Doctor's Note

For more videos on dietary supplements:
Some Dietary Supplements May Be More Than a Waste of Money
PCBs in Children's Fish Oil Supplements
Treating Asthma With Plants vs. Supplements?
Broccoli: Sprouts vs. Supplements
Risk Associated With Iron Supplements
Dietary Supplement Snake Oil
Vitamin D Supplements May Be Necessary
The Wrong Way to Boost Serotonin

Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. And check out the other “HHH” videos (Harmful, Harmless, or Helpful?). Also, there are over a thousand subjects covered in the rest of my videos–please feel free to explore them as well!

For some context, please check out my associated blog posts: Soymilk: shake it up! and Eating To Extend Our Lifespan.

  • Michael Greger M.D.

    Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. And check out the other “HHH” videos (Harmful, Harmless, or Helpful?). Also, there are over a thousand subjects covered in the rest of my videos–please feel free to explore them as well!

  • evanbrand

    The work of dr matthias rath and, possibly, other sources, would suggest that vitamin C offers significant benefits..

    Second, is frozen fruit and, specifcally, frozen acai limited or void of nutritional benefit? If so, what can US residents do to get optimal acai?

    • Laurie K.

      Hello Evanbrand, yes, indeed you (and the others) are correct, vitamin C does have healthful benefits…if it’s obtained by eating whole foods. When you get your vitamin C from sources such as mangos, papayas, cantaloupes and yams, for example, you get other nutrients and antioxidants that are also vital for optimal health, like the beta carotene that is also abundant in these foods. The video discusses vitamin C from supplements, which can not only be a waste of money, but can be potentially detrimental to your health, particularly in large doses like vitamin A, see:®-supplement-liver-toxicity/ There is also evidence that rather than protecting from disease, multivitamins can actually increase the risk of breast cancer: Also, I wouldn’t put so much emphasis on one particular “superfood”, because there are many others that contribute to longevity, like cocoa (but of course without the milk and sugar that many folks tend to add for palatability), see: and: If you want to include acai in your diet, no need to concern yourself with the freezing process, it has very little (if any) impact on the quality and/or amount of antioxidants it contains. You should make every effort to eat a widely varied, plant based diet to ensure that you get as many phytonutrients as possible. It’s also very economical to eat this way, see: Have a wonder, healthy holiday!

  • mjordana

    Hmm, I think Dr Greger is being entirely too dismissive of the powers of Vitamin C in convenient supplement form. Just note that in the antioxidant study he draws on for many of his videos, namely The total antioxidant content of more than 3100 foods, beverages, spices, herbs, and supplements used worldwide, Vitamin C (specifically, CVS Vitamin C (as ascorbic acid), 500 mg) has 1,019.69 mmol/100g of antioxidant content. Compare this with the paltry 261.53 mmol/100g of antioxidant content of powdered amla (Indian gooseberries) which he lauds so much. Almost 4 times more! I rest my case.

  • GC

    Hi Dr. Greger. I am currently taking D-Mannose for “IC-Like” symptoms (mainly urinary retention/trouble emptying). I was going to take Glucosamine in addition, but I was advised to take high doses of Vitamin C instead to help repair the bladder wall. What do you think?

    • DrDons

      As always it is important to get the diagnosis right. Many common problems with bladder function reflect difficulties with muscle, hormones, lifestyle and aging. Others seem to be inflammatory and involve the bladder itself. Bladder Pain Syndrome of which Interstitial Cystitis(IC) is a subcategory is a poorly understood group of conditions of unknown cause which are difficult to treat. As a primary care physician I have had several patients plus one relative with the diagnosis of IC. I think it is best to find a physician who is experienced with treating patients with IC and who uses evidence based therapies. From my experience foods seem to have a significant effect on many bladder conditions but it can be hard to figure out. I think keeping a food diary is important to see if you can relate certain foods to improvement or aggravation of symptoms. If the problem seems to be one of the inflammatory conditions such as IC it would seem reasonable to follow a plant based diet with an emphasis on foods that improve the immune function and emphasize antiinflammatory over inflammatory foods while avoiding substances such as caffeine and alcohol which can have a detrimental effect. I would view the videos under the appropriate links. These include videos on the importance of a variety of plant foods in decreasing inflammation see… or the importance of avoiding meat to minimizing inflammation see Lifestyle issues such as sleep see… and exercise seem to help. I would only try isolated nutrients or therapies that have been supported in the literature and would discontinue them if after a fair trial they don’t seem to help. It is very important to work with your physicians to help sort all this out. Good luck.

