Plasma-Saturating intakes of vitamin C confer maximal antioxidant protection to plasma

The effects of vitamin C on respiratory, allergic and immunological diseases: an experimental and clinical-based review

Vitamin C is used in modern medicine supplements for treatment of various disorders associated with oxidative stress, inflammation and immune dysregulation. In this review article, experimental and clinical results regarding the effects of vitamin C on respiratory immunologic, and allergic diseases are reviewed. Various databases and appropriate keywords are used to search the effect of vitamin C on respiratory diseases until the end of May 2022. Books, theses and articles were included. These studies assessed the effects of vitamin C on respiratory disorders including asthma, chronic obstructive pulmonary disease (COPD), lung infection and lung cancer. Vitamin C showed relaxant effect on tracheal smooth muscle via various mechanisms. The preventive effects of vitamin C were mediated by antioxidant, immunomodulatory and anti-inflammatory mechanisms in the experimental animal models of different respiratory diseases. Some clinical studies also indicated the effect of vitamin C on lung cancer and lung infections. Therefore, vitamin C could be used a preventive and/or relieving therapy in respiratory diseases.

The Role of Vitamin C in Human Immunity and Its Treatment Potential Against COVID-19: A Review Article

The outbreak of the COVID-19 pandemic has left clinicians around the world searching for viable prevention and treatment options to use against the virus. The important physiologic properties of vitamin C have been well documented regarding its use by immune cells and its role as an antioxidant. It has previously shown potential as a prophylactic and treatment option for other respiratory viruses, and because of this, there has been intrigue into whether these positive outcomes translate into a cost-effective prevention and treatment option for COVID-19. To this point, there have only been a few clinical trials performed to assess the validity of this notion, with very few showing definitive positive outcomes when vitamin C has been incorporated into prophylactic or treatment protocols to use against coronavirus. When being used to specifically treat the severe complications that arise from COVID-19, vitamin C is a reliable option to treat COVID-19-induced sepsis but not pneumonia or acute respiratory distress syndrome (ARDS). As a treatment option, high-dose therapy has shown flashes of promise in a few studies although investigators in these studies often subject the testing group to multimodal therapies that include vitamin C as opposed to just vitamin C alone. Given the role that vitamin C has shown to uphold regarding the human immune response, it is currently advised for all individuals to maintain a normal physiologic range of plasma vitamin C through diet or supplements for adequate prophylactic protection against the virus. More research with definitive outcomes will be needed before it is recommended to provide high-dose vitamin C therapy to prevent or treat COVID-19.

Vitamin C and its therapeutic potential in the management of COVID19

COVID19 has emerged as one of the worst pandemics in the history of mankind. Several vaccines have been approved by different government agencies worldwide, but data on their efficacy and safety are limited, and distribution remains a massive challenge. As per WHO, personal immunity is vital for protection against COVID19. Earlier, Vitamin C-mediated pathways have been shown to play critical role in boosting immunity attributed to its antioxidant properties. Recently, the involvement of such pathways in protection against COVID19 has been suggested. The controlled doses of Vitamin C administered through intravenous (IV) injections are being studied for determining its role in the prognosis of COVID19. In this article, we have discussed the potential role of Vitamin C in the management in COVID19 patients and presented recent clinical trials data. Additionally, we have elaborated the possibility of administering Vitamin C through inhalers in order to achieve local high concentration and the challenges of such approach.

High-Dose Vitamin C in Advanced-Stage Cancer Patients

High-dose intravenously administered vitamin C (IVC) is widely used in cancer patients by complementary and alternative medicine practitioners. The most frequent indications for IVC therapy result from the belief in its effectiveness as a potent anti-cancer agent which additionally enhances chemosensitivity of cancer cells and reduces chemotherapy-related toxicities and fatigue intensity. In this narrative review, we decided to deal with this issue, trying to answer the question whether there is any scientific evidence supporting the rationale for application of high-dose IVC therapy in advanced-stage cancer patients. Although results obtained from preclinical studies demonstrated that millimolar ascorbate plasma concentrations achievable only after IVC administration were cytotoxic to fast-growing malignant cells and inhibited tumor growth as well as prolonged the survival of laboratory animals, such positive effects were not found in human studies with advanced-stage cancer patients. We also have not found the rationale for the use of IVC to increase the effectiveness of chemotherapy and to reduce the chemotherapy-induced toxicity in the above mentioned group. Nevertheless, in palliative care, high-dose IVC might be considered as a therapy improving the quality of life and reducing cancer-related symptoms, such as fatigue and bone pain. However, because of the absence of placebo-controlled randomized trials on IVC efficacy in advanced-stage cancer patients, the placebo effect cannot be excluded.

