Orange - a source of vitamin CHave questions about vitamin C? As part of the webinar by our resident expert on vitamin C, Alexander Michels, PhD, answered questions submitted online.

If you have more questions you would like answered, see part 2 of this FAQ or feel free to ask!

Vitamin C in the Body

How long does vitamin C stay in the body?

Vitamin C can stay in the body for weeks. Levels of vitamin C in the blood are controlled by the kidneys through a process known as ‘renal reabsorption,’ which prevents vitamin C from being lost in the urine. Taking large doses of it can overwhelm this system, so the extra amount is lost in the urine in a matter of hours.

When someone who already has high levels in the blood takes some vitamin C, the increase in the body is only temporary – the majority is lost in the urine. When someone who doesn’t have high blood levels of vitamin C takes it, the vitamin stays in the system longer.

How should doses of vitamin C be divided to maximize the blood concentration and the time it stays in my body?

Supplement BottleI should start by saying there is no known advantage of keeping plasma levels above the threshold set by your kidney. It may have advantages, but they have not been determined (yet).

That said, if you want to keep plasma vitamin C levels as high as possible over time, it is best to take multiple doses spread out throughout the day. While small doses (under 200 mg) are completely absorbed, only a fraction of a single large dose of ascorbic acid can be absorbed at one time (500 mg or more). Spacing the doses out will increase the overall absorption.

You can take vitamin C every few hours, but it becomes a difficult practice to keep up. Some people recommend taking vitamin C supplements twice a day, and this likely strikes the best balance between practicality and maintaining high levels in the blood.

Just be aware that when ascorbic acid levels are high in the blood for a long period of time, the body tries to remove it by increasing the amount excreted in the urine. Thus, if you take multiple large doses throughout the day (say, every two hours), most will be either unabsorbed or quickly excreted.

Does taking large amounts of ascorbic acid add too much acid to my system? Is buffered vitamin C preferred?

The body can handle the acid in large amounts of ascorbic acid. Remember, the acid in your stomach is much stronger than ascorbic acid, and the body can neutralize that easily. In addition, your cells and blood have buffering systems that prevent the pH from getting too low or too high.

The only reason you might want to consider “buffered” vitamin C is if you have stomach distress or heartburn after taking ascorbic acid. Many buffered preparations aren’t buffered at all – they are mineral ascorbates with nearer-to-neutral pH. In other words, they are much less likely to upset your stomach than regular ascorbic acid.

Are there other ways to get high blood vitamin C levels, similar to intravenous injection?

Not orally. Many products may claim to increase bioavailability of vitamin C (like lipospheric formulas) , but currently there is no clinical support for these claims. High doses of ascorbic acid  have been administered to rats and mice by injection in the space surrounding the intestines or intro muscles, avoiding the need for finding a vein, but still requiring sterile preparations of ascorbic acid. Not something that is recommended for home use.


Vitamin C Supplements

I have read that vitamin C is not ascorbic acid, and that there are other components that make of vitamin C. Is this true?

Redox Vitamin CAbsolutely not.

Ascorbic acid is vitamin C because it can prevent and cure the disease that forms from its deficiency – scurvy. This is part of the definition of a vitamin.

Some people have postulated that vitamin C does not work alone in the body, i.e., that it needs to be present in a “complex” of other factors to work properly. This is contrary to all the scientific literature. At one point in time, the man who discovered the chemical structure of ascorbic acid, Albert Szent-Györgyi, thought he had found that bioflavonoids were necessary for the action of vitamin C and were found in a complex in plants, but this turned out to be a false lead.

Ascorbic acid, as recommended by Linus Pauling over 40 years ago, is sufficient to satisfy your body’s requirements for vitamin C.

Is there a difference between natural and synthetic ascorbic acid? Are there differences in bioavailability between natural sources and synthetic supplements containing vitamin C?

No. Unlike some vitamins, such as vitamin E, the natural and synthetic forms of ascorbic acid are identical. The chemical mirror image of ascorbic acid (an isoform called sodium erythorbate) is not the same as ascorbic acid because it does not have any vitamin activity. It is often used as a food preservative because it has antioxidant activity.

There is currently no evidence that natural source supplements have greater bioavailability than synthetic supplements, or straight ascorbic acid. There is some literature to support that there are differences in animal models (such as mice or rats) in bioavailability when ascorbic acid is presented in a mixture of food or plant-based material, but studies in humans have shown no differences. This is likely due the differences between many animal species (who can make ascorbic acid in the liver) and humans (who are dependent on ascorbic acid from the diet), but the reasons for these differences on a molecular level are not clear.

Should I take ascorbic acid with rose hip flavonoids or other bioflavonoids to increase its absorption or activity?

