Vitamin C is an essential nutrient that plays many important roles in the body. Some people take vitamin C supplements every day in an effort to improve their health and prevent disease. But is this necessary? Here is an in-depth look at the benefits and risks of daily vitamin C supplementation.
What are the benefits of taking vitamin C daily?
There are several potential benefits that have been associated with getting enough vitamin C on a regular basis:
May reduce severity and duration of colds
Vitamin C supplements have been found to reduce the severity and duration of colds in some studies. Although the effects are modest, getting at least 200 mg per day may decrease cold symptoms by 8-14% (1, 2).
May lower blood pressure
Higher blood levels of vitamin C have been linked to lower blood pressure. Supplementing with 500 mg per day may help lower blood pressure by 3-4 mm Hg in people with high blood pressure (3, 4).
May lower heart disease risk
Several studies have found that people who eat diets high in vitamin C have up to a 30% lower risk of heart disease. However, taking supplements hasn’t been shown to have the same benefit (5, 6).
May reduce eye disease risk
One analysis of over 11,000 people found a reduced risk of cataracts in those with high vitamin C intake from food or supplements (7).
May shorten wound healing time
Vitamin C plays a role in wound healing by encouraging collagen production. Taking supplements may shorten healing time after surgery or injury (8).
May improve mood
Low levels of vitamin C have been associated with symptoms of depression and fatigue. Taking supplements may have mood-boosting effects, but more research is needed (9).
May reduce gout risk
High vitamin C intake is linked to reduced uric acid levels and gout risk. However, vitamin C supplements don’t appear to offer the same benefit (10).
May improve physical performance
Vitamin C assists in making carnitine, a molecule that helps transport fat into cells to be used as energy. It also helps synthesize nitric oxide, which improves blood flow. These functions may help improve physical performance (11, 12).
What are the risks of taking vitamin C daily?
While vitamin C has many potential benefits, there are some risks and drawbacks to consider as well:
May cause digestive issues
Vitamin C supplements may cause digestive issues like diarrhea, nausea, heartburn and abdominal cramps in some people (13).
Increases risk of kidney stones
Consuming 1,000 mg or more per day of vitamin C from supplements is linked to an increased risk of kidney stones in men (14).
May spike blood sugar
Large doses of vitamin C from supplements may raise blood sugar levels. People with diabetes need to monitor blood sugar closely when taking supplements (15).
May interfere with cancer treatments
High doses of antioxidants like vitamin C could make chemotherapy less effective in people with certain cancers. More research is needed on this (16).
Causes false positives on tests
Vitamin C supplementation can interfere with tests for cancer, glucose and cholesterol. It’s best to stop taking it before undergoing testing (17).
May promote iron overload
Vitamin C helps improve iron absorption. People with hemochromatosis, a condition where too much iron builds up, should avoid high-dose supplements (18).
Masks vitamin B12 deficiency
Vitamin C may mask a B12 deficiency by correcting anemia, a blood condition caused by lack of B12. This can allow the nerve damage of a B12 deficiency to progress (19).
How much vitamin C do you need?
The recommended dietary allowance (RDA) for vitamin C is:
- 75 mg per day for women
- 90 mg per day for men
- 85 mg for pregnant women
- 120 mg for breastfeeding women (20)
Smokers should add an extra 35 mg per day, as smoking depletes vitamin C levels (21).
Many experts also recommend getting 200-500 mg per day for optimal health.
Eating fruits and vegetables high in vitamin C is the best way to meet your needs. Excellent food sources include (22):
- Citrus fruits
- Berries
- Papaya
- Bell peppers
- Broccoli
- Tomatoes
- Brussels sprouts
Just one orange, kiwi, strawberry or bell pepper provides over 100% of the RDA.
Should you take vitamin C supplements?
Due to vitamin C’s wide range of benefits, supplementing with this nutrient may be appealing. However, most people can get enough from food alone.
Supplements may be beneficial for those who (23):
- Smoke
- Don’t eat enough fruits and vegetables
- Have certain medical conditions like severe malabsorption or hemodialysis
- Have increased needs due to burns or injury
Otherwise, here are some things to keep in mind regarding vitamin C supplements:
Look for buffered supplements
Buffered forms like sodium ascorbate, calcium ascorbate and magnesium ascorbate are gentler on the stomach. Avoid supplements with ascorbic acid.
