References
161. Immunostimulation by
vitamin C.
Int J Vitam Nutr Res Suppl 1982;23:49-52
Banic S
A review of the literature shows that vitamin C
undoubtedly has a positive effect on some mechanisms of the
natural resistance against infections as well as on the
immune response. It is generally accepted that vitamin C
increases the chemotaxis of granulocytes and of macrophages.
There is also ample evidence that vitamin C increases the
phagocytic activity of granulocytes as well as of
macrophages. As to the effect of vitamin C on the immune
response, the available data allow the conclusion that
vitamin C is necessary for the induction of delayed
hypersensitivity, i.e. cellular immunity. Its effect on the
antibody production appears, however, to be minimal or none.
In our previous in vivo studies we obtained the results which
were consistent with the conclusion that high doses of
vitamin C increase the efficiency of immunization with a
human cell culture rabies vaccine in guinea-pigs. The purpose
of this study was to establish whether relatively low doses
(10 mg/kg body weight) of vitamin C have a similar effect as
megadoses (100 mg/kg body weight). We observed that the
efficiency of immunization with the human diploid cell
culture rabies vaccine (Merieux/Lyon) was better in the group
of guinea-pigs treated with the vaccine plus vitamin C (10
mg/kg body weight) than in the group treated with the vaccine
alone. The difference in the number of survivors in both
groups of animals was statistically not significant, but
considering the factor of repetition (a similar result in
repeated experiments) we nevertheless conclude that vitamin C
acts in the doses used as an immunopotentiator.
162. J Bioenerg Biomembr 1994
Aug;26(4):349-58
The role of ascorbate in antioxidant protection of
biomembranes: interaction
with vitamin E and coenzyme Q.
Beyer RE
Department of Biology, University of Michigan, Ann Arbor
48109.
One of the vital roles of ascorbic acid (vitamin C) is to
act as an antioxidant
to protect cellular components from free radical damage.
Ascorbic acid has been
shown to scavenge free radicals directly in the aqueous
phases of cells and the
circulatory system. Ascorbic acid has also been proven to
protect membrane and
other hydrophobic compartments from such damage by
regenerating the antioxidant form of vitamin E. In addition,
reduced coenzyme Q, also a resident of hydrophobic
compartments, interacts with vitamin E to regenerate its
antioxidant form. The mechanism of vitamin C antioxidant
function, the myriad of pathologies resulting from its
clinical deficiency, and the many health benefits it
provides, are reviewed.
163. Int J Epidemiol 2000
Apr;29(2):260-5
Saturated fat, vitamin C and smoking predict long-term
population all-cause
mortality rates in the Seven Countries Study.
Kromhout D, Bloemberg B, Feskens E, Menotti A, Nissinen
A
Division of Public Health Research, National Institute of
Public Health and the
Environment, Bilthoven, The Netherlands.
daan.kromhout@RIVM.nl
BACKGROUND: The Seven Countries Study has shown that
population mortality rates for various chronic diseases are
related to diet and smoking. This paper
addresses the associations between diet, smoking and 25-year
all-cause
mortality. METHODS: Baseline surveys were carried out
between 1958 and 1964 on 12,763 middle-aged men constituting
16 cohorts in seven countries. In 1987/88 equivalent food
composites representing the average food intake of each
cohort at baseline were collected and chemically analysed in
one central laboratory. During 25 years of follow-up 5973 men
died and age-adjusted population mortality rates were
calculated for each cohort. RESULTS: Multivariate linear
regression analyses showed that the population intake of
saturated fat and the prevalence of smoking were positively
associated with population all-cause mortality rates.
Population vitamin C intake was inversely associated with
all-cause mortality. It was calculated that a reduction in
saturated fat intake of 5% of energy, a 20 mg/d increase in
vitamin C and a 10% decrease in the prevalence of smokers may
decrease the 25-year all-cause population mortality rate by
12.4% (95% CI: 5.6, 19.4%) at an average population all-cause
mortality rate of 45%. CONCLUSION: At the population level
saturated fat, vitamin C and cigarette smoking are important
determinants of all-cause mortality.
164. Nutr Rev 2000 Mar;58(3
Pt 1):73-5
Does vitamin C intake protect against lead toxicity?
Houston DK, Johnson MA
Department of Foods and Nutrition, Faculty of Gerontology,
University of
Georgia, Athens 30602, USA.
Although several animal studies suggest a protective
relationship between blood
lead concentrations and ascorbic acid, there are
inconclusive results regarding
the beneficial effect of ascorbic acid on lead
concentrations in human studies.
Data from the Third National Health and Nutrition
Examination Survey examined
the association between ascorbic acid and blood lead
concentrations in 19,578
participants ages 6-90 years without a history of lead
poisoning. Elevated blood
lead concentrations were found in 0.4% of adults and 0.5% of
youths. Serum
ascorbic acid concentrations were inversely associated with
the prevalence of
elevated blood lead concentrations. However, there was no
significant
relationship between dietary ascorbic acid intake and blood
lead concentrations.
