Vitamin C is touted for its many health benefits: It boosts immunity, improves heart health, bolsters iron absorption, and much more.
Vitamin C is an essential nutrient needed for tissue growth, development, and repair. An antioxidant, it helps protect cells from free radicals—unstable molecules that damage cells.
The body cannot produce vitamin C and must get it through diet or supplements. Vitamin C–rich foods include citrus fruits, berries, broccoli, cabbage, peppers, potatoes, and tomatoes. Vitamin C supplements are available as capsules, chewable tablets, and powder that is added to water.
This article discusses vitamin C benefits, uses, and sources. It also explains the symptoms of vitamin C deficiency, possible side effects, precautions, and interactions.
Dietary supplements are not regulated in the United States. The U.S. Food and Drug Administration (FDA) does not test products for safety and effectiveness. Quality control testing is often done by a third party, such as USP (United States Pharmacopeia), Consumer Labs, or NSF International. This helps ensure the supplements contain the ingredients on the label.
However, third-party testing does not mean the supplement is effective or safe for everyone. Before taking any supplements, talk to your healthcare provider. Some supplements have negative interactions with medications or other supplements.
What Is Vitamin C?
Vitamin C, or L-ascorbic acid, is an essential nutrient. That means your body doesn't make it, so you have to get it through diet or supplements. Vitamin C is in many foods, such as oranges, red and green peppers, and kiwi.
Research shows vitamin C has many general health benefits. However, when it comes to using vitamin C to treat or prevent specific health conditions, the science is inconclusive.
Vitamin C Benefits and Uses
Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or healthcare provider. No supplement is intended to treat, cure, or prevent any disease.
Vitamin C has been marketed for use to treat and/or prevent many conditions, from the common cold and COVID-19 to arthritis and Alzheimer's disease. Even so, there's scant evidence to support most claims about vitamin C.
What researchers have learned is that vitamin C appears to play a lot of important roles in your body. The most beneficial aspect may be its antioxidant activity.
Supplement use should be tailored to your specific health issues and needs. Before starting a supplement, talk to a qualified healthcare provider, such as a Registered Dietitian or pharmacist.
Fights Free Radicals
Vitamin C is an antioxidant, meaning it's one of many natural substances that may help treat, slow, or prevent some health problems. It does this by neutralizing free radicals, which are unstable molecules that can damage cells and cause disease.
When you have a lot of free radicals in your system, it can cause a condition called oxidative stress (OS). Research has linked many chronic diseases to OS.
Preventing or reducing OS may help stave off health problems by:
However, research into using antioxidants to treat or prevent specific conditions has been a mixed bag.
Free radicals come in many types; some are harder for antioxidants to scavenge. Their location in your body can also make a difference, as certain environments (e.g., inside a cell versus in fluids outside the cell) can make the antioxidant activity more or less successful.
Moreover, researchers say it's important to be "realistic about where, when and to what extent oxidative stress is part of a disease." So, as they learn more about the disease processes and the role of OS, researchers may find roles for antioxidants like vitamin C.
In the meantime, while they're generally considered good for your health, don't expect vitamin C or any other antioxidants to take the place of other treatments.
Lowers Heart Disease Risk
Oxidative stress is believed to play a role in the development of some cardiovascular diseases ("cardio" means heart, "vascular" refers to blood vessels).
A major reason for this is that oxidative stress can trigger atherosclerosis, which is the thickening or hardening of arteries due to the buildup of plaque made from cholesterol, fat, and other substances. This can lead to coronary artery disease.
Studies have also suggested that oxidative stress may play some role in:
Ischemia
(impaired blood flow)Cardiomyopathy
(conditions of the heart muscle)hypertrophy
(enlargement and thickening of the heart muscle)Even so, research into vitamin C for treating and preventing heart disease has mostly found no effect.
One promising bit of information came out in a 2020 study. It showed that vitamin C supplements helped lower blood pressure in people with hypertension. Hypertension, especially when combined with atherosclerosis, is a risk factor for heart disease.
Molecules in your body become free radicals when they're exposed to things like environmental pollutants, cigarette smoking, and chronic inflammation.
May Help Reduce Risk of Certain Cancers
A lot of research has investigated the role of antioxidants, including vitamin C, in cancer care and prevention. However, the results have yielded inconsistent results.
Most studies have found that vitamin C supplementation, either on its own or in combination with other supplements, cannot prevent or treat cancer.
Some studies have shown that when used in supportive care, high-dose intravenous (IV) vitamin C can improve quality of life and reduce the side effects of standard cancer treatments. However, studies have also shown that antioxidants can have a downside. They may:
Some healthcare providers recommend eating more antioxidant-containing fruits and vegetables, as people with diets rich in vitamin C may have a lower risk of getting certain types of cancer. However, it's important to remember that no one food will prevent cancer.
Moreover, vitamin C supplements themselves do not appear to prevent cancer. Eating a well-balanced diet in general, including antioxidants, is beneficial for your overall health.
Future studies are needed to establish the role of antioxidants like vitamin C in cancer. Talk to your oncologist before starting any supplements during cancer treatment.
Can Prevent Gout Attacks
Gout is a common and extremely painful type of arthritis that mainly affects the big toes. It's caused by excess uric acid (a waste product) in the blood, which causes crystals to form in the joints. The crystals then cause inflammation, which leads to painful attacks.
