Vitamin/ Supplements
Vitamin C
High Vitamin C Levels May Affect Risk of GI Disorders
Evidence suggests that low levels of ascorbic acid in the blood may increase the risk of several gastrointestinal disorders, including peptic ulcers and gastric cancer. Chronic infection with theHeliobacter pylori bacteria - particularly a strain known as cagA - may also contribute to gastric cancer and peptic ulcers.
Some research suggests that H. pyloriand ascorbic acid concentrations are not related, but these studies had small sample sizes. Prior to the current study, no large-scale studies had examined the relationship between blood ascorbic acid and H. pylori levels.
Researchers tested blood samples of 6,746 adults enrolled in the Third National Health and Nutrition Examination Survey. Of the test subjects, 32% tested positive for H. pylori; of those, 54% had the cagA strain. The gender, percentage of current cigarette smokers and self-reported use of NSAIDs were similar among those who tested positive for H. pylori and those who tested negative.
Analysis of the blood samples revealed that ascorbic acid rates were inversely related to the prevalence of H. pylori. In patients whose serum ascorbic levels were 0.35 milligrams or less, the infection rate with H. pylori was 37.2%. For patients with serum ascorbic levels of 0.36 or higher, the infection rate dropped to 30.8 percent, even after adjusting for variables such as age, race, body mass index, physical activity level, use of aspirin or NSAIDs, and cigarette smoking. This finding was statistically significant. In Caucasian subjects, the analysis found that a 0.5 milligram increase in blood ascorbic acid levels was associated with a 31 percent decrease in the prevalence of the cagA strain of H. pylori.
The researchers concluded: "Serum ascorbic acid is significantly correlated with seropositivity to both H. pylori and to the pathogenic cagA-positive strain of H. pylori among white Americans. To our knowledge, this report is the first
Researchers tested blood samples of 6,746 adults enrolled in the Third National Health and Nutrition Examination Survey. Of the test subjects, 32% tested positive for H. pylori; of those, 54% had the cagA strain. The gender, percentage of current cigarette smokers and self-reported use of NSAIDs were similar among those who tested positive for H. pylori and those who tested negative.
Analysis of the blood samples revealed that ascorbic acid rates were inversely related to the prevalence of H. pylori. In patients whose serum ascorbic levels were 0.35 milligrams or less, the infection rate with H. pylori was 37.2%. For patients with serum ascorbic levels of 0.36 or higher, the infection rate dropped to 30.8 percent, even after adjusting for variables such as age, race, body mass index, physical activity level, use of aspirin or NSAIDs, and cigarette smoking. This finding was statistically significant. In Caucasian subjects, the analysis found that a 0.5 milligram increase in blood ascorbic acid levels was associated with a 31 percent decrease in the prevalence of the cagA strain of H. pylori.
The researchers concluded: "Serum ascorbic acid is significantly correlated with seropositivity to both H. pylori and to the pathogenic cagA-positive strain of H. pylori among white Americans. To our knowledge, this report is the first
population-based study of Americans to report such associations. If these findings are confirmed by other investigators and are linked causally, higher intakes of ascorbic acid may be a protective factor in the prevention of H. pylori infection."
More Evidence that Vitamin C Helps Cold/Flu Symptoms
The U.S. recommended daily allowance of vitamin C is 75 mg for an adult man and 70 mg for an adult woman, although popular literature often suggests much higher doses as a means of treating respiratory infections.
Whether megadoses of vitamin C are effectively absorbed by the body or are passed off in the urine, as is the case with most water-soluble vitamins, has long been debated.
This study observed 252 students for 10 days to see if cold or flu symptoms were different between students receiving high doses of vitamin C compared to a control group. Subjects reporting symptoms received hourly doses of vitamin C (1,000 mg) for the first six hours, then three times daily there after. Subjects not reporting symptoms received 1,000-mg doses three times daily. A control group of 463 students also participated and were administered pain relievers and decongestants when necessary.
Methods of recording baseline data from subjects were different between groups; those in the control group were not asked whether or not they had cold or flu symptoms, while the vitamin C group patients were. Observation of the data demonstrates that reported overall flu and cold symptoms may decrease faster in those who take megadoses of vitamin C compared to a control group.
