# How does the biology of mega doses of vitamin C work **URL:** \ **Category:** Factual Questions\ **Created:** [July 7, 2012, 3:49pm UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523 "2012-07-07T15:49:19Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [July 7, 2012, 3:49pm UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/1 "2012-07-07T15:49:19Z")
I’m not so much asking about whether people like or dislike the idea, but there are people claiming 3-20g a day of vitamin C intake and I do not understand the biology of that. So how does bioavailability work at those levels? It was my understanding that absorption follows a curve, absorption is close to 80-100% under 200mg at a time, a lot of what it taken above 200-500mg taken at a time oversaturates the transport system and is just passed into the digestive system and causes bloating, gas and diarrhea. At doses of 1-1.5g the absorption is 33-50%, and at higher doses it drops into the teens. > **[Health, Nutrition & Care](https://www.dsm-firmenich.com/en/businesses/health-nutrition-care.html?id=43)** > > Beyond ingredients, we’re a purpose-led partner, elevating science-backed human health, nutrition and care products and customized solutions. > [@](#): > > Absorption and body stores > > Intestinal absorption of vitamin C depends on the amount of dietary intake, decreasing with increasing intake levels. At an intake of 30 to 180 milligrams, about 70% to 90% is absorbed; about 50% of a single dose of 1 to 1.5 grams is absorbed; and only 16% of a single dose of 12 grams is absorbed. Up to about 500 milligrams are absorbed via a sodium-dependent active transport process, while at higher doses simple diffusion occurs. > **[Vitamin C](https://en.wikipedia.org/wiki/Vitamin_C#Absorption.2C_transport.2C_and_disposal)** > > Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits, berries and vegetables. It is also a generic prescription medication and in some countries is sold as a non-prescription dietary supplement. As a therapy, it is used to prevent and treat scurvy, a disease caused by vitamin C deficiency. > Vitamin C is an essential nutrient involved in the repair of tissue, the formation of collagen, and the enzymatic production of certain neurotr... > [@](#): > > With regular intake the absorption rate varies between 70 to 95%. However, the degree of absorption decreases as intake increases. At high intake (1.25g), fractional human absorption of ascorbic acid may be as low as 33%; at low intake (\<200 mg) the absorption rate can reach up to 98%.[39] Ascorbate concentrations over renal re-absorption threshold pass freely into the urine and are excreted. At high dietary doses (corresponding to several hundred mg/day in humans) ascorbate is accumulated in the body until the plasma levels reach the renal resorption threshold, which is about 1.5 mg/dL in men and 1.3 mg/dL in women. Concentrations in the plasma larger than this value (thought to represent body saturation) are rapidly excreted in the urine with a half-life of about 30 minutes. Concentrations less than this threshold amount are actively retained by the kidneys, and the excretion half-life for the remainder of the vitamin C store in the body thus increases greatly, with the half-life lengthening as the body stores are depleted. This half-life rises until it is as long as 83 days by the onset of the first symptoms of scurvy.[40] > **[精品女同一区二区三区在线播放器|欧美一区二区三区四区情侣|日韩人妻无码精品视频|久久久久对白国产](http://www.allvitaminc.com/Lypo-Studies.asp)** > > 日韩人妻欧美中文版久久精品中文字幕大胸国产精品一区二区在线观看蜜国产欧美日本综合在线一区二区亚洲不卡的av在线国产欧美日韩在线一区国产成人一区二区在线不卡久国产精品正在播放一区二区三区h免费观看视频精品欧美国产偷窥一区二区 > [@](#): > > Steady-state plasma and tissue concentrations were determined at seven daily doses of vitamin C from 30 to 2500 mg. Vitamin C steady-state plasma concentrations as a function of dose displayed sigmoid kinetics. The steep portion of the curve occurred between the 30- and 100-mg daily dose, the current RDA of 60 mg daily was on the lower third of the curve, the first dose beyond the sigmoid portion of the curve was 200 mg daily, and complete plasma saturation occurred at 1000 mg daily. Neutrophils, monocytes, and lymphocytes saturated at 100 mg daily and contained concentrations at least 14-fold higher than plasma. Bioavailability was complete for 200 mg of vitamin C as a single dose. No vitamin C was excreted in urine of six of seven volunteers until the 