Vit C O/D

cjmcork

Ok - I appreciate that this isn't a medical forum, but I've become fond of Boots chewable Vit C tabs.......and have definitely gone over the 5-a-day recommended dose..........but are there actually any serious dangers from taking an extra few - they're yummy - I take it that the body excretes what it doesn't need!

PS - title is a bit of an over-reaction just to get some responses!!:p

challengemaster

ask your doctor

AARRRGH

I remember my brother (kidney expert) telling me the body just pisses away excess vitamin C.

However if I were you I wouldn't risk it. Who knows what we'll find out in a few years about consuming too much vitamin C...

cjmcork

fair point - best invest in a pack of orange-flavoured boiled sweets - they're bloody yummy - they should have made them taste horrible!!

Piste

How many grammes a day are you taking?

Vit C is a water soluble vitamin, so your kineys just clear it out, however more than 10g of vitamin C in a pregnant woman can cause a miscarriage so if you're a pregnant woman it might be a good idea to stop.

bug

Its never a good idea to go over the recommended dosage of any medication whether it be herbal, vitamins or prescribed.

If you do a quick google you can look into the recent research topics of o/d of Vitamin C.

However I would strongly suggest you dont take anymore than the RDA on the packaging.

TEH REAL CDP

excess ascorbate is excreted. do not overdose, follow the rda guidelines and supplement your diet with other natural sources of vit c.

go to your doctor for authorised bona fide advice.

dudara

Moved to Biology & Medicine

dudara

cjmcork

Piste wrote: »

How many grammes a day are you taking?

Vit C is a water soluble vitamin, so your kineys just clear it out, however more than 10g of vitamin C in a pregnant woman can cause a miscarriage so if you're a pregnant woman it might be a good idea to stop.

not pregnant - unless Bethleham has severely been moved by wind erosion!:D and I doubt they'd find 3 wise men in the Cork direction!

Kevster

Vitamin C is not stored in the body - Excess is just excreted. Basically, you're fine, but it would still be beneficial to get this problem under control. This 'obsession' may lead onto other obsessions that may not be as harmless to your health.

Chunky Monkey

Tesco value OJ is €1.07 for a litre.

cjmcork

it's not really an obsession - just been taking them for the past week - I needed to find out if I was ballsing up any systems - have feiced them out and replaced with tasteless ones -boring

N8

bug wrote: »

Its never a good idea to go over the recommended dosage of any medication whether it be herbal, vitamins or prescribed.

However I would strongly suggest you dont take anymore than the RDA on the packaging.

TEH REAL CDP wrote: »

do not overdose, follow the rda guidelines and supplement your diet with other natural sources of vit c.

go to your doctor for authorised bona fide advice.

How are RDAs established? What did Linus Pauling say about vitamin c?

I have seen reports recommending anything up to 10 grams a day (http://www.naturalnews.com/022586.html).

Plus would your well meaning and best intentioned GP today really be able to give any independent advice on vitamin intake given the rapid explosion in the knowledge base and political storm that has taken over health and nutrition these days i.e. medicopharma trying to take over the supplement and food for health market?

Personally I doubt it. Our own family GP has given us advice that frankly bordered on the unhealthy and that was even with him knowing I was a colleague. This is when I decided to look at the evidence for myself in many areas. You would be startled. And they are often surprised and disbelieving when you tell them what you have uncovered.

DrIndy

Piste wrote: »

How many grammes a day are you taking?

Vit C is a water soluble vitamin, so your kineys just clear it out, however more than 10g of vitamin C in a pregnant woman can cause a miscarriage so if you're a pregnant woman it might be a good idea to stop.

Can you provide a link supporting this?

Excess vitamin C causes diaorrhea and in sensitive people, triggers kidney stone formation.

The rest is broken down and excreted.

Follow the vitamin guidelines - if the RDA is X taking 10 times that does not make it 10 times better! jeeez....

Tree

N8 wrote: »

How are RDAs established? What did Linus Pauling say about vitamin c?