This study provokes many interesting questions. However, before substantial conclusions can be made, more rigorous patient handling and statistical methodologies will need to be implemented. For example, no statistical analyses were conducted to assess whether or not the two groups were dissimilar prior to the study, nor were the observed differences between the groups after the study statistically checked to see if they were due to chance alone.
This study observed 252 students for 10 days to see if cold or flu symptoms were different between students receiving high doses of vitamin C compared to a control group. Subjects reporting symptoms received hourly doses of vitamin C (1,000 mg) for the first six hours, then three times daily there after. Subjects not reporting symptoms received 1,000-mg doses three times daily. A control group of 463 students also participated and were administered pain relievers and decongestants when necessary.
Methods of recording baseline data from subjects were different between groups; those in the control group were not asked whether or not they had cold or flu symptoms, while the vitamin C group patients were. Observation of the data demonstrates that reported overall flu and cold symptoms may decrease faster in those who take megadoses of vitamin C compared to a control group.
This study provokes many interesting questions. However, before substantial conclusions can be made, more rigorous patient handling and statistical methodologies will need to be implemented. For example, no statistical analyses were conducted to assess whether or not the two groups were dissimilar prior to the study, nor were the observed differences between the groups after the study statistically checked to see if they were due to chance alone.
New Vitamin C Recommendations
This paper alerts health care professionals to the news that the Food and Nutrition Board of the National Academy of Sciences is revising its recommendations for vitamin C intake. The revision is required because since the current 60 mg recommended daily allowance (RDA) was set in 1989, extensive new biochemical, molecular, epidemiologic, and clinical data have become available.
The board will base its new recommendations (expected to be less than 1 g daily) on some or all of the following criteria to determine the estimated average requirement (EAR) in order to compute a specific RDA:
* dietary availability;
* steady-state concentrations in tissues relative to dose;
* bioavailability,
* urine excretion,
* adverse effects,
* biochemical and molecular function relative to vitamin concentration
* direct beneficial effects and epidemiologic observations relative to dose,
* prevention of deficiency.
Conclusions: "If the estimated average requirement (EAR) cannot be determined, an adequate intake (AI) amount is recommended instead of an RDA.
The board will base its new recommendations (expected to be less than 1 g daily) on some or all of the following criteria to determine the estimated average requirement (EAR) in order to compute a specific RDA:
* dietary availability;
* steady-state concentrations in tissues relative to dose;
* bioavailability,
* urine excretion,
* adverse effects,
* biochemical and molecular function relative to vitamin concentration
* direct beneficial effects and epidemiologic observations relative to dose,
* prevention of deficiency.
Conclusions: "If the estimated average requirement (EAR) cannot be determined, an adequate intake (AI) amount is recommended instead of an RDA.
The AI was estimated to be either 200mg/d from
5 servings of fruits and vegetables or 100mg/d of vitamin C to prevent deficiency with a margin of safety."
Vitamin C Influences Blood Lead Levels
In an effort to prevent lead toxicity, the Centers for Disease Control and Prevention (CDC) has developed screening programs to identify childhood blood lead levels. Among adults, work-related lead exposure has been targeted as an area of concern by the Occupational Safety and Health Administration.
As part of these efforts, data gathered from the Third National Health and Nutrition Examination Survey (1988-1994) was utilized in a study that evaluated the relationship of ascorbic acid (vitamin C) to blood lead levels. The study compared vitamin C intake (as evidenced by serum ascorbic acid levels) and blood lead levels in 4,213 children (age 6-16) and 15,365 adults (age 17 or older), with the results presented as follows:
* Children with the highest vitamin C intake were 89% less likely to have elevated blood lead levels compared with youths with the lowest intake.
* Adults with the highest vitamin C intake were 65-68% less likely to have elevated blood lead levels compared with adults with the lowest intake.
These findings suggest that high levels of ascorbic acid are independently associated with decreased incidence of elevated blood lead levels. The authors note that "if a causal relationship is confirmed, higher intakes of ascorbic acid may have public health implications for the prevention of lead toxicity."
