Vitamin C benefit, side effects dosage, 500 mg, 1000 mg - Information on overdose, what is the amount you should take daily?
September 20 2018 by Ray Sahelian, M.D

Also known as ascorbic acid, vitamin C was isolated in 1928. This vitamin serves as an excellent antioxidant and could protect various cells and tissues in the body, including brain cells and cells in the eye. The eye is highly susceptible to damage by sunlight, oxygen, various chemicals, and pollutants. Because of an aging Western world population and a continued depletion of ozone, having adequate antioxidants in the eye is very important, perhaps helping to protect against macular degeneration and deteriorating eyesight.

Vitamin C protects the immune system, reduces the severity of allergic reactions and helps to fight off infections. However the significance and beneficial effect in respect to human disease such as cancer, atherosclerosis, diabetes, neurodegenerative disease and metal toxicity however remains to be fully understood.

How much is enough to benefit our cells?
Ever since Nobel Prize winner Linus Pauling extolled the benefits of megadosing, the medical community has been debating the optimal dosage intake of this vitamin. Although many doctors stood firm for a long time asserting that the RDA of 60 mg for this vitamin provided adequate benefits, more and more doctors are now realizing that higher dosages can confer additional antioxidant benefits. However, the optimal daily intake of vitamin C has not yet been determined, nor is it likely to be determined soon. Nevertheless, we now suspect that excessive intake of vitamin C, except perhaps in the therapy of a particular medical condition, may not be necessary.
   A study published in the American Journal of Clinical Nutrition points that large doses of ingested vitamin C may be excreted without being utilized. When the dosage given to a group of healthy men was increased from 200 mg a day to 2,500 mg a day, blood levels increased only negligibly. Blood levels of vitamin C generally reflect the levels found in the rest of the body. Therefore, there seems to be a vitamin C dosage beyond which no further benefits may be noticed.


MultiVit Rx - High Quality Daily Vitamins and Minerals with Vitamin C and Rose hips

MultiVit Rx product has 500 mg of Vitamin C and rose hips per daily dose.

Q. What's your opinion on the ideal daily dose of Vitamin C and the benefit of taking such supplements?
   A. If you ask a dozen doctors this question, you are likely to get a dozen different answers. I would say that for those who have an excellent diet with plenty of fresh fruits (including citrus) and vegetables, they many not need to take any vitamin C supplements. For those whose diet is not ideal, it would seem reasonable to take between 50 to 300 mg once or twice a day, preferably a formula that includes bioflavonoids.


Rev Prat. Oct 2013. Vitamin C is a water soluble vitamin which is mainly fresh fruits and vegetables foodborne. Deficiency is most often due to a lack of daily amount. Scurvy is characterized by the occurrence of fatigue, myalgia, arthralgia, purpura, bleeding disorders, and later by dental manifestations. Biological signs are nonspecific: anemia, hypocholesterolemia, hypoalbuminemia. Clinical suspicion is confirmed by the decrease in ascorbic acid level (< 2 mg/L). It must be interpreted in light of the acute phase reactants. The treatment is the administration of 1 g of vitamin C per day for 15 days.

Eyesight Rx
Benefits Healthy Vision
Supplement Facts:
Vitamin C - 15 mg
Citrus bioflavonoids  (eriocitrin, hesperidin, flavonols, flavones, flavonoids, naringenin, and quercetin)
Mixed carotenoids (alpha carotene, astaxanthin, beta carotene is a popular carotenoid, beta cryptoxanthin,
Lutein is commonly found in eye formulas, Lycopene is found in high amounts in tomato and watermelon, Zeaxanthin)
Bilberry extract (Vaccinium myrtillus)
Eyebright extract (Euphrasia officianales)
Jujube extract (Zizyphus jujube)
Ginkgo biloba (Ginkgo biloba)
Suma extract (Pfaffia paniculata)
Mucuna pruriens extract, see also Mucuna-Pruriens supplement information.
Cinnamon (Cinnamomum zeylanicum)
Lycium berry extract (Lycium Barbarum) - also known as Goji Berry extract supplement.
Sarsaparila (Sarsaparilla Smilax)
Alpha lipoic acid antioxidant that helps maintain visual acuity

