHL (January 2010 to November 2012), LILACS (January 2010 to November 2012) and Web of Science (January 2010 to November 2012). We also searched the U.S. National Institutes of Health trials register and WHO ICTRP on 29 November 2012.

SELECTION CRITERIA

We excluded trials which used less than 0.2 g per day of vitamin C and trials without a placebo comparison. We restricted our review to placebo-controlled trials.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data. We assessed 'incidence' of colds during regular supplementation as the proportion of participants experiencing one or more colds during the study period. 'Duration' was the mean number of days of illness of cold episodes.

MAIN RESULTS

Twenty-nine trial comparisons involving 11,306 participants contributed to the meta-analysis on the risk ratio (RR) of developing a cold whilst taking vitamin C regularly over the study period. In the general community trials involving 10,708 participants, the pooled RR was 0.97 (95% confidence interval (CI) 0.94 to 1.00). Five trials involving a total of 598 marathon runners, skiers and soldiers on subarctic exercises yielded a pooled RR of 0.48 (95% CI 0.35 to 0.64).Thirty-one comparisons examined the effect of regular vitamin C on common cold duration (9745 episodes). In adults the duration of colds was reduced by 8% (3% to 12%) and in children by 14% (7% to 21%). In children, 1 to 2 g/day vitamin C shortened colds by 18%. The severity of colds was also reduced by regular vitamin C administration.Seven comparisons examined the effect of therapeutic vitamin C (3249 episodes). No consistent effect of vitamin C was seen on the duration or severity of colds in the therapeutic trials.The majority of included trials were randomised, double-blind trials. The exclusion of trials that were either not randomised or not double-blind had no effect on the conclusions.

AUTHORS' CONCLUSIONS

The failure of vitamin C supplementation to reduce the incidence of colds in the general population indicates that routine vitamin C supplementation is not justified, yet vitamin C may be useful for people exposed to brief periods of severe physical exercise. Regular supplementation trials have shown that vitamin C reduces the duration of colds, but this was not replicated in the few therapeutic trials that have been carried out. Nevertheless, given the consistent effect of vitamin C on the duration and severity of colds in the regular supplementation studies, and the low cost and safety, it may be worthwhile for common cold patients to test on an individual basis whether therapeutic vitamin C is beneficial for them. Further therapeutic RCTs are warranted.

Vitamin C and asthma in children: modification of the effect by age, exposure to dampness and the severity of asthma

BACKGROUND

We previously found a significant benefit of vitamin C supplementation in asthmatic children.

PURPOSE

To test whether the effect of vitamin C on asthma is heterogeneous over the participant population.

METHODS

Egyptian asthmatic children between 7 and 10 years of age (n = 60) were included in the cross-over trial. They were administered 0.2 grams per day of vitamin C and placebo for separate 6-week periods. The variation in the vitamin C effect on two clinically relevant outcomes was analyzed: the childhood asthma control test (C-ACT), which measures the severity of asthma symptoms (the scale ranges from 0 to 27 points, < 20 points indicating unsatisfactory asthma control), and FEV1. We used linear modeling to examine the variation of the vitamin C effect in the subgroups.

RESULTS

The effect of vitamin C on the C-ACT was significantly modified by age and baseline C-ACT levels. In the children aged 7.0-8.2 years with a baseline C-ACT of 18 to 19 points, vitamin C increased the C-ACT score by 4.2 points (95% CI: 3.3-5.3); whereas in the children aged 8.3-10 years who had a baseline C-ACT of 14 to 15 points, vitamin C increased the C-ACT score by only 1.3 points (95% CI: 0.1-2.5). The effect of vitamin C on the FEV1 levels was significantly modified by age and exposure to dampness. In the children aged 7.0-8.2 years with no exposure to dampness, vitamin C increased the FEV1 level by 37% (95% CI: 34-40%), whereas in the children aged 8.3-10 years with exposure to dampness or mold in their bedroom more than one year prior to the study, vitamin C increased the FEV1 level by only 21% (95% CI: 18-25%).

CONCLUSIONS

We found strong evidence that the effect of vitamin C on asthmatic children is heterogeneous. Further research is needed to confirm our findings and identify the groups of children who would receive the greatest benefit from vitamin C supplementation.