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Clinical Updates
Vitamin C
Liposomal Vitamin C
July 11, 2025
We recently wrote about a liposomal "hydrogel" vitamin C product from Life Extension purported to have improved bioavailability, but we could not locate a supporting published study. Life Extension recently directed us to the study, now discussed in the Forms of Vitamin C section of our Vitamin C Supplements Review, which includes our Top Picks for vitamin C.
Liposomal Vitamin C?
June 19, 2025
Some vitamin C supplements, including one from Life Extension, use a liposomal "hydrogel" to sustain higher vitamin C levels. Is this better than regular or other liposomal versions? Learn more in the Forms of Vitamin C section of our Vitamin C Supplements Review, which includes our Top Picks for vitamin C.
Vitamin C & Urine Tests
November 25, 2024
Taking vitamin C may interfere with certain urine tests, including those for glucose and bilirubin. See the details in the Concerns and Cautions section of our Vitamin C Supplements Review, which includes our Top Picks for vitamin C.
Scurvy After Stomach Surgery
October 31, 2024
A man developed scurvy (due to vitamin C deficiency) years after undergoing gastric sleeve surgery. Be aware of this and other risk factors for vitamin C deficiency, in the Deficiency section of our Vitamin C Supplements Review, which includes our Top Picks for vitamin C.
Also see: Which supplements are important after bariatric surgery?
Vitamin C & Kidney Injury
October 17, 2024
Be aware that high-dose vitamin C can contribute to kidney stones in some people and even cause kidney injury as highlighted in our Vitamin C Supplements Review, which includes our Top Picks for vitamin C.
Also see: Which supplements and foods reduce or increase the risk of kidney stones?
Liposomal Vitamin C?
September 12, 2024
Is it worth spending more for the liposomal form of vitamin C? Find out what a recent study showed in our Forms of vitamin C section of our Vitamin C Supplements Review, which includes our Top Picks for vitamin C.
Vitamin C for Colds?
April 25, 2023
Does vitamin C shorten the duration of colds? Get the details, and learn about one study that was recently retracted. See the Colds and immune system health section of our Vitamin C Supplements Review.
Also see our Top Picks among vitamin C supplements.
Do Antioxidants Reduce Exercise Gains?
April 11, 2023
Does supplementing with high doses of vitamin C and/or vitamin E hinder beneficial changes that occur during high-intensity interval training? Find out what a recent study showed in the Concerns and Cautions section of our Vitamin C Supplements Review.
Also see our Top Picks for vitamin C.
Vitamin C or Melatonin for COVID?
August 05, 2022
Vitamin C & Kidney Stones
June 17, 2022
High intake of vitamin C has been linked with an increased risk of kidney stones, but is the risk similar among men vs women?
Vitamin C & Blood Thinners
May 03, 2022
Is it safe to take vitamin C if you take anticoagulants like warfarin? See the answer in the Concerns and Cautions section of our Vitamin C Supplements Review.
Vitamin C & Mortality
April 26, 2022
Higher blood levels of vitamin C were associated with increased risk of death over a 10-year period in a recent study. Get the details in the Concerns and Cautions section of our Vitamin C Supplements Review. Also see adequate intake amounts for vitamin C.
Vitamin C for Mood?
December 20, 2021
Can vitamin C from the diet or supplements help boost mood, including symptoms of depression? Find out what current evidence suggests in the Vitality and Mood section of our Vitamin C Supplements Review, which includes a list of foods high in vitamin C and our Top Picks for vitamin C.
Vitamin C Serums for Wrinkles?
November 22, 2021
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.
Vitamin C For Fatty Liver?
September 16, 2021
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.
Vitamin C & Statins
September 04, 2021
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.
Vitamin C for Bleeding Gums?
February 02, 2021
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.
High-Dose Vitamin C for COVID-19?
January 12, 2021
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.
Vitamin C to Boost Iron?
November 03, 2020
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.
Vitamin C for COVID-19?
October 30, 2020
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.
Vitamin C for Vitality?
October 15, 2020
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.
Vitamin C for Foot Ulcers?
October 02, 2020
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.
Vitamin C & Lungs
February 10, 2020
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.
Not Enough Vitamin C
January 30, 2020
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.
Vitamin C and Kidney Damage
December 02, 2019
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.
Vitamin C Blunts Exercise Benefits
March 25, 2019
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.
Vitamin C for Blood Sugar Control
February 11, 2019
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.
Vitamin C and Kidney Damage
December 08, 2018
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.
Vitamin C and Prostate Cancer
September 21, 2018
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.)
Vitamin C for Colds?
August 02, 2018
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.)
Exercise Benefit Lost With High-Dose Vitamins
April 07, 2017
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 >>
Is Ester-C Better?
August 02, 2016
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 >>
Vitamin C and Breast Cancer
July 22, 2016
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 >>
Vitamin C: The Exercise Replacement?
September 08, 2015
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 >>
When Vitamin C May Curb a Cold
August 05, 2014
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 >>
Vitamins C & E Blunt Exercise Effect
February 06, 2014
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 >>
Antioxidants: Too Much of a Good Thing?
August 24, 2013
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:
Vitamin C: Does It Fight Colds?
June 08, 2013
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 >>
Vitamin C and Blood Pressure
April 29, 2012
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 Review. More >>
