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Vitamin C

Vitamin C Supplements Tested by ConsumerLab.com

Trying to find the best brand of vitamin C supplement based on independent tests? Want facts about health benefits of vitamin C such as for colds or collagen production? Read our reviews and comparisons of popular vitamin C pills, gummies, powders and liquids and learn when to use different forms of vitamin C (ascorbic acid, sodium ascorbate, calcium ascorbate, liposomal vitamin C), and about dosage, safety, and potential side effects of vitamin C.

Vitamin C Review

Product Reviews (63)

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CL Answers (100)

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Recalls & Warnings (191)

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Clinical Updates (36)

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8/06/2014

When Vitamin C May Curb a Cold

A recent small study among men with low to adequate levels of vitamin C showed that supplementing with vitamin C reduced the incidence of colds compared to placebo. The men taking vitamin C also reported having more energy -- although this finding was not statistically significant. Learn more about what vitamin C can and cannot do, the dose used in this study, and results of our tests of vitamin C supplements, in the update to the Vitamin C Supplements Review >>
1/31/2020

Not Enough Vitamin C

Vitamin C deficiency is known to cause scurvy, characterized by bleeding gums and other connective tissue problems. But vitamin C deficiency was recently reported to cause a very different array of symptoms in several people. Learn more in the What It Does section of the Vitamin C Supplements Review. Also see our Top Picks for vitamin C.
9/22/2018

Vitamin C and Prostate Cancer

Does taking vitamin C reduce the chance of developing prostate cancer? Find out what studies are showing, including one reported this month, in the What It Does section of the Vitamin C Supplements Review. (Also learn about vitamin C and cataracts and see our Top Picks for vitamin C.)
10/16/2020

Vitamin C for Vitality?

Can taking a vitamin C supplement or eating a vitamin C-rich food improve mood, energy, or overall well-being? Find out what a recent study showed in the What It Does section of the Vitamin C Supplements Review. Also see our Top Picks for vitamin C.
10/03/2020

Vitamin C for Foot Ulcers?

Can taking vitamin C help heal foot ulcers in people with diabetes or vascular disease? Find out what a new study showed in the What It Does section of our Vitamin C Supplements Review. Also see our Top Picks for vitamin C.
10/31/2020

Vitamin C for COVID-19?

Does high-dose vitamin C help people critically ill with COVID-19? Find out what a new report showed in the COVID-19 section of our Vitamin C Supplement Review. Also see our Top Picks for vitamin C.
2/03/2021

Vitamin C for Bleeding Gums?

Does vitamin C supplementation reduce the tendency for gums to bleed? Find out what research shows in the What It Does section of our Vitamin C Supplements Review. Also see our Top Picks for vitamin C.
9/17/2021

Vitamin C For Fatty Liver?

Can taking high-dose vitamin C improve liver function or insulin resistance in people with NAFLD (non-alcoholic fatty liver disease)? Find out what a recent study showed in the What It Does section of our Vitamin C Supplements Review. Also see our Top Picks among vitamin C supplements.
11/23/2021

Vitamin C Serums for Wrinkles?

Can applying vitamin C to the skin reduce wrinkles or help prevent sun damage? Find out in the Skin Health section of our Vitamin C supplements review.

Also learn what features you should look for if selecting a vitamin C serum.

2/12/2019

Vitamin C for Blood Sugar Control

High-dose vitamin C was found to help control blood sugar levels in people with type 2 diabetes in a recent study. For details, see the What It Does section of the Vitamin C Supplements Review. Also see our latest Top Picks for vitamin C.
8/03/2018

Vitamin C for Colds?

Taking vitamin C may modestly help with colds, according to a new study -- but there's a catch. Find out in the What It Does section of the Vitamin C Supplements Review. (Also see our Top Picks for vitamin C supplements.)
2/11/2020

Vitamin C & Lungs

Supplementing with vitamin C to correct deficiency can reverse a form of lung disease, as exemplified in a recent report. For details, see the What It Does section of the Vitamin C Supplements Review. Also see our Top Picks for vitamin C.
12/03/2019

Vitamin C and Kidney Damage

High doses of vitamin C have been reported to cause a form of kidney damage, although this is more common in people with certain pre-existing medical conditions. For details, see the Concerns and Cautions section of the Vitamin C Supplements Review. Also see our Top Picks for vitamin C supplements.
7/23/2016

Vitamin C and Breast Cancer

Higher intakes of vitamin C from foods are linked to lower risk of postmenopausal breast cancer in women, but getting vitamin C from supplements on top of that may increase the risk, says a new study. Get the details in the Vitamin C Supplements Review >>
8/03/2016

Is Ester-C Better?