There is no evidence to suggest that taking vitamin C with flavonoids will increase the absorption or activity of ascorbic acid. On the contrary, there is a study that suggests taking a large amount of quercetin (a flavonoid in rose hips) inhibits absorption. This inhibitory effect is small and likely insignificant, but it certainly does not suggest any benefit to combining flavonoids with vitamin C.

The man who first characterized ascorbic acid, Albert Szent-Györgyi, thought of flavonoids as a vitamin that worked with vitamin C based on work in guinea pigs. However, after finding out that removal of flavonoids from the diet was not necessary for life (and not a vitamin) or the activity of ascorbic acid, the work did not progress any further. Unfortunately, some use that older work as evidence that flavonoids are necessary for vitamin C activity and absorption.

Studies of this on flavonoids and vitamin C have not yet been performed in humans, making it difficult to say anything conclusively about it.

Is there an advantage to taking liposomal, esterified, time-release, or mineral forms of ascorbic acid compared to taking plain ascorbic acid?

There has been no proven benefit to taking any other form of vitamin C over plain ascorbic acid. Many companies claim their product has a greater bioavailability, but there is little in the scientific, peer-reviewed literature to support such claims. For more specific information about forms of vitamin C, see the Micronutrient Information Center.

I found claims online supporting the consumption of dehydroascorbic acid (DHAA) for superior bioavailability compared to ascorbic acid. Is this true?

While in cells dehydroascorbic acid can be absorbed faster than ascorbic acid, the evidence is not clear in humans. Dehydroascorbic acid is very unstable and can breaks down in a matter of minutes – simply with contact with water. Likely, consuming a large amount of dehydroascorbic acid will do nothing as it will degrade before it has a chance to enter your system. Even if stabilized, it is not advisable to take dehydroascorbic acid, especially in large amounts.

Many regulatory agencies have warnings about dehydroascorbic acid because of reports that it can actually stress or kill cells in culture by placing excessive demands on cellular metabolism. Rats administered intravenous dehydroascorbic acid at levels where ascorbic acid causes no toxic effects has caused death. The toxic levels of dehydroascorbic acid is estimated to be much higher than ascorbic acid in rats, rabbits, and mice.

Furthermore, dehydroascorbic acid degradation products include oxalate – so anyone concerned about oxalate consumption or kidney stones should be aware of that fact. Some reports have linked dehydroascorbic acid breakdown products to protein glycation – a process where small carbohydrates can attach to proteins and cause them to lose function (depending on the site of attachment). There have been reports of kidney damage and diabetes-like symptoms after animals were injected with high amounts of dehydroascorbic acid. This may be due to protein modification, a halmark of diabetes.

What exactly happens to the body after oral consumption of dehydroascorbic acid is still unclear. No adequate amount of testing has been done on high doses of it, but does pose a potential risk and should be regarded with caution.

Should I take ascorbic acid alone or with food? What about over-the-counter, pharmaceutical drugs, or other supplements?

There are no known advantages or disadvantages to taking ascorbic acid alone or with food in terms of how much reaches your bloodstream. People who want to maximize their iron absorption should take vitamin C with iron-rich foods or supplements. If you have hemochromatosis (iron overload disease) you should avoid taking vitamin C with iron sources in your diet, and do not take more than 500 mg/day of vitamin C supplements.

It is possible that calcium (or calcium contianing foods)can inhibit absorption slightly, but it might not make a noticeable difference.

Great care should be taken when taking vitamin C with drugs of any sort. This will likely not affect the amount your body absorbs, but there may be interactions between the drug and ascorbic acid that could inadvertently decrease the effectiveness of the drug. Many of these have been documented on databases online, so check your medication. See the Micronutrient Information Center for more information.

Does GMO corn or other GMO crops used as a source of glucose have any effect on ascorbic acid synthesized from these materials?

No. The process of synthesizing ascorbic acid removes other materials from the source of glucose. Multiple manufacturing steps are needed to isolate and purify ascorbic acid. In some cases, the vitamin comes from a living organism that performed intermediate steps in the transformation of glucose into ascorbic acid. During these many levels of production, all traces of the material from the previous step have to be eliminated to result in pure vitamin C.


Vitamin C in Food

If heat destroys vitamin C, is the consumption of raw fruit and vegetables the only way to get vitamin C?

