Nutrition Investigator Peer-reviewed article on safety and benefits of taking 500 mg of vitamin C twice-a-day- ABSTRACT: This review provides information determining how much vitamin C to take, including analysis of the recent findings, which demonstrate advantages and problems with higher daily doses. The Daily Value for vitamin C was raised to 90 mg for men in 2000, and Upper Limit of 2,000 mg per day was established as being safe. This followed a study of urinary excretion of vitamin C (AA) that demonstrated 500 mg twice a day provides levels sufficient to cause continuous urinary excretion in humans. That is the lowest oral dosage evaluated that significantly saturates blood plasma. A later study endorsed 200 mg from dietary sources for the RDA. Even though plasma concentration of AA is then significantly lower, at 200 mg daily certain white blood cells are saturated with AA. Recently many studies have indicated the benefit of high levels of AA to maintain the brain, bones, and heart, reduce damage from stroke, brain trauma, and cataracts, and lower the risk of cancer metastasis and colds. Pro-oxidant activity has been found only for i.v. adminstration, where high concentrations appear effective destroying tumor cells while not harming normal cells. This review evaluates recent research and finds it consistent with the hypothesis that people, especially older people and soldiers in combat environments, are likely to benefit if they maintain the saturating level of AA by taking 500mg supplements twice a day.

TABLE 1: SUMMARY OF POTENTIAL DAMAGE BY OXIDATIVE STRESS AND BENEFITS OF AA INTAKES OF 500 MG TWICE A DAY TO HUMANS

BRAIN	ROS contribute to Alzheimer's (Su et al 2008) AA reduces cognitive decline (Araujo et al 2005) AA reduces reperfusion injury(Rozell 1998) AA reduces damage from head trauma (Polidori et al 2001) AA generates new neurons (Prozorovski et al 2008)
HEART	AA reverses endothelial dysfunction (Levine GN et al 1996). AA generates new cardiac myocytes (Takahashi et al 2003) AA (500 mg twice daily) protects plasma (Moser et al 2006)
EYES	AA reduced cataract odds 64% (Valero et al 2002)
COLDS	AA (500 mg) reduced frequency of colds by 66% (Saszuki et al 2006)
BONES	Highest tertile had less bone loss (Sahni et al 2008)
CANCER	AA reduced mutations causing metastases (Ishikawa et al 2008) iv AA reduced tumor growth in mice and did not harm normal cells in vitro (Chen et al 2008)
SAFETY	Up to 2,000 mg AA daily is safe (Hathcock et al 2005)
DEATH	No significant effect on mortality (Bjelakovic et al 2007)

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