100-mg dose. At single doses of 500 mg and higher, bioavailability declined and the absorbed amount was excreted. Oxalate and urate excretion were elevated at 1000 mg of vitamin C daily compared to lower doses. Based on these data and Institute of Medicine criteria, the current RDA of 60 mg daily should be increased to 200 mg daily, which can be obtained from fruits and vegetables. Safe doses of vitamin C are less than 1000 mg daily, and vitamin C daily doses above 400 mg have no evident value. The impression I am getting is that anything above around 400-1000mg a day \*absorbed \* (which could mean, in the case of 1g a day, 10g taken at once with 10% absorption, or it could mean 250mg taken 4x a day with 100% absorption) is just not absorbed by the digestive system and if it is, it is removed via the kidneys due to shortening of the half life of vitamin C until it is a low as 30 minutes. Is that a correct assumption? How long does it take for the transportation system in the digestive system to reset? If someone is taking 250mg at a time and wants to get to 1000mg a day absorbed, how long do they wait between doses? Do people who take 500-1000mg an hour manage to overwhelm the kidney half life, and get plasma levels above what is normally seen? Or is that passed out of the system too? ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [July 7, 2012, 9:45pm UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/2 "2012-07-07T21:45:11Z")
The concept of megadoses of vitamin C was fostered by Linus Pauling, who took 18 grams a day. As you know, he was a biologist and had two Nobel awards (a Peace prize and an award based on his work, not anything to do with vitamin C). He, and Albert Szent-Gyorgy (who isolated the vitamin) each took megadoses. Pauling wrote his first book on vitamin C, _Vitamin C and the Common Cold_. He wrote another book claiming it helped to cure cancer. Critcisms were made of his conclusions, and he rebutted those criticisms (at least in his own mind.) He always maintained that clinical studies did not have enough C. Grudgingly, the establishment upped the recommeded dosage, as you note in one of your links, to 200-400 mg, but I think the RDA remains at 60, for some strange reason. More recent studies, which did try more C, noted slight decrease in severity and longevity of the colds with megadoses, but doses well below 18g. Anecdotally, when I caught a cold in the past, I would take several grams every several hours, as soon as symptoms rearose, until I got diarhhea. Then I backed off. I found in my experience that continous intake of C stifles the symptoms. (The diarrhea stops once you stop the C.) I found that the temporary diarrhea is a small price to pay to be symptom-free. I think megadoes act in the same way as antihistamines, such as Contacts (if that is still being made). ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [July 7, 2012, 11:09pm UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/3 "2012-07-07T23:09:15Z")
> [@barbitu8](#): > > The concept of megadoses of vitamin C was fostered by Linus Pauling, who took 18 grams a day. As you know, he was a biologist and had two Nobel awards (a Peace prize and an award based on his work, not anything to do with vitamin C). He, and Albert Szent-Gyorgy (who isolated the vitamin) each took megadoses. Pauling wrote his first book on vitamin C, _Vitamin C and the Common Cold_. He wrote another book claiming it helped to cure cancer. Critcisms were made of his conclusions, and he rebutted those criticisms (at least in his own mind.) He always maintained that clinical studies did not have enough C. Grudgingly, the establishment upped the recommeded dosage, as you note in one of your links, to 200-400 mg, but I think the RDA remains at 60, for some strange reason. More recent studies, which did try more C, noted slight decrease in severity and longevity of the colds with megadoses, but doses well below 18g. > > Anecdotally, when I caught a cold in the past, I would take several grams every several hours, as soon as symptoms rearose, until I got diarhhea. Then I backed off. I found in my experience that continous intake of C stifles the symptoms. (The diarrhea stops once you stop the C.) I found that the temporary diarrhea is a small price to pay to be symptom-free. I think megadoes act in the same way as antihistamines, such as Contacts (if that is