Vitamin C and common cold
Taking extra vitamin C daily does little to stop most people from catching the common cold, but it helps stop those exposed to extreme physical conditions from coming down with the sniffles. Soldiers, marathon runners, and skiers are among those most likely to benefit from taking extra doses of vitamin C unless perhaps for the temporary treatment of a medical condition. Use of about 5 grams right at the earliest onset of cold symptoms could be of benefit.


Testimonial received in 2018
I would also like to mention a favorable reaction to three other supplements. Ever since I was a kid, there was no such thing as a simple cold or flu. I would always get so sick that I would be incapacitated for a month or more followed by a bacterial infection and antibiotics. I learned that at the first sign of a cold, I would take 100mg of zinc and 50,000 IU of vitamin D every day until I felt no symptoms (2-4 days). This worked in 13 of the last 15 years. Well, I am coming off a short bout of flu. This time, I took 10 grams of buffered Vitamin C with a product called C-Salts. I cannot tell you what a difference this made. I go hit hard on a Wednesday. I took the two servings of 5 grams that day. While I felt no better the next day in total, most of my headache was gone and 90% of the muscle aches were gone. By Friday, that feeling of I want to lay down when standing was largely gone, but my cough was a little worse. On Saturday, I did a lot around the house, and by Sunday (only 4-5 days of feeling bad) I was feeling pretty good. Unheard of, in my case. I am still coughing a little (sixth day) , but finding little need to blow my nose. The vitamin C kept the mucus clear the whole time which was probably why my chest has remained clear throughout.

Atrial fibrillation
Oral vitamin C appears to cut the risk of early recurrence of atrial fibrillation after patients undergo electrical cardioversion. It also appears to reduce the low-level inflammation that accompanies this condition. Early atrial fibrillation recurrence after cardioversion may be due to electrophysiological changes in the chambers of the heart, known as atrial remodeling. To investigate whether vitamin C can reduce atrial fibrillation recurrence, a research team randomized 44 consecutive patients who had undergone cardioversion for persistent atrial fibrillation to standard therapy plus oral vitamin C or standard treatment only. Patients given the vitamin received a 2-gram loading dose 12 hours before cardioversion and 500 mg twice daily for the next seven days. One (4.5 percent) of the patients given vitamin C had a relapse of atrial fibrillation, while eight (36.3 percent) of patients not given the vitamin did. The researchers also found that white blood cell levels and fibrinogen levels fell significantly in the group given vitamin C, but did not drop in the control patients. Markers of inflammation were also significantly higher among patients who had a recurrence of atrial fibrillation, compared with those who did not. SOURCE: International Journal of Cardiology, 2005.

Cancer treatment
Large doses of intravenous vitamin C have the potential to boost chemotherapy's ability to kill cancer cells, ovarian cancer, according to new laboratory research involving human cells and mice. Feb. 5, 2014, Science Translational Medicine.

Bladder cancer
Clin Epigenetics. 2018. Vitamin C increases 5-hydroxymethylcytosine level and inhibits the growth of bladder cancer.

Vitamin C treatment reduces elevated C-reactive protein.
Free Radic Biol Med. 2008. University of California, Berkeley, CA, USA.
Treatment with vitamin C but not vitamin E significantly reduced CRP among individuals with CRP >/=1.0 mg/L. Among the obese, 75% had CRP >/=1.0 mg/L.

Cataract benefit, eye health
Acta Ophthalmol. 2015. Association of vitamin C with the risk of age-related cataract: a meta-analysis.

Vitamin C benefit for gout
Supplementation may lower uric acid levels which could be beneficial in those who have gout.