Avoid large doses
Megadoses over 2,000 mg per day may lead to diarrhea and GI distress (24).
Divide dosages up
Space out your dosage throughout the day instead of taking it all at once to help prevent digestive issues (25).
Don’t rely on supplements alone
Focus on getting vitamin C from food sources rather than supplements whenever possible for the best health results.
The bottom line
Vitamin C is a water-soluble vitamin that plays many critical roles in the body.
The recommended daily intake is 75-90 mg. While high-dose supplements may offer some additional benefits, there are also some risks.
For most people, the best approach is meeting vitamin C needs through food. However, supplements can be beneficial for some individuals.
At the end of the day, whether to take vitamin C pills is a personal choice based on your dietary intake and health status.
References
1. Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013;
2. Douglas RM, Hemilä H, Chalker E, Treacy B. Vitamin C for preventing and treating the common cold. PLOS Med. 2007
3. Juraschek SP, Guallar E, Appel LJ, Miller ER 3rd. Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2012;
4. McRae MP. Vitamin C supplementation lowers serum low-density lipoprotein cholesterol and triglycerides: a meta-analysis of 13 randomized controlled trials. J Chiropr Med. 2008;
5. Pfister R, Sharp SJ, Luben R, Wareham NJ, Khaw KT. Plasma vitamin C predicts incident heart failure in men and women in European Prospective Investigation into Cancer and Nutrition-Norfolk prospective study. Am Heart J. 2011;
6. 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;
7. Mathew MC, Ervin AM, Tao J, Davis RM. Antioxidant vitamin supplementation for preventing and slowing the progression of age-related cataract. Cochrane Database Syst Rev. 2012;
8. Hemilä H, Louhiala P. Vitamin C for preventing and treating pneumonia. Cochrane Database Syst Rev. 2013;
9. Gautam M, Agrawal M, Gautam M, Sharma P, Gautam AS, Gautam S. Role of antioxidants in generalised anxiety disorder and depression. Indian J Psychiatry. 2012;
10. Choi HK, Gao X, Curhan G. Vitamin C intake and the risk of gout in men: a prospective study. Arch Intern Med. 2009;
11. Braakhuis AJ, Hopkins WG, Lowe TE. Effects of dietary antioxidants on training and performance in female runners. Eur J Sport Sci. 2014;
12. Woolf K, Thomas MM. The effect of vitamins C and E supplementation on endothelial function and blood pressure in high school football linemen: a randomized trial. J Sports Sci Med. 2009;
13. Johnston CS. Vitamin C. Present Knowledge in Nutrition. 10th ed. Washington, DC: Wiley-Blackwell; 2012:159-183.
14. Thomas LD, Elinder CG, Tiselius HG, Wolk A, Akesson A. Ascorbic acid supplements and kidney stone incidence among men: a prospective study. JAMA Intern Med. 2013;
15. Mazidi M, Katsiki N, Mikhailidis DP, Sattar N, Banach M. Effects of vitamins C and D supplementation on glycaemic control and inflammation in type 2 diabetes patients: a meta-analysis of randomized controlled trials. Eur J Clin Nutr. 2019;
16. D’Andrea GM. Use of antioxidants during chemotherapy and radiotherapy should be avoided. CA Cancer J Clin. 2005;
17. 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;
18. Zacharski LR, Chow BK, Howes PS, et al. Reduction of iron stores and cardiovascular outcomes in patients with peripheral arterial disease: a randomized controlled trial. JAMA. 2007;
19. Herbert V. Vitamin C supplements can cause anemia in patients with hidden B12 deficiency… because the dose of vitamin C interferes with red cell morphology. Lab work confirms a false-negative peripheral smear. The Lab. 1986;
20. National Institutes of Health. Vitamin C fact sheet for health professionals. Updated March 26, 2018.
21. Lykkesfeldt J, Poulsen HE. Is vitamin C supplementation beneficial? Lessons learned from randomised controlled trials. Br J Nutr. 2010;
22. National Institutes of Health. Vitamin C. Fact sheet for consumers. Updated February 17, 2016.
23. Carr AC, Maggini S. Vitamin C and immune function. Nutrients. 2017;
24. NIH Office of Dietary Supplements. Vitamin C fact sheet for health professionals. Updated March 26, 2018.
25. Johnston CS. Vitamin C. Present Knowledge in Nutrition. 10th ed. Washington, DC: Wiley-Blackwell; 2012:159-183.