still being made). I’ve read Pauling (he was a chemist, but I don’t know if it matters since his work wasn’t related to his orthomolecular research), and one of his arguments is that animals that make vitamin C themselves up production drastically during times of illness or stress. I was interested in his ideas that arterisclerosis is a tool the body uses to compensate for too little collagen in blood vessels, and that large doses of vitamin C can help prevent this. The diarrhea itself wouldn’t bother me, but I tried 1000mg pills once a day and got a lot of gas and bloating from doing that. It wasn’t pleasant, and there is no way I could do that for life. However I took a 500mg pill today and so far nothing bad has happened, so I’m assuming most of it was absorbed. Here is the chart from one of the studies I listed earlier: [http://www.fao.org/docrep/004/Y2809E/y2809e07.gif](http://www.fao.org/docrep/004/Y2809E/y2809e07.gif) It shows pretty drastic improvements in plasma ascorbic acid levels from 0-200mg/day, going from about 8uM up to about 66uM in those doses (people were on a low vitamin C diet before the study started). Going from 200-400mg/day results in a minor boost (maybe from 66 up to 70). But going above that does virtually nothing, everything above 500mg/day is essentially a horizontal line relative to the dose. Raising the dose to 2500mg/day ups the plasma levels to 80uM, up from about 70uM at 400mg. I don’t get the appeal of going over 500-1000mg a day. Seems like the kidneys just get rid of it, or it isn’t absorbed in the first place. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [July 8, 2012, 9:51am UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/4 "2012-07-08T09:51:10Z")
I didn’t get the gas or bloating. Just diarrhea. I guess everybody reacts differently. But even if the C is just flushed out, wouldn’t the execretory cells absorb some of it on the way out? And if it isn’t absorbed, how does megadoses stifle the symptoms of a cold? It appears to have an antihistamine effect. One of his other ideas was that C is a hormone and most other animals synthesize it (except for primates and possibly one or two others - I don’t recall), and if we were to synthsize it, we would be synthesizing 20g a day, but we lost the ability to do so since C was so abundant in our food. (You are, of course, right in that he was a chemist. I didn’t think I was right when I typed biologist.) As to the interesting questions you asked, I have no idea, but would like to know myself. ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [July 8, 2012, 1:23pm UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/5 "2012-07-08T13:23:52Z")
> [@Wesley\_Clark](#): > > I don’t get the appeal of going over 500-1000mg a day. Seems like the kidneys just get rid of it [Yes](http://www.ajcn.org/content/66/5/1165.full.pdf). “Ascorbic acid (vitamin C) is commonly used as a dietary supplement, often in megadoses. However, as the daily oral dose is increased, the concentration of ascorbic acid in the plasma and other body fluids does not increase proportionally, but instead tends to approach an upper limit…This analysis is based on the renal clearance of ascorbic acid, which rises sharply with increasing plasma concentrations as a result of saturable tubular reabsorption. The analysis indicates that both saturable gastrointestinal absorption and nonlinear renal clearance act additively to produce the ceiling effect in plasma concentrations. As a consequence of this ceiling effect, there is no pharmacokinetic justification for the use of megadoses of ascorbic acid.” Linus Pauling was a brilliant man, but his foray into vitamin C as a cure-all was not one of his finer achievements. ---
**Author:** ![oreally](https://avatars.discourse-cdn.com/v4/letter/o/7ab992/32.png) [@oreally](https://boards.straightdope.com/u/oreally)\ **Post date:** [July 8, 2012, 1:45pm UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/6 "2012-07-08T13:45:25Z")
Pauling was great till he went out of his realm and generally got full of himself, esp with his “cures cancer” idiocy. But wild (and unproven) claims about curing cancer aren’t exactly rare. “megadosing” simply doesn’t work. Your body flushes out any excess. ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [July 8, 2012, 2:54pm UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/7 "2012-07-08T14:54:20Z")