I have seen reports recommending anything up to 10 grams a day (http://www.naturalnews.com/022586.html).

Plus would your well meaning and best intentioned GP today really be able to give any independent advice on vitamin intake given the rapid explosion in the knowledge base and political storm that has taken over health and nutrition these days i.e. medicopharma trying to take over the supplement and food for health market?

Personally I doubt it. Our own family GP has given us advice that frankly bordered on the unhealthy and that was even with him knowing I was a colleague. This is when I decided to look at the evidence for myself in many areas. You would be startled. And they are often surprised and disbelieving when you tell them what you have uncovered.

linus pauling was nuts for the overconsumption of micronutrients, a few of which arent teh best thing to be overdoesing on.

Jeapy

DrIndy wrote: »

triggers kidney stone formation.

The rest is broken down and excreted.

Yup, thats the jist of too much Vit C alright. (Go Indy!)

N8

Tree wrote: »

linus pauling was nuts for the overconsumption of micronutrients, a few of which arent teh best thing to be overdoesing on.

nuts? like what?

Chunky Monkey

Jeapy you need to put a forward slash in the last quote tag, like so... [/quote]

Tree

vit e i think recently came under fire for a link w/ increased lung cancer.

siochain

Tree wrote: »

vit e i think recently came under fire for a link w/ increased lung cancer.

I'm sure thats vit A (retinol not beta).

The RDA issue is debatable, RDA for vit c is 60mg and we need much more to have any benefit.

DrIndy

siochain wrote: »

I'm sure thats vit A (retinol not beta).

The RDA issue is debatable, RDA for vit c is 60mg and we need much more to have any benefit.

Evidence for this please?

siochain

DrIndy wrote: »

Evidence for this please?

Hi DrIndy not sure if you asking about the vit c or A or both
and simple google will turn up loads of studies on this and most of the modern diet and nutrition journals recommend way above 60mg of vit c,

the key message in most of the studies is '60 mg/day is far too low to provide for optimum health and protection against disease.'

Vitamin C: Your Ultimate Health Insurance

by Hans R. Larsen, MSc ChE



When tallying the achievements of medical research in the latter part of the 20th century one discovery will stand out - the discovery that vitamin-C is uniquely important to the health and wellbeing of humans.
Vitamin C was first isolated in 1928 by the Hungarian biochemist and Nobel prize winner Dr. Szent-Gyorgyi. Vitamin-C plays an important role as a component of enzymes involved in the synthesis of collagen and carnitine; however, its most vital role is no doubt that of the primary, water-soluble antioxidant in the human body(1,2,3).

Two-time Nobel prize winner, Dr. Linus Pauling was the first to realize vitamin C's crucial importance in the maintenance of a healthy immune system. In 1970 he proposed that regular intake of vitamin-C in amounts far higher than the officially sanctioned RDA (Recommended Daily Allowance) could help prevent and shorten the duration of the common cold. Although the medical establishment immediately voiced their strong opposition to this idea, many ordinary people believed Dr. Pauling and began taking large amounts of vitamin-C. Most immediately noticed a great decrease in the frequency and severity of their colds(4).

Recent medical research has confirmed Dr. Pauling's original idea. Not only does a high vitamin C intake markedly reduce the severity of a cold, it also effectively prevents secondary viral or bacterial complications. Vitamin C works by stimulating the immune system and protecting against damage by the free radicals released by the body in its fight against the infection(1,5,6).

Dr. Pauling recommended vitamin C intakes of 1000 mg/day or more. The official RDA is 60 mg/day (100 mg/day for smokers). So who is right? How much do we need? To answer this question it is crucial to realize that the RDA is not, in anyway, based on what is required for optimum health. The RDA is simply the amount required to avoid scurvy, the most obvious deficiency disease. Actually the RDA is based on the vitamin C content of the average diet. The logic goes somewhat like this: "The average "healthy" North American diet provides about 60 mg/day of vitamin C, so since scurvy is virtually unknown in the USA today 60 mg/day must be adequate." So much for science!

