Vitamin C is naturally present in citrus fruits such as oranges and lemons, green vegetables and strawberries. It plays an important role in immune function, bone structure, iron absorption, and healthy skin. Vitamin C is also well-known for its antiviral properties.
The most extensively studied human infection is the common cold which is caused by many types of viruses. Some evidence showed that vitamin C supplementation (at least 200mg/day) failed to reduce the incidence of common cold among the general population but regular supplementation may reduce the duration of cold. A review conducted in 2018 suggested that high doses of vitamin C administered at the onset of cold could help reduce its duration, shorten the time of confinement indoors and relieve the symptoms associated with it including chest pain, fever and chills. The researchers further recommended a daily dose of 1g vitamin C to boost immunity and a larger dose of 3-4g/day during the common cold to speed up the recovery. However, more studies are required to establish the dosage.
Some online posts claimed that vitamin C can stop or treat the new coronavirus. However, there is no evidence that loading up on vitamin C will do the trick. Zhongnan Hospital of Wuhan University, China is currently conducting a clinical trial on vitamin C infusion at a very high dose (24g/day) for the treatment of Covid-19. We shall see what the outcome of the research tells us in the near future.
There is some evidence that vitamin C may also have effects on infections such as herpes and flu but evidence is not conclusive yet.
What you should do
If you want to benefit from vitamin C, you will need to consume it everyday preferably from food instead of supplementation so that you also get other important nutrients from food. Vitamin C content of some foods is listed below. The recommended intake by the Health Promotion Board for normal healthy adults is 105mg for men and 85mg for women. Consuming at least 2 servings of fruits and vegetables everyday will help you get enough vitamin C.
|Orange, 1 medium||70mg||Red pepper, sweet, raw, ½ cup||95mg|
|Kiwi, 1 medium||64mg||Broccoli, cooked, ½ cup||51mg|
|Strawberries, ½ cup||49mg||Cabbage, cooked, ½ cup||28mg|
|Cantaloupe ½ cup||29mg||Potato, baked, 1 medium||17mg|
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Hemilä H, Chalker E 2013. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews 2013, Issue 1.
Li et al, 2018. 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 Volumne 2018, Article ID 1837634, 12 pages
Vitamin C Infusion for the Treatment of Severe 2019-nCoV Infected Pneumonia 2020, viewed 29 Feb 2020, <https://clinicaltrials.gov/ct2/show/NCT04264533>
National Institute of Health 2020. Vitamin C, viewed 2 Mar 2020, <https://ods.od.nih.gov/factsheets/VitamincC-HealthProfessional/>