> [@barbitu8](#): > > I didn’t get the gas or bloating. Just diarrhea. I guess everybody reacts differently. But even if the C is just flushed out, wouldn’t the execretory cells absorb some of it on the way out? And if it isn’t absorbed, how does megadoses stifle the symptoms of a cold? It appears to have an antihistamine effect. > > One of his other ideas was that C is a hormone and most other animals synthesize it (except for primates and possibly one or two others - I don’t recall), and if we were to synthsize it, we would be synthesizing 20g a day, but we lost the ability to do so since C was so abundant in our food. > > (You are, of course, right in that he was a chemist. I didn’t think I was right when I typed biologist.) > > As to the interesting questions you asked, I have no idea, but would like to know myself. Even if the vitamin C is absorbed in the digestive system it seems like the kidneys would just get rid of it. The half life seems to change based on plasma levels. It said in one of the articles the half life can drop to 30 minutes if plasma levels are too high, but can be extended to 83 days if you are in a very vitamin C deficient environment (like one that causes scurvy). I have no idea how the cold symptoms work wrt vitamin C. I don’t understand tons about it but earlier I mentioned how proponents of megadose theory talk about how animals that produce their own vitamin C produce higher amounts when sick. Studies on megadoses seem to have been done on healthy people. I wonder if the absorption or plasma levels would differ for those under physical or psychological stress, as both can increase the need for vitamin C. > **[Scientists Say Vitamin C May Alleviate The Body's Response To Stress](http://www.sciencedaily.com/releases/1999/08/990823072615.htm)** > > Large doses of vitamin C can prevent illness by alleviating the body's normal response to stress, according to a scientist at the University of Alabama in Huntsville. That study found giving mice vitamin C helped them cope with stress better, and the dose for the mice at 200mg a day, which seems like it works out to about 10g/kg of bodyweight, considering that mice weigh about 20g. Mice make their own vitamin C though, so I don’t know how all of that would ft together. Even though there are foods high in vitamin C, there is nowhere near 20g a day available via diet. Strawberries are one of the highest vitamin C per calorie food out there, they have more vitamin C per calorie than oranges (about 200mg vitamin C per 100 calories, vs about 100mg per 100 calories in an orange). But even if you eat nothing but strawberries and ingest 3000 calories a day, that is still only 6g a day of vitamin C. Far far short of the 20g megadoses people say we’d be producing inside our own body. And diets are going to be far more varied than just strawberries. Even in a diet high in citrus fruits and green vegetables I would assume that average vitamin C intake rarely goes over 1-3g a day or so. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [July 8, 2012, 7:44pm UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/8 "2012-07-08T19:44:28Z")
Yeah, I always wondered how our ancestors would’ve gotten so much abscorbic acid from diet alone. However, even if in megadoses much is not absorbed and excreted through the renal system, couldn’t some be absorbed in the urinary tract? Further, in megadoses it does have an antihistamine effect. ---
**Author:** ![dataguy](https://avatars.discourse-cdn.com/v4/letter/d/eada6e/32.png) [@dataguy](https://boards.straightdope.com/u/dataguy)\ **Post date:** [July 8, 2012, 8:47pm UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/9 "2012-07-08T20:47:51Z")
You may want to investigate something called liposomal vitamin C. It is a form of vitamin C encapsulated in fat the is absorbed through the liver rather than the intestine, allowing for much higher absorption and blood plasma levels and none of the gas or diarrhea. Just search the term “liposomal vitamin C”. You can form your own conclusions. I have tried it. I have no conclusive results to report. ---
