What is vitamin C?
Vitamin C is a water-soluble essential vitamin that can be found in fruits and vegetables, especially citrus. Humans are unable to synthesize vitamin C from their bodies, so it must be acquired through dietary intake. Vitamin C is important for immune system function and is a powerful antioxidant. It also acts as a cofactor for collagen synthesis.[2]
What are vitamin C’s main benefits?
People often supplement with vitamin C when they have a cold. According to various studies, vitamin C may be effective in reducing the duration of a cold, but does not seem to reduce the frequency of colds in a population.[3][4] The available literature suggests that a dose ranging from 200 mg to 2,000 mg could be beneficial for reducing cold duration.
Often utilized for its antioxidant effects, vitamin C has been studied for its potential role in Alzheimer’s disease and cancer. Lower vitamin C levels are present in people with Alzheimer’s, even with adequate dietary intake.[5] It is thought that oxidative stress plays a major role in the pathogenesis of the disease, so vitamin C’s antioxidative effects could be beneficial.[6][7] In rodent studies, oral vitamin C was able to reduce oxidative and inflammatory biomarkers.[8] In recent cancer research, vitamin C was found to promote oxidative stress in cancer cells, leading to cytotoxic effects at high doses in mice.[9] While promising, further research and human studies are required to determine efficacy.
What are vitamin C’s main drawbacks?
In general, vitamin C supplementation at recommended doses seems to be safe. However, higher doses (3,000–10,000 mg) may cause diarrhea.[2] One meta-analysis noted an increased risk of dental erosion with chewable vitamin C tablets.[10] A rare but noteworthy possibility of nephrotoxicity after high dose administration has also been observed,[11][12] but this is unlikely to occur with typical oral supplementation.
How does vitamin C work?
Vitamin C acts as a cofactor for various enzymes, notably enzymes involved in collagen synthesis, and as an antioxidant.[13] It is an essential vitamin that humans cannot synthesize, so it must be acquired through dietary intake. Deficiencies in this vitamin results in scurvy, a condition caused by a lack of vitamin C.[13]
What are other names for Vitamin C
- Ascorbic Acid
- Ascorbate
- L-ascorbic acid
- L-Threonic Acid (a metabolite)
Dosage information
According to the WHO, most adults need only 45 mg of vitamin C per day, but more recent research has shown this number to be too low. The minimum has been set at 75 mg for women and 90 mg for men in the U.S., and 95 mg for women and 110 mg for men in the E.U.
Moreover, a 2022 study using 110 mg as its starting number recommended adding 10 mg per 10 kg (22 lb) above 60 kg (132 lb) of body weight.[1]
Any of these numbers are easily attained through the diet, so supplementation of such low doses is usually unnecessary. Higher doses of vitamin C, up to 2,000 mg, are used to support the immune system (for athletes) or reduce the duration of the common cold.
Most studies on vitamin C prescribe one dose per day. The claim that taking 2,000 mg up to five times a day to optimally reduce cold symptoms is not sufficiently tested and requires more evidence.
Frequently asked questions
Vitamin C is a water-soluble essential vitamin that can be found in fruits and vegetables, especially citrus. Humans are unable to synthesize vitamin C from their bodies, so it must be acquired through dietary intake. Vitamin C is important for immune system function and is a powerful antioxidant. It also acts as a cofactor for collagen synthesis.[2]
People often supplement with vitamin C when they have a cold. According to various studies, vitamin C may be effective in reducing the duration of a cold, but does not seem to reduce the frequency of colds in a population.[3][4] The available literature suggests that a dose ranging from 200 mg to 2,000 mg could be beneficial for reducing cold duration.
Often utilized for its antioxidant effects, vitamin C has been studied for its potential role in Alzheimer’s disease and cancer. Lower vitamin C levels are present in people with Alzheimer’s, even with adequate dietary intake.[5] It is thought that oxidative stress plays a major role in the pathogenesis of the disease, so vitamin C’s antioxidative effects could be beneficial.[6][7] In rodent studies, oral vitamin C was able to reduce oxidative and inflammatory biomarkers.[8] In recent cancer research, vitamin C was found to promote oxidative stress in cancer cells, leading to cytotoxic effects at high doses in mice.[9] While promising, further research and human studies are required to determine efficacy.
In general, vitamin C supplementation at recommended doses seems to be safe. However, higher doses (3,000–10,000 mg) may cause diarrhea.[2] One meta-analysis noted an increased risk of dental erosion with chewable vitamin C tablets.[10] A rare but noteworthy possibility of nephrotoxicity after high dose administration has also been observed,[11][12] but this is unlikely to occur with typical oral supplementation.
