Vitamin C (also known as ascorbic acid) is an essential nutrient in our body. Our body doesn’t make it on its own and we must get it from our diet.
Vitamin C has several important functions in our bodies including:
- Working as an antioxidant (protects cells from damage from free radicals)
- Helping to make collagen (protein that provides the structure for your skin, ligaments, and bones)
- Enhancing absorption of iron (a mineral needed to deliver oxygen to tissues)
- Supporting the immune system
- Serving as a cofactor in several physiologic processes
Vitamin C is available in many of the foods that we eat like citrus fruits and vegetables. It is fairly easy to meet the Recommended Dietary Allowance (RDA). Deficiencies of Vitamin C are rare in the U.S.
Nutritional supplements are common in the U.S. but how do you know if you need Vitamin C supplements?
Many will take vitamin C supplements because friends swear by how it benefits them, celebrities endorse them on social media, or they simply believe that if “some is good, more must be better”.
In order to determine if vitamin C supplements would be of benefit for you, consider your health status and current diet. This should also be discussed with your medical provider.
This article provides an overview of Vitamin C, when supplementation may be beneficial, and when it isn’t necessary. After reading this article you should understand whether Vitamin C supplements are a good idea for you.
How Much Vitamin C Should I Take Daily?
The National Academy of Sciences sets recommendations for the intake of essential nutrients. For vitamin C, the recommended dietary allowance (RDA) ranges between 65-120 milligrams (mg) daily.
The RDA for men is 90 mg daily and for women 75 mg daily. Requirements increase during pregnancy (85 mg), breastfeeding (120 mg), and for smokers (an additional 35 mg to counteract the oxidative damage from smoking) (1, 2, 3).
What Are the Benefits of Taking Vitamin C?
There are several potential benefits of taking vitamin C supplements. Taking vitamin C may offer assurance that you are meeting your requirements.
Vitamin C works as an antioxidant that may protect cells from free radicals and oxidative stress. It also plays a role in nutrient absorption (especially for people that rely on plant-based foods as a source of iron) and wound healing (through collagen production).
Additional health benefits of vitamin C supplements are reviewed in detail below.
8 Health Benefits of Vitamin C
1. Shorter Duration of the Common Cold
Vitamin C is often promoted to prevent the common cold. Yet, scientific evidence does not support this. There are some studies that suggest vitamin C can shorten the duration of cold symptoms (4, 5).
The best way to keep your immune system well-tuned and able to fight infection is by ensuring you are getting adequate vitamin C from your diet. Men with marginal vitamin C status did benefit from supplementation to reduce the duration of symptoms (6).
Given that supplements are reasonably safe, rarely do harm, and are relatively cheap, adding them to your regimen when you feel a cold coming on is reasonable.
Vitamin C supplementation may also reduce the duration of pneumonia symptoms (7).
2. Help Lowering Blood Pressure
A large study on the effects of vitamin C supplementation (500 mg/d) on blood pressure found a significant reduction in blood pressure. The change was greater for those that were hypertensive (have high blood pressure) at the start of the study (8).
However, the change was not as great as seen with following the DASH diet (9). Therefore, a total approach to manage hypertension including a healthy diet, physical activity, maintaining a healthy weight, and supplements will result in the greatest reduction of blood pressure.
3. May Reduce Heart Disease Risk
Supplemental Vitamin C may reduce heart disease risk (10).
Research has shown that a 500 mg Vitamin C supplement daily, reduced LDL-cholesterol (bad cholesterol) and triglyceride levels (10, 11). High LDL-cholesterol levels are a risk factor for developing heart disease.
Other studies have not found antioxidant supplementation (including Vitamin C) to change LDL- and HDL-cholesterol levels (12).
Further reviews of research suggest that Vitamin C did not affect cholesterol levels. However, certain groups of people may benefit from the effect of Vitamin C. Those groups maybe people with higher body mass indexes (BMI), higher glucose and cholesterol levels, and marginal vitamin C status (13).
Varying research methods and types and doses of supplements, make it hard to draw conclusions on whether Vitamin C can reduce risk factors for heart disease (14).
Additional research found that Vitamin C improved endothelial function (endothelium is the membrane in blood vessels), particularly in those that had risk factors (15).
4. Help With Nutrient Absorption
Vitamin C is needed for your body to absorb iron, particularly plant-based sources of iron.
Adequate intake of vitamin C can enhance the absorption of non-heme iron from plant sources by as much as 2-4 times (2). This is an important consideration for vegetarians and those who are moving towards more plant-based eating patterns.
Vitamin C also plays a role in the absorption of folate (2).
5. Reduce Uric Acid Levels and Risk of Gout
Vitamin C supplementation is associated with a lower incidence of gout (16).
Taking a vitamin C supplement of 500 mg daily had an effect of reduced serum uric acid levels. High levels of uric acid is a risk factor for developing gout (17).
6. Prevent Age-Related Cognitive Decline
Supplementing with Vitamin C is associated with a lower prevalence of cognitive decline and Alzheimer’s disease (18, 19).