Heat destroys vitamin C in a time- and temperature-dependent fashion. The hotter the cooking temperature, the more vitamin C is destroyed, and the amount of vitamin C lost will increase the longer the heat is applied. That is not to imply that raw fruit and vegetables are the only good sources of the vitamin. Some fruits and vegetables contain enzymes (like ascorbate oxidase) that will slowly oxidize ascorbic acid after they are chopped, crushed, or chewed. Brief cooking can destroy these enzymes and stabilize ascorbic acid. Additionally, the fibrous nature of raw vegetables makes the bioavailability of ascorbic acid low in their uncooked (not softened) form.Orange Juice Vitamin C

Frying at high temperatures destroys ascorbic acid. Baking can also destroy some, but that is highly dependent on time and temperature. Steaming is preferable to boiling because it destroys less, and cooking in the microwave is considered to be preferable to either method. Ascorbic acid is most stable in acid, so that may help prevent the loss of ascorbic acid during any cooking method. For example, the addition of vinegar or lemon juice to a fruit or vegetable purée when heated may preserve it even when it is cooked for a short period of time.

How much variation is seen in fruit and vegetable vitamin C? Does it vary with season?

There is a tremendous amount of variability in the fruit and vegetable content of vitamin C. Of course, different types of fruit and vegetables contain different amounts of ascorbic acid, but variation can also occur from region to region and from plant to plant. Stage of maturation, growth conditions, seasonal variations, and storage conditions also are likely to contribute, but the magnitude of these effects are not well documented.

How well does vitamin C fare in food that is stored, or kept on the shelf?

This can depend greatly on the method of storage. Vitamin C levels in most foods are affected by excessive heat, light, alkaline conditions, and oxygen exposure. Vitamin C that has exposed to light for long periods of time will begin to degrade over time. This has been demonstrated in orange juice on the shelf in a supermarket.

Pasteurization or irradiation of foods (to destroy bacteria) tends to destroy ascorbic acid as well – one reason there is no appreciable vitamin C content of store-bought milk. Some packaged foods are processed with acid and oxygen-free conditions to limit the loss of the vitamin. Often, manufacturers will add ascorbic acid to foods to prevent oxidation, and those that claim to have a particular amount of vitamin C on the label will add more than is stated to account for some loss over time.

Frozen fruit anjuice aisled vegetables are good sources, as the freezing process destroys some of the enzymes that would otherwise degrade vitamin C in fresh fruit and vegetables. Also, the cold temperatures tend to preserve ascorbic acid. Canned fruit has also been shown to be a good source of vitamin C – likely because the products are canned shortly after harvest with minimal additional processing, and the use of brief amounts of heat in the canning process can destroy enzymes that would otherwise degrade it.


More questions about vitamin C?

See the Linus Pauling Institute’s  webinar by Alexander Michels, PhD or part 2 of this FAQ.

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50 thoughts on “Questions about Vitamin C

  1. Way too conservative for me. Just because something isn’t written up in the “peer reviewed” literature does not mean that it isn’t so. He sounds more like he is working for a pharmaceutical company than he is for the people of the State of Oregon.

    • He’s just stating the facts as they are known to him mate. And yes, he does seem to be working for/with the university and that’s how uni folks write articles and represent facts in them – by stating peer reviewed literature. That’s the system and not his fault. I do also agree with your statement about the fact that if something isn’t peer reviewed doesn’t necessarily mean that it’s not so, at least not yet, but the author and uni folks in general isn’t willing to hazard a guess on that. No hard feelings, in fact, I like uni folks for that sort of reason. I also get info from non-uni sources and you can make up your own mind. 🙂 My only critique is that I’d have like to have heard about some of the newest science on the benefits of high dose vitamin c experiments but I guess I’ll need to find and read another article for that answer. 🙂

      • We could use a lot more studies about high-dose vitamin C, especially in conjunction with the immune system. Our major limitation now is research funding for anything related to vitamin C. Many people want to see the studies done except those that control, but not the people in charge of paying for it.

        • This excretion theory is simply not true. For every molecule of C ingested the body will absorb two electrons of anti-oxidant benefit which helps the body systems dramatically. The excreted amount is ascorbic acid plus dehydroascorbic acid. The body is benefitting from every bit of C you ingest. These prevailing excretion theories are simply not accurate.

          Check out Dr. Thomas Levy. He is the authority on vitamin C.

          Megadoses are tremendous for humans and all creatures in my opinion. Why do you think a 150 pound goat produces 13 GRAMS a day? When injured or confronted with illness the same creature will produce up to 100,000 mgs. per day – 100 GRAMS!

          • I am aware of the theories Dr. Levy has provided, but they do not fit the facts. The literature on vitamin C transport in animals and people is clear – There is a limit to vitamin C absorption in both the intestine and other tissues of the body. Whatever is not absorbed by the body will be excreted, and we have yet to find a way to change that limit of absorption.

            Also, the idea (straight from Dr. Pauling’s own calculations) that a goat produces many grams of vitamin C per day has not withstood the test of time. We now know much more about how vitamin C is synthesized in animals, and that the rate of vitamin C production is high not as high as Pauling suggested, nor is it constant.

            I can’t say that there aren’t any effects of taking megadoses of vitamin C, but to date they have not been conclusively established. We continue to home more research is done in this area.