Many experts are now realizing that the RDA of 60 mg/day is far too low to provide for optimum health and protection against disease. A team of medical researchers at the National Institutes of Health in the USA recently completed a study designed to determine the vitamin C requirements of healthy, young men. They found that a minimum intake of 1000 mg/day was required to completely saturate the blood plasma with vitamin C. They also found that vitamin C should be taken in divided doses throughout the day as urinary excretion increases rapidly when individual doses exceed 500 mg. The researchers conclude that the RDA should be raised to 200 mg/day. This amount of vitamin C can be obtained from a diet containing five daily servings of fresh fruit and vegetables; unfortunately, less than 15 per cent of children and adults in the USA actually consume such a diet(3,7).

While 200 mg/day of vitamin C may be sufficient to maintain a reasonable health status in healthy, young men, it is clear that such a relatively low intake is far from adequate for older and sick people. It is also evident that far greater amounts are required to provide optimum protection against degenerative diseases such as cancer and heart disease.

It has long been accepted that a diet rich in vitamin C from fruits and vegetables provides protection against cancer and heart disease(1,8-28). However, very little evidence has been available as to whether that supplementation with vitamin C can increase this protective effect. This, however, is now changing. Researchers from the National Institute on Aging report that elderly people who take vitamin C and E supplements have a 50 per cent lower risk of dying prematurely from disease than do people who do not supplement(29). A Californian study concluded that people who consume more than 750 mg/day of vitamin C reduce their risk of dying prematurely by 60 per cent(30). Italian researchers have concluded that older people, especially the sick are exposed to a much higher level of oxidative stress than are younger people and that their low blood levels of vitamin C reflect this(31). Other researchers have found that people who suffer from asthma, arthritis, cancer, diabetes, and heart disease have much lower levels of vitamin C in their blood than do healthy people(8,32-34).

Large doses (1-2 g/day) of vitamin C have been found to reduce asthma symptoms significantly. Recent studies have shown that vitamin C concentrations in the blood from rheumatoid arthritis patients are extremely low and that vitamin C may protect against further damage to inflamed joints(32,33,35).

Numerous studies have shown that an adequate intake of vitamin C is effective in lowering the risk of developing cancers of the breast, cervix, colon, rectum, esophagus, larynx, lung, mouth, prostate, and stomach(7,11,12,14,16- 23,36).

Daily supplementation with 500 mg of vitamin C for 10 years or more has been found to cut the risk of developing bladder cancer by 60 per cent(37). The spread of breast cancer (metastasis) is now believed to be predominantly due to free radical damage which can be controlled through intake of increased amounts of vitamin C(38). Supplementation with 3 g/day of vitamin C has been found to effectively prevent further polyp growth in colon cancer and a vitamin C intake of more than 157 mg/day has been found to reduce the risk of developing colon cancer by 50 per cent(19,39).

Drs. Pauling and Cameron pioneered the use of large doses of vitamin C (>10 g/day) in the treatment of cancer patients. From their experiments at the Vale of Leven Hospital in Scotland they concluded that terminal cancer patients who received large, daily doses of vitamin C along with their regular treatment lived much longer than patients who did not receive vitamin C; they also had less pain and in general, a much improved quality of life(8).

Dr. Hoffer of Victoria, Canada later expanded on the Pauling/Cameron treatment protocol by adding large amounts of vitamin E, niacin, other B vitamins, beta-carotene, and some minerals. Those of Dr. Hoffer's cancer patients who followed this regimen lived, on the average, about 16 times longer than those who did not(8).

Dr. Pauling believed that vitamin C combats cancer by promoting collagen synthesis and thereby preventing growing tumors from invading adjacent tissue(8). Many researchers now believe that vitamin C prevents cancer by deactivating free radicals before they can damage DNA and initiate tumor growth while others believe that vitamin C may sometimes act as a prooxidant helping the body's own free radical defense mechanism destroy tumors in their early stages(11-14,16,40). Whatever the mechanism, it is now clear that vitamin C is effective in preventing cancer, alleviating its symptoms, and in some cases, halting its progress.

