blinded, controlled trial.

 

Vitamin C Supplementation and Respiratory

Infections: a Systematic Review...

Eight of these trials were double blind and placebo controlled and seven were randomized. Five small trials found a statistically significant 45 to 91% reduction in common cold incidence in the vitamin C group. These trials were short and the participants were under heavy exertion during the trial. Furthermore, three other trials found a statistically significant 80 to 100% reduction in the incidence of pneumonia in the vitamin C group.

This site is a virtual treasure trove of vitamin research and other health information

http://www.vitamincfoundation.org/

 

 

Research:

Vitamin C Could Help Lower Body Fat Levels

ProHealthNetwork.com, 04-10-2006, Source: Decision News

Increasing intake of vitamin C improves the body’s ability to oxidize fat and can reduce fatigue, said US researchers at this week’s Experimental Biology 2006 in San Francisco.

Lead researcher, Professor Carol Johnson, told NutraIngredients.com: “This is all important because about 30 per cent of Americans have poor vitamin C status as indicated by blood vitamin C concentrations.�?

Despite these deficiency statistics, the image of vitamin C supplements with consumers is strong. According to Frost and Sullivan, the US market generated $151.7m (�?27.4m) in 2005. In Europe, revenue was calculated at $160.3m (�?34.6m) for 2005, and is expected to grow to $192.5m (�?61.6m) by 2011.

Bonnie Beezhold and Professor Johnston from Arizona State University presented the results of a double-blind, placebo-controlled trial of 20 obese men and women on a low-fat diet. One group's diet was supplemented with a 500 mg vitamin C capsule, while the other group received an identical-looking placebo.

The diet was formulated to provide 67 percent of the US RDA (recommended daily allowance) for vitamin C.

At the beginning of the trial, volunteers with the lowest serum concentrations of vitamin C were found to have the highest body fat mass.

After four weeks, the supplemented group had increased serum concentrations of vitamin C of 30 per cent, while the control (placebo) group's blood levels decreased by 27 per cent.

As vitamin C blood concentrations fell, so did the participants' ability to oxidize fat (an 11 per cent reduction). Interestingly, both groups lost the same amount of weight (4.1 kg, 9 lbs). While body fat mass decreased more in the vitamin C supplemented group, the difference was not statistically significant.

The study supported earier findings by Professor Johnston of a decrease in fat oxidation, and the researchers are now studying whether the impact of vitamin C status is associated with a gradual gain in body fat in non-dieting individuals.

The mechanism behind the vitamin C effect is linked to its essential role in the synthesis of carnitine, an amino acid responsible for the transport of fatty acids.

“Carnitine is important for fat oxidation - and the reduced ablility to oxidize fat creates fatigue and possibly retention of body fat,�?explained Johnston.

“Since fatigue is the earliest sign of a vitamin C deficiency, I am particularly interested in documenting this fatigue and whether it has a significant impact in metabolism,�?she said.

The recommended daily intake of the vitamin in Europe is 60 mg. In the US, men are recommended to consume 90 mg per day, and women 75 mg per day.

© 2001/2006 �?Decision News Media SAS �?All Rights Reserved.
 
From:   http://www.prohealthnetwork.com/library/bulletinarticle.cfm?ID=2833

VITAMIN C FIGHTS WEIGHT GAIN

Older adults may be able to use vitamin C to fight a condition in their cells that leads to lowered metabolism - a major cause of weight gain. University of Colorado researchers have found that adults between 60 and 74 years old who take vitamin C can boost their average metabolism by almost 100 calories a day. It has long been known that vitamin C is an antioxidant, meaning it fights the effects of oxygen-related free radicals in the body. Free radicals are a major cause of the cumulative tissue damage associated with aging. They also tend to suppress the body's resting metabolism, reducing its ability to burn of fat. By fighting free radicals, vitamin C helps older adults to maintain a healthier resting metabolism rate, thereby fighting some of the weight gain associated with aging.

From:   aomega.com/ahs/newsletters/nl030407.htm

07/01/2008- Increased blood levels of vitamin C may reduce the risk of stroke by 42 per cent, suggests a large European-based study.

Increased levels of the vitamin, associated with increased intake of fruit and vegetables, were found to offer significant cardiovascular benefits among the 20,649 men and women taking part in the European Prospective Investigation into Cancer.