Vitamin C-Sources, Physiological Role, Kinetics, Deficiency, Use, Toxicity, and Determination

Vitamin C (L-ascorbic acid) has been known as an antioxidant for most people. However, its physiological role is much larger and encompasses very different processes ranging from facilitation of iron absorption through involvement in hormones and carnitine synthesis for important roles in epigenetic processes. Contrarily, high doses act as a pro-oxidant than an anti-oxidant. This may also be the reason why plasma levels are meticulously regulated on the level of absorption and excretion in the kidney. Interestingly, most cells contain vitamin C in millimolar concentrations, which is much higher than its plasma concentrations, and compared to other vitamins. The role of vitamin C is well demonstrated by miscellaneous symptoms of its absence-scurvy. The only clinically well-documented indication for vitamin C is scurvy. The effects of vitamin C administration on cancer, cardiovascular diseases, and infections are rather minor or even debatable in the general population. Vitamin C is relatively safe, but caution should be given to the administration of high doses, which can cause overt side effects in some susceptible patients (e.g., oxalate renal stones). Lastly, analytical methods for its determination with advantages and pitfalls are also discussed in this review.

New-onset atrial fibrillation: an update

New-onset atrial fibrillation (NOAF) is the most common perioperative complication of heart surgery, typically occurring in the perioperative period. NOAF commonly occurs in patients who are elderly, or have left atrial enlargement, or left ventricular hypertrophy. Various factors have been identified as being involved in the development of NOAF, and numerous approaches have been proposed for its prevention and treatment. Risk factors include diabetes, obesity, and metabolic syndrome. For prevention of NOAF, β-blockers and amiodarone are particularly effective and are recommended by guidelines. NOAF can be treated by rhythm/rate control, and antithrombotic therapy. Treatment is required in patients with decreased cardiac function, a heart rate exceeding 130 beats/min, or persistent NOAF lasting for ≥ 48 h. It is anticipated that anticoagulant therapies, as well as hemodynamic management, will also play a major role in the management of NOAF. When using warfarin as an anticoagulant, its dose should be adjusted based on PT-INR. PT-INR should be controlled between 2.0 and 3.0 in patients aged < 70 years and between 1.6 and 2.6 in those aged ≥ 70 years. Rate control combined with antithrombotic therapies for NOAF is expected to contribute to further advances in treatment and improvement of survival.

Efficacy and safety of vitamin C for atrial fibrillation after cardiac surgery: A meta-analysis with trial sequential analysis of randomized controlled trials

OBJECTIVES

Antioxidant supplement is an option in preventing postoperative atrial fibrillation (AF) after cardiac surgery. However, the benefits and adverse effects of vitamin C have not been well assessed. We aimed to systematically evaluate the efficacy and safety of vitamin C in preventing postoperative AF in adult patients after cardiac surgery.

METHODS

PubMed, EMBASE, and the Cochrane library databases from inception to September 2016 were searched. Randomized controlled trials (RCTs) that evaluated the efficacy and safety of vitamin C in preventing postoperative AF in adult patients after cardiac surgery were identified. The primary outcome was the incidence of postoperative AF. Secondary outcomes included the length of intensive care unit (ICU) stay, length of hospital stay, and stroke events.

RESULTS

Eight RCTs incorporating 1060 patients were included. Compared with placebo group, vitamin C treatment was associated with a substantial reduction in postoperative AF (OR, 0.47; 95% CI, 0.36-0.62; evidence rank: moderate), with no significant heterogeneity (I² 44%; P = 0.09). Trial sequential analysis showed that the cumulative Z-curve crossed the trial sequential monitoring boundary for benefit, establishing sufficient and conclusive evidence. In addition, vitamin C administration was not associated with any length of stay, including in the ICU (evidence rank: low) and hospital (evidence rank: low), respectively.

CONCLUSIONS

Short-term treatment with vitamin C is safe, and may reduce the incidence of postoperative AF after cardiac surgery. Future studies as well as more high quality RCTs are still warranted to confirm the effects of different durations of vitamin C on cardiac surgery.

Circulating omega-6 polyunsaturated fatty acids and total and cause-specific mortality: the Cardiovascular Health Study

BACKGROUND

Although omega-6 polyunsaturated fatty acids (n-6 PUFA) have been recommended to reduce coronary heart disease (CHD), controversy remains about benefits versus harms, including concerns over theorized proinflammatory effects of n-6 PUFA. We investigated associations of circulating n-6 PUFA including linoleic acid (the major dietary PUFA), γ-linolenic acid, dihomo-γ-linolenic acid, and arachidonic acid, with total and cause-specific mortality in the Cardiovascular Health Study, a community-based U.S. cohort.