Additional research suggests maintaining healthy Vitamin C levels (from diet alone) protect against age-related cognitive decline and Alzheimer’s (19, 20). However, avoiding Vitamin C deficiency is likely more beneficial than just supplementing an already healthy diet (21).
Additional studies were not able to show the intake of antioxidants consistently improved cognition. Further research is needed in this area (22).
7. Reduce Inflammation
Vitamin C supplementation does not appear to prevent people from developing diabetes (23) or improve insulin resistance (24).
One study found that providing 500 mg vitamin C twice daily to people with diabetes reduced markers of inflammation (C-reactive protein, interleukin-6), as well as, fasting glucose and triglyceride levels (25). Another study found that 500 mg Vitamin C twice daily total and LDL-cholesterol and triglyceride levels (26).
8. May Reduce Age-Related Eye Dysfunction
Research has shown that a Vitamin C supplement (in addition to Vitamin E, beta-carotene, and zinc) has reduced the odds of developing macular degeneration (27).
Vitamin C may also protect against cataracts (28).
How to Get More Vitamin C in Your Diet
Vitamin C is found mainly in fruits and vegetables.
You can meet your daily requirement of Vitamin C by including just one of the following (1 cup serving):
- Kiwi – 164 mg
- Red bell pepper – 190 mg
- Tomato juice – 72 mg
- Orange slices – 95.8mg
- Orange juice – 72 mg
- Halved strawberries – 89.4 mg (29)
Additional good sources of vitamin C include green bell pepper, grapefruit, and other citrus fruits, papaya, broccoli, cantaloupe, mango, cabbage, tomatoes, and collard greens (29).
Does Vitamin C Give You Energy?
Vitamin C does not provide energy in the form of calories.
It has a role in many functions in the body including acting as a cofactor or reducing agent for several chemical processes. It can indirectly result in the production of energy.
To confuse matters, signs of Vitamin C deficiency are similar to an energy deficiency. Fatigue, anemia, weakening of collagen, and anorexia, can all be signs of a vitamin C deficiency.
Can You Get Too Much Vitamin C?
While our daily requirements for vitamin C (ascorbic acid) are less than 100 mg, the tolerable upper limit is up to 2,000 mg daily (1). Our daily requirements are simply the amount people need to prevent deficiency.
Sometimes our bodies are able to control what it needs. Vitamin C is a good example of this since your body will absorb more of the vitamin when it needs it.
Once your blood levels reach a point of “saturation”, absorption of the vitamin will decrease and your kidneys will work harder to clear it. If you have heard the expression “having expensive urine” from supplements it is often in reference to this vitamin, which is excreted through urine when consumed in excess. The rate of absorption can fall to 50% when taking 1,000 mg vitamin C daily.
It is rare to see reports of Vitamin C toxicity. There are reports of experiencing nausea and vomiting after taking 5,000-15,000 mg per day of Vitamin C. (3).
For most healthy people, there is no risk to supplementing vitamin C. Yet, there is no reason to go beyond the tolerable upper limit of 2,000 mg/day.
People with kidney disease, kidney stones, or iron overload should avoid supplementing Vitamin C. Additional Vitamin C can promote oxalate formation (3, 30). It may also exacerbate iron overload because of its role in helping iron absorption.
The Final Word
Vitamin C (ascorbic acid) is an essential nutrient and our needs are often met by eating a healthy diet with a variety of foods. Deficiency is rare in the U.S.
Some research has shown benefit from taking Vitamin C to alleviate cold symptoms sooner, reduce blood pressure, improve the function of blood vessels, reduce heart disease risk, and help with nutrient absorption. Supplementation also may have an effect on damage from free radicals and the risk of Gout, Alzheimers, and eye dysfunction.
Before starting supplements it is important to discuss with your health care provider to be sure that supplementing will be of benefit to you.
- National Academy of Sciences. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. 2000. National Academies Press, Washington, DC. Accessible at www.nap.edu.
- Academy of Nutrition and Dietetics. Vitamins and Minerals. In: Duyff RL, ed. Complete Food & Nutrition Guide. New York, NY: Houghton Mifflin Harcourt; 2017:408-442.
- Clark S. Vitamins and Minerals. In: Mueller CM, ed. The A.S.P.E.N. Adult Nutrition Support Core Curriculum. 2nded. Silver Spring, MD: The American Society of Parenteral and Enteral Nutrition. 2012:121-151.
- Hemila H, Chalker E. Vitamin C for Preventing and Treating the Common Cold. Cochrane Database Syst Rev. 2013;(1):CD000980. Published 2013 Jan 31. Doi:10.1002/14651858.CD000980.pub4.
- Ran L, Zhao W, Wang J, et al. Extra dose of vitamin C based on a daily supplementation shortens the common cold: a meta-analysis of 9 randomized controlled trials. BioMed Research International. 2018.
- Johnston CS, Barkyoumb GM, Schumacher SS. Vitamin C supplementation slightly improves physical activity levels and reduces cold incidence in men with marginal vitamin C status: a randomized controlled trial. Nutrients. 2014;6:2572-2583.