Although the fact that diabetics are vitamin C deficient has been clearly established, large scale clinical trials are still needed to determine whether supplementation with large doses of vitamin C is safe and beneficial. Some smaller trials have found that supplementation with 2 g/day lowered fasting glucose levels (a beneficial effect) and reduced capillary fragility in diabetics. Megadoses of vitamin C may, however, be toxic in diabetics with certain kidney disorders(10,34).

Vitamin C lowers blood pressure and cholesterol levels, helps thin the blood and protect it against oxidation and works in close synergism with vitamin E(9,25,41-45). Vitamin C also helps prevent atherosclerosis by strenghtening the artery walls through its participation in the synthesis of collagen, and by preventing the undesirable adhesion of white blood cells to damaged arteries(9,46,47). An adequate intake of the vitamin is highly protective against stroke and heart attack(28,48,49).

A recent study shows that people who supplement with more than 700 mg/day of vitamin C have a 62 per cent lower risk of dying from heart disease than do people with a daily intake of 60 mg/day or less(49). Supplementation with 2 g/day of vitamin C has been found to reduce adhesion of monocytes (white blood cells) to the lining of blood vessels and thereby reduce the risk of atherosclerosis(46,47,50). Vitamin C supplementation (2 g/day) also effectively reverses the vasomotor dysfunction often found in patients with atherosclerosis(51). Some very recent research carried out in Japan has shown that restenosis (reclosing of opened arteries) after angioplasty can be significantly reduced by supplementing with ascorbic acid (500 mg/day)(52).

Supplementing with vitamin C has been found to significantly lower the risk of cataracts and glaucoma and some very recent work has shown that open angle glaucoma can be reversed by supplementing with large doses of vitamin C(53,54).

Vitamin C supplementation (1000 mg/day) has also been found to significantly decrease the risk of developing pressure sores in surgical patients(55).

Vitamin C is truly a wonder nutrient and there is no doubt that many of the serious degenerative diseases plaguing the civilized world today can be prevented or even reversed through an adequate intake of this essential vitamin. The current RDA of 60 mg/day is clearly far too low and the proposed new RDA of 200 mg/day, while perhaps adequate for healthy, young males, would seem to be quite inadequate for older people and certainly way too low for sick people. As a matter of fact, a scientific advisory panel to the U.S. Government sponsored Alliance for Aging Research recently recommended that all healthy adults increase their vitamin C intake to 250- 1000 mg/day(24). A daily intake of 250-1000 mg of vitamin C may be adequate for preventive purposes, but far larger quantities are required in halting or reversing cancer and heart disease. Although there has been some concern that people suffering from hemochromatosis (a tendency to iron overload) may be sensitive to high dosages of vitamin C most researchers now agree that vitamin C is entirely safe even in daily quantities of 10 g or more(3,56,57). An adequate intake of vitamin C is surely the best and most cost effective health insurance available today!





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Woodhouse, P.R. and Khaw, Kay-Tee. Seasonal variations in vitamin C status, infection, fibrinogen and cardiovascular disease - Are they linked? Age and Ageing, Vol. 23, Supplement No. 2, 1994, p. P5
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siochain