This study suggests that there may be a protective
relationship between ascorbic
acid and lead. Questions remain regarding the unique roles
of dietary vitamin C
versus supplemental vitamin C in explaining this
relationship.
165. Cochrane Database Syst
Rev 2000;2:CD000980
Vitamin C for preventing and treating the common cold.
Douglas RM, Chalker EB, Treacy B
National Centre for Epidemiology and Population Health, The
Australian National
University, Canberra, ACT, AUSTRALIA, 0200.
Bob.Douglas@anu.edu.au
[Record supplied by publisher]
BACKGROUND: The role of oral ascorbic acid (vitamin C) in
the prevention and
treatment of colds remains controversial despite many
controlled trials. There
have also been a number of efforts to synthesize and/or
overview the results of
these trials, and controversy over what these overviews tell
us. OBJECTIVES: The objective of this review was to answer
the following two questions: (1) Does
regular high dosage supplementation with vitamin C reduce
the incidence of
colds? (2) Does taking vitamin C in high doses at the onset
of a cold have a
therapeutic effect? SEARCH STRATEGY: This review currently
deals only with
published trials from two previously published reviews by
Kleijnen 1989 and
Hemila 1992. SELECTION CRITERIA: Randomised and
non-randomised trials of vitamin C taken to prevent or treat
the common cold. DATA COLLECTION AND ANALYSIS: Two reviewers
independently extracted data and assessed trial quality. MAIN
RESULTS: Thirty trials were included. The quality of the
included trials was variable. Vitamin C in doses as high as
one gram daily for several winter months, had no consistent
beneficial effect on incidence of the common cold. For both
preventive and therapeutic trials, there was a consistently
beneficial but generally modest therapeutic effect on
duration of cold symptoms. This effect was variable, ranging
from -0.07% to a 39% reduction in symptom days. The weighted
difference across all of the studies revealed a reduction of
a little less than half a symptom day per cold episode,
representing an 8% to 9%
reduction in symptom days. There was no clear indication of
the relative
benefits of different regimes or vitamin C doses. However in
trials that tested
vitamin C after cold symptoms occurred, there was some
evidence that a large
dose produced greater benefits than lower doses. REVIEWER'S
CONCLUSIONS: Long term daily supplementation with vitamin C
in large doses daily does not appear to prevent colds. There
appears to be a modest benefit in reducing duration of cold
symptoms from ingestion of relatively high doses of vitamin
C. The relation of dose to therapeutic benefit needs further
exploration.
166. Evidence for a
recommended dietary allowance for vitamin C from
pharmacokinetics: a comment and analysis.
Proc Natl Acad Sci U S A 1996 Dec 10;93(25):14344-
Young VR Laboratory of Human Nutrition, Clinical Research
Center Massachusetts Institute of Technology, Cambridge
02139, USA.
The current recommended dietary allowance (RDA) for vitamin
C, as proposed by the Food and Nutrition Board/National
Research Council in 1980 and reconfirmed in 1989, is 60 mg
daily for nonsmoking adult males. Levine et al. [Levine, M.,
Conry-Cantilena, C., Wang, Y., Welch, R. W., Washko, P. W.,
et al. (1996) Proc. Natl. Acad. Sci. USA 93, 3704-3709],
based on a study of vitamin C pharmacokinetics in seven
healthy men, have now proposed that the RDA should be
increased to 200 mg daily. I have examined, in brief, the
experimental and conceptual bases for this new recommendation
and its implications for public health and nutrition policy
and programs. Using, for illustrative purposes only, data
extracted from each of two recent dietary surveys of
noninstitutionalized adult males living in households in the
Netherlands and the United States, it is predicted that the
prevalence of intakes inadequate to meet the individual's own
requirement would be about 96% or 84%, respectively, if the
criteria of adequacy used for derivation of the 200 mg RDA
are accepted. Depending upon the particular average
requirement value for ascorbic acid that might be derived
from their data, the proposal by Levine et al. would mean a
desirable increase in mean intakes in these two populations
by as much about 2-to 3-fold. Hence, before an action of this
kind is to be recommended, an answer must be sought to the
question whether
167. Selenium in ischaemic
heart disease. Salonen JT Int J Epidemiol, 1987 Jun, 16:2,
323?8 Ecological between?area comparisons, hospital?based
case?control studies and cross?sectional angiography studies
have provided data on the role of selenium (Se) deficiency in
the aetiology of ischaemic heart disease (IHD), but this
evidence is, at best, suggestive because of the potential
selection biases and the lack of certainty of the temporal
direction of the observed associations. Out of the four
cohort?based population studies published so far, one
observed a moderate association between a reduced serum Se
and an increased risk of IHD and all cardiovascular (CVD)
deaths, one was equivocal and two did not find any
association between serum Se and IHD. There are, however,
several potential sources of biases acting towards the null
hypothesis in these studies. In the pooled data of the two
separate cohorts from eastern Finland including 377 people
who experienced a CVD death or a non?fatal myocardial
infarction and equally many event?free risk?factor matched
controls, people with serum Se of less than 45 micrograms/l
had a 1.7?fold (95% confidence interval 1.2?2.7) risk of an
CVD event compared to those with higher serum Se. This
association could, however, be explained by the covariation
of Se with other nutrients, as for example n?3
polyunsaturated fatty acids. As the evidence concerning the
role of serum Se in IHD is inconclusive, we need new
epidemiological studies to test the association and
experiments exploring the possible mechanisms.