- Hemila, H; Louhiala P. Vitamin C for preventing and treating pneumonia. Cochrane Database Syst. Rev. 2013, CD005532.
- Juraschek SP, Guallar E, Appel LJ, Miller ER. Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials. Am J Clin Nutr.2012;95:1079-88.
- Blumenthal JA, Babyak MA, Hinderliter A, et al. Effects of the DASH diet alone and in combination with exercise and weight loss on blood pressure and cardiovascular biomarkers in men and women with high blood pressure. Arch Intern Med.2010;170(2):126-135.
- Knekt P, Ritz J, Pereira MA, et al. Antioxidant vitamins and coronary heart disease risk: a pooled analysis of 9 cohorts. Am J Clin Nutr. 2004;80:1508-1520.
- McRae MP. Vitamin C supplementation lowers serum low-density lipoprotein cholesterol and triglcerides: a meta-analysis of 13 randomized controlled trials. J Chiropractic Med. 2008;7:48-58.
- Brown BG, Zhao XQ, Chait A, et al. Simvastatin and niacin, antioxidant vitamins, or the combination for the prevention of coronary disease. N Engl J Med.2001;345:1583-92.
- Ashor AW, Brown R, Keenan PD, et al. Limited evidence for a beneficial effect of vitamin C supplementation on biomarkers of cardiovascular diseases: an umbrella review of systematic reviews and meta-analysis. Nutrition Research. 2019;61:1-12.
- Lykkesfeldt J, Poulsen HE. Is vitamin C supplementation beneficial: lessons learned from randomised controlled trials. Brit J Nutr. 2010;103:1251-1259.
- Ashor AW, Lara J, Mathers JC, Siervo. Effect of vitamin C on endothelial function in health and disease: a systematic review and meta-analysis of randomised controlled trials. Atherosclerosis. 2014;235:9-20.
- Choi HK, Gao XG, Curhan G. Vitamin c intake and the risk of gout in men – a prospective study. Arch Intern Med. 2009;169(5):502-507.
- Juraschek SP, Miller ER, Gelber AC. Effect of oral vitamin c supplementation on serum uric acid: a meta-analysis of randomized controlled trials. Arthritis Care Res. 2011;63(9):1295-1306.
- Paleologos M, Cumming RG, Lazarus R. Cohort study of vitamin C intake and cognitive impairment. Am J Epidemiol1998;148:45-50.
- Zandi PP, Anthony JC, Khackaturian AS, et al. Reduced risk of Alzheimer disease in users of antioxidant supplements. Arch Neurol. 2004;61:82-88.
- Li FJ, Shen L, Ji HF. Dietary intakes of vitamin E, vitamin C, and B-carotene and risk of Alzheimer’s Disease: A meta-analysis. J Alzheimer’s Disease. 2012:253-258.
- Harrison FE. A critical review of vitamin c for the prevention of age-related cognitive decline and Alzheimer’s disease. J Alzheimers Dis. 2012;29(4):711-726.
- Crichton GE, Bryan J, Murphy KJ. Dietary antioxidants, cognitive function and dementia – a systematic review. Plant Foods Hum Nutr. 2013;68(3):279-292.
- Song Y, Cook NR, Albert CM, Denburgh MV, Manson JE. Effects of vitamins C and E and B-carotene on the risk of type 2 diabetes in women at high risk of cardiovascular disease: a randomized controlled trial. Am J Clin Nutr. 2009;90:429-37.
- Chen H, Karne RJ, Hall G, et al. High-dose oral vitamin C partially replenishes vitamin C levels in patients with Type 2 diabetes and low vitamin C levels but does not improve endothelial dysfunction or insulin resistance. Am J Physiol Heart Circ Physiol.2009;290:H137-H145.
- Ellulu MS, Rahmat A, Patimah I, Khaza’ai H, Abed Y. Effect of vitamin C on inflammation and metabolic markers in hypertensive and/or diabetic obese adults: a randomized controlled trial. Drug Design, Development and Therapy. 2015;9:3405-3412.
- Paolisso G, Balbi V, Volpe C, et al. Metabolic benefits deriving from chronic vitamin c supplementation in aged non-insulin dependent diabetics. J Am Coll Nutr. 1995;4:387-392.
- Chew EY, Clemons TE, Agron E, et al. Long-term effects of Vitamins C, E, Beta-Carotene and Zinc on Age-Related Macular Degeneration. AREDS Report No. 35.Ophthalmology. 2013;12(8):1604-1611.
- Wei L, Liang G, Cai C, Lv J. Association of vitamin C with the risk of age-related cataract: a meta-analysis. Acta Ophthalmol. 2016;94:e170-176.
- U.S. Department of Agriculture. FoodData Central. Accessed May 20, 2020. https://fdc.nal.usda.gov.
- D’Costa MR, Winkler NS, Milliner DS, et al. Oxalosis associated with high-dsoe vitamin c ingestion in a peritoneal dialysis patient. Am J Kidney Dis. 2019;74(3):417-420.