  2. After I drink a fresh fruit smoothie in the morning, I believe I should wait for a period of time before I drink my morning coffee, because the coffee will flush some nutrients out of my system. First, is this true? Second, is a half hour long enough so that I have had the benefit of the fruit? Should I wait longer?

  3. Hi!
    Many thanks for the Q & A 🙂

    I have a question, if you’re still here –

    Many people suggest Ascorbate over Ascorbic. They suggest adding a bit of Sodium Bi Carbonate to make it more Alkali (better absorption, etc.).

    Question: Is any of this necessary / useful? Or any OTC Vitamin C tablet / brand will do?

    Many Thanks!

    • Ali,
      Mineral ascorbates are suggested for people who have acidic stomach after taking the acid form. It will not improve the absorption. There is a risk of adding sodium bicarbonate to ascorbic acid, however, as pH can affect stability. Ascorbic acid likes to be in acid environments to stay in its active form. If the pH gets above neutral, slightly alkaline, there is a possibility it could oxidize quickly. Therefore, I wouldn’t recommend adding sodium bicarbonate on your own, especially if your stomach doesn’t have problems with the acidic form.

      • Does this mean that mineral ascorbate supplements are unstable and could already be oxidized by the time you ingest them?
        Is it better to take ascorbic acid?
        But then what about a multivitamin pill that has ascorbic acid in it together with calcium carbonate and magnesium carbonate and other vitamins and minerals, will this affect stability?

        • Mineral ascorbates are less shelf-stable than plain ascorbic acid, but besides pH, time, temperature, light, and water all play roles in how ascorbate degrades. So it depends on the specific situation.

          Carbonates are not likely to alter stomach pH to a degree that ascorbate will be degraded. Degradation of ascorbate usually only occurs above pH 7, and antacids can’t even raise stomach pH that high. A greater concern would be bile acids in the intestines – as long as the pH is not increased too much in the intestines, ascorbate will stay stabilized.

  4. The science on liposome encapsulations is very much established.
    The author should have taken the time to research it just a little before stating that liposomal delivery has no benefit over standard oral dosing.

    • The science on liposome encapsulations for other vitamins and compounds is established, but the efficacy of vitamin C delivery from liposomal encapsulation is still debated. No peer reviewed, rigorous studies have been performed showing that vitamin C delivery to the blood stream is enhanced with liposomal formulations. The only “studies” that exist are poor and by no means definitive. That is not to say that liposomes are unable to provide ascorbic acid to the body in higher amounts, we are just saying there is no quality evidence to support that claim. Until there is, we cannot recommend that delivery system.

      • I was shown one liposomal vitamin C study, where a vitamin C blood serum level of 600mmol/l was achieved on a dose of 36g. This is because regular systematic dosages of liposomal nutrients will accumulate in the body exponentially. Considering apoptosis will occur at around the 270 mmol/l of vitamin C, this paves the way for liposomal nutrients being of tremendous therapeutic value.

        Bioavailability is incredibly poor with oral dosing, and many people anecdotally (Liposomal Vitamin C Facebook group for example) have discovered that they can consume far more vitamin C when taken as a liposome, because they do not experience the bowel intolerance they would have with oral dosing.

  5. do you think drinking orange juice in the morning can keep you on your feet and on the move. because i have school and i want to stay awake during classes.


    • Orange juice can be a good way to start your day, but the carbohydrates should be balanced with something containing protein to give you some lasting energy. Unfortunately the vitamin C won’t do much for an energy boost unless you are very low in the vitamin to begin with.

  6. Dear Dr. Michels,
    Regarding certain statements you have made here about dehydroascorbic acid (DHAA):

    You said, Likely, consuming a large amount of dehydroascorbic acid will do nothing as it will completely degrade before it gets a chance to enter your system.

    Contrary to that, the peer-reviewed literature contains many, many studies demonstrating that DHAA is efficiently absorbed and utilized by humans and animals. Some of these references date back to the 1930s, and just one example of a human study is
    Human Utilization of Dehydroascorbic Acid published clear back in 1958. For a more recent example see l-dehydroascorbic acid can substitute l-ascorbic acid as dietary vitamin C source in guinea pigs which was published just this year. This later reference includes stability data for the DHAA solutions they used demonstrating that 90% of the DHAA was retained over a period of 24 hours (far more stable, in fact than the comparable ascorbic acid solutions). The consensus among most scientists is that AA and DHAA are equivalent sources of dietary vitamin C when taken orally in doses in the range of RDA amounts.