METHODS AND RESULTS

Among 2792 participants(aged ≥65 years) free of cardiovascular disease at baseline, plasma phospholipid n-6 PUFA were measured at baseline using standardized methods. All-cause and cause-specific mortality, and total incident CHD and stroke, were assessed and adjudicated centrally. Associations of PUFA with risk were assessed by Cox regression. During 34 291 person-years of follow-up (1992-2010), 1994 deaths occurred (678 cardiovascular deaths), with 427 fatal and 418 nonfatal CHD, and 154 fatal and 399 nonfatal strokes. In multivariable models, higher linoleic acid was associated with lower total mortality, with extreme-quintile hazard ratio =0.87 (P trend=0.005). Lower death was largely attributable to cardiovascular disease causes, especially nonarrhythmic CHD mortality (hazard ratio, 0.51; 95% confidence interval, 0.32-0.82; P trend=0.001). Circulating γ-linolenic acid, dihomo-γ-linolenic acid, and arachidonic acid were not significantly associated with total or cause-specific mortality (eg, for arachidonic acid and CHD death, the extreme-quintile hazard ratio was 0.97; 95% confidence interval, 0.70-1.34; P trend=0.87). Evaluated semiparametrically, linoleic acid showed graded inverse associations with total mortality (P=0.005). There was little evidence that associations of n-6 PUFA with total mortality varied by age, sex, race, or plasma n-3 PUFA. Evaluating both n-6 and n-3 PUFA, lowest risk was evident with highest levels of both.

CONCLUSIONS

High circulating linoleic acid, but not other n-6 PUFA, was inversely associated with total and CHD mortality in older adults.

Plasma phospholipid long-chain ω-3 fatty acids and total and cause-specific mortality in older adults: a cohort study

BACKGROUND

Long-chain ω-3 polyunsaturated fatty acids (ω3-PUFAs), including eicosapentaenoic acid (EPA) (20:5ω-3), docosapentaenoic acid (DPA) (22:5ω-3), and docosahexaenoic acid (DHA) (22:6ω-3), have been shown to reduce cardiovascular risk, but effects on cause-specific and total mortality and potential dose-responses remain controversial. Most observational studies have assessed self-reported dietary intake and most randomized trials have tested effects of adding supplements to dietary intake and evaluated secondary prevention, thus limiting inference for dietary ω3-PUFAs or primary prevention.

OBJECTIVE

To investigate associations of plasma phospholipid EPA, DPA, DHA, and total ω3-PUFA levels with total and cause-specific mortality among healthy older adults not receiving supplements.

DESIGN

Prospective cohort study.

SETTING

4 U.S. communities.

PARTICIPANTS

2692 U.S. adults aged 74 years (±5 years) without prevalent coronary heart disease (CHD), stroke, or heart failure at baseline.

MEASUREMENTS

Phospholipid fatty acid levels and cardiovascular risk factors were measured in 1992. Relationships with total and cause-specific mortality and incident fatal or nonfatal CHD and stroke through 2008 were assessed.

RESULTS

During 30 829 person-years, 1625 deaths (including 570 cardiovascular deaths), 359 fatal and 371 nonfatal CHD events, and 130 fatal and 276 nonfatal strokes occurred. After adjustment, higher plasma levels of ω3-PUFA biomarkers were associated with lower total mortality, with extreme-quintile hazard ratios of 0.83 for EPA (95% CI, 0.71 to 0.98; P for trend = 0.005), 0.77 for DPA (CI, 0.66 to 0.90; P for trend = 0.008), 0.80 for DHA (CI, 0.67 to 0.94; P for trend = 0.006), and 0.73 for total ω3-PUFAs (CI, 0.61 to 0.86; P for trend < 0.001). Lower risk was largely attributable to fewer cardiovascular than noncardiovascular deaths. Individuals in the highest quintile of phospholipid ω3-PUFA level lived an average of 2.22 more years (CI, 0.75 to 3.13 years) after age 65 years than did those in the lowest quintile.

LIMITATION

Temporal changes in fatty acid levels and misclassification of causes of death may have resulted in underestimated associations, and unmeasured or imperfectly measured covariates may have caused residual confounding.

CONCLUSION

Higher circulating individual and total ω3-PUFA levels are associated with lower total mortality, especially CHD death, in older adults.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Ascorbic acid mitigates the myocardial injury after cardiac arrest and electrical shock

PURPOSE

To examine the effects of ascorbic acid (AA) administrated during cardiopulmonary resuscitation (CPR) on the myocardial injury in a rat model of ventricular fibrillation (VF) and electrical shock (ES).