Heart disease
A major study has found that taking supplemental Vitamin C (more than 700 mg. a day may be of benefit by reducing the rate of coronary heart disease. However, taking additional Vitamin E or carotenoids showed no reduced risk. The study, which was published in the American Journal of Clinical Nutrition, was an epidemiological study, which suggests a relationship between two or more things but does not prove that one thing causes another.

Heart surgery benefit
Intravenous vitamin C before elective percutaneous coronary intervention (PCI) improves microcirculatory reperfusions. This finding indicates oxidative stress is to blame for the impaired myocardial reperfusion that follows up to 40% of PCI cases. Dr. Stefania Basili of the University of Rome "La Sapienza" randomly assigned 56 patients with stable angina undergoing elective PCI to receive 1 g vitamin C, infused at 16 mg/min during the hour before the procedure, or placebo. Rates of Thrombolysis in Myocardial Infarction (TIMI) myocardial perfusion grade < 2 were 89% in the placebo group and 86% in the intervention group at baseline. After PCI, however, rates were 32% in the placebo group vs 4% in the vitamin C group.Also, 79% of vitamin C patients achieved TIMI perfusion grade 3 - or complete microcirculatory perfusion - compared to 39% of placebo patients.To confirm the antioxidant effect of vitamin C, the authors also monitored plasma levels of 8-hydroxy-2-deoxyguanosine and 8-iso-prostaglandin F-2-alpha as markers of oxidative stress and inflammation. At 60 minutes after balloon inflation, levels had increased significantly in the placebo group but had decreased significantly in the patients who received vitamin C. The authors point out that vitamin C has a short half-life, which means that any impact on reperfusion "would probably be a consequence of a short-term effect on arterial dilation." J Am Coll Cardiol Intv 2010.

Topical Vitamin C cream
Cosmeceuticals containing antioxidants are among the most popular antiaging remedies. Topically applied antioxidants exert their benefits by offering protection from damaging free radicals produced when skin is exposed to ultraviolet light or allowed to age naturally. Vitamin C is a naturally occurring potent water-soluble antioxidant. Accordingly, it has been incorporated into a variety of cosmeceuticals designed to protect and rejuvenate photoaged skin.

Vitamin C cream or lotion products sold online
Avalon Organics, Intense Defense with Vitamin C Renewal Cream, 2 oz (57 g)
Beauty Without Cruelty, Hand and Body Lotion, Vitamin C, with CoQ10, 8.5 fl oz

By injection
When vitamin C is ingested by mouth, plasma and tissue concentrations are tightly controlled by at least 3 mechanisms in healthy humans: absorption, tissue accumulation, and renal reabsorption. A 4th mechanism, rate of utilization, may be important in disease. With ingested amounts found in foods, plasma concentrations do not exceed 100 mmol/L. Even with supplementation approaching maximally tolerated doses, ascorbate plasmaconcentrations are always <250 mmol/L and frequently <150 mmol/L. By contrast, when ascorbate is i.v. injected, tight control is bypassed until excess ascorbate is eliminated by glomerular filtration and renal excretion. With i.v. infusion, pharmacologic ascorbate concentrations of 2530mmol/L are safely achieved. Pharmacologic ascorbate can act as a pro-drug for hydrogen peroxide (H2O2) formation, which can lead to extracellular fluid at concentrations as high as 200 mmol/L. Pharmacologic ascorbate can elicit cytotoxicity toward cancer cells and slow the growth of tumors in experimental murine models. Adv Nutr 2011.

Q. I would like to know your opinion on the nanotechnology of liposomal Vitamin C. Is this form really absorbed much more efficiently than other types of vitamin C? Is the nano-bio technology safe for use?
   A. I do not see any advantage using the liposomal form of vitamin C.

Vitamin C supplements can help reduce the high rate of vitamins E depletion that occurs in smokers.