    Studies with large doses are much more difficult to find, but at least one study in rats given 12 mg doses of AA and DHAA demonstrated much greater bioavailability of DHAA Intestinal Dehydroascorbic Acid (DHA) Transport Mediated by the Facilitative Sugar Transporters, GLUT2 and GLUT8. And at least one study in one human being, who took 5 grams of AA and 5 grams of DHAA on different days, also demonstrated much greater bioavailability of DHAA video (this study is not “peer-reviewed literature,” so you can ignore it if you wish).

    You said, Regardless, it is not advisable to take dehydroascorbic acid, especially in large amounts. Many regulatory agencies have listed dehydroascorbic acid as potentially harmful if swallowed because of reports that it can actually stress or kill cells.

    Although you may find the phrase “potentially harmful if swallowed” on an MSDS sheet for DHAA, you will find a similar warning on many MSDS sheets for plain old ascorbic acid as well. Perhaps this is the source of your claim about many regulatory agencies, but I have never seen or heard of any organization that can be properly called a regulatory agency that has listed DHAA as potentially harmful. Please correct me if I’m wrong.

    DHAA represents about 10-20% of the vitamin C found in foods, so we all eat some amount of it every day. It is clear that a significant fraction of a large intravenous dose of ascorbate is oxidized in vivo, because the peroxide you refer to is formed in the oxidation process, and because the accumulation of DHAA in cancer cells demonstrates this as well Vitamin C selectively kills KRAS and BRAF mutant colorectal cancer cells by targeting GAPDH. Thus it is suggested that DHAA can stress or kill cancer cells, but the authors emphasize that this effect arises by exploiting characteristics of cancer cells (i.e., the selective expression of GLUT1 and the metabolic liability that comes with increased reliance on glycolysis). Otherwise, high-dose ascorbate IVs have been shown to be safe time and time again. Humans have a huge capacity to recycle DHAA; the RBCs alone have the capacity to reduce the entire body amount of vitamin C every three minutes. DHAA has been administered intravenously in many studies over the decades without harm to the subjects; in recent studies in mice and baboons, doses up to 500 mg/kg have been evaluated Dehydroascorbic acid, a blood–brain barrier transportable form of vitamin C, mediates potent cerebroprotection in experimental stroke. Preclinical evaluation of postischemic dehydroascorbic acid administration in a large-animal stroke model. Therefore I think that your comment about the safety of oral DHAA is overly-cautious.

    • Literature references that suggest that DHAA is more bioavailable than ascorbic acid are poor. The best case scenario is that it is equivalent to ascorbic acid. Such is evidenced from the recent study in Guinea Pigs that you mentioned, “…(DHAA) constitutes an equally good vitamin C source as its reduced form ascorbate in guinea pigs.”

      Other papers in humans have shown that it is certainly not superior, but as best equally as good. Thus, the results that are show in the YouTube video must be scrutinized – How did vitamin C levels go up that quickly in the plasma? What was the time between vitamin C experiments? What was the actual dose of DHAA in the drink? How was vitamin C in the plasma measured?

      I should urge caution to anyone attempting to use DHAA as a supplement, and there are four reasons for this:
      The first is that it has been shown to kill cells in culture. Not just cancer cells, but neurons and other sensitive cells. The reasons for this are not entirely clear, but may have to do with the next two points, below.

      The second is that DHAA is immediately cleared by the body as soon as it is able to do so. DHAA will flood into cells via the glucose transport proteins, and is immediately reduced through mechanisms that ultimately deplete the NADH or NADPH in cells – molecules that the cell uses for energy. This could represent a reductive stress on cells that can dramatically alter cellular metabolism. Some cells may be unable to recover from such a stress.

      The last point is that DHAA is an unstable oxidation product. Water is all that is needed to break the ring structure and render it no longer able to contribute to ascorbic acid levels in cells, plasma, body fluids, etc. The carbohydrates that are formed from DHAA destruction are also unstable, forming a wide variety of smaller carbohydrates. This includes oxalate, which is a compound familiar to anyone who has calcium oxalate kidney stones. Other carbohydrate molecules formed in DHAA breakdown have been implicated in glycation reactions – where the carbohydrates attach themselves to proteins and can lead to protein dysfunction.

      I will concede that small doses of DHAA are unlikely to be harmful, as they will be found in the normal ingestion of anything containing vitamin C. However consuming high doses of DHAA is not well tested, and is not recommended unless a benefit is found from such treatment. Current studies have not provided enough evidence to suggest that this is a good idea for anyone to consume.

      In the future, I encourage anyone with financial interests in a vitamin C-related product to disclose such information in their comments. The YouTube video cited is also from the same company. This will help make readers informed of financial interests at stake:

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  8. Hi,
    on the Linus Pauling Institute micronutrient information page about copper it says that there are 2 studies showing that vitamin C supplementation of 605 mg/day and 1500 mg/day lowers ceruloplasmin oxidase activity.
    What is ceruloplasmin oxidase and what happens when it gets lowered by vitamin C?
    Are there any other known interactions with other nutrients or adverse effects to taking vitamin C in doses of 600 to 1500 mg?