Several studies have shown that vitamin C can prevent gout by lowering levels of uric acid in the blood. This may, at least in part, be due to its antioxidant activity. Uric acid levels appear to be higher in people with significant oxidative stress.
However, a 2021 review of studies concluded that, while results have been promising, more high-quality studies on humans need to be done to say for sure that it's a safe and effective treatment or preventive measure.
Prevents Iron-Deficiency Anemia
With anemia, your blood doesn't contain enough red blood cells, which carry oxygen from your lungs to your body's tissues. The most common type of anemia involves a deficiency of iron, which your body needs to make red blood cells.
Vitamin C is known to help your body absorb some nutrients. Among healthcare providers, that led to a long-standing practice of recommending vitamin C supplements with iron supplements for treating anemia.
A 2019 article found that vitamin C increased iron absorption by 67%. A 2020 study casts doubt on that, though. It found that iron supplements alone improved anemia just as much as iron plus vitamin C.
The different results may be related to what kind of iron people took. Nonheme iron from plant sources is better absorbed with vitamin C. Heme iron, the form found in meat, is better absorbed in general because it has higher bioavailability than nonheme iron. More research is needed to sort this out.
Boosts Immunity and Speeds Healing
Vitamin C's best-known use is for boosting the immune system. It does this by:
Studies show vitamin C's effect on the immune system may help with certain infections, such as:
Vitamin C is also sometimes used orally (by mouth) or topically (applied to the skin) for skin healing. According to research, vitamin C use may:
These abilities are believed to be largely due to vitamin C's antioxidant activity along with its ability to promote collagen production in the skin.
This is likely better achieved with nutritional intake (including supplements) rather than topically because collagen is present in deeper layers of skin and can't penetrate the outer layers to get there.
Collagen is a protein in your body that makes tissues strong, resilient, and able to tolerate stretching. It's in skin, bones, muscles, tendons, and cartilage.
Fights the Common Cold
Traditional wisdom about taking vitamin C for the common cold may not be as wise as you think. Research has provided mixed evidence about vitamin C for treating or preventing these respiratory infections.
Several studies, including a large systematic review of the evidence, suggest vitamin C supplements:
Even these points aren't firmly conclusive, though. For example, one systematic review including eight studies found vitamin C may only have a minimal or no effect on how long your cold lasts. However, a separate meta-analysis found it may shorten the duration.
More research needs to be done before researchers can draw any firm conclusions.
Slows Age-Related Macular Degeneration
Age-related macular degeneration (AMD) is an eye disorder that can, over time, cause blindness. Research has been inconclusive on whether vitamin C and other antioxidants can prevent AMD. But some research suggests it may slow it down.
The Age-Related Eye Disease Study (AREDS), a large clinical trial, included almost 3,600 older adults with AMD. The participants were divided into four groups and given different treatments:
After six years, the participants who got supplements had less AMD progression. However, researchers can't be sure that vitamin C itself made a difference.
This is an older study, though, and since then, a number of other studies have failed to show that vitamin C alone is helpful against AMD. Research from 2017 concludes that vitamin C "probably" doesn't prevent or delay AMD and that vitamin E and beta carotene do not.
Protects Brain Health
Vitamin C's antioxidant activity may play a role in brain health.
Research suggests regular dietary intake plus supplements may protect you from neurodegeneration related to aging and diseases such as:
Vitamin C may even help treat or lower your risk of mental health disorders, including:
Studies suggest vitamin C deficiency may contribute to the development of these mental and neurodegenerative conditions and that supplementation may help alleviate symptoms. However, this work is preliminary, and more research is needed.
Vitamin C Deficiency
Vitamin C deficiency is rare in developed countries. In the United States, only about 8.4% of the population is believed to be vitamin C deficient.
You'd have to get less than 10 milligrams (mg) per day from food for about a month to feel the effects of a vitamin C deficiency. In severe cases, this can lead to scurvy (which is rare in the U.S.).
Symptoms of scurvy include:
Vitamin C deficiency is treated with vitamin C supplements. Some symptoms improve within the first 24 hours of treatment. Others may take a few weeks to go away.
What Causes a Vitamin C Deficiency?
A deficiency occurs either from insufficient nutrient intake in the diet or increased losses due to poor absorption.
People who don't consume various foods, mainly fruits and vegetables, are at greater risk of vitamin C deficiency. Smokers have a higher requirement for vitamin C, so smoking may also be a risk factor.
Additionally, people with malabsorption disorders may become deficient because they can't absorb enough vitamin C.
How Do I Know if I Have a Vitamin C Deficiency?
Symptoms of a vitamin C deficiency include:
If you have these symptoms and know your vitamin C intake is low, or if you rarely eat fruits and vegetables, talk with your healthcare provider about whether supplements are right for you.
What Are the Side Effects of Vitamin C?
Vitamin C is generally considered safe, but high doses can cause side effects. These may include:
Higher doses are more likely to lead to side effects. Doses over 2,000 milligrams a day may increase the risk of diarrhea and kidney stones. If you have a history of kidney stones, taking more than 1,000 milligrams a day may increase your chances of having more.
Precautions
Vitamin C supplements are not right for everyone. Talk to your healthcare provider first if you are experiencing any of the following:
Dosage: How Much Vitamin C Should I Get?
Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs.
For most healthy people, it is easy to get adequate amounts of vitamin C through food. You can meet your recommended dietary allowance (RDA) for vitamin C each day by eating just one of the following:
The RDA for vitamin C is as follows:
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