Vitamin C may help people who suffer from respiratory
symptoms after exercise
Physical activity increases oxidative stress, and therefore,
as an antioxidant vitamin C might have particularly evident effects on people
who are participating in vigorous exercise. In several studies, vitamin C
administration attenuated the increases in oxidative stress markers caused by
exercise. Furthermore, 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.
A meta-analysis of three studies found that vitamin C halved
post-exercise FEV1 decline in participants who suffered from exercise-induced
bronchoconstriction. Five other studies examined subjects who were under
short-term, heavy physical stress and a meta-analysis revealed that vitamin C
halved the incidence of respiratory symptoms. Another trial reported that
vitamin C halved the duration of the respiratory symptoms in male adolescent
competitive swimmers.
FEV1 is the standard pulmonary function outcome for
assessing whether a person suffers from exercise-induced bronchoconstriction.
However, exercise-induced decline in FEF25-75 is twice as great as the decline
in FEV1. FEV1 measures the large-airway obstruction, whereas FEF25-75 measures
small-airway obstruction. Therefore, FEF25-75 or the closely related FEF50
might provide relevant additional information about the possible effects of
vitamin C.
Harri Hemila, MD, PhD, of the University of Helsinki,
Finland, carried out a secondary analysis of a study which had 12 participants.
The participants had asthma, were on average 26 years, and suffered from
exercise-induced bronchoconstriction. The FEV1 and FEF60 levels before and
after exercise were reported on vitamin C and placebo days, but the data was
not thoroughly analyzed originally.
In five out of the 12 participants, exercise caused a
decline greater than 60% in FEF60. Such a dramatic FEF60 decline indicates that
the absolute post-exercise level of FEF60 becomes an important outcome in its
own right, in addition to its change from the pre-exercise level. Vitamin C
administration increased the post-exercise FEF60 level in these 5 participants
by between 50% and 150%. In contrast, no mean difference between the vitamin C
and placebo days was detected in the other 7 participants.
- The increase in post-exercise FEF60 level by vitamin C is
a novel finding, which indicates that vitamin C may have substantial effects on
the small airways, Dr. Hemilä states.
Dr. Hemila concludes that "given the safety and low
cost of vitamin C, and the consistency of positive findings in the nine
randomized trials on vitamin C against exercise-induced bronchoconstriction and
respiratory symptoms, it seems reasonable for physically active people to test
whether vitamin C is beneficial on an individual basis, if they have documented
exercise-induced bronchoconstriction or suffer from respiratory symptoms such
as cough or sore throat after taking vigorous exercise."
Vitamin C supplements hamper endurance training
Vitamin
C and E supplements may blunt the improvement of muscular endurance – by
disrupting cellular adaptions in exercised muscles – suggests a new study
published February 2014 in The Journal of
Physiology.
As
vitamin C and E supplements are widely used, understanding if they interfere
with cellular and physiological adaptations to exercise is of interest to
people exercising for health purposes as well as to athletes.
Dr
Gøran Paulsen, who led the study at the Norwegian School of Sport Sciences,
explains:
"Our
results show that vitamin C and E supplements blunted the endurance
training-induced increase of mitochondrial proteins, which are needed to
improve muscular endurance."
In
the 11-week trial, 54 young, healthy men and women were randomly allocated to
receive either 1000mg vitamin C and 235mg vitamin E (consistent with amounts
found in shop supplements), or a placebo (a pill containing no active
ingredients). Neither the subjects nor the investigators knew which participant
received the vitamins or placebos.
The
participants completed an endurance training programme, consisting of three to
four sessions per week, of primarily running. Fitness tests, blood samples and
muscle biopsies were taken before and after the intervention.
Whilst
the supplements did not affect maximal oxygen uptake or the results of a 20
metre shuttle test, the results showed that markers for the production of new
muscle mitochondria – the power supply for cells – increased only in the group
without supplements.
The
National Health Service (NHS) says taking less than 540mg vitamin E and 1000mg
vitamin C supplements per day is unlikely to cause any harm.