One of the forms of vitamin C in supplements is Ester-C. In addition to being non-acidic, a recent study suggests another possible benefit over regular vitamin C (ascorbic acid). Get more information about this and other forms of vitamin C in the "ConsumerTips" section of the Vitamin C Supplements Review >>
9/09/2015

Vitamin C: The Exercise Replacement?

A small clinical study recently found that taking vitamin C had a positive effect on blood vessels similar to a daily walk. The study focused on overweight and obese individuals, in whom blood vessel tone is compromised. Long-term effects were not studied. Get details about the study (including dose) and other pros and cons of vitamin C in the Vitamin C Supplements Review >>
4/30/2012

Vitamin C and Blood Pressure

Vitamin C supplements may modestly reduce blood pressure, particularly among people with elevated blood pressure, according to a review of the latest clinical studies. Get the details, as well as our tests of vitamin C supplements, in the updated Vitamin C Supplements ReviewMore >>
9/05/2021

Vitamin C & Statins

Does taking vitamin C reduce the cholesterol-lowering effects of statins? Find out in the What to Consider When Using section of our Vitamin C Supplements Review.
1/13/2021

High-Dose Vitamin C for COVID-19?

Does high-dose vitamin C help in people with severe COVID-19? See what a new study showed in the COVID-19 section of our Vitamin C Supplements Review.
12/09/2018

Vitamin C and Kidney Damage

High doses of vitamin C can cause kidney stones and damage kidneys. People with certain diets or medical conditions may be more prone to these problems. Get the details, including those of a recent case, in the Concerns and Cautions section of the Vitamin C Supplements Review.
3/26/2019

Vitamin C Blunts Exercise Benefits

If you are trying to build muscle with resistance exercise, go easy on vitamins C and E, according to a recent study. Get the details in the Concerns and Cautions section of the Vitamin C Supplements Review.
6/09/2013

Vitamin C: Does It Fight Colds?

A new analysis says it can help — a little. Get the bottom line, plus test results for 27 products, in the updated Vitamin C Supplements Review >>
2/07/2014

Vitamins C & E Blunt Exercise Effect

A recent study found that giving high-dose vitamin C or vitamin E to people involved in intensive exercise training blunted cellular changes thought to be important for improving muscular endurance. These and similar results recently reported with resveratrol raise concerns about high-dose antioxidant supplementation during exercise training. For details, see the updates to the "Concerns and Cautions" sections of the Vitamin C Supplements Review >>  and the Vitamin E Supplements Review >> 
11/04/2020

Vitamin C to Boost Iron?

Vitamin C is often touted to boost iron absorption. But does it really work? Find out what a recent study found in the ConsumerTips section of our Iron Supplements Review. Also, see our Top Picks for iron.
8/25/2013

Antioxidants: Too Much of a Good Thing?

A new, long-term study of Americans found the risk of dying over the course of the study (about 14 years) was lowest when antioxidant levels in the blood were above the lowest levels (the bottom 20% of the population). However, for people in the top 20% of blood levels for vitamins A and E, the risk of death increased compared to people with moderate levels. For selenium and beta-carotene, there was no significant difference in the death rate between moderate and high levels, although for vitamin C some additional benefit was seen at high, but not the highest, levels.
 