Vitamin C overdose - side effect of too much
Vitamin C is helpful for many conditions and it is one of the safest supplements on the market. High doses are taken at the onset of a cold. I have personally taken up to 8 grams at one time with the only side effects being nausea. It is very difficult to overdose. Another symptom of overdose is diarrhea and some people report other gastrointestinal disturbances. I am not aware of any fatalities from vitamin C overdose. Too much vitamin C is not necessary, and any dosage above 500 or 1000 mg a day may not provide any further benefit.

Excess intake of vitamin C from supplements is usually excreted harmlessly in the urine, but in patients with kidney failure, it is retained and can combine with oxalate to form crystals that deposit in the kidney tubules. High-dose vitamin C supplement use should be avoided in patients with kidney failure.

Vitamin C intravenously and Cancer
High-dose intravenously administered vitamin C led to longer-than-expected survival in three patients with advanced cancer. Two of the three patients are still alive without evidence of disease. In the three cases described in the Canadian Medical Association Journal, vitamin C was given intravenously at doses ranging from 15 to 65 grams to produce plasma concentrations that cannot be achieved by taking it by mouth. The first patient was a 51 year-old-women with advanced renal cancer who underwent surgical removal of the kidney but had evidence that the cancer had spread to the lungs. She received IV vitamin C 65 grams twice a week for 10 months, in combination with other alternative therapies. Repeat chest x-ray revealed one small spot, assumed to be a scar. Five years later, new lung masses were detected. The patient again received intravenous vitamin C, with unsuccessful results. The second patient, a 49-year-old man, had bladder cancer with multiple satellite tumors. He received IV vitamin C 30 grams twice a week for three months, followed by 30 grams vitamin C once every 1-2 months for four years. Nine years after diagnosis, the patient is in good health, without signs of disease. Case three was a 66-year-old woman with lymphoma invading spinal muscle and bone. She received IV vitamin C 15 g twice weekly for 7 months, then 15 g every 2-3 months for about one year. Ten years after diagnosis, the patient is in good health. It appears all three patients survived for longer than expected for the types and stages of cancers that they had. Canadian Medical Association Journal, 2006.

If a pregnant woman's waters break too early, her unborn baby can be put in danger of complications. The risk of this happening, however, may be reduced if she takes daily supplements of 100 mg vitamin C after the half-way point of pregnancy.

The effects of vitamin C supplementation on serum concentrations of uric acid: results of a randomized controlled trial.
Arthritis Rheum. 2005.
Supplementation with 500 mg/day of vitamin C for 2 months reduces serum uric acid, suggesting that vitamin C might be beneficial in the prevention and management of gout and other urate-related diseases.

Older women with diabetes who take high doses of vitamin C for the sake of their hearts may be doing more harm than good, new research suggests. The study, which followed nearly 2,000 postmenopausal women with diabetes for 15 years, found that those who took heavy doses of vitamin C supplements -- 300 milligrams (mg) a day or more -- were roughly twice as likely to die of heart disease or stroke compared with women who took no supplemental C. The researchers did find statistically weak evidence that lower supplement doses -- up to 99 mg per day -- curbed the risk of cardiovascular death, and high intakes of vitamin C from food were not related to a greater risk of death from cardiovascular causes. The findings appear in the November 2004 issue of the American Journal of Clinical Nutrition.

Researchers who set out to prove that a mega-dose of vitamin C can improve exercise performance in fact showed it has no effect at all. The vitamin, given intravenously to younger and older volunteers, did nothing to help them work harder on a treadmill, the team at the University of Colorado found. But the vitamin, given as ascorbic acid, did reduce oxidative stress - chemical damage done to cells and proteins in the body, the researchers found. "We did see a decrease in oxidative stress with large doses of vitamin C, but this decrease didn't improve aerobic abilities either for younger or older subjects," said Christopher Bell, now at Colorado State University, who led the research.
     We received this email: Dear Dr. Sahelian, I was very pleased to see your excellent "Vitamin C Research Update" on Chris Bell's "mega-dose" (as well as "chronic" dose study on potential effects on endurance exercise. However, it would be great if you could note that the Vitamin C study appeared in the Journal of Applied Physiology, published by the American Physiological Society. Best wishes, Mayer R. Resnick, Communications Officer, American Physiological Society, Bethesda, MD.