    • First, the terminology used in the article is a little misleading – its not ‘ceruloplasmin oxidase’ as an enzyme, but referring to the oxidase activity of ceruloplasmin. The paper noted that ceruloplasmin – a copper binding protein – blood levels and activity went down when ascorbic acid supplements were taken. This accompanied a reduction of serum copper in these subjects, but the decline was not significant. Overall, the subjects stayed within the normal ranges for copper, and no deficiencies were reported. However, no other reports have suggested that copper status is a problem in people taking large amounts of vitamin C.

      A possible concern for people taking high amounts of vitamin C is iron. More many people iron status is normal, but some people suffer from hemochromatosis – also known as iron overload. Since vitamin C can stimulate iron uptake, it is suggested that people with hemochromatosis avoid taking iron and vitamin C together. However, it is still important (and perhaps more important) for people iron overload to get adequate levels of vitamin C, since they are at risk for increased free radical damage due to excessive iron levels.

      Vitamin C supplementation was previously linked to low B12 levels in some research studies, but this was found to be an unfounded claim.

  9. Hi have recently been dealing with high blood pressure.Have been taking a vitamin called provascalin which is combination of natural things. As opposed to taking rampril prescribed.
    I have hemachromatosis and have taken interest in Dr Gifford Jones and his work with Dr Pauling in regards to taking viamin c with lisine to clear arteries. My iron ferritin levels is under control quite low now 30 by canadian standards.So could I start the program of vitamin c and lisine ?
    Appreciate your opinion.
    Thank you

    • It is difficult to comment on your specific situation, because anyone with a condition such as hemochromatosis should be monitored by a physician. Thus, we cannot recommend a certain course of action with vitamin C and lysine. However, I can say that anyone with hemochromatosis should take great care taking vitamin C – especially in high doses. Vitamin C can increase the absorption of iron from the diet, even if it is an inadvertent side-effect of supplementation. Although vitamin C is certainly beneficial to people with hemochromatosis, the supplements should be divided such that vitamin C and iron aren’t in the stomach/small intestine at the same time, which may make it difficult to take large amounts and eat a normal diet. Hope that helps.

  10. Dear Dr. Michels,
    My father is 81 years old with arthritis and possible Gerd or ulcer or some type of gastric condition… we are not sure yet.
    I am giving him 2, 000 of pure Vit C a day not buffered.
    Because of his age, I am afraid to offset his mineral balance and cause depleting of other minerals.He takes 500mg of glycinate magnesium, B-complex, digestive enzymes My question is what is the best powder form of Vit.C to give to senior people in your opinion and can he benefit from higher dose of vit.C??

    • There is a common misconception that unbuffered ascorbic acid somehow depletes minerals in the body. There are individuals that will try to sell you a different formula based on these ideas, which are usually more expensive than the plain ascorbic acid/vitamin C (they may also claim that ‘ascorbic acid is not vitamin C’ – this could not be further from the truth). Ascorbic acid has never been shown to cause any mineral depletion in any clinical studies.

      More to your question – The typical reason to take ‘buffered’ vitamin C (also known as mineral ascorbates) to avoid stomach upset. The minerals in these formulations are usually not high, but if there are additional concerns with sodium, magnesium, or calcium levels they can be a concern. Some other formulations may also be gentle on the stomach, but haven’t been specifically targeted for that like lipospheric vitamin C or ester-C.

      As for your question on dose, that’s a difficult one to answer. We don’t know enough about high doses of vitamin C in the body, much less older people. All our experience to date says that 2000 mg per day should be good, but there are many people that will argue with that opinion.

  11. Dr Michels,
    I heard that vit C helps remove Persistive Organic Pesticides (POPs we ingest from food and surroundings) from the body. Any research on this that you know about?

    • I can start out by saying there is limited clinical research on this topic. Pesticide removal requires one of two things: An alteration the chemical structure of the pesticide, or enhancing natural detoxification mechanisms to metabolize those compounds. Although vitamin C has been shown to limit the toxicity after exposure to a variety of different compounds or heavy metals, it does not seem to enhance these ‘removal’ mechanisms in the body. However, limiting the toxic effects may allow the body to naturally remove the compound better, but there is very little data to support those claims.

      Another possible route of limiting exposures is that vitamin C may interact with certain compounds (a select few that may or may not fall in the pesticide category) directly to alter their chemical structure. This only happens when vitamin C is in very high concentrations: Concentrations many times higher than what is normally seen in the blood stream. Thus, the only likely place for this interaction is the digestive tract, when vitamin C is ingested.