The authors, led by Phyo Myint from the University of Cambridge, state that blood levels of the vitamin could be used as a biological marker of lifestyle used to identify people at high risk of stroke.

"An intriguing possibility is that the plasma vitamin C concentration is a good marker of a wider range of health behaviors, such as fruit and vegetable consumption, that may be protective against stroke," wrote Myint in the American Journal of Clinical Nutrition.

"It is also plausible that vitamin C may biochemically affect stroke risk."

Strokes occur when blood clots or an artery bursts in the brain and interrupts the blood supply to a part of the brain. It is the leading cause of disability and the third leading cause of death in Europe and the US. According to the Stroke Alliance for Europe (SAFE), about 575,000 deaths are stroke related in Europe every year. In the US, every 45 seconds someone will experience a stroke, according to the American Stroke Association.

Myint and co-workers followed the subjects for 9.5 years and documented 448 strokes during this time. The subjects completed a health and lifestyle questionnaire at the start of the study, and blood samples were taken to measure vitamin C levels.

The highest average blood levels of vitamin C (greater than 66 micromoles per litre) were associated with a 42 per cent lower risk of stroke, compared to the lowest average blood levels (less than 41 micromoles per litre), after adjusting the results for potentially confounding factors such as age, sex, smoking habits, alcohol consumption, blood pressure, cholesterol levels, BMI, physical activity, and use of supplements.

When the Cambridge researchers excluded participants who consumed vitamin C-containing supplements the results were the same, indicating that the benefits could have been from vitamin C-rich foods, such as fruit and vegetables.

"We believe that these findings are of interest for several reasons," stated the authors.  "First, the strong inverse association between plasma vitamin C and stroke suggests that plasma vitamin C is likely to be a good biomarker of whatever causal factors affect stroke risk, most plausibly the dietary intake of plant foods.

"Second, irrespective of any causal associations, plasma vitamin C appears to be a good predictive risk indicator of stroke, independent of known risk factors such as age, BP, smoking, lipids, diabetes, and BMI.

"Given that about half of the risk of stroke is unexplained by conventional cardiovascular disease risk factors and that the predictive validity of traditional cardiovascular disease risk factors appears to diminish with age, risk markers that may help to identify those persons at greatest risk of stroke for targeted preventive interventions with established therapies, such as BP reduction, may be of interest."

While further study is necessary, Myint and co-workers aid that it is unlikely that long-term randomised controlled trials using isolated vitamin C supplementation would be conducted using cardiovascular disease as an end-point.

"Nevertheless, the magnitude of the association between plasma vitamin C and subsequent stroke is substantial and independent of known major risk factors for stroke," they concluded.

In an accompanying editorial, Sebastian Padayatty and Mark Levine from the National Institutes of Health (NIH) welcomed the study as "refreshing in that its findings are both clear and not overstated".

"We need readily measurable and reliable biomarkers of fruit and vegetable intake," they continued. "Vitamin C is an attractive marker of fruit and vegetable intake because these foods are the primary sources of dietary vitamin C.

"However, use of vitamin C as an intake indicator has limitations. With ingestion of pure vitamin C, there is a steep sigmoidal dose-concentration relation in humans for doses between 30 and 100 mg. At 100 mg, fasting steady state plasma vitamin C concentrations are about 60 micromoles per litre. At 200 mg, corresponding to an intake of about 5 servings of fruit and vegetables, fasting steady state plasma concentrations are about 70 micromol/L and do not increase much with higher doses.

"It is unknown whether the same dose- concentration relationships hold for vitamin C in foods."

The take-home message from the study, said Padayatty and Levine, was that the public should aim for between five and nine servings of fruit and vegetables per day and to consume a wide variety of such foods.

Source: American Journal of Clinical Nutrition
January 2008, Volume 87, Pages 64-69
"Plasma vitamin C concentrations predict risk of incident stroke over 10 y in 20 649 participants of the European Prospective Investigation into Cancer - Norfolk prospective population study"
Authors: P.K. Myint, R.N. Luben, A.A. Welch, S.A. Bingham, N.J. Wareham, and K.-T. Khaw

Editorial: American Journal of Clinical Nutrition
January 2008, Volume 87, Pages 5-7
"Fruit and vegetables: think variety, go ahead, eat!"
Authors: S.J. Padayatty and M. Levine

From:  [http://www.nutraingredients.com/news/ng.asp?n=82354&m=1NIE107&c=wncpliawyjwyafc]