vit c

Vitamin C and longevity
CAMBRIDGE, UNITED KINGDOM. A couple of recent test tube experiments widely reported by the popular press have managed to create doubt as to the benefits of vitamin-C. A report just released by researchers at Cambridge University will hopefully lay these doubts to rest. The study measured blood plasma concentrations of ascorbic acid (vitamin-C) in 8,860 men and 10,636 women. The study participants were followed for approximately four years. During this period a total of 692 men and women died - a total of 268 from cardiovascular disease, 189 from ischemic heart disease (angina or heart attack) and 284 from cancer. After adjusting for age, systolic blood pressure, cholesterol, body mass index, smoking, diabetes and the use of supplements the researchers concluded that men with an ascorbic acid level of 72.6 micromol/L or higher had a 36 per cent lower risk of dying from cardiovascular disease than did men with a level of 20.8 micromol/L or lower. The decrease in risk for death from ischemic heart disease, cancer and all causes was 37 per cent, 24 per cent and 23 per cent respectively. Women with a plasma level of 85.1 micromol/L had a 19 per cent lower cardiovascular disease mortality, a 44 per cent lower ischemic heart disease mortality, and a 15 per cent lower all-cause mortality than did women with an ascorbic acid level of 30.3 micromol/L. There was no correlation between cancer mortality and vitamin-C level among the women.
The researchers conclude that a 20 micromol/L rise in plasma ascorbic acid level can reduce all-cause mortality rate by 20 per cent independent of age and other risk factors. A 20 micromol/L increase can be obtained by increasing fruit and vegetable intake by 50 grams per day. The researchers also noted that higher vitamin-C levels were associated with lower systolic blood pressure and body mass index as well as with a higher level of "good" (HDL) cholesterol.
Khaw, Kay-Tee, et al. Relation between plasma ascorbic acid and mortality in men and women in EPIC-Norfolk prospective study: a prospective population study. The Lancet, Vol. 357, March 3, 2001, pp. 657-63

'

siochain

vit c

wrote:

Vitamin C helps prevent heart disease
HELSINKI, FINLAND. A new international cohort study sheds further light on the long-standing debate about the role of vitamin-C in coronary heart disease (CHD). The study combined the results of nine prospective studies on intakes of vitamin C, carotenoids and vitamin E.

The authors found that while intake of these vitamins through diet only slightly reduced CHD risk, vitamin C supplementation was associated with significantly lower CHD rates in both men and women. In recent decades, many studies have suggested that vitamin C and other essential nutrients play a role in heart health, possibly by preventing atherosclerosis (hardening of the arteries) that can contribute to CHD. Led by Dr Paul Knekt of the National Public Health Institute in Helsinki, the researchers analyzed data from nearly 300,000 participants and looked at all major CHD events and CHD mortality over a ten-year follow-up period.

Dietary intake of the carotenoid lutein was linked to slightly reduced CHD risk in the first two years of follow-up, as was vitamin-E intake in women, but overall the effect of dietary vitamin E and carotenoids on CHD risk after adjustment for other risk factors was small.

However, taking high doses of vitamin C (more than 700 mg a day) lowered the risk of major CHD events by 25 per cent. As vitamin C supplementation could merely act as an indicator of a generally "healthy" lifestyle, fiber and fat intake were taken into account, but the association remained just as strong. The results are supported by several previous studies suggesting a reduced CHD risk with vitamin C intake over 500 mg per day. On the other hand, no CHD benefit was found from vitamin E supplementation.

An interaction between vitamins C and E was expected, as vitamin C can help regenerate oxidized vitamin E, but the effect was not observed in this study. Despite the significant results concerning vitamin C, the authors conclude that the study does not provide unqualified support for high dose supplementation as they say the effects are not as yet fully understood.
Knekt P, et al. Antioxidant vitamins and coronary heart disease risk: a pooled analysis of 9 cohorts. American Journal of Clinical Nutrition, Vol. 80, December 2004, pp. 1508-1520

siochain

vit c

Vitamins C and E protect against Alzheimer's disease
BALTIMORE, MARYLAND. A distinguished group of medical researchers from four US universities has concluded that supplementation with vitamins C and E in combination is associated with a reduced prevalence and incidence of Alzheimer's disease (AD). Their study included almost 5,000 residents of Cache County aged 65 years or older. The prevalence (total number of AD cases at baseline) and the incidence (newly diagnosed cases per year of AD) over a 3-year follow-up period were determined and correlated with the reported use of multivitamins, vitamin B-complex supplements, and vitamins C and E.