* Children with the highest vitamin C intake were 89% less likely to have elevated blood lead levels compared with youths with the lowest intake.
* Adults with the highest vitamin C intake were 65-68% less likely to have elevated blood lead levels compared with adults with the lowest intake.
These findings suggest that high levels of ascorbic acid are independently associated with decreased incidence of elevated blood lead levels. The authors note that "if a causal relationship is confirmed, higher intakes of ascorbic acid may have public health implications for the prevention of lead toxicity."
Vitamin C Is in Your Brain
The blood-brain barrier is a fortress of blood vessels which forms a protective barrier between the blood and the brain. Researchers are studying vitamin C absorption in the brain to determine why it is present and at higher concentrations than any other area of the body.
Unlike many other substances which are screened out by the blood-brain barrier, vitamin C crosses as dehydroascorbic acid and is retained as ascorbic acid in the brain. These findings indicate that increasing the blood level of dehydroascorbic acid can potentially increase vitamin C concentrations in the brain.
Vitamin C has antioxidant properties which may slow the progression of moderately severe Alzheimer�s disease, and its role as a free-radical scavenger may help prevent other diseases.
Vitamin C has antioxidant properties which may slow the progression of moderately severe Alzheimer�s disease, and its role as a free-radical scavenger may help prevent other diseases.
Vitamin C Helps Lung Function?
Chronic obstructive pulmonary disease (COPD) is a major cause of death and disability among adults throughout the world. Cigarette smoking is a principal risk factor, but only 15 percent of smokers develop COPD, which suggests other factors may contribute to susceptibility.
The data for this study were collected in 1989 in 69 rural counties in China.
The data for this study were collected in 1989 in 69 rural counties in China.
Within each county, 120 subjects aged 35-64 years underwent pulmonary function testing, completed a detailed questionnaire and provided blood samples.
Among the 3,085 subjects for whom there were complete data, dietary intake of vitamin C was significantly related to protection against the loss of pulmonary function. The magnitude of the association between vitamin C intake and lung function equaled approximately one year of age-related decline in lung function for every 100-mg/day decrease in vitamin C intake. This association was observed among individuals and when comparing counties, and it held true for both dietary vitamin C and plasma vitamin C data.
A long-term study is needed to gauge the effect of vitamin C over time and its role in protecting the lung against age-related changes in pulmonary function.
Among the 3,085 subjects for whom there were complete data, dietary intake of vitamin C was significantly related to protection against the loss of pulmonary function. The magnitude of the association between vitamin C intake and lung function equaled approximately one year of age-related decline in lung function for every 100-mg/day decrease in vitamin C intake. This association was observed among individuals and when comparing counties, and it held true for both dietary vitamin C and plasma vitamin C data.
A long-term study is needed to gauge the effect of vitamin C over time and its role in protecting the lung against age-related changes in pulmonary function.
Vitamin C Favorably Alters Cholesterol Levels
Elevated lipoprotein levels (levels of protein/fat compounds in blood plasma) contribute directly to the buildup of cholesterol in the bloodstream. A study of 10 women examined the effects of vitamin C (ascorbic acid) supplements on plasma lipoprotein levels.
Subjects were supplemented with 1000 mg of vitamin C daily for four weeks. Vitamin C concentrations were significantly higher in blood plasma after two and four weeks of supplementation compared with baseline; levels appeared to peak after two weeks and were maintained through the four-week mark. Plasma concentrations of low-density lipoprotein cholesterol (LDLC) were found to be 16% lower at four weeks compared with baseline, and although high-density lipoprotein cholesterol (HDLC) levels did not change significantly with vitamin C supplementation, the minimal reduction in HDLC was positively associated with the increase in plasma vitamin C levels.
These findings parallel previous studies in suggesting that increases in vitamin C intake may favorably alter lipoprotein levels and thus reduce the risk of heart disease and other cholesterol-related disorders.
These findings parallel previous studies in suggesting that increases in vitamin C intake may favorably alter lipoprotein levels and thus reduce the risk of heart disease and other cholesterol-related disorders.
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