werner@aecom.UUCP (01/14/86)
Well, for those you objected that Vitamin C does more for the body than just prevent Scurvy, you are right. The body needs approximately 3 times as much Vitamin C as is needed to prevent Scurvy (5X for children.) (It should be noted that in the additional fraction, Ascorbic Acid is not really acting as a Vitamin, by the definition of a Vitamin.) HOWEVER, the British estimate that the dose of Vitamin C neccessary to prevent Scurvy is at the most, 10 mg/day. Triple that is 30mg/day. For children and pregnant women, 50mg. The US RDA, just to be sure, is 20mg/day above that, or 70 mg, which if it were any other topic, would be considered an ample margin of safety. Another calculation. The body tries very hard to maintain the blood level of Vitamin C between 0.4 and 1.5 mg/100 ml Blood. Assuming Ascorbic Acid is not sequestered in the blood (and it is to an extent, so this will be an OVERestimate), then a 70kg man (60% water or 42 liters) will store 170-630mg total Vitamin C in his body - as an upper limit! Hence it makes absolutely no sense to take more in a single dose, every day, than the body can possibly hold. If that isn't working AGAINST the body, I don't know what is! -- Craig Werner !philabs!aecom!werner "The world is just a straight man for you sometimes"
avg@diablo.ARPA (01/17/86)
Thanks to Craig Werner fro providing some data on Vitamin C. However, the reasoning from the data is questionable. Let's accept that my body tries to maintain 170-630 mg. of Vitamin C in my blood. To determine a sensible dose rate and a sensible single dose, I need to consider my metabolism rate for Vit C and my digestion. The Metabolism rate tells how fast VitC is consumed. It probably depends on availability, up to a maximum. I.e., the more in my blood stream, the faster my body will use it up, up to a saturation rate. I don't know how much my body will use in a day, or how it varies with conditions, but let's say that it will use as much as 500 mg / day IF my blood level is 600 mg. Then I should take at least 500 mg / day. But not all Vit C that I take enters my blood stream, so I really need to take a little (a lot?) extra. Say 600 mg taken will deliver 500 mg to my blood, for the sake of discussion. The final question is absorption rate. How long does it take for one dose to be absorbed? Assumption 1: It takes 1 hr to absorb a dose. Then I start with 600 mg in my blood and pop a pill. One hour later, my body has used up 500/24 of my reservoir (using my pretend numbers) = 21 mg. So if I took 300 mg and absorbed 250, my new level is 829 -- too high. According to Craig, my body will excrete about 200 without using it. I am getting only 20% benefit (50/250). Assumption 2: It takes 8 hrs to absorb a dose. Then I start with 600 mg in my blood and pop a pill. 8 hours later, my body has used up 500/3 of my reservoir (using my pretend numbers) = 170 mg. So if I took 300 mg and absorbed 250, my new level is 680 -- only slightly too high. According to Craig, my body will excrete about 50 without using it. I am getting 80% benefit (200/250). Much better. Assumption3: It takes 24 hrs to absorb a dose. Then I start with 600 mg in my blood and pop a pill. 24 hours later, my body has used up 500 mg of my reservoir (using my pretend numbers). So if I took 300 mg and absorbed 250, my new level is 350, down from 600. Continuing assumption 3 to the second day, it's reasonable to assume that my body now uses Vit C at half the rate, since only half as much is available. Assuming I take another 300 mg pill, I will use 250 and absorb 250 over the next 24 hrs, and stay at the 350 level in my blood. CONCLUSION: (At last!) It may (or may not) be fine to take 1000 mg in 24 hrs, but it is apparently not a good idea to take it all at once. Your body will excrete a large portion of it, if we believe Craig. We need more data to know the right amount of Vit C to take. How much can the body metabolize? What is absorption efficiency? What is absorption rate? If anybody can supply these, I'll be glad to re-do these calculations with the real numbers.