Comprehensive study on vitamin C equivalent antioxidant capacity (VCEAC) of various polyphenolics in scavenging a free radical and its structural relationship.
Crit Rev Food Sci Nutr. 2004. Department of Food Science and Technology, Cornell University, Geneva, New York
Antioxidant capacity for a wide range of natural or synthetic polyphenols was comprehensively evaluated by vitamin C equivalent antioxidant capacity (VCEAC) assay using free blue/green ABTS radicals. The polyphenolics tested are grouped into the following categories: vitamins (beta-carotene, alpha-tocopherol, vitamin A, and vitamin C), phenolic acids (benzoic acid, phenylacetic acid, cinnamic acid, and their derivatives), flavonoids (anthocyanidin, flavanol, chalcone, flavanone, flavone, flavonol, isoflavone, and their derivatives), synthetic food additives (BHA, BHT, TBHQ, and PG), and other miscellaneous polyphenolics (ellagic acid, sesamol, eugenol, thymol, etc.). A positive linear relationship between VCEAC and the number of free OH groups around the flavonoid framework was found, whereas, for phenolic acids, the linear relationship was not as good as with the flavonoid aglycones. Groups of chemicals having comparable structures generally showed similar trends. Synthetic antioxidant food additives (BHA, TBHQ, and BHT) conventionally used in the food industry were less effective antioxidants than ascorbic acid.

Bone Mineral Density in Postmenopausal Women
J Bone Miner Res 2001. The purpose of this study was to evaluate the independent relation of daily vitamin C supplement use with BMD in a population-based sample of post menopause women. Subjects were 994 women from a community-based cohort of whom 277 women were regular vitamin C supplement users. Daily vitamin C supplement intake ranged from 100 to 5,000 mg; the mean daily dose was 745 mg. Average duration of use was 12 years. Women who took vitamin C plus calcium and estrogen had the highest BMD at the femoral neck, total hip, ultradistal radius, and lumbar spine. Vitamin C supplement use appears to have a beneficial effect on levels of BMD, especially among postmenopausal women using concurrent estrogen therapy and calcium supplements.

Q. For what it is worth, I have megadozed on vitamin C for nearly forty years. From age 40 to age sixty, when I retired, I walked fifteen miles a day with a heavy satchel on my back delivering mail to some 549 houses on a foot route (no vehicle) in every type of weather. I averaged about 10,000 milligrams of vitamin C a day during those years. Today at 68 I take no precription drugs and am in apparently good health, except for a degree of arthritis in my lower back, likely a result of walking 75,000 miles over twenty years. Today I average about 14,000 milligrams of vitamin C a day.

Q. Is there an acne vitamin, I mean does vitamin C help acne?
   A. We are not aware of any vitamin supplements that help improve acne. Diet is the most important.

Q. I was informed by various sources that natural vitamins are better than synthetic and donate photogenic energy that only occurs in live source materials. Natural vitamins cost so much more and have lower dosages. Isolated vitamins are missing all the elements found in whole food source derivatives. Can you shed some light in this and maybe help save me money at the same time?
   A. The chemical structure of a vitamin, whether extracted from nature such as a plant, or whether made in a laboratory, will be the same and have the same exact role in the body. There are times, though, that an extract of a vitamin from a plant could contain additional beneficial substances. In the case of vitamin C, whether it is from nature or made in the lab, it will have the same effect. But there are extracts of vitamin C that come from certain fruits that will also contain substances known as bioflavonoids that have a lot of health benefits. In the latter case, the vitamin bottle supplement fact panel will indicate that there are bioflavonoids in addition to vitamin C.

