Multiple Chemical Sensitivity Etiology
Airway Genetics and Ambient Combustion Aerosol
Vitamin C
Known for role as antioxidant - including scavenging reactive oxidants in respiratory mucosa, and diminished lipid peroxidation as measured by urinary isoprostane excretion (DRI 2006) - most vitamin C is in cells - with a lesser plasma concentration (Padayatty 2003, RDA 1989, Garry 1987, Moser 1987, Kallner 1979). Cells saturate before plasma at intakes between 100 and 200 mg daily with nearly the maximum 2000-3000 mg body store achieved at approx 200 mg/day - though plasma concentrations rise slightly as intakes increase to over 1000 mg/day.
Intakes of 60-100 mg/day result in nearly one half the body store (1500 mg) which at full deprivation may fall into the scorbutic range in 30 days - overt symptoms of scurvy occurring at under 10 mg/day with stores below 300 mg. Low but non-scorbutic plasma vitamin C concentrations may produce fatigue.
90% of 30 mg and less than half a 1250 mg dose is absorbed. At daily intakes of less than 100 mg metabolic byproducts - principally oxalate - are excreted. At intakes over 200 mg much vitamin C spills into the urine as the originally composed ascorbic acid.
Observing the minimal rise in plasma concentration at intakes over 200 mg/day and no change in the marker of oxidative stress (plasma T bars - thio barbituric acid - reactive substances) - Rousseau 2004 concluded the optimal bioavailability of vitamin C seems to be reached at 200 mg/day - higher amounts apparently conferring no additional value with increased energy expenditure.
The DRI has been set at 60-90 mg/day which not reaching near maximum saturation - may seem low. 200 mg may be best - fully saturating the cells which comprise most of the store while not resulting in large amounts of ascorbic acid or its metabolites in the urine and feces - reducing risk of undesirable side effects that may occur at higher intakes (Rautiainen 2010, Gomez-Cabrera 2008, DRI 2006).
Intakes of 60-100 mg/day result in nearly one half the body store (1500 mg) which at full deprivation may fall into the scorbutic range in 30 days - overt symptoms of scurvy occurring at under 10 mg/day with stores below 300 mg. Low but non-scorbutic plasma vitamin C concentrations may produce fatigue.
90% of 30 mg and less than half a 1250 mg dose is absorbed. At daily intakes of less than 100 mg metabolic byproducts - principally oxalate - are excreted. At intakes over 200 mg much vitamin C spills into the urine as the originally composed ascorbic acid.
Observing the minimal rise in plasma concentration at intakes over 200 mg/day and no change in the marker of oxidative stress (plasma T bars - thio barbituric acid - reactive substances) - Rousseau 2004 concluded the optimal bioavailability of vitamin C seems to be reached at 200 mg/day - higher amounts apparently conferring no additional value with increased energy expenditure.
The DRI has been set at 60-90 mg/day which not reaching near maximum saturation - may seem low. 200 mg may be best - fully saturating the cells which comprise most of the store while not resulting in large amounts of ascorbic acid or its metabolites in the urine and feces - reducing risk of undesirable side effects that may occur at higher intakes (Rautiainen 2010, Gomez-Cabrera 2008, DRI 2006).
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