      • GC

        Thanks, DrDons! I’m 25 and I’ve been plant-based for almost a year now, getting plenty of leafy greens, superfoods, and avoiding processed foods. I avoid alcohol since I know all too well that it makes it worse. I had all those unpleasant tests performed when I was younger and they could not find anything, but sent me for biofeedback, anyway, and prescribed Detrol. The biofeedback didn’t do anything but the Detrol helped a tiny bit (not enough to keep taking it, and I also did not like the ingredients in the drug). I’ve tried many others things including naturopathic medicine, diet modifications, bodywork, rebirthing, energy healing, and acupuncture. The only thing that helps is holistic Chiropractic, but only if I get adjusted at least twice a week, and still it does not provide the relief I am looking for. Rebirthing/Breathwork also helped once, it was the only relief I’ve had in YEARS, but then it stopped. I have noticed that it is worse if I am angry, anxious, or emotionally irritated about something, so I try to stay calm. I read that “pockets” can form in the bladder wall and trap bacteria (but does not show up on tests), which can lead to IC-like and UTI-like symptoms including urinary retention, and women suffering from the same thing suggested D-Mannose. I’m going to try it for a few months and see if I notice a difference.

  • dfdf

    is it good to take vitamin c as pills

    • John

      Better absorbtion has better result. If it can’t be absorbed it waste the money. Recommend you use the isotonix one. Check istonix here:

  • Michael Dean

    Just because vitamin C didn’t prove beneficial for things like lifespan, cancer or heart attack risk? Its possible that it could assist with the flu, common cold, athletic performance, mood or a multitude of other factors that the study didn’t address. It might not be a waste of money after all.

    • Toxins

      “Vitamin C is used as a dietary supplement because of its antioxidant activity, although a high dose (500 mg) may act as a pro-oxidant in the body1, 2. Here we show that 100 g of fresh apples has an antioxidant activity equivalent to 1,500 mg of vitamin C, and that whole-apple extracts inhibit the growth of colon- and liver- cancer cells in vitro in a dose-dependent manner. Our results indicate that natural antioxidants from fresh fruit could be more effective than a dietary supplement.”

      • Michael Dean

        “May act as a pro-oxidant”

  • katieorourke

    this is one of the most misleading statements I have ever heard…a waste of money….where’s the evidence….what studies….who else is in agreement with this one study ??????

  • katieorourke

    What about new research just published that found vitamin c warded off stroke ???

    • Toxins

      I have not seen the study, but vitamin c is may be a marker of how much fruits and vegetables consumed, not necessarily how much vitamin c you isolated then consumed.

      “Vitamin C is used as a dietary supplement because of its antioxidant activity, although a high dose (500 mg) may act as a pro-oxidant in the body1, 2. Here we show that 100 g of fresh apples has an antioxidant activity equivalent to 1,500 mg of vitamin C, and that whole-apple extracts inhibit the growth of colon- and liver- cancer cells in vitro in a dose-dependent manner. Our results indicate that natural antioxidants from fresh fruit could be more effective than a dietary supplement.”

      • katieorourke

        vitamin c supplements do not contain pesticide which is found on fruits and vegetables, unless you can afford to buy organic…Also vitamin C leaves the body within 12 hours, and your body rids itself of any amount it does not need. That’s why unless you take a time released capsule it is recommended that you take it every 12 hours to ensure round the clock does not accumulate in your body and any excess is rid through urinating.

        • Toxins

          Taking a supplement does not replace a whole food, and it will never be the case. I know of no studies showing vitamin c to be more protective then regular fruit and vegetable consumption. Again, I shared with you the above study showing that the whole is greater then the sum of its parts. I know of no reason to supplement vitamin c when a plant based diet can supply mass quantities of this single nutrient. When studies show no benefit or worse, I tend to open my eyes and follow the trail of evidence.