METHODS

VF was induced in male Wistar rats and left untreated for 5 min, followed by 1 min of CPR, and then one ES of 5 J. At the start of CPR, animals received either intravenous administration of AA (100 mg/kg) or Tempol (30 mg/kg), two antioxidants, or 0.9% saline (VF + ES group). After ES, animals were immediately killed. Myocardial lipoxidation was determined by malondialdehyde (MDA) assay. The histology and ultrastructural changes of myocardium were also evaluated. The mitochondrial permeability transition pore (mPTP) opening was measured based on the mitochondrial swelling rate. The complex activities and respiration of mitochondria were assessed, too.

RESULTS

Increased myocardial injury and mitochondrial damage in the VF + ES group were noted. AA and Tempol alleviated such damages. Both AA and Tempol improved accelerated mitochondrial swelling; decreased complex activities and respiratory dysfunction occurred in the VF + ES group. The animals receiving AA and Tempol during CPR had better successful resuscitation rates and 72-h survival than the VF + ES group.

CONCLUSIONS

Intravenous administration of AA and Tempol at the start of CPR may reduce lipid peroxidation and myocardial necrosis, diminish mitochondrial damage, facilitate resuscitation, and improve outcomes after VF + ES.

Vitamin C: Overview and Update

Vitamin C functions in enzyme activation, oxidative stress reduction, and immune function. There is considerable evidence that vitamin C protects against respiratory tract infections and reduces risk for cardiovascular disease and some cancers. Current trials are examining the efficacy of intravenous vitamin C as cancer therapy. Many experts believe that the recommended intakes for vitamin C (45 to 90 mg daily) are several orders of magnitude too low to support optimal vitamin C functionality. Also, there is a misperception that vitamin C deficiency disease (scurvy) is largely historical and rarely observed in developed nations. Physical symptoms of scurvy include swelling of the lower extremities, bleeding gums, fatigue, and hemorrhaging, as well as psychological problems, including depression, hysteria, and social introversion. The long-term safety of vitamin C supplementation seems evident as large investigations have noted reduced risk of mortality in vitamin C supplementing populations and in those with elevated plasma vitamin C concentrations.

Atrial Remodeling And Atrial Fibrillation: Mechanistic Interactions And Clinical Implications

Atrial fibrillation (AF) is the most common arrhythmia in clinical practice. The prevalence of AF increases dramatically with age and is seen in as high as 9% of individuals by the age of 80 years. In high-risk patients, the thromboembolic stroke risk can be as high as 9% per year and is associated with a 2-fold increase in mortality. Although the pathophysiological mechanism underlying the genesis of AF has been the focus of many studies, it remains only partially understood. Conventional theories focused on the presence of multiple re-entrant circuits originating in the atria that are asynchronous and conducted at various velocities through tissues with various refractory periods. Recently, rapidly firing atrial activity in the muscular sleeves at the pulmonary veins ostia or inside the pulmonary veins have been described as potential mechanism,. AF results from a complex interaction between various initiating triggers and development of abnormal atrial tissue substrate. The development of AF leads to structural and electrical changes in the atria, a process known as remodeling. To have effective surgical or catheter ablation of AF good understanding of the possible mechanism(s) is crucial.Once initiated, AF alters atrial electrical and structural properties that promote its maintenance and recurrence. The role of atrial remodeling (AR) in the development and maintenance of AF has been the subject of many animal and human studies over the past 10-15 years. This review will discuss the mechanisms of AR, the structural, electrophysiologic, and neurohormonal changes associated with AR and it is role in initiating and maintaining AF. We will also discuss briefly the role of inflammation in AR and AF initiation and maintenance, as well as, the possible therapeutic interventions to prevent AR, and hence AF, based on the current understanding of the interaction between AF and AR.

The biochemical basis of antioxidant therapy in critical illness

During critical illness free radical production may increase as a result of, for example, sepsis or tissue trauma. In addition, because of a potential for increased losses, and the possibility of inadequate nutrition, the antioxidant defences of the body may become compromised. Thus, the delicate balance between free radicals and antioxidants may be disturbed. Various nutritional and pharmacological strategies to enhance antioxidant defences have been proposed, which aim either to maintain or enhance endogenous antioxidant stores or to provide alternative antioxidant agents. Trace elements and amino acids are particularly important, and their synergistic role in the maintenance of the body's antioxidant defence network will be discussed.

