Browsing by Subject "vitamin C"

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  • Louhiala, Pekka; Hemilä, Harri (2014)
    In this article, we first take a critical look at the definitions of evidence-based medicine (EBM) and complementary and alternative medicine (CAM). We then explore the question of whether there can be evidence-based forms of CAM. With the help of three examples, we show that EBM and CAM are not opposites, but rather concepts pointing at different dimensions. Each of the three examples is an evidence-based treatment according to three to five randomised, double-blind placebo controlled trials with consistent findings and narrow pooled confidence intervals. The most reasonable interpretation for the existence of evidence-based CAM treatments seems to be that the opposite of CAM is ‘mainstream medicine’, and the demarcation line between CAM and mainstream medicine is not simply defined by the question of whether a treatment works or not. Some effective treatments may belong to the CAM domain for historical reasons and because of preconceptions within mainstream medicine. Therefore, some treatments that currently lie outside mainstream medicine can be evidence-based.
  • Mattila, Markus; Hakola, Leena; Niinisto, Sari; Tapanainen, Heli; Takkinen, Hanna-Mari; Ahonen, Suvi; Ilonen, Jorma; Toppari, Jorma; Veijola, Riitta; Knip, Mikael; Virtanen, Suvi M. (2021)
    Our aim was to study the associations between maternal vitamin C and iron intake during pregnancy and the offspring's risk of developing islet autoimmunity and type 1 diabetes. The study was a part of the Finnish Type 1 Diabetes Prediction and Prevention (DIPP) prospective birth cohort including children genetically at risk of type 1 diabetes born between 1997-2004. The diets of 4879 mothers in late pregnancy were assessed with a validated food frequency questionnaire. The outcomes were islet autoimmunity and type 1 diabetes. Cox proportional hazards regression analysis adjusted for energy, family history of diabetes, human leukocyte antigen (HLA) genotype and sex was used for statistical analyses. Total intake of vitamin C or iron from food and supplements was not associated with the risk of islet autoimmunity (vitamin C: HR 0.91: 95% CI (0.80, 1.03), iron: 0.98 (0.87, 1.10)) or type 1 diabetes (vitamin C: 1.01 (0.87, 1.17), iron: 0.92 (0.78, 1.08)), neither was the use of vitamin C or iron supplements associated with the outcomes. In conclusion, no association was found between maternal vitamin C or iron intake during pregnancy and the risk of islet autoimmunity or type 1 diabetes in the offspring.
  • Hemilä, Harri (2013)
    Feedback to the following Cochrane review: Jefferson T, et al.: Neuraminidase inhibitors for preventing and treating influenza in healthy adults and children. Cochrane Database Syst Rev. 2012 Jan 18;1:CD008965 http://www.ncbi.nlm.nih.gov/pubmed/22258996
  • Suihkonen, Terhi (Helsingfors universitet, 2013)
    The literature review dealed with the composition of lingonberry, manufacture of juice powder and the effects of different carriers on properties of juice powder, especially glass transition temperature and stickiness. In addition, physical, functional and nutritional properties and the effect of storage conditions on juice powders were covered. The aim of the experimental work was to investigate the effect of spray- and freeze-drying and carriers on glass transition temperature and water sorption of lingonberry juice as well as the stability of vitamin C and phenolic compounds during drying and storage. The same amounts of maltodextrin (MD), whey protein isolate (WPI) or combination of MD/WPI in equal proportions were added to each sample. All samples were spray- and freeze-dried. After storage of powders at different relative humidities, glass transition temperature, water sorption, content of L-ascorbic acid and content of phenolic compounds were examined. Water sorption was examined by static and dynamic vapour sorption methods. The small particle size of containing WPI was problematic with spray-drying because not all of the powder in the drying air could be separated in the cyclone. Adding water back into the spray-dried samples was most difficult when the samples were stored at low relative humidities (0–11%). The smallest water sorption was observed with both static and dynamic vapour sorption methods in samples which contained only MD. Water contents of freeze-dried samples were lower than those of spray-dried samples. BET sorption isotherm described the water sorption behaviour of the lingonberry juice powders well. Glass transition temperatures of all samples decreased as the relative humidity increased. During storage, the amount of phenolic compounds in samples containing WPI remained the same, whereas the amount of phenolic compounds in samples with MD decreased. Enzymatic spectrophotometric determination was un suitable for determing L-ascorbic acid in lingonberry powder because the sample colour disturbed the measurement. MD and the combination of MD and WPI were suitable carriers in lingonberry juice. The amount of phenolic compounds in lingonberry juice powders were preserved well by whey protein isolate. Therefore, the spray-drying process should be developed in a way that brings about increase in particle size of powder containing WPI.