  • Peter

    What do you think of Liposomal C? I have experienced great benefits myself from taking it. I didn’t experience any benefits of taking “normal” vitamin c pills (although I didn’t try mega doses). There is even some research indicating that liposomal c kills cancer ( What do you think?

  • R. Martinez

    Dr. Greger, I started taking vitamin C supplements to increase progesterone, per Dr. Sara Gottfried’s book, The Hormone Cure. Do you see any research that there is this benefit, hormonally? Also, what’s your take on the famous chemist, Linus Pauling, and all the benefits he claimed with vitamin C? Here is a link to a recent acticle on Medical News Today:

    Thank you for all your work. I use and share your site, and it has been invaluable!

  • Ruud

    Hello Dr. Greger,

    I like your site very much, really!
    I saw your video about vitamin c pills, but there was nothing about vitamin c powder.
    There’s a lot of confusion about vitamin c on the Internet.
    Lots of people pretend to know all about it.
    Some of them have very promising solutions, one of them especially.
    So to read the article, is it very clear (although I am Dutch), it looks like a new science.
    But to be sure I would like you to read it and share your honest opinion about it.

    Thanks for reply,

    • dogulas

      Just eat the whole plant foods. It’s always best.

      • Tom Goff

        Well ,yes, that’s sound advice but I eat whole plant foods and when I don’t supplement with vitamin C I get a bad cold/flu two or three times a year. When I supplement (1-2 grams daily), I don’t get colds or flu at all.

        I have seen no evidence that such doses are harmful. Rami below provides a quote that says “although a high dose (500 mg) may act as a pro-oxidant in the body”.

        However, the reference I found stated that “ascorbate at pharmacologic concentrations was a prooxidant, generating hydrogen-peroxide-dependent cytotoxicity toward a variety of cancer cells in vitro without adversely affecting normal cells.”

        In other words, it only acts as a prooxidant towards cancer cells not normal cells. This sounds like a good thing to me, not a bad thing which was the impression I got when I read Rami’s post.

        That said, I would be interested to see any other papers people may be aware of, that suggest vitamin c supplementation may be harmful.

    • Joseph Gonzales R.D.

      Hi Rudd. Thanks for your note. I think the pills and powders are similar. The website offers no studies about vitamin C. I like to find references online when searching websites that have information about nutrition. Hope that helps.

      Best regards,

  • phariseesdotorg

    Re: Natural Vit. C Molecule versus Synthetic Ascorbic Acid

    It appears synthetic ascorbic acid (AA) is NOT harmless.

    Hoffman-La Roche, a Swiss company, was the first company to manufacturer synthetic AA. According to wiki, Roche is the 3rd largest pharma company in the world.

    Roche remains among the top manufacturers of AA in the world. Would a pharma company be producing a relatively unprofitable product that generates health, creating a healthy population, or at least health among some people, therefore reducing or eliminating their need for pharma drugs?

    IT IS A SCAM of Roche to call AA vitamin c, a scam joined in by many, among them some who are ignorant of the fact that AA is NOT Vitamin C.

    AA increases body acidity and can cause kidney pain if slightly dehydrated, blood in urine if moderately to severely dehydrated.

    Vitamin C is the entire Vit. C molecule, not just the AA which is only the outer coating of the Vitamin C molecule that protects the inner contents of the molecule

    In some people AA causes bruising which is evidence, perhaps, that AA increases the need for vitamin C, or by some other mechanism is causing harm resulting in bruising. Bruising not from an exogenous injury, but occurring from harm within the body simply from taking AA.

    Many harmful ingredients are permitted in foods in US, to a lesser extent Europe, and even lesser extent Asia, at least officially, but not always in practice. Bromide in flour (other products) is prohibited in Asia, I think it is banned also in Europe, but permitted in the US. It would appear foods in US are deliberately ‘posioned’ in order to generate customers for the pharmaceutical industry, bromide being one good example of a toxic ingredient in US food products. AA is disease promoting, not health promoting.

