Health Benefits of Vitamin C

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.