The prevalence of AD in the segment of the study population not using any supplements was 4.9%. This compared to 0.9% among users of relatively high daily doses of vitamin-C (500-1000 mg/day or more) and vitamin E (up to 1000 IU/day). After adjusting for known AD risk factors, including the presence of apolipoprotein E epsilon 4 alleles, the researchers conclude that supplementation with both vitamins C and E is associated with a 78% lower prevalence of AD. The use of vitamin C containing multivitamins in combination with vitamin-E was associated with a 66% lower prevalence.

The annual incidence of AD was 1.1% among participants not taking supplements as compared to 0.4% per year among those supplementing with vitamins C and E in combination. After adjusting for other risk factors the researchers conclude that supplementation with vitamins C and E is associated with a 64% lower incidence of AD. Supplementation with vitamin E and vitamin C containing multivitamins was associated with a 53% reduction in risk.

The researchers found no association between a reduced prevalence or incidence and the use of multivitamins, vitamin B complex or vitamin C or E on their own. They conclude that vitamin C enhances the beneficial effects of vitamin E by regenerating vitamin E after it has been oxidized in its effort to combat oxidative stress. They also conclude that the amounts of vitamin C and vitamin E contained in multivitamins (RDA levels) are insufficient to provide any meaningful protection against AD. They urge randomized clinical trials to confirm their findings.
Zandi, PP, et al. Reduced risk of Alzheimer's disease in users of antioxidant vitamin supplements. Archives of Neurology, Vol. 61, January 2004, pp. 82-88

Editor's comment: These findings add additional weight to the importance of supplementing, specifically with vitamin E and vitamin C in amounts long advocated by alternative health practitioners (400- 800 IU/day of vitamin E combined with 3 x 400-500 mg/day of vitamin C). There is continually growing evidence that these two antioxidants are instrumental in preventing a large variety of degenerative diseases including heart disease, cancer, and stroke.

siochain

http://news.bbc.co.uk/1/hi/health/330827.stm

A substance rich in a vitamin that helps prevent cancer can increase the chances of smokers developing the disease in their lungs, scientists have said.
Vitamin A is found in beta carotene, a substance found in green vegetables and carrots.

Some forms of the vitamin are thought to protect against cancer because they contain chemicals called antioxidants.

But a large-scale trial has shown that beta carotene increases the risk of lung cancer in heavy smokers and asbestos workers.

Explaining the paradox

Dr Marvin Legator led a team of researchers at the University of Texas in Galveston.

Publishing their findings in the journal Nature, they offered a possible explanation as to why the paradox exists.

They said it could be down to an enzyme found in beta carotene that activates particles found called polycyclic aromatic hydrocarbons, or PAHs.

PAHs are found in tobacco smoke and are known to cause cancer.

Rats fed high doses of beta carotene were found to have increased levels of the enzyme - called CYP - in their lungs.

The researchers said: "In humans, correspondingly high levels of CYPs would predispose an individual to cancer risk from the widely bioactived tobacco-smoke procarcinogens."

Large-scale studies

A study involving nearly 30,000 participants found that there were 18% more lung cancers and 8% more deaths in smokers taking beta carotene.

Another, involving more than 18,000 people, found 28% more lung cancers and 17% more deaths in smokers and asbestos workers who took beta carotene and vitamin A supplements.

The researchers said: "We think our findings are relevant to public health policy and that they should be considered before widespread supplementation with these micronutrients is recommended."

tallaght01

I can't remember where I read it, but I think there was a higher incidence of birth defects in the babies of women who took "superdoses" of vit C, in the 80s. Taking huge doses was popular in California, and this population had a higher rate of childhood deformities. Proving direct causation is another thing enitirely, though

DrIndy

tallaght01 wrote: »

I can't remember where I read it, but I think there was a higher incidence of birth defects in the babies of women who took "superdoses" of vit C, in the 80s. Taking huge doses was popular in California, and this population had a higher rate of childhood deformities. Proving direct causation is another thing enitirely, though

maybe thats what happened to George Bush?