The results suggest that antioxidant supplements may be useful for those who are nutritionally deficient, but, as noted by the researchers, "beyond a certain threshold, higher levels do not lead to additional benefit, and may potentially be toxic." More details (including specific serum levels) are found in the linked updates to the following reviews, which include our test results and quality ratings of products:
 
 
  
  
4/08/2017

Exercise Benefit Lost With High-Dose Vitamins

Older men asked to perform resistance (strength) training for 12 weeks showed less gain in bone density if they were given high daily doses of vitamins C & E than if they were given a placebo. This is not the first time that  high-dose antioxidant supplements have been shown to reduce benefits from exercise. For details, see the "Concerns and Cautions" section of the Vitamin C Supplements Review >>
1/19/2014

Multivitamin Lowers Cataract Risk

A large, long-term study using a low-dose multivitamin found that it reduced the risk of developing cataract (a clouding of the lens of the eye) by 9% compared to placebo. Interestingly, the reduced risk of cataract was negated when a separate vitamin C supplement was also taken. For details about the study and dosage, as well as our tests and comparison of multivitamins, see the updated Multivitamin and Multimineral Supplements Review.   
2/19/2019

Kidney Stones Due to Supplement?

An unusual type of kidney stone has been reported in several people who regularly consumed large amounts of a vitamin and amino acid supplement containing a particular form of choline and vitamin C. For details, see the Concerns and Cautions section of the Choline Supplements Review.
3/25/2020

Surprising Role of Potassium in COVID-19

New research out of China suggests that many patients hospitalized with COVID-19 are low in potassium. For details see the information about Potassium in our answer to the question: What are natural remedies for coronavirus (COVID-19)? Do supplements like zinc, vitamin C, or herbals work?
1/08/2012

Additional Nutrients For the Brain

An new study found that various nutrients and fats in the blood correlate with better brain functioning and brain volume in the elderly (mean age of 87). Higher levels of B vitamins and vitamins C, D, and E, as well as marine omega-3 fatty acids (EPA and DHA) appeared helpful. On the other hand, higher levels of trans-fats (from hydrogenated oils) had a negative impact. You can learn more about each of these nutrients in our various reports. An abstract of the study is online.
1/22/2012

Vitamin D and Inflammation

A new study found that raising low levels of vitamin D appears to reduce inflammation in the body (based on measurements of C-reactive protein, or CRP, a marker of inflammation). However, once vitamin D levels reached what some people consider to be barely sufficient, CRP slowly but progressively increased, suggesting an inflammatory action of vitamin D at higher levels. The study raises the question of what is the ideal level of vitamin D in the body. 

Be sure you have the latest information! See the update to the Vitamin D Supplements Review, which includes details on this and other vitamin D studies, as well as our latest product tests.
7/03/2021

Probiotics for C. difficile infection?

New guidelines recommend against probiotics for treating or preventing C. difficile infection, one cause of diarrhea in people taking antibiotics. Find out why in the What They Do section of our Probiotic Supplements Review.
11/25/2012

Probiotics Reduce Risk of Diarrhea After Antibiotics

Taking a broad-spectrum antibiotic can disturb the natural organisms in your gut. In some cases, particularly among older, hospitalized individuals, diarrhea can result due to infection with C. difficile. This can be life-threatening. A new review of 20 clinical trials shows that probiotics can reduce the risk of C. difficile-associated diarrhea by 50% to 75% depending on the type of probiotic used. Find out more, including the type of probiotic associated with most benefit, in the updated Probiotic Supplements Review, which includes our tests and reviews of 29 probiotic supplements. More >>
10/10/2014

Caution with St. John's Wort

St. John's wort is known to interact with a large number of prescription drugs. That number grew larger recently when the FDA approved two new drugs to cure hepatitis C infection. Taking these drugs while using St. John's wort may lead to reduced therapeutic effect and is not recommended. More information about this and other drug interactions with St. John's wort is found in the "Concerns and Cautions" section of the St. John's Wort Supplements Review >>
2/28/2017

Timing Probiotics with Antibiotics Is Key

Probiotics can reduce the risk of C. difficile infection due to antibiotics by nearly 70% if probiotics are started at the right time, according to a new study. Get the details in the "What It Does" section of the Probiotic Supplements Review (which includes our tests of products) >>
6/09/2020

Probiotics That Do or Don't Work

An expert panel of gastroenterologists reviewed the clinical evidence for probiotics in preventing or treating C. difficile infection, IBS, ulcerative colitis, Crohn's disease, pouchitis, and necrotizing enterocolitis. Find out for which conditions they recommend probiotics and for which they don't in the What They Do section of the Probiotic Supplements Review (we've highlighted their recommendations in yellow). Also see our Top Picks for probiotics.

News Releases (74)

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