  • Hemilä, Harri (2011)
    Proponents of evidence-based medicine (EBM) emphasize that conclusions about medical interventions should be based on controlled trials with clinically relevant outcomes, so that the greatest weight should be given to the systematic reviews of the trials. One of the most comprehensive EBM databases is the Cochrane Library, which contains thousands of systematic reviews on medical interventions. The Cochrane review on vitamin C and the common cold analyzed 29 trial comparisons on the preventive effects of vitamin C, 29 comparisons on the effect of regular vitamin C on common cold duration and severity, and 7 comparisons on the therapeutic effect of vitamin C.1 The review concludes: “Implications for practice: The prophylaxis trials found a reduction in common cold duration of 8% in adults and 13% in children…. So far, therapeutic supplementation has not been shown to be effective. Nevertheless, given the consistent effect of vitamin C on duration and severity 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.”
  • Hemilä, Harri; Al-Biltagi, Mohammed; Baset, Ahmed A. (2011)
    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.
  • Hemilä, Harri (2010)
    Vitamin C and the common cold is a particularly important topic in the history of systematic reviews because three of the earliest systematic reviews examined that topic. Nevertheless, Bastian et al.'s brief mention of this issue is misleading.
  • Hemilä, Harri (1997)
    Three controlled trials have reported the number of pneumonia cases in a vitamin C group and a control group, each trial finding a considerably lower incidence of pneumonia in the group given vitamin C. Each of these three trials found a > or = 80% lower incidence of pneumonia in the vitamin C group. It is highly unlikely that the differences reported between the study groups in favor of the vitamin C groups would have occurred purely by chance (P = 0.00002).
  • Hemilä, Harri (2013)
    OBJECTIVE: To determine whether vitamin C administration influences exercise-induced bronchoconstriction (EIB). DESIGN: Systematic review and meta-analysis. METHODS: MEDLINE and Scopus were searched for placebo-controlled trials on vitamin C and EIB. The primary measures of vitamin C effect used in this study were: (1) the arithmetic difference and (2) the relative effect in the postexercise forced expiratory volume in 1 s (FEV1) decline between the vitamin C and placebo periods. The relative effect of vitamin C administration on FEV1 was analysed by using linear modelling for two studies that reported full or partial individual-level data. The arithmetic differences and the relative effects were pooled by the inverse variance method. A secondary measure of the vitamin C effect was the difference in the proportion of participants suffering from EIB on the vitamin C and placebo days. RESULTS: 3 placebo-controlled trials that studied the effect of vitamin C on EIB were identified. In all, they had 40 participants. The pooled effect estimate indicated a reduction of 8.4 percentage points (95% CI 4.6 to 12) in the postexercise FEV1 decline when vitamin C was administered before exercise. The pooled relative effect estimate indicated a 48% reduction (95% CI 33% to 64%) in the postexercise FEV1 decline when vitamin C was administered before exercise. One study needed imputations to include it in the meta-analyses, but it also reported that vitamin C decreased the proportion of participants who suffered from EIB by 50 percentage points (95% CI 23 to 68); this comparison did not need data imputations. CONCLUSIONS: Given the safety and low cost of vitamin C, and the positive findings for vitamin C administration in the three EIB studies, it seems reasonable for physically active people to test vitamin C when they have respiratory symptoms such as cough associated with exercise. Further research on the effects of vitamin C on EIB is warranted.
  • Hemilä, Harri (1996)
    A large number of placebo-controlled studies have shown that vitamin C supplementation alleviates the symptoms of the common cold, but widespread skepticism that vitamin C could have any significant effect remains. One of the most influential common cold studies, published in 1975, was carried out by Thomas Karlowski et al, at the National Institutes of Health. Their placebo consisted of lactose, which can easily be distinguished from ascorbic acid by taste. Karlowski et al, found a 17% decrease in the duration of cold episodes in the group administered vitamin C (6 g/day); however, they suggested that the decrease was entirely due to the placebo effect. In this article it will be shown that the placebo effect is not a valid explanation for the results of the Karlowski study, as it is inconsistent with their results. This is an important conclusion for two reasons. First, the placebo explanation becomes even more unreasonable as regards the reported benefits found in several other studies with valid placebo tablets. Second, as the results from the Karlowski study are not due to the placebo effect, their results can be used to assess the quantitative effects of vitamin C supplementation. The most important conclusions from Karlowski's study are that therapeutic vitamin C supplementation during a common cold episode appears to be as effective as regular supplementation, and that there appears to be linear dose dependency at least up to 6 g/day. These findings suggest that large therapeutic vitamin C doses might alleviate the symptoms of the common cold substantially.