Additional Antioxidants to consider.
Aceytylcysteine is a powerful antioxidant used in hospitals also. Acetyl l Carnitine is best taken less than 300 mg since higher amounts can cause nausea and restlessness. CoQ10 30 mg can be used daily, higher amounts such as 50 or above should be taken every other day.

Choline which helps form acetylcholine and phospholipids

Ester-C, Vitamin C 500 mg, 180 Tablets
Note: the paragraph below is provided by the manufacturer. In my opinion, I don't really see the benefit of Ester C over vitamin C except for bioflavonoids and calcium.

The Key to the Power of Vitamin C: ESTER - C is a form of vitamin C ascorbate containing essential C metabolites.  Unlike ordinary vitamin C, Ester-C is produced through an exclusive water based manufacturing process, providing anon acidic form that is gentle on your stomach.  ESTER-C also has added bioflavonoids which play a role in maintaining good health.

Amount per tablet:
Vitamin C - 500 mg - 830% Daily value
     (as calcium ascorbate Ester-C
Calcium - 90 mg - 10% DV as calcium ascorbate Ester-C
Bioflavonoid Complex - 130 mg
Rutin - 36 mg
Hesperidin Complex - 35 mg


Q. What's your opinion of Ester-C vitamin ?
   A. Honestly I just don't see the necessity of taking Ester-C vitamin as opposed to regular vitamin C. I know Larry King has been promoting Ester C on radio, but what does he know about optimal health and nutrition? He doesn't even ask though questions to his political guests let alone asking the company he is the spokesperson for the easy question: What is the research that says Ester C vitamin is preferable to regular vitamin C? Most people who take a vitamin C supplement ingest as much or more vitamin C than they need if the supplement has at least 200 mg of vitamin C. And most vitamin C supplement tablets are often 250 mg or 500 mg. There are no long term human studies that say Ester C is a healthier option than regular C. However, if there are bioflavonoids in Ester C preparations, that could offer some additional benefits, but then again it's cheaper to buy a vitamin C supplement with bioflavonoids as opposed to Ester C.
   Chewable vitamin C could cause tooth enamel erosion if left in the mouth too long. I am not sure whether Ester C vitamin would have the same effect on tooth enamel.
   Here's a study on Ester C that supports my viewpoint:

Pharmacokinetics in dogs after oral administration of two different forms of ascorbic acid.
Res Vet Sci. 2001. Department of Pharmacology, School of Pharmacy, University of Oslo.
The dog is able to synthesise vitamin C, but is frequently given the vitamin in an attempt to improve health and performance. The pharmacokinetics of vitamin C in this species, however, are not well studied. Using a selective analytical method and careful stability control, the pharmacokinetics of orally given vitamin C was studied in 20 dogs, at two dosage levels (15 and 50 mg kg(-1)) and with two forms of supplement [crystalline vitamin C and the vitamin C product Ester-C (Inter-Cal Corp., Prescott, AZ, USA)]. After oral administration, a rapid increase was found in the plasma level of vitamin C, indicating a possible intestinal active transport mechanism in this species. The obtained C (max) and AUC values were found to increase in a non-linear fashion when the dose of vitamin C was increased. The pharmacokinetic modeling of the elimination of vitamin C was made difficult by a pronounced secondary peak appearing after about 9 hours. The comparison of crystalline vitamin C and Ester-C did not indicate any significant differences in pharmacokinetic parameters between the two preparations of the vitamin.


Doctor's Best, Best Vitamin C, 500 mg, 120 Veggie Caps
Buy Vitamin C 500 mg, 120 Capsules
Buy Vitamin C 500 mg


Supplement Facts
Serving Size: 1 capsule
Servings Per Container: 120 servings
  Amount Per Serving % Daily Value
Vitamin C (as Quali-C ascorbic acid) 500 mg 833%
Daily Value not established.