;-)

thanks Siochain - i appreciate quotations when conversations become very specific on scientific issues - it gives credence to your arguments and also provides an interesting read for someone stumbling onto the thread.

beeno67

Some of the evidence quoted for the use of high doses of vit C is very old (20 years in some cases) and the benefits of vit C have been quoted selectively. I am not saying vit C does not help prevent, heasrt disease or colds but I am saying the case is far from proven.
This is from 2007 and is a review of all studies over the paast few years
Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: systematic review and meta-analysis.

Bjelakovic G, Nikolova D, Gluud LL, Simonetti RG, Gluud C.
The Cochrane Hepato-Biliary Group, Copenhagen Trial Unit, Center for Clinical Intervention Research, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark. goranb@junis.ni.ac.yu
CONTEXT: Antioxidant supplements are used for prevention of several diseases. OBJECTIVE: To assess the effect of antioxidant supplements on mortality in randomized primary and secondary prevention trials. DATA SOURCES AND TRIAL SELECTION: We searched electronic databases and bibliographies published by October 2005. All randomized trials involving adults comparing beta carotene, vitamin A, vitamin C (ascorbic acid), vitamin E, and selenium either singly or combined vs placebo or vs no intervention were included in our analysis. Randomization, blinding, and follow-up were considered markers of bias in the included trials. The effect of antioxidant supplements on all-cause mortality was analyzed with random-effects meta-analyses and reported as relative risk (RR) with 95% confidence intervals (CIs). Meta-regression was used to assess the effect of covariates across the trials. DATA EXTRACTION: We included 68 randomized trials with 232 606 participants (385 publications). DATA SYNTHESIS: When all low- and high-bias risk trials of antioxidant supplements were pooled together there was no significant effect on mortality (RR, 1.02; 95% CI, 0.98-1.06). Multivariate meta-regression analyses showed that low-bias risk trials (RR, 1.16; 95% CI, 1.04[corrected]-1.29) and selenium (RR, 0.998; 95% CI, 0.997-0.9995) were significantly associated with mortality. In 47 low-bias trials with 180 938 participants, the antioxidant supplements significantly increased mortality (RR, 1.05; 95% CI, 1.02-1.08). In low-bias risk trials, after exclusion of selenium trials, beta carotene (RR, 1.07; 95% CI, 1.02-1.11), vitamin A (RR, 1.16; 95% CI, 1.10-1.24), and vitamin E (RR, 1.04; 95% CI, 1.01-1.07), singly or combined, significantly increased mortality. Vitamin C and selenium had no significant effect on mortality. CONCLUSIONS: Treatment with beta carotene, vitamin A, and vitamin E may increase mortality. The potential roles of vitamin C and selenium on mortality need further study.
PMID: 17327526 [PubMed - indexed for MEDLINE]

Also in terms of the common cold a review of evidence over the last 40 years.
Vitamin C for preventing and treating the common cold.