168. Primary and secondary
prevention of atherosclerosis: is there a role for
antioxidants?
Paolisso G; Esposito R; DAlessio MA; Barbieri M
Institute of Cardiology, II University of Naples, Italy.
gpaoliss@tin.it
Diabetes Metab, 1999 Sep, 25:4, 298?306
Elevated plasma free radical concentration (expression of
enhanced oxidative stress) is related to different
pathophysiological conditions such as ageing, cancer and
diabetes. Nevertheless, even in healthy subjects a rise in
plasma free radicals is due to hyperglycaemia, elevated free
fatty acids and hyperinsulinaemia. Once elevated oxidative
stress occurs, accelerated atherosclerosis may be present.
Thus, antioxidants might potentially be useful in preventing
or delaying the development of atherosclerosis. Several
epidemiological studies have provided conflicting results,
whereas interventional studies have demonstrated that
antioxidant administration at pharmacological doses is useful
for secondary prevention of atherosclerosis. The role of
antioxidants in diabetic patients is still debatable, and it
is too early to suggest this means for the prevention of
atherosclerosis. Concerning trace elements, several studies
have indicated that iron, copper, zinc and selenium may play
a role in the pathogenesis of atherosclerosis. Nevertheless,
only future longitudinal studies can provide a final
response. In conclusion, the whole body of studies to date
clearly demonstrates that antioxidants may be useful for
secondary prevention of coronary heart disease.
169. "The SU.VI.MAX Study": a
primary prevention trial using nutritional doses of
antioxidant vitamins and minerals in cardiovascular diseases
and cancers. SUpplementation on VItamines et Minéraux
AntioXydants.
Hercberg S; Preziosi P; Galan P; Faure H; Arnaud J; Duport
N; Malvy D; Roussel AM; Briançon S; Favier A
Institut Scientifique et Technique de la Nutrition et de
l'Alimentation/CNAM, Paris, France.
Food Chem Toxicol, 1999 Sep, 37:9?10, 925?30
Study is a randomized double?blind, placebo?controlled,
primary?prevention trial which started in 1994 in France.
This epidemiologic study is designed to test the efficacy of
a daily supplementation with antioxidant vitamins (vitamin C,
120 mg, vitamin E, 30 mg, and beta?carotene, 6 mg) and
minerals (selenium, 100 microg, and zinc, 20 mg) at
nutritional doses, in reducing the main causes of premature
death (cancers and cardiovascular diseases); 12,735 eligible
subjects (women aged 35 to 60 years, and men aged 45 to 60
years) were included in 1994 and will be followed up for 8
years. Participants undergo a yearly visit consisting, every
other year, of either biological sampling or clinical
examination. They also regularly provide information on
health events and dietary intake by filling out computerized
questionnaires using the Minitel Telematic Network. After 2
years of supplementation, biochemical indicators of vitamin
and trace element status reach reasonable level without
reaching concentrations as high as those observed in
intervention studies, which tested relatively high doses of
antioxidants, and ended up with higher risk of pathology.
170. Primary and secondary
prevention of atherosclerosis: is there a role for
antioxidants?
Paolisso G, Esposito R, D'Alessio MA, Barbieri M
Institute of Cardiology, II University of Naples, Italy.
gpaoliss@tin.it
Diabetes Metab 1999 Sep;25(4):298?306
Elevated plasma free radical concentration (expression of
enhanced oxidative stress) is related to different
pathophysiological conditions such as ageing, cancer and
diabetes. Nevertheless, even in healthy subjects a rise in
plasma free radicals is due to hyperglycaemia, elevated free
fatty acids and hyperinsulinaemia. Once elevated oxidative
stress occurs, accelerated atherosclerosis may be present.
Thus, antioxidants might potentially be useful in preventing
or delaying the development of atherosclerosis. Several
epidemiological studies have provided conflicting results,
whereas interventional studies have demonstrated that
antioxidant administration at pharmacological doses is useful
for secondary prevention of atherosclerosis. The role of
antioxidants in diabetic patients is still debatable, and it
is too early to suggest this means for the prevention of
atherosclerosis. Concerning trace elements, several studies
have indicated that iron, copper, zinc and selenium may play
a role in the pathogenesis of atherosclerosis. Nevertheless,
only future longitudinal studies can provide a final
response. In conclusion, the whole body of studies to date
clearly demonstrates that antioxidants may be useful for
secondary prevention of coronary heart disease.