Vitamin C acts as a cofactor for various enzymes, notably enzymes involved in collagen synthesis, and as an antioxidant.[13] It is an essential vitamin that humans cannot synthesize, so it must be acquired through dietary intake. Deficiencies in this vitamin results in scurvy, a condition caused by a lack of vitamin C.[13]
Powdered, chewable, and gummy vitamin C supplements are acidic, so depending on the amount of exposure, they could lead to enamel erosion.
Did you know that orange juice causes about as much dental erosion as soda, on a per-cup basis? Luckily, dose matters, and people are more likely to drink multiple cans of soda each and every day than multiple glasses of orange juice.
But that brings up an interesting question: ascorbic acid (aka vitamin C) is at fault for orange juice’s erosive effect. So what happens when you drink a powdered vitamin C supplement, which can contain up to 10 times more vitamin C than orange juice?
Let’s go through the existing research, in order to better understand the potential risk.
What does the research show?
In 2012, a meta-analysis found that chewing vitamin C tablets (in the form of ascorbic acid) significantly increased dental erosion. Chewable tablets, gummies, and liquids all contact the teeth, so a similar line of reasoning applies for each. Gummies and tablets may stick to teeth more, and powdered drinks less, but powdered drinks often contain more vitamin C. Swallowed pills, however, are in the clear.
So what exactly happens to the tooth enamel?
Oral bacteria are the most common culprit for stripping away tooth enamel, stealing some of the sugar you eat and producing enamel-eroding acid from it. But acid in the mouth can also come from non-bacterial sources, such as from chronic vomiting or directly from things you eat and drink. The usual suspects are soft drinks and acidic foods and beverages, while milk and yogurt can help protect enamel.
More specifically, enamel can dissolve at pH levels under 5.5, and chewable vitamin C tablets have a pH of around 2.3. Now that isn’t quite as scary as it sounds, since saliva can protect you by buffering some acid. But this only works to a degree, and continual exposure will lead to enamel loss. One study showed that salivary pH can drop quite a bit with vitamin C tablets, allowing enamel erosion to proceed, and a typical dose of 500 mg will lower the pH for up to 25 minutes.
Vitamin C supplements that contact your teeth (chewable tablets, gummies, liquids) can impact enamel to varying degrees. Exposure time and frequency of dosing are important factors.
What should you watch out for?
Watching might not actually help! You might not notice dental erosion at all, since the process can be slow, and tooth sensitivity won’t show up as long as the dentin under the enamel isn’t very affected. That means going to a dentist regularly is quite important.
As far as preventive measures, it depends on how safe and/or obsessive you want to be.
If you frequently drink those popular effervescent vitamin C packets aimed at reducing colds (oh, the lengths we’ll go to at Examine.com to avoid brand names …), drinking them through a straw will help avoid prolonged contact with our teeth. And whether you use vitamin C powder, tablets, or gummies, brushing within an hour of taking them substantially raises your risk for dental erosion.
Using Occam’s razor, another method would be to simply not use these products. Plain old ascorbic acid is much cheaper (albeit not as colorful and artificially tasty), and sporadically taking vitamin C isn’t shown to help prevent colds.
A third method is to avoid prolonged exposure. There isn’t much data out there, but six weeks of chewing a lot of vitamin C didn’t impact oral health in one trial, while a case study of three YEARS of nearly continuous vitamin C chewing and sucking led to massive dental erosion. Another case study also showed that three years of chewable vitamin C (but limited to three tablets a day) caused severe dental erosion.
Obviously, there’s a wide range in between six weeks and three years that has not been studied. Plus other other vitamin C forms haven’t been studied much, although vitamin C chewing gum actually helped reduce gingival calculus (which is basically hardened plaque, with plaque being the home of bacteria).
A final option would be to take a non-ascorbic-acid form of vitamin C, such as liposomal C or a mineral ascorbate. These are more expensive than ascorbic acid though.
Considering the large number of people who take vitamin C supplements, there’s surprisingly little research on vitamin C and dental erosion. While no effect was seen after six weeks of vitamin C tablet chewing in a very small trial, years of chewing has been associated with very severe enamel loss. Unfortunately, nobody knows how long you’d have to supplement to cause damage, and this could also vary depending on other oral health factors.
Luckily, vitamin C can be easily obtained in forms that aren’t powdered, chewable, or gummy. Just go to the grocery store and look for an amazing non-proprietary food product called: Fruits and Vegetables™, which also taste better than supplements. If you want to supplement for certain health goals, consider a method that doesn’t give your teeth prolonged exposure to ascorbic acid. For example: swallowed pills, liposomal C, or mineral ascorbates. If you drink powdered vitamin C or use chewables or gummies, consider swishing water around afterwards to reduce the enamel impact.
Please, for the love of all that’s evidence-based, don’t routinely brush your teeth after taking vitamin C chewables, gummies, or liquids. This same line of reasoning applies to brushing after drinking your morning orange juice.
Update History
New meta analysis added