Dr
Paulsen says:
"Our
results indicate that high dosages of vitamin C and E – as commonly found in
supplements – should be used with caution, especially if you are undertaking
endurance training."
A
significant trend has been identified, but the molecular processes requires
further research. Dr Paulsen says:
"Future
studies are needed to determine the underlying mechanisms of these results, but
we assume that the vitamins interfered with cellular signalling and blunted
expression of certain genes."
Previous
studies show that exercising increases muscle oxidant production, which
participates in the signalling processes leading to muscle adaption. It is
possible that high doses of vitamins C and E act as antioxidants and take away
some of this oxidative stress, hence blocking muscular endurance development.
Vitamin C and beta-carotene might protect against dementia
Study
examines the influence of antioxidants on the pathogenesis of Alzheimer's
disease
Forgetfulness,
lack of orientation, cognitive decline… about 700, 000 Germans suffer from
Alzheimer's disease (AD). Now researchers from the University of Ulm, among
them the Epidemiologist Professor Gabriele Nagel and the Neurologist Professor
Christine von Arnim, have discovered that the serum-concentration of the
antioxidants vitamin C and beta-carotene are significantly lower in patients
with mild dementia than in control persons. It might thus be possible to influence
the pathogenesis of AD by a person's diet or dietary antioxidants. 74
AD-patients and 158 healthy controls were examined for the study that has been
published in the "Journal of
Alzheimer's Disease" (JAD).
AD
is a neurodegenerative disease: Alterations in the brain caused by
amyloid-beta-plaques, degeneration of fibrillae and a loss of synapses are held
responsible for the characteristic symptoms. Oxidative stress, which constrains
the exploitation of oxygen in the human body, is suspected to promote the
development of AD. Whereas so called antioxidants might protect against
neurodegeneration. In their study, the researchers have investigated whether
the serum-levels of vitamin C, vitamin E, beta-carotene as well as lycopene and
coenzyme Q10 are significantly lower in the blood of AD-patients. "In
order to possibly influence the onset and development of Alzheimer's disease,
we need to be aware of potential risk factors", says Gabriele Nagel.
Participants
were recruited from the cross-sectional study IMCA ActiFE (Activity and
Function in the Elderly in Ulm) for which a representative population-based
sample of about 1,500 senior citizens has been examined. The 65 to 90 years old
seniors from Ulm and the surrounding area underwent neuropsychological testing
and answered questions regarding their lifestyle. What is more, their blood has
been examined and their body mass index (BMI) was calculated. For the present
study, scientists have compared 74 patients with mild dementia (average age
78.9 years) with a control group consisting of 158 healthy, gender-matched
persons of the same age.
Results
are quite interesting: The concentration of vitamin C and beta-carotene in the
serum of AD-patients was significantly lower than in the blood of control
subjects. Whereas no such difference between the groups could be found for the
other antioxidants (vitamin E, lycopene, coenzyme Q10). Potential confounding
factors such as education, civil status, BMI, consumption of alcohol and
tobacco have been considered in the statistical analysis. Nevertheless,
additional parameters such as the storage and preparation of food as well as
stressors in the life of participants might have influenced the findings.
Therefore, results need to be confirmed in prospective surveys.
"Longitudinal
studies with more participants are necessary to confirm the result that vitamin
C and beta-carotene might prevent the onset and development of Alzheimer's
disease", says Gabriele Nagel. Vitamin C can for example be found in
citrus fruits; beta-carotene in carrots, spinach or apricots.
INCREASE IN RDA
FOR VITAMIN C COULD HELP REDUCE HEART DISEASE, STROKE, CANCER
The
recommended dietary allowance, or RDA, of vitamin C is less than half what it
should be, scientists argue in a recent report, because medical experts insist
on evaluating this natural, but critical nutrient in the same way they do
pharmaceutical drugs and reach faulty conclusions as a result.
