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Can Vitamin C Prevent Colds and Flu?

November 14, 2019

Have you ever been told to eat more oranges the moment you feel a cold lurking? Or to take vitamin C supplements and stock up on immune supplements like Airborne? But is vitamin C a magic cure for cold and flu season?

By: Liza Iv, Zona Jin, Logan Joyner, Kristen Maloney, and Vika Nolen – Dietetic Interns, Meredith College 

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Colds and flus are common infectious diseases that mostly affect the upper respiratory area and are often seen in the fall and winter months.1 They last for days and make people feel miserable and prevent them from participating in regular daily activities. Signs and symptoms include chills, cough, congestion, runny nose, fever, headache, and sore throat. Adults have around two to four common-cold episodes annually, whereas children may have six to ten colds per year (and up to twelve colds per year for school children).1 

About Vitamin C

For many years, vitamin C has been popular as a natural cold remedy. Nobel Prize winner Linus Pauling first popularized the theory that vitamin C could treat or prevent the common cold.2 Vitamin C (ascorbic acid) is a water-soluble vitamin known for its antioxidant properties and role in immune function.2 Our bodies cannot make vitamin C and it must come from the foods that we eat. It is naturally found in foods like broccoli, bell pepper, strawberries, oranges, kiwis, grapefruit, potatoes, and tomatoes. The recommended dietary allowance for vitamin C (or the average intake necessary for most people to meet nutrition requirements) is 90mg for men, 75mg for women, and 25-75 mg for kids ages 4-18.2 

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What are the Benefits of Vitamin C?

Vitamin C helps with several functions in the human body such as tissue strength, iron absorption, and cancer prevention:

  • Research shows that vitamin C improves tissue strength and promotes the formation of collagen, which is essential in wound healing and skin integrity.3
  • Besides, vitamin C helps the body absorb iron.3 4
  • People with high intakes of vitamin C from fruits and vegetables might have a lower risk of getting many types of cancer, such as lung, breast, and colon cancer.5

However, taking vitamin C supplements, with or without other antioxidants, doesn’t seem to protect people from getting cancer. Research suggests that high doses of vitamin C can delay the progression of tumor cells.5 Further research is needed to confirm the results.

How Much Vitamin C Do You Need?

The Food and Nutrition Board of the Institute of Medicine set the upper limit for vitamin C intake at 2000 mg per day.3 while one cannot overdose on vitamin C by getting it from food sources, taking vitamin C supplements may put people at risk. Large doses of vitamin C supplements (greater than 1,000 mg per day) are not linked to any benefits. Too much vitamin C can lead to gastrointestinal upset, such as nausea and diarrhea.3 

Vitamin C and Colds

Although vitamin C has recently been used to prevent or treat the common cold, it is unclear whether vitamin C can prevent upper respiratory tract infections or make them shorter or less severe.6 7 One study showed that 1,000 mg of vitamin C for 8 weeks (n=30) reduced cold incidence in young men with low or average serum vitamin C levels.6 Another study showed that vitamin C supplementation can reduce cold incidence but not the duration or intensity of the cold.7 While getting plenty of vitamin C from natural food is recommended, further research is needed to prove vitamin C can reduce cold symptoms.

“To stay healthy during the cold season, be sure to get plenty of rest and eat a well-balanced diet including vitamin C-rich foods. Minimize your exposure to illness by washing your hands regularly. If you do get sick, be extra careful to get more rest and especially stay hydrated to let your body heal itself.” 

How can I stay healthy?

Duke Diet and Fitness Center Registered Dietitian Christine Tenekjian says, “To stay healthy during the cold season, be sure to get plenty of rest and eat a well-balanced diet including vitamin C-rich foods. Minimize your exposure to illness by washing your hands regularly. If you do get sick, be extra careful to get more rest and especially stay hydrated to let your body heal itself.” 

Instead of increasing vitamin C levels with supplements, Tenekjian recommends eating chicken soup with vegetables. Chicken soup with vegetables provides fluid to help hydrate the body, as well as vitamins, potassium, and sodium for the body.8 It also helps to increase mucus flow and relieve congestion symptoms.8 Tenekjian says, “Keep a batch of homemade chicken vegetable soup in your freezer just in case! Try this recipe from Rebecca Katz.”

While vitamin C does play an important part in aiding the immune system, it’s unclear if boosting vitamin C levels can help you avoid getting sick, or can shorten the duration of sickness. Instead of looking to vitamin C, create healthy habits in areas like eating, exercise, sleep, hand washing, and hydration. 

For assistance on creating healthy life patterns, the Duke Diet and Fitness Center is available to help you meet your dietary and exercise goals. Learn more about the programs and specialty nutrition, behavioral and medical consults available at the Duke Diet and Fitness Center at www.dukedietandfitness.org

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1. Maggini S, Beveridge S, Suter M. A Combination of High-Dose Vitamin C plus Zinc for the Common Cold. Journal of International Medical Research. 2012;40(1):28-42. doi:10.1177/147323001204000104.

2. Vitamin C fact sheet for professionals. National Institutes of Health. https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/#en1. Updated July 9, 2019. Accessed November 1st, 2019. 

3. Pullar JM, Carr AC, Vissers MCM. The Roles of Vitamin C in Skin Health. Nutrients. 2017;9(8):866. Published 2017 Aug 12. doi:10.3390/nu9080866. 

4. John N Hathcock, Angelo Azzi, Jeffrey Blumberg, Tammy Bray, Annette Dickinson, Balz Frei, Ishwarlal Jialal, Carol S Johnston, Frank J Kelly, Klaus Kraemer, Lester Packer, Sampath Parthasarathy, Helmut Sies, Maret G Traber, Vitamins E and C are safe across a broad range of intakes, The American Journal of Clinical Nutrition, Volume 81, Issue 4, April 2005, Pages 736–745, https://doi.org/10.1093/ajcn/81.4.736

5. Yun, J., Mullarky, E., Lu, C., Bosch, K. N., Kavalier, A., Rivera, K., ... & Muley, A. (2015). Vitamin C selectively kills KRAS and BRAF mutant colorectal cancer cells by targeting GAPDH. Science, 2015; 350(6266): 1391-1396. 

6. 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.

7. Sasazuki S, Sasaki S, Tsubono Y, Okubo S, Hayashi M, and Tsugane S. Effect of vitamin C on the common cold: Randomized controlled trial. European Journal of Clinical Nutrition. 2006;60: 9-17. 

8. Escott-Stump S. Section 15: HIV-AIDS and immunology, burns, sepsis, and trauma: Nutrition Diagnosis-Related Care. 8th ed. Philadelphia; PA: Lippincott Williams & Wilkins. 2015: 849. 


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