      So you can imagine a scenario when someone eats a potentially toxic compound and a large amount of vitamin C together. The compound may react with the vitamin C before reaching the intestine. This reaction could prevent it from being absorbed, or alter it in such a way that it is easily handled by the body. This has been shown – to some degree – with certain nitrogen compounds (some might fall in the pesticide category), or reactive aldehydes like acrolein (from fried foods). However, I know of no clinical studies that show how much this reaction would be protective, or a definitive list of compounds where this reaction can occur. It’s just another limitation of the science.

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  15. May I ask this question is regard to your statement: “Thus, if you take multiple large doses throughout the day (say, every two hours), most will be either unabsorbed or quickly excreted.”…..Isn’t there research that indicates in the presence of illness that most IS absorbed? Furthermore, that those with illness will require much higher dosage to reach their bowel tolerance, based on the fact that most of the C is being used?

    • Joe,

      There has been speculation that more is absorbed in the presence of illness, but it has never been positively demonstrated. Usually this analysis is done in the urine, since it is less invasive, but unfortunately also less informative. Also, bowel tolerance is not a good indicator of absorption. People can see changes in bowel tolerance for a variety of reasons, and those could be altered during an illness.

      Careful studies need to be performed to determine if the rate of absorption of vitamin C does actually change under certain circumstances. Right now, there is no quality data to support either conclusion. By default, however, we assume that rate does not change until such a study is performed.

  16. Dr. Michels,
    I currently take Adderall, and have learned that Vit C stops the uptake of it. This explains my limited focus in the morning, when I take 1000mg of Vit C and 10mg of amphetamine salts. My afternoon dose is much more effective, which is ~5-6 hours after the Vit C.

    Might you suggest a better timing for me… would it be better to wait an hour or so to take the first dose of Adderall, or would it be better to shift the Vit C to the pre-bed with Zinc-Magnesium-B6 and probiotic?

    • Although I can’t give medical advice, I will say this: the issue is anything that will acidify the stomach pH even further. Not just vitamin C, but any acid you may be consuming along with amphetamines. There are two ways you can approach this – neutralize the acid from vitamin C/ascorbic acid or space out the dose.

      Your suggestion of waiting is good; I would think 2 hours would be better than 1, however. However, vitamin C is also available in ‘buffered’ forms, which is a fancy name for mineral salts of ascorbate. These mineral salts are not acidic, and are usually recommended for people who get heartburn after taking vitamin C in large doses. It’s really up to you what works best for your routine.

      • Hello Dr. Michels,

        Thank you for taking the time to answer our questions, this has truly been an insightful writeup and I appreciate how you simplify the concepts for people like me, outside of academia.

        A couple quick questions if you have the time:

        (1) Is calcium carbonate (~tums) safe to take with vitamin c, or will it alter the absorption or deplete other vitamins/minerals e.g. calcium? I ask because I take tums after most meals containing vitamin c or store bought foods which frequently list ascorbic acid as a preservative (in unknown quantities). Will supplementing vitamin c daily (500mg – 1000mg) affect absorption of any other vitamins/minerals?

        Also, I have lost a certain joy in life, having to screen and turn away any store bought food containing ascorbic acid or fruits/vegetables containing vitamin C, due to a medication regimen, unless I accompany it with tums. (2) Any advice or rule of thumb on how I can quickly estimate urine acidity from vitamin C content in a meal taken from the RDA value listed on the nutrition label?? I wonder if it is worth investing in PH test strips or some non-invasive methods to determine PH as I fear I am making my urine PH too basic with the tums and casuing havoc on my internal organs in this daily struggle with food consumption.


        • Calcium ascorbate has been reported to have slightly lower absorption than other forms of ascorbic acid. Nobody has really looked at the combination of calcium-containing antacids with ascorbic acid, but its probably likely to be the same. Is that lower absorption a big deal? Based on the data, I would guess not – especially if you are taking large amounts of vitamin C anyway.

          As for vitamin C prevent the absorption of other vitamins and minerals, it’s not entirely clear. Minerals in particular might be affected by very large doses of ascorbic acid, but it hasn’t been well documented in the literature. We know that iron absorption is higher in people taking ascorbic acid, but there are some reports that other minerals might be less absorbed. Again, it’s probably not much a concern, assuming you’re getting enough of the minerals you need each day.

          As for your other concern about pH – I’m not exactly sure of the medical issue you speak of, but pH of ascorbic acid usually is only a problem in two areas: the stomach and the urine. Outside of these areas, such as in the blood stream or other parts of your body, the pH of ascorbate is neutral. Your body works hard to maintain a balanced pH environment, and no consumption of an acid is going to upset that. When outside the body, high amounts of ascorbic acid can cause some pH issues – so people on certain drugs do need to worry about interactions in the stomach or urine, for instance.