    AA has been used in cancer therapy but acidosis from AA limits its use. AA’s only use in cancer therapy is to increase hydrogen peroxide in cancer cells.

    AA increases oxidative stress to the body, it increases oxalates in the body. AA is a pro-inflammatory agent. AA increases body acidity.

    AA generates genotoxins:

    AA reduces endurance capacity, decreases muscle mitochondria biogenesis

    AA apart from the entire vitamin C molecule is harmful to the body. I give link to search results above, and there are conflicting reports as to the harm/benefits of AA. The confusing part is where AA is called Vitamin C and so need to examine did the research study use just AA and they are calling AA Vitamin C, or were other components of the Vtamin C molecule included along with AA, or just natural whole Vitamin C administered as food (orange juice or other high C food)?

    2-6 grams of AA can cause gastrointestinal disturbances, can cause diarrhea.

    Has anyone who has eaten a diet high in natural Vitamin C experienced GI distress from the Vitamin C in those foods? But synthetic AA is an irritant to the GI tract one reason may be it is very acidi. There are buffered forms of AA and whether 2 grams or more of buffered AA can cause GI distress, haven’t seen anything on that.

    Does AA cause DNA damage? Lee et al demonstrated AA DOES cause DNA damage because AA induces decomposition of lipid hydroperoxide in the presence of transition metals to form DNA reactive electro-philes, among the electro-philes formed are a genotoxin that can react with DNA to form mutations. And that is why ROCHE, the world’s 3rd largest pharma company continues to manufacture AA and that is why many foods in the US have AA added to them. But the Nutrition Journal does not believe AA generates genotoxins, despite the experiment by Lee et al showing that it does. The Nut. Journal states, without any citation to back up their claim, that lipid hydroperoxides form only when AA is exhausted. The Nut. J. states AA prevents the formation of LH, but no citation to back up their claim that AA does prevent formation of LH.

    Linus Pauling was a long term user of AA, he died of cancer. Pauling’s long-time partner in research is purported to have said that everyone who they put on long-term AA use developed cancer. And that is consistent with the findings of Lee et al. that AA starts a chain reaction that in the end produces genotoxins. The information at link below is good, for the most part, except their including Linus Pauling, for to make the claim (which I do not dispute) that every person who has cancer has an acidic pH and yet include Pauling’s highly acidic AA regimen as an alleged cancer preventative flies in the fact of Otto Warburg (and others) showed that cancer cannot survive in an alkaline, oxygen rich environment. Otto Warburg is not stated to have died from cancer, but Pauling is stated to have died from prostate cancer. no citation given unfortunately,,stated at No. 4 is that the blood of people given natural Vitamin C molecule in the form of orange juice showed significant antioxidant activity 4 hours after ingestion, but the people given AA showed no antioxidant activity 4 hours after ingestion.

    AA is a harmful substance overall. There is no way the world’s third largest pharma company would be producing a substance for alleged healthy fortification of food products if indeed AA could have any role in promoting health and thereby keep some people away from the need for pharma drugs.
    Switzerland is a corrupt, evil nation, protectors of the Vatican, founded by Knights Templar in 1291, still their possession. Not disparaging all Swiss people in Swissy land, though. Switzerland funded Hitler, took in the gold from Hitler’s victims, mostly Jews; and its level of evil and corruption is ony second to the most corrupt entity on the planet, the City State of Vatican. Switzerland is home of the central bank of western central banks, the secret bank that runs most of the world, the Bank for International Settlements. And Swissy bring GMOs to the world through Switzerland based Sygenta, but refuses Sygenta’s GMOs to be available in Swissy land.

    • phariseesdotorg

      Correction: Not Cameron, but rather Dr. Arthur Robinson, one of Pauling’s research scientist, said everyone they put on long term AA developed cancer.

      There is NO Vitamin C in corn starch, and it is corn starch from which ascorbic acid is manufactured by use of sulphuric acid. There are doctors who say that use of AA does cause side effects associated with Vitamin C deficiency, such as bleeding gums,, spider veins, varicose veins and bruising, which demonstrates that AA causes deficiency in Vitamin C.