Douglas RM, Hemilä H, Chalker E, Treacy B.
BACKGROUND: The role of vitamin C (ascorbic acid) in the prevention and treatment of the common cold has been a subject of controversy for 60 years, but is widely sold and used as both a preventive and therapeutic agent. OBJECTIVES: To discover whether oral doses of 0.2 g or more daily of vitamin C reduces the incidence, duration or severity of the common cold when used either as continuous prophylaxis or after the onset of symptoms. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 4, 2006); MEDLINE (1966 to December 2006); and EMBASE (1990 to December 2006). SELECTION CRITERIA: Papers were excluded if a dose less than 0.2 g per day of vitamin C was used, or if there was no placebo comparison. DATA COLLECTION AND ANALYSIS: Two review authors independently extracted data and assessed trial quality. 'Incidence' of colds during prophylaxis was assessed as the proportion of participants experiencing one or more colds during the study period. 'Duration' was the mean days of illness of cold episodes. MAIN RESULTS: Thirty trial comparisons involving 11,350 study participants contributed to the meta-analysis on the relative risk (RR) of developing a cold whilst taking prophylactic vitamin C. The pooled RR was 0.96 (95% confidence intervals (CI) 0.92 to 1.00). A subgroup of six trials involving a total of 642 marathon runners, skiers, and soldiers on sub-arctic exercises reported a pooled RR of 0.50 (95% CI 0.38 to 0.66).Thirty comparisons involving 9676 respiratory episodes contributed to a meta-analysis on common cold duration during prophylaxis. A consistent benefit was observed, representing a reduction in cold duration of 8% (95% CI 3% to 13%) for adults and 13.6% (95% CI 5% to 22%) for children.Seven trial comparisons involving 3294 respiratory episodes contributed to the meta-analysis of cold duration during therapy with vitamin C initiated after the onset of symptoms. No significant differences from placebo were seen. Four trial comparisons involving 2753 respiratory episodes contributed to the meta-analysis of cold severity during therapy and no significant differences from placebo were seen. AUTHORS' CONCLUSIONS: The failure of vitamin C supplementation to reduce the incidence of colds in the normal population indicates that routine mega-dose prophylaxis is not rationally justified for community use. But evidence suggests that it could be justified in people exposed to brief periods of severe physical exercise or cold environments.
PMID: 17636648 [PubMed - indexed for MEDLINE]

And for Alzheimers
Vitamin C and vitamin E for Alzheimer's disease.Boothby LA, Doering PL.
Harrison School of Pharmacy, Auburn University, AL, USA. lisa.boothby@crhs.net

OBJECTIVE: To evaluate the literature on supplemental vitamin C and vitamin E therapy in the prevention and treatment of Alzheimer's disease (AD). DATA SOURCES: Literature retrieval was accessed through MEDLINE (1966-March 2005) using the key words antioxidants, vitamin C, vitamin E, Alzheimer's disease, and dementia. International Pharmaceutical Abstracts (1970-March 2005), Current Contents (1996-March 2005), Cochrane Database of Systematic Reviews (1994-March 2005), and Ebsco's Academic Search Elite (1975-March 2005) were searched with the same key words. STUDY SELECTION AND DATA EXTRACTION: Articles related to the objective that were identified through PubMed were included. DATA SYNTHESIS: Oral supplementation of vitamin C (ascorbic acid) and vitamin E (D-alfa-tocopherol acetate) alone and in combination have been shown to decrease oxidative DNA damage in animal studies in vivo, in vitro, and in situ. Recent results of a prospective observational study (n = 4740) suggest that the combined use of vitamin E 400 IU daily and vitamin C 500 mg daily for at least 3 years was associated with the reduction of AD prevalence (OR 0.22; 95% CI 0.05 to 0.60) and incidence (HR 0.36; 95% CI 0.09 to 0.99). Contradicting this is a previous prospective observational study (n = 980) evaluating the relationship between 4 years of vitamin C and E intake and the incidence of AD, which detected no difference in the incidence of AD during the 4-year follow-up. Recent meta-analysis results suggest that doses of vitamin E > or =400 IU daily for more than one year are associated with increased all-cause mortality. Mega-trial results suggest that vitamin E doses > or =400 IU daily for 6.9 years in patients with preexisting vascular disease or diabetes mellitus increase the incidence of heart failure, with no other outcome benefits noted. CONCLUSIONS: In the absence of prospective, randomized, controlled clinical trials documenting benefits that outweigh recently documented morbidity and mortality risks, vitamin E supplements should not be recommended for primary or secondary prevention of AD. Although the risks of taking high doses of vitamin C are lower than those with vitamin E, the lack of consistent efficacy data for vitamin C in preventing or treating AD should discourage its routine use for this purpose.

PMID: 16227450 [PubMed - indexed for MEDLINE]