**Author:** ![oreally](https://avatars.discourse-cdn.com/v4/letter/o/7ab992/32.png) [@oreally](https://boards.straightdope.com/u/oreally)\ **Post date:** [July 8, 2012, 9:17pm UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/10 "2012-07-08T21:17:18Z")
> [@dataguy](#): > > You may want to investigate something called liposomal vitamin C. > It is a form of vitamin C encapsulated in fat the is absorbed through the liver rather than the intestine, allowing for much higher absorption and blood plasma levels and none of the gas or diarrhea. Do you have a credible source/study/etc which has proven this? ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [July 9, 2012, 3:47am UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/11 "2012-07-09T03:47:08Z")
> [@oreally](#): > > Do you have a credible source/study/etc which has proven this? > **[It Kills Cancer - LewRockwell](https://www.lewrockwell.com/2010/01/bill-sardi/it-kills-cancer/)** > > Researchers Achieve Cancer-Killing Effect With Oral-Dose Vitamin C by Bill Sardi Recently by Bill Sardi: The Tax Trap: How a Florida Couple Declined Participation in a Government Ponzi Scheme and Ended Up in Prison In an overlooked study first... > [@](#): > > Design. This was a single blind study, measuring plasma levels in two subjects, in samples taken half-hourly or hourly for 6 hours, following ingestion of vitamin C. Data were compared with published results and with data from 10 years of laboratory plasma determinations. > > Materials and methods. Standard 1-gram tablets of vitamin C; liposomal vitamin C. Plasma levels were analysed using the method of Butts and Mulvihill. > > Results. Preliminary investigations of the effects of liposomal and standard formulation ascorbate showed that blood plasma levels in excess of the previously assumed maximum of 220 µm L—1 are possible. Large oral doses of liposomal ascorbate resulted in plasma levels above 400 µm L—1. > > Conclusions. Since a single oral dose can produce plasma levels in excess of 400 µm L—1, pharmacokinetic theory suggests that repeated doses could sustain levels well above the formerly assumed maximum. The study I and someone else posted earlier on ascorbic acid showed the plasma concentration of vitamin C growing rapidly at low doses, going from near zero up to about 60 uM/L at 180-200mg, then tapering off drastically only growing to 85 uM/L at doses as high as 2500mg a day. The study I just posted above found a 1,000mg dose of lipo-C resulted in plasma concentrations of 400uM/L, which is far higher than what people who took 2500mg of ascorbic acid in the other study had (85uM/L). However, that doesn’t change the fact that the kidneys would eliminate it pretty rapidly at that kind of concentration. ---
**Author:** ![Smashed\_Ice\_Cream](https://avatars.discourse-cdn.com/v4/letter/s/ed8c4c/32.png) [@Smashed\_Ice\_Cream](https://boards.straightdope.com/u/Smashed_Ice_Cream)\ **Post date:** [July 9, 2012, 7:45am UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/12 "2012-07-09T07:45:56Z")
Regarding the above citation: TWO subjects??!!?! ---
**Author:** ![oreally](https://avatars.discourse-cdn.com/v4/letter/o/7ab992/32.png) [@oreally](https://boards.straightdope.com/u/oreally)\ **Post date:** [July 9, 2012, 11:06pm UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/13 "2012-07-09T23:06:52Z")
> [@Wesley\_Clark](#): > > [It Kills Cancer - LewRockwell](http://www.lewrockwell.com/sardi/sardi144.html) :rolleyes: Still waiting. ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [July 10, 2012, 10:35pm UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/14 "2012-07-10T22:35:13Z")
> [@oreally](#): > > :rolleyes: Still waiting. If a study with two test subjects, taken from the internet, isn’t proof enough for you then I feel sorry for you and the cynical world you inhabit. ---
**Author:** ![oreally](https://avatars.discourse-cdn.com/v4/letter/o/7ab992/32.png) [@oreally](https://boards.straightdope.com/u/oreally)\ **Post date:** [July 11, 2012, 4:23am UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/15 "2012-07-11T04:23:45Z")
lol Yes we all know if it’s on the internet, it must be true. And wow 2 whole test subjects? Sure sounds conclusive to me. I noticed you didn’t point out any specific links (there are only about 100 on the site you referenced). You can’t be serious. If you call that “proof” then I feel sorry for you and the naive/deluded world you inhabit. ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [July 11, 2012, 4:27am UTC](https://boards.straightdope.com/t/how-does-the-biology-of-mega-doses-of-vitamin-c-work/627523/16 "2012-07-11T04:27:52Z")
He was joking. God, I hope he was joking.