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      Vitamin C and Infections

      review-article
      Nutrients
      MDPI
      ascorbic acid, bacteria, bacterial toxins, common cold, herpes zoster, pneumonia, protozoa, respiratory tract infections, viruses, tetanus

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          Abstract

          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.

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          The economic burden of non-influenza-related viral respiratory tract infection in the United States.

          Viral respiratory tract infection (VRTI) is the most common illness in humans. Despite the high incidence, the economic impact of non-influenza-related VRTI has not been rigorously explored. Our objectives were to obtain an updated incidence of non-influenza-related VRTI in the United States and to quantify the health care resource use (direct costs) and productivity losses (indirect costs) associated with these infections. A nationwide telephone survey of US households (N = 4051) was conducted between November 3, 2000, and February 12, 2001 to obtain a representative estimate of the self-reported incidence of non-influenza-related VRTI and related treatment patterns. Direct treatment costs measured included outpatient clinician encounters, use of over-the-counter and prescription drugs, and associated infectious complications of non-influenza-related VRTI. Absenteeism estimates for infected individuals and parents of infected children were extrapolated from National Health Interview Survey data. Of survey respondents, 72% reported a non-influenza-related VRTI within the past year. Respondents who experienced a self-reported non-influenza-related VRTI averaged 2.5 episodes annually. When these rates are extrapolated to the entire US population, approximately 500 million non-influenza-related VRTI episodes occur per year. Similarly, if the treatment patterns reported by the respondents are extended to the population, the total economic impact of non-influenza-related VRTI approaches $40 billion annually (direct costs, $17 billion per year; and indirect costs, $22.5 billion per year). Largely because of the high attack rate, non-influenza-related VRTI imposes a greater economic burden than many other clinical conditions. The pending availability of effective antiviral therapies warrants increased attention be paid to this common and expensive illness.
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            Direct observation of a free radical interaction between vitamin E and vitamin C.

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              Role of vitamin C in the function of the vascular endothelium.

              Vitamin C, or ascorbic acid, has long been known to participate in several important functions in the vascular bed in support of endothelial cells. These functions include increasing the synthesis and deposition of type IV collagen in the basement membrane, stimulating endothelial proliferation, inhibiting apoptosis, scavenging radical species, and sparing endothelial cell-derived nitric oxide to help modulate blood flow. Although ascorbate may not be able to reverse inflammatory vascular diseases such as atherosclerosis, it may well play a role in preventing the endothelial dysfunction that is the earliest sign of many such diseases. Beyond simply preventing scurvy, evidence is mounting that ascorbate is required for optimal function of many dioxygenase enzymes in addition to those involved in collagen synthesis. Several of these enzymes regulate the transcription of proteins involved in endothelial function, proliferation, and survival, including hypoxia-inducible factor-1α and histone and DNA demethylases. More recently, ascorbate has been found to acutely tighten the endothelial permeability barrier and, thus, may modulate access of ascorbate and other molecules into tissues and organs. The issue of the optimal cellular content of ascorbate remains unresolved, but it appears that low millimolar ascorbate concentrations are normal in most animal tissues, in human leukocytes, and probably in the endothelium. Although there may be little benefit of increasing near maximal cellular ascorbate concentrations in normal people, many diseases and conditions have either systemic or localized cellular ascorbate deficiency as a cause for endothelial dysfunction, including early atherosclerosis, sepsis, smoking, and diabetes. A key focus for future studies of ascorbate and the vascular endothelium will likely be to determine the mechanisms and clinical relevance of ascorbate effects on endothelial function, permeability, and survival in diseases that cause endothelial dysfunction.
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                Author and article information

                Journal
                Nutrients
                Nutrients
                nutrients
                Nutrients
                MDPI
                2072-6643
                29 March 2017
                April 2017
                : 9
                : 4
                : 339
                Affiliations
                Department of Public Health, University of Helsinki, Helsinki FI-00014, Finland; harri.hemila@ 123456helsinki.fi ; Tel.: +358-41-532-9987
                Article
                nutrients-09-00339
                10.3390/nu9040339
                5409678
                28353648
                b9c7324c-6646-4e25-9900-41f237752c69
                © 2017 by the author.

                Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

                History
                : 31 January 2017
                : 15 March 2017
                Categories
                Review

                Nutrition & Dietetics
                ascorbic acid,bacteria,bacterial toxins,common cold,herpes zoster,pneumonia,protozoa,respiratory tract infections,viruses,tetanus

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