Design for a study to determine optimal dosage of ascorbic acid and alpha-tocopherol in humans

Some clinical trials of vitamins C and E have neglected important design features. Our objective was to demonstrate a detailed design that includes essential elements for an effective study of these vitamins in vivo. While taking 400 IU (international units) of vitamin E, subjects took different dosages of vitamin C during three distinct periods. Dosages were 200 mg in food, 500 mg as supplements twice a day (500 × 2), and 1,000 mg as supplements twice a day (1000 × 2). Ten participants spent 3 weeks at each dosage before plasma was drawn on two consecutive days. Final samples were taken after a week with no supplementation. Selected by investigators at four institutions, endpoints were protein carbonyls, TBARs (thiobarbituric reactive substances), and Heinz body formation in RBCs (red blood cells). TBARs and protein carbonyls did not change significantly with dosage. However, Heinz body formation increased at either higher or lower intakes of vitamin C. Even with daily vitamin E, Heinz bodies were significantly fewer at 500 × 2. Results indicate that even with 400 IU vitamin E daily, it is possible to distinguish the effect of different levels of vitamin C with Heinz bodies. This effect may be due to pro-oxidant action of vitamin C or to prolonged survival of RBCs.

Oral vitamin C administration reduces early recurrence rates after electrical cardioversion of persistent atrial fibrillation and attenuates associated inflammation

BACKGROUND

Inflammation and oxidative stress have been recently implicated in the pathophysiology of atrial fibrillation (AF). The aim of this study was to examine the potential benefit of vitamin C on the early recurrence rates and on inflammatory indices after successful cardioversion of persistent AF, as well as to investigate the time course of changes in these indices post-cardioversion.

METHODS

We prospectively studied 44 consecutive patients after successful electrical cardioversion of persistent AF. All patients received standard treatment and were randomised in one to one fashion to either oral vitamin C administration or no additional therapy. We followed-up the patients for 7 days performing successive measurements of white blood cell (WBC) count, C-reactive protein (CRP), fibrinogen, and ferritin levels.

RESULTS

One week after successful cardioversion, AF recurred in 4.5% of patients in the vitamin C group and in 36.3% of patients in the control group (p=0.024). Compared to baseline values, inflammatory indices decreased after cardioversion in patients receiving vitamin C but did not change significantly in the control group. A significant variance was found in the serial measurements of WBC counts (F=5.86, p=0.001) and of fibrinogen levels (F=4.10, p=0.0084) in the two groups. In the vitamin C group CRP levels were lower on the seventh day (p<0.05). CRP and fibrinogen levels were higher in patients who relapsed into AF compared to patients who maintained sinus rhythm (F=2.77, p=0.044 and F=3.51, p=0.017, respectively).

CONCLUSIONS

These findings suggest that vitamin C reduces the early recurrence rates after cardioversion of persistent AF and attenuates the associated low-level inflammation. These effects indicate that therapeutic approaches targeting at inflammation and oxidative stress may exert favourable effects on atrial electrical remodeling.

Vitamins E and C are safe across a broad range of intakes

A robust database shows that dietary supplements of vitamins E and C are safe for the general population. Because these nutrients supply antioxidant and other functions for homeostasis and protection against free radical damage, supplementation has been intensively studied. Because of perceived benefits, many persons consume quantities of vitamins E and C well above the recommended dietary allowances. As safety guidance, tolerable upper intake levels have been established by the Food and Nutrition Board, Institute of Medicine, at 1000 mg for vitamin E and 2000 mg for vitamin C in adults. Many clinical trials with these vitamins have involved subjects with various diseases, and no consistent pattern of adverse effects has occurred at any intake. Numerous studies of vitamin C supplementation have provided no pattern of evidence to support concerns about safety other than occasional gastrointestinal upset or mild diarrhea resulting from the osmotic effects of unabsorbed quantities of vitamin C. Evidence of bleeding effects and other potential adverse effects of high vitamin E intakes in humans is not convincing. Evidence of adverse effects of vitamin C that result from its effects on iron absorption and metabolism has not been confirmed in clinical trials. Thus, we conclude from clinical trial evidence that vitamin E supplements appear safe for most adults in amounts </=1600 IU (1073 mg RRR-alpha-tocopherol or the molar equivalent of its esters) and that vitamin C supplements of </=2000 mg/d are safe for most adults.

Nutritional assessment and support during pregnancy

This article thoroughly updates the authors' previous review of nutritional assessment and support during pregnancy. After briefly reviewing nutrient metabolism and requirements, the authors discuss the nutritional assessment of the pregnant woman and review the nutritional support principles in hyperemesis gravidarum and other conditions that can compromise the nutritional health of mother or fetus.