  17. Thank you Dr. Michels for taking your time to give us this valuable information, I wish there could be an institution established that would further medical research without government and corporate funding. Someone did this for technology and the physical sciences, I forgot their name, but there was an explosive burst of creativity and productivity when research was done outside the normal constraints of the NIH.
    Kudos to you and all other scientist that devote your life to seek the truth as best you can.

    • The Linus Pauling Institute was first established to operate outside of the constraints of government funding. We still receive many generous gifts from private donors, yet we do seek government funding where appropriate.

  18. There are so many contradictions in this article i don’t know where to begin. Bottom line is that vitamins C, ascorbic acid is one of the easiest molecules to destroy. And one of the many contradictions in this article is just how easy – exposure to light, oxygen, mild or high heat, sustained heat. That molecule, extracted from a fruit, or made in a lab will have zero bioavailability. You can’t say, steaming won’t hurt the molecules – cause if you steam them, you are also exposing them to light and oxygen. You can’t tell us if we chop the food up, this destroys C and then just let that hang out there…..Pasteurization doesn’t just effect the enzymes – it also effects C! This article is so all over the place – with zero true lab work behind it.

    • If I read your comment correctly, I think the issue is the use of the word ‘destroy’. The molecule we know as ascorbic acid is extremely easy to break down into other molecules, but that doesn’t mean that every molecule of vitamin C will be broken down under a given condition. Light, oxygen, and heat are factors that accelerate degradation of vitamin C, but only under extremes will it become completely destroyed.

      The idea that vitamin C extracted from a plant or made in a lab has zero activity is not true – I have done the experiments myself to prove otherwise. If you would like me to describe other experiments that back up my claims, I’ll gladly talk about them too.

      • When you say “accelerate” – this is vague. Is it seconds, minutes, hours – next month. Clarity is essential. When we bit an apple, it is withing minutes that we can see some dynamic of oxidation. Also, vitamin c has many cofactors that act in absolute concert with ascorbic acid – or else vitamin C doesn’t do what vitamin does. And there is no science lab in the world that can replicate the full organic assemblage of these components.

        I too have done experiments – and a human can go for as long as they like, months, years, without dietary or vitamin C supplements – and zero mal effects. Humans are able to synthesize their own vitamin C. And since no one, as in NO ONE, knows with even remote certainty just how much we need, the amount that we can synthesize on our own – is just fine and adequate.

        • There is no evidence that vitamin C has any cofactors that exist in biology that is necessary for its activity – there is no modern scientific study that supports that conclusion (although there are many claims in literature that later turned out to be mistaken).

          Studies in human participants have consistently demonstrated their inability to synthesize vitamin C – we lack the genetic capacity to do so. Therefore the deficiency disease known as scurvy. I will admit that people do get vitamin C from surprising sources, but ingesting it is an absolute necessity for life. If you believe otherwise, you are welcome to present your evidence.

          • Are you the same AJ Michels that did the article – Myths, Artifacts, and Fatal Flaws: Identifying Limitations and Opportunities in Vitamin C Research. First, let me applaud you. It was the best bit of writing on the subject of vitamin C I have ever come across. Mostly, I appreciate the honesty and the forthrightness in the efforts and difficulties in finding some level of constant – ness, if you will and and a result a lack of the best understandings of supplements and dietary C and studying it.

            It was published late in 2013 but I’m guessing it was more like a few years prior. My point being – I was hoping you had spoke to some findings regarding bacteria’s role in the synthesis of vitamin C in humans.

            For now – I will say, that what I extracted most from reading your article, is what I had spoke to: Vitamin C – is the most uber fragile of all the nutrient molecules on earth. A wee bit of hyperbole, but still, your article spoke in great depth to this “Factor” – among other problems involved with the science study of Vitamin C.

      • You also used the term words completely destroyed – to imply, it seems that a little damaged is okay – and still capable of being biologically active. Yet this is impossible. You can’t be a little pregnant. It’s not like a car with a flat tire can still make it’s way to the station for repair. A damaged molecule, even slightly is a destroyed molecule. In a lab, samples get damaged/destroyed for any number of reasons all the time. Many samples of cells, proteins etc. are always at hand as a result.

        • If this term is misleading, you can substitute the words “100% degraded” for “completely destroyed”. Any ascorbic acid that has it’s chemical ring structure broken (known as hydrolytic ring cleavage) is lost to the body as vitamin C. Ascorbic acid that is oxidized is still able to be reduced back to its active form – the body has excellent vitamin C recycling capabilities, but they aren’t perfect.

          As for your previous comment about the vagaries of the degradation process, it was intentional. It is impossible to lump all ascorbate chemistry into one blanket statement. Instead, I was providing general terms to help people understand the factors at hand.


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