The
researchers, in Critical Reviews in Food
Science and Nutrition, say there’s compelling evidence that the RDA of
vitamin C should be raised to 200 milligrams per day for adults, up from its
current levels in the United States of 75 milligrams for women and 90 for men.
Rather
than just prevent the vitamin C deficiency disease of scurvy, they say, it’s
appropriate to seek optimum levels that will saturate cells and tissues, pose
no risk, and may have significant effects on public health at almost no expense
– about a penny a day if taken as a dietary supplement.
“It’s
time to bring some common sense to this issue, look at the totality of the
scientific evidence, and go beyond some clinical trials that are inherently
flawed,” said Balz Frei, professor and director of the Linus Pauling Institute
at Oregon State University, and one of the world’s leading experts on the role
of vitamin C in optimum health.
“Significant
numbers of people in the U.S. and around the world are deficient in vitamin C,
and there’s growing evidence that more of this vitamin could help prevent
chronic disease,” Frei said. “The way clinical researchers study micronutrients
right now, with the same type of so-called ‘phase three randomized
placebo-controlled trials’ used to test pharmaceutical drugs, almost ensures
they will find no beneficial effect. We need to get past that.”
Unlike
testing the safety or function of a prescription drug, the researchers said,
such trials are ill suited to demonstrate the disease prevention capabilities
of substances that are already present in the human body and required for
normal metabolism. Some benefits of micronutrients in lowering chronic disease
risk also show up only after many years or even decades of optimal consumption
of vitamin C – a factor often not captured in shorter-term clinical studies.
A
wider body of metabolic, pharmacokinetic, laboratory and demographic studies
suggests just the opposite, that higher levels of vitamin C could help reduce
the chronic diseases that today kill most people in the developed world – heart
disease, stroke, cancer, and the underlying issues that lead to them, such as
high blood pressure, chronic inflammation, poor immune response and
atherosclerosis.
“We
believe solid research shows the RDA should be increased,” Frei said. “And the
benefit-to-risk ratio is very high. A 200 milligram intake of vitamin C on a
daily basis poses absolutely no risk, but there is strong evidence it would
provide multiple, substantial health benefits.”
An
excellent diet with the recommended five to nine daily servings of fruits and
raw or steam-cooked vegetables, together with a six-ounce glass of orange
juice, could provide 200 milligrams of vitamin C a day. But most Americans and
people around the world do not have an excellent diet.
Even
at the current low RDAs, various studies in the U.S. and Canada have found that
about a quarter to a third of people are marginally deficient in vitamin C, and
up to 20 percent in some populations are severely deficient – including college
students, who often have less-than-perfect diets. Smokers and older adults are
also at significant risk.
Even
marginal deficiency can lead to malaise, fatigue, and lethargy, researchers
note. Healthier levels of vitamin C can enhance immune function, reduce
inflammatory conditions such as atherosclerosis, and significantly lower blood
pressure.
•
A recent analysis of 29 human studies concluded that daily supplements of 500
milligrams of vitamin C significantly reduced blood pressure, both systolic and
diastolic. High blood pressure is a major risk factor for heart disease and
stroke, and directly attributes to an estimated 400,000 deaths annually in the
U.S.
•
A study in Europe of almost 20,000 men and women found that mortality from
cardiovascular disease was 60 percent lower when comparing the blood plasma
concentration of vitamin C in the highest 20 percent of people to the lowest 20
percent.
•
Another research effort found that men with the lowest serum vitamin C levels
had a 62 percent higher risk of cancer-related death after a 12-16 year period,
compared to those with the highest vitamin C levels.
Laboratory
studies with animals – which may be more accurate than human studies because
they can be done in controlled conditions and with animals of identical genetic
makeup - can document reasons that could explain all of these findings, Frei
said.
Critics
have suggested that some of these differences are simply due to better overall
diet, not vitamin C levels, but the scientists noted in this report that some
health benefits correlate even more strongly to vitamin C plasma levels than
fruit and vegetable consumption.
What are some
effects of vitamin C on health?
Scientists
are studying vitamin C to understand how it affects health. Here are several
examples of what this research has shown.
Cancer
prevention and treatment
People
with high intakes of vitamin C from fruits and vegetables might have a lower
risk of getting many types of cancer, such as lung, breast, and colon cancer.
However, taking vitamin C supplements, with or without other antioxidants,
doesn't seem to protect people from getting cancer.
It
is not clear whether taking high doses of vitamin C is helpful as a treatment
for cancer. Vitamin C's effects appear to depend on how it is administered to
the patient. Oral doses of vitamin C can't raise blood levels of vitamin C
nearly as high as intravenous doses given through injections. A few studies in
animals and test tubes indicate that very high blood levels of vitamin C might
shrink tumors. But more research is needed to determine whether high-dose
intravenous vitamin C helps treat cancer in people.
Vitamin
C dietary supplements and other antioxidants might interact with chemotherapy
and radiation therapy for cancer. People being treated for cancer should talk
with their oncologist before taking vitamin C or other antioxidant supplements,
especially in high doses.
Cardiovascular
disease
People
who eat lots of fruits and vegetables seem to have a lower risk of
cardiovascular disease. Researchers believe that the antioxidant content of
these foods might be partly responsible for this association because oxidative
damage is a major cause of cardiovascular disease. However, scientists aren't
sure whether vitamin C itself, either from food or supplements, helps protect
people from cardiovascular disease. It is also not clear whether vitamin C
helps prevent cardiovascular disease from getting worse in people who already
have it.
Age-related
macular degeneration (AMD) and cataracts
AMD
and cataracts are two of the leading causes of vision loss in older people.
Researchers do not believe that vitamin C and other antioxidants affect the
risk of getting AMD. However, research suggests that vitamin C combined with
other nutrients might help keep early AMD from worsening into advanced AMD.
In
a large study, older people with AMD who took a daily dietary supplement with
500 mg vitamin C, 80 mg zinc, 400 IU vitamin E, 15 mg beta-carotene, and 2 mg
copper for about 6 years had a lower chance of developing advanced AMD. They
also had less vision loss than those who did not take the dietary supplement.
More
research is needed before doctors can recommend dietary supplements containing
vitamin C for patients with AMD. However, people who have or are developing the
disease might want to talk with their doctor about taking dietary supplements.
The
relationship between vitamin C and cataract formation is unclear. Some studies
show that people who get more vitamin C from foods have a lower risk of getting
cataracts. But further research is needed to clarify this association and to
determine whether vitamin C supplements affect the risk of getting cataracts.
The
common cold
Although
vitamin C has long been a popular remedy for the common cold, research shows
that for most people, vitamin C supplements do not reduce the risk of getting
the common cold. However, people who take vitamin C supplements regularly might
have slightly shorter colds or somewhat milder symptoms when they do have a
cold. Using vitamin C supplements after cold symptoms start does not appear to
be helpful.
Vitamin C Boosts the Reprogramming of Adult Cells Into Stem Cells
Famous
for its antioxidant properties and role in tissue repair, vitamin C is touted
as beneficial for illnesses ranging from the common cold to cancer and perhaps
even for slowing the aging process. Now, a study published online on December
24, 2009 by Cell Press in the journal Cell
Stem Cell uncovers an unexpected new role for this natural compound:
facilitating the generation of embryonic-like stem cells from adult cells.
Over
the past few years, we have learned that adult cells can be reprogrammed into
cells with characteristics similar to embryonic stem cells by turning on a
select set of genes. Although the reprogrammed cells, called induced
pluripotent stem cells (iPSCs), have tremendous potential for regenerative
medicine, the conversion is extremely inefficient.
"The
low efficiency of the reprogramming process has hampered progress with this
technology and is indicative of how little we understand it. Further, this
process is most challenging in human cells, raising a significant barrier for
producing iPSCs and serious concerns about the quality of the cells that are
generated," explains senior study author Dr. Duanqing Pei from the South
China Institute for Stem Cell Biology and Regenerative Medicine at the Guangzhou
Institutes of Biomedicine and Health, Chinese Academy of Sciences.
Dr.
Pei and colleagues measured the production of reactive oxygen species or ROS
during reprogramming and discovered a potential link between high ROS and low
reprogramming efficiency. They became particularly interested in antioxidants,
hypothesizing that they might suppress ROS and cell senescence, which seems to
be a major roadblock for the generation of iPSCs.
The
researchers found that adding vitamin C, an essential nutrient that is abundant
in citrus fruits, enhanced iPSC generation from both mouse and human cells.
Vitamin C accelerated gene expression changes and promoted a more efficient
transition to the fully reprogrammed state. Somewhat to their surprise, they
found that other antioxidants do not have the same effect, but vitamin C does
seem to act at least in part through slowing cell senescence.
"Our
results highlight a simple way to improve iPSC generation and provide
additional insight into the mechanistic basis of reprogramming," concludes
Dr. Pei. "It is also of interest that a vitamin with long-suspected
anti-aging effects has such a potent influence on reprogramming, which can be
considered a reversal of the aging process at the cellular level. It is likely
that our work may stimulate further research in this area as well."
Vitamin C aids in skin protection
Researchers
at the University of Leicester and Institute for Molecular and Cellular Biology
in Portugal studied new protective properties of vitamin C in cells from the
human skin, which could lead to better skin regeneration.
The
work, by Tiago Duarte, Marcus S. Cooke and G. Don Jones, found that a form of
Vitamin C helped to promote wound healing and also helped protect the DNA
damage of skin cells. Their findings have been published in the journal Free Radical Biology and Medicine. This
report is the latest in a long line of publications from these researchers, at
the University of Leicester, concerning vitamin C. Previously, the group has
published evidence that DNA repair is upregulated in people consuming vitamin C
supplements. The researchers have now provided some mechanistic evidence for
this, in cell culture, using techniques such as Affymetrix microarray, for
looking at gene expression, and the 'Comet' assay to study DNA damage and
repair.
Tiago
Duarte, formerly of the University of Leicester, and now at the Institute for
Molecular and Cellular Biology in Portugal, said: "The exposure to solar
ultraviolet radiation increases in summer, often resulting in a higher
incidence of skin lesions. Ultraviolet radiation is also a genotoxic agent
responsible for skin cancer, through the formation of free radicals and DNA
damage.
"Our
study analysed the effect of sustained exposure to a vitamin C derivative, ascorbic
acid 2-phosphate (AA2P), in human dermal fibroblasts. We investigated which
genes are activated by vitamin C in these cells, which are responsible for skin
regeneration.
"The
results demonstrated that vitamin C may improve wound healing by stimulating
quiescent fibroblasts to divide and by promoting their migration into the
wounded area. Vitamin C could also protect the skin by increasing the capacity
of fibroblasts to repair potentially mutagenic DNA lesions."
Even
though vitamin C was discovered over 70 years ago as the agent that prevents
scurvy, its properties are still under much debate in the scientific community.
In fact, the annual meeting of the International Society for Free Radical
Biology and Medicine, which will be held this year in San Francisco (USA), will
feature a session dedicated to vitamin C, entitled "New discoveries for an
old vitamin".
Dr
Marcus S. Cooke from the Department of Cancer Studies and Molecular Medicine
and Department of Genetics, at the University of Leicester, added: "The
study indicates a mechanism by which vitamin C could contribute to the
maintenance of a healthy skin by promoting wound healing and by protecting
cellular DNA against damage caused by oxidation". "These findings are
particular importance to our photobiology interests, and we will certainly be
looking into this further".
These
results will be of great relevance to the cosmetics industry. Free radicals are
associated with premature skin aging, and antioxidants, such as vitamin C, are
known to counter these highly damaging compounds. This new evidence suggest
that, in addition to 'mopping up' free radicals, vitamin C can help remove the
DNA damage they form, if they get past the cell's defences.
The
study has the potential to lead to advances in the prevention and treatment of
skin lesions specifically